Thursday, February 7, 2013

Leaked Report Shows UN Admitting Solar Activity Plays Significant Role in Global Warming - Complete Leaked Report Here


In the interest of public knowledge and fear that this site will be deleted soon. Here is the full report from http://www.stopgreensuicide.com/


Full AR5 draft leaked here, contains game-changing admission of enhanced solar forcing
Posted by Alec Rawls, 12/13/12
I participated in "expert review" of the Second Order Draft of AR5 (the next IPCC report), Working Group 1 ("The Scientific Basis"), and am now making the full draft available to the public. I believe that the leaking of this draft is entirely legal, that the taxpayer funded report is properly in the public domain under the Freedom of Information Act, and that making it available to the public is in any case protected by established legal and ethical standards, but web hosting companies are not in the business of making such determinations so interested readers are encouraged to please download copies of the report for further dissemination in case this content is removed as a possible terms-of-service violation. My reasons for leaking the report are explained below. Here are the chapters:
Summary for Policymakers
Chapter 1: Introduction
Chapter 2: Observations: Atmosphere and Surface
Chapter 3: Observations: Ocean
Chapter 4: Observations: Cryosphere
Chapter 5: Information from Paleoclimate Archives
Chapter 6: Carbon and Other Biogeochemical Cycles
Chapter 7: Clouds and Aerosols
Chapter 8: Anthropogenic and Natural Radiative Forcing
Chapter 8 Supplement
Chapter 9: Evaluation of Climate Models
Chapter 10: Detection and Attribution of Climate Change: from Global to Regional
Chapter 11: Near-term Climate Change: Projections and Predictability
Chapter 12: Long-term Climate Change: Projections, Commitments and Irreversibility
Chapter 13: Sea Level Change
Chapter 14: Climate Phenomena and their Relevance for Future Regional Climate Change
Chapter 14 Supplement
Technical Summary


Why leak the draft report?
 By Alec Rawls (email)
General principles
The ethics of leaking tax-payer funded documents requires weighing the "public's right to know" against any harm to the public interest that may result. The press often leaks even in the face of extreme such harm, as when the New York Times published details of how the Bush administration was tracking terrorist financing with the help of the private sector Society for Worldwide Interbank Financial Telecommunication (SWIFT), causing this very successful anti-terror program to immediately collapse.

That was a bad leak, doing great harm to expose something that nobody needed to know about. With the UN's IPCC reports the calculus is reversed. UN "climate chief" Christina Figueres explains what is at stake for the public:

... we are inspiring government, private sector, and civil society to [make] the biggest transformation that they have ever undertaken. The Industrial Revolution was also a transformation, but it wasn’t a guided transformation from a centralized policy perspective. This is a centralized transformation that is taking place because governments have decided that they need to listen to science.

So may we please see this "science" on the basis of which our existing energy infrastructure is to be ripped out in favor of non-existent "green" energy? The only reason for secrecy in the first place is to enhance the UN's political control over a scientific story line that is aimed explicitly at policy makers. Thus the drafts ought to fall within the reach of the Freedom of Information Act.
The Obama administration implicitly acknowledged this when it tried to evade FOIA by setting up private "backdoor channels" for communications with the IPCC. If NCAR's Gerald Meehl (a lead author of AR5's chapter on near-term climate change), has working copies of the draft report (and he's only one of dozens of U.S. government researchers who would), then by law the draft report (now finished) should be available to the public.

The IPCC's official reason for wanting secrecy (as they explained it to Steve McIntyre in  January 2012) is so that criticisms of the drafts are not spread out across the internet but get funneled through the UN's comment process. If there is any merit to that rationale it is now moot. The comment period ended November 30th so the comment process can no longer be affected by publication.

As for my personal confidentiality agreement with the IPCC, I regard that as vitiated by the systematic dishonesty of the report ("omitted variable fraud" as I called it in my FOD comments). This is a general principle of journalistic confidentiality: bad faith on one side breaks the agreement on the other. They can't ask reviewers to become complicit in their dishonesty by remaining silent about it.

Then there is the specific content of the Second Order Draft where the addition of one single sentence demands the release of the whole. That sentence is an astounding bit of honesty, a killing admission that completely undercuts the main premise and the main conclusion of the full report, revealing the fundamental dishonesty of the whole.

Lead story from the Second Order Draft: strong evidence for solar forcing beyond TSI now acknowledged by IPCC
Compared to the First Order Draft, the SOD now adds the following sentence, indicated in bold (page 7-43, lines 1-5, emphasis added):

Many empirical relationships have been reported between GCR or cosmogenic isotope archives and some aspects of the climate system (e.g., Bond et al., 2001; Dengel et al., 2009; Ram and Stolz, 1999). The forcing from changes in total solar irradiance alone does not seem to account for these observations, implying the existence of an amplifying mechanism such as the hypothesized GCR-cloud link. We focus here on observed relationships between GCR and aerosol and cloud properties.

The Chapter 7 authors are admitting strong evidence ("many empirical relationships") for enhanced solar forcing (forcing beyond total solar irradiance, or TSI), even if they don't know what the mechanism is. This directly undercuts the main premise of the report, as stated in Chapter 8 (page 8-4, lines 54-57):

There is very high confidence that natural forcing is a small fraction of the anthropogenic forcing. In particular, over the past three decades (since 1980), robust evidence from satellite observations of the TSI and volcanic aerosols demonstrate a near-zero (–0.04 W m–2) change in the natural forcing compared to the anthropogenic AF increase of ~1.0 ± 0.3 W m–2.

The Chapter 8 authors (a different group than the Chapter 7 authors) are explicit here that their claim about natural forcing being small compared to anthropogenic forcing is based on an analysis in which the only solar forcing that is taken into account is TSI. This can be verified from the radiative forcing table on page 8-39 where the only solar variable included in the IPCC's computer models is seen to be "solar irradiance."

This analysis, where post-1980 warming gets attributed to the human release of CO2 on the grounds that it cannot be attributed to solar irradiance, cannot stand in the face of the Chapter 7 admission of substantial evidence for solar forcing beyond solar irradiance. Once the evidence for enhanced solar forcing is taken into account we can have no confidence that natural forcing is small compared to anthropogenic forcing.

The Chapter 8 premise that natural forcing is relatively small leads directly to the main conclusion of the entire report, stated in the first sentence of the Executive Summary (the very first sentence of the entire report): that advances since AR4 "further strengthen the basis for human activities being the primary driver in climate change" (p.1-2, lines 3-5). This headline conclusion is a direct descendant of the assumption that the only solar forcing is TSI, a claim that their own report no longer accepts.

The report still barely hints at the mountain of evidence for enhanced solar forcing, or the magnitude of the evidenced effect. Dozens of studies (section two here) have found between a .4 and .7 degree of correlation between solar activity and various climate indices, suggesting that solar activity "explains" in the statistical sense something like half of all past temperature change, very little of which could be explained by the very slight variation in TSI. At least the Chapter 7 team is now being explicit about what this evidence means: that some mechanism of enhanced solar forcing must be at work.

My full submitted comments (which I will post later) elaborate several important points. For instance, note that the Chapter 8 premise (page 8-4, lines 54-57) assumes that it is the change in the level of forcing since 1980, not the level of forcing, that would be causing warming. Solar activity was at historically high levels at least through the end of solar cycle 22 (1996), yet the IPCC is assuming that because this high level of solar forcing was roughly constant from 1950 until it fell off during solar cycle 23 it could not have caused post-1980 warming. In effect they are claiming that you can't heat a pot of water by turning the burner to maximum and leaving it there, that you have to keep turning the flame up to get continued warming, an un-scientific absurdity that I have been writing about for several years (most recently in my post about Isaac Held's bogus 2-box model of ocean equilibration).

The admission of strong evidence for enhanced solar forcing changes everything. The climate alarmists can't continue to claim that warming was almost entirely due to human activity over a period when solar warming effects, now acknowledged to be important, were at a maximum. The final draft of AR5 WG1 is not scheduled to be released for another year but the public needs to know now how the main premises and conclusions of the IPCC story line have been undercut by the IPCC itself.

President Obama is already pushing a carbon tax premised on the fear that CO2 is causing dangerous global warming. Last week his people were at the UN's climate meeting in Doha pretending that Hurricane Sandy was caused by human increments to CO2 as UN insiders assured the public that the next IPCC report will "scare the wits out of everyone" with its ramped-up predictions of human-caused global warming to come, but this is not where the evidence points, not if climate change is in any substantial measure driven by the sun, which has now gone quiet and is exerting what influence it has in the cooling direction.

The acknowledgement of strong evidence for enhanced solar forcing should upend the IPCC's entire agenda. The easiest way for the UN to handle this disruptive admission would be to remove it from their final draft, which is another reason to make the draft report public now. The devastating admission needs to be known so that the IPCC can't quietly take it back.

Will some press organization please host the leaked report?
Most of us have to worry about staying within cautiously written and cautiously applied terms-of-service agreements. That's why I created this new website. If it gets taken down nothing else gets taken with it. Media companies don't have this problem. They have their own servers and publishing things like the draft IPCC report is supposed to be their bailiwick.

If the press has First Amendment protection for the publication of leaked materials even when substantial national security interests are at stake (the Supreme Court precedent set in the Pentagon Papers case), then it can certainly republish a leaked draft of a climate science report where there is no public interest in secrecy. The leaker could be at risk (the case against Pentagon leaker Daniel Ellsberg was thrown out for government misconduct, not because his activity was found to be protected) but the press is safe, and their services would be appreciated.

United States taxpayers have funded climate science to the tune of well over 80 billion dollars, all channeled through the funding bureaucracy established by Vice President Albert "the end is nigh" Gore when he served as President Clinton's "climate czar."  That Gore-built bureaucracy is still to this day striving to insure that not a penny of all those taxpayer billions ever goes to any researcher who is not committed to the premature conclusion that human contributions to atmospheric CO2 are causing dangerous global warming (despite the lack of any statistically significant warming for more than 15 years).

Acolytes of this bought "consensus" want to see what new propaganda their tax dollars have wrought and so do the skeptics. It's unanimous, and an already twice-vetted draft is sitting now in thousands of government offices around the world. Time to fork it over to the people.
Alec Rawls
Palo Alto, California

Reactions to the leak
I am an occasional co-blogger at Anthony Watts' climate skeptic website, Watts Up With That. Shortly after I posted the leak here Anthony copied the leak to his website as well and, over the next couple of days, provided numerous links to reactions from climate scientists, journalists and the blogosphere.
From WUWT:

Rebuttals
Two prominent IPCC authors (Steven Sherwood and Joanna Haigh) came out to rebut my claims about the importance of the admission of strong evidence for some substantial mechanism of solar amplification. Another prominant rebuttal came from Dana Nucitelli at the "consensus" sanctioned website Credulous Science Skeptical Science. Below are my rebuttals to these rebuttals. Since Sherwood is Australian, the first is a team-up with Aussie journalist Joanne Nova:

Other related posts of mine
My submitted "expert review" comments on the First Order Draft of AR5 (February 2012):
My detailed responses to the rapid-ocean-equilibrium assumptions that many climatologists use to dismiss a solar explanation for late 20th century warming:
And my most recent follow up:

My other websites
My personal blog is Error Theory: "Moral science has two halves. There are the implications of thinking straight about fact and value (ideal theory) and there are the implications of not thinking straight. Ideal theory is the foundation, error theory the daily battle."

My Rawls.org website ("A Republican Form of Government") has a couple of very important essays: how to protect liberty directly rather than indirectly (which we currently do by tying the hands of the police); and how to vastly improve the accuracy and efficiency of our system of criminal justice by having juries hand down multiple verdicts on multiple standards of guilt.
The Rawls.org site also contains my 2003 appeal to the Supreme Court over the California law that limits candidates for Sheriff (a top executive officer, independent of governor and president) to members of the incumbent regime, making it impossible to throw the bums out, in violation of the Article IV Section 4 guarantee to the states that they shall have "a republican form of government." ("The true principle of republicanism," according to Alexander Hamilton, is "that the people should choose whom they please to govern them.")

The republican guarantee has been thought by many Supreme Court justices to be non-justiciable, but only because all previous suits on this grounds raised "political question" conflicts. My suit did not and should have been the vehicle for rescuing the guarantee clause from its present state of constitutional duesetude (which violates Justice Marshall's dictum that constitutional provisions are not to be held impotent "unless the words require it").

The bottom of the home page of my Rawls.org site recreates my old Rawls For Sheriff website. What could have been. Amongst other things, this older site collects many of my old Stanford Review articles and some old Thinker articles, like my Mr. Knowitall columns.

My Crescent of Betrayal website exposes the numerous Islamic design features in what was originally called the Crescent of Embrace memorial to Flight 93. Yes, it really is true that a person standing between the tips of the half-mile wide Islamic-shaped crescent and facing into the center of the crescent will be facing almost exactly at Mecca, and you can verify it for yourself in about 2 minutes. Just print out a graphic of the Crescent design and place it over an online mecca direction calculator on your computer screen, with the calculator set to Somerset PA. Links here.
These calculators are used by Muslims to find the direction they are supposed to pray from their present zip code.  You will see that the Mecca direction line almost exactly bisects the crescent. What is the religious significance of a crescent that Muslims face into to face Mecca? I'm betting you can guess.

For several years I have been working with Tom Burnett Senior, father of Flight 93 hero Tom Burnett Junior, to try to get this abomination stopped. Someday, once the nation has managed to free itself from domination by media elites who systematically suppress whatever information they perceive to be harmful to the left, architect Paul Murdoch's terrorist memorial mosque WILL be removed from that hallowed ground.


First Order Draft Summary for Policymakers IPCC WGI Fifth Assessment Report

Do Not Cite, Quote or Distribute SPM-1 Total pages: 26
1
2 Climate Change 2013: The Physical Science Basis
3
4 Summary for Policymakers
5
6 Drafting Authors: Lisa Alexander (Australia), Simon Allen (Switzerland), Nathaniel Bindoff (Australia),
7 Francois-Marie Breon (France), John Church (Australia), Ulrich Cubasch (Germany), Seita Emori (Japan),
8 Piers Forster (United Kingdom), Pierre Friedlingstein (United Kingdom), Nathan Gillett (Canada), Jonathan
9 Gregory (United Kingdom), Dennis Hartmann (USA), Eystein Jansen (Norway), Ben Kirtman (USA), Reto
10 Knutti (Switzerland), Krishna Kumar Kanikicharla (India), Peter Lemke (Germany), Jochem Marotzke
11 (Germany), Valerie Masson-Delmotte (France), Gerald Meehl (USA), Igor Mokhov (Russia), Shilong Piao
12 (China), Gian-Kasper Plattner (Switzerland), Qin Dahe (China), Venkatachalam Ramaswamy (USA), David
13 Randall (USA), Monika Rhein (Germany), Maisa Rojas (Chile), Christopher Sabine (USA), Drew Shindell
14 (USA), Thomas Stocker (Switzerland), Lynne Talley (USA), David Vaughan (United Kingdom), Shang-
15 Ping Xie (USA)
16
17 Draft Contributing Authors (list to be updated): Olivier Boucher (France), Philippe Ciais (France), Peter
18 Clark (USA), Matthew Collins (United Kingdom), Joey Comiso (USA), Gregory Flato (Canada), Jens
19 Hesselbjerg Christensen (Denmark), Albert Klein Tank (Netherlands), Gunnar Myhre (Norway), Scott
20 Power (Australia), Stephen Rintoul (Germany), Matilde Rusticucci (Argentina), Michael Schulz (Germany),
21 Peter Stott (United Kingdom), Donald Wuebbles (USA)
22
23 Date of Draft: 5 October 2012
24
25 Notes: TSU Compiled Version
26
27
28
First Order Draft Summary for Policymakers IPCC WGI Fifth Assessment Report
Do Not Cite, Quote or Distribute SPM-2 Total pages: 26
1 1. Introduction
2
3 The Working Group I contribution to the IPCC's Fifth Assessment Report presents new evidence of past and
4 projected future climate change from many independent scientific studies ranging from observations of the
5 climate system, paleoclimate archives, theoretical studies on climate processes and simulations using climate
6 models.
7
8 The evidence that formed the basis for the IPCC Fourth Assessment Report (AR4)1 has further strengthened.
9 The physical science contributions to the recent Special Report on Managing the Risk of Extreme Events and
10 Disasters to Advance Climate Change Adaptation (SREX)2 serves as a basis of the current assessment
11 regarding extreme weather and climate events.
12
13 A new set of emissions scenarios, the Representative Concentration Pathways (RCP) were used for the new
14 climate model simulations carried out under the framework of the Coordinated Model Intercomparison
15 Project 5 (CMIP5). The RCPs are mitigation scenarios which explore the effects of 21st century climate
16 policies and thus differ from the no-climate policy scenarios used in previous assessment reports. The four
17 RCPs span the range of year-2100 radiative forcing3 values in the literature of 2.6 (RCP2.6) to 8.5 W m–2
18 (RCP8.5).
19
20 The degree of certainty in key findings in this assessment is expressed as a qualitative level of confidence
21 and, when possible, probabilistically4.
22
23 The basis for substantive paragraphs in this Summary for Policymakers can be found in the chapter sections
24 specified in curly brackets.
25
26
27
28 2. Observation of Changes in the Climate System
29
30 Widespread changes in the atmosphere are observed across spatial and temporal scales. Strong evidence
31 has emerged that the physical and biogeochemical state of the oceans has changed during the past forty
32 years. Important parts of the cryosphere, in particular the extent and volume of snow and ice, have changed
33 over the latter half of the 20th century. Paleoclimate archives provide quantitative information on the range
34 of naturally driven changes in the climate system on time scales from centuries to millions of years.
35
36 AR4 concluded that warming of the climate system is unequivocal. New observations, longer data sets, and
37 more paleoclimate information give further support for this conclusion. Confidence is stronger that many
38 changes, that are observed consistently across components of the climate system, are significant, unusual or
39 unprecedented on time scales of decades to many hundreds of thousands of years.
40
1 IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth
Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M.
Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom
and New York, NY, USA, 996 pp.
2 IPCC, 2012: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. A Special
Report of Working Groups I and II of the Intergovernmental Panel on Climate Change [Field, C.B., V. Barros, T.F.
Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M.
Midgley (eds.)]. Cambridge University Press, Cambridge, UK, and New York, NY, USA, 582 pp.
3 Radiative Forcing (RF) is defined as the change in net irradiance at the tropopause since 1750 after allowing for
stratospheric temperatures to readjust to radiative equilibrium, while holding surface and tropospheric temperatures and
state variables fixed at the unperturbed values. Positive forcing tends to warm the surface while negative forcing tends
to cool it. In this report, radiative forcing values are expressed in watts per square metre (W m–2). (see Glossary)
4 Mastrandrea, M.D., C.B. Field, T.F. Stocker, O. Edenhofer, K.L. Ebi, D.J. Frame, H. Held, E. Kriegler, K.J. Mach,
P.R. Matschoss, G.-K. Plattner, G.W. Yohe, and F.W. Zwiers, 2010: Guidance Note for Lead Authors of the IPCC Fifth
Assessment Report on Consistent Treatment of Uncertainties. Intergovernmental Panel on Climate Change (IPCC).
First Order Draft Summary for Policymakers IPCC WGI Fifth Assessment Report
Do Not Cite, Quote or Distribute SPM-3 Total pages: 26
1 Atmosphere Observations
2
3 Widespread warming is observed from the surface of the Earth throughout the troposphere and cooling is
4 identified in the stratosphere. Globally averaged near surface temperatures have increased since the
5 beginning of the 20th century and the warming has been particularly marked since the 1970s. Each of the last
6 three decades has been significantly warmer than all preceding decades since 1850. {2.4}
7
8
9 [INSERT FIGURE SPM.1 HERE]
10 Figure SPM.1: Multiple observed indicators of a changing global climate. Each line represents an independently
11 derived estimate of change in various large-scale quantities from the atmosphere, the cryosphere, the land, and the
12 ocean. In panels where individual datasets overlap, the datasets have been normalized to a common period of record.
13 Anomalies are relative to the mean of 1981–2000 (panels a and b), 1971–2000 (panel c), 1961–1990 (panels e and f),
14 and the year 1971 (panel h). Panel c provides the 13-year running mean of the March-April Snow Cover Extent (SCE)
15 anomaly for the full observational record, and June SCE (x’s) for the satellite period only. Full details of the datasets
16 shown here are provided in the Supplementary Material to Chapters 2 and Chapter 4. Where available, uncertainties in
17 the observations are indicated by a shaded range. {Figure 2.15, Figure 2.19, Figure 2.24, Figure 3.2, Figure 3.13, Figure
18 4.3, Figure 4.19}.
19
20
21 • The global combined land and ocean temperature data show an increase of about 0.8°C over the period
22 1901–2010 and about 0.5°C over the period 1979–2010 when described by a linear trend. The warming
23 from 1886–1905 (early-industrial) to 1986–2005 is 0.66 [0.60 to 0.72] °C5 (see Figure SPM.1). The
24 warming since 1901 is generally greater over land than oceans and greater in mid-to-high latitude
25 regions. {2.4.3}
26
27 • It is virtually certain that globally the troposphere has warmed and the lower stratosphere has cooled
28 since the mid 20th century (see Figure SPM.1). There is at best medium confidence in the rates of these
29 changes and their vertical structure. {2.4.4, Table 2.8}
30
31 Confidence in global precipitation change over land is low prior to 1950 and medium afterwards
32 because of incomplete data coverage. Precipitation data indicates little change in the global mean since
33 1900, which is a revision from previous assessments. {2.5.1, Figure 2.28}
34
35 • The mid-latitudes and higher latitudes of the northern hemisphere show an overall increase in
36 precipitation from 1900–2010, however confidence is low because of much uncertainty in the data
37 records for the early 20th century. Insufficient evidence exists to define a long-term temporal change of
38 precipitation in the mid-latitudes of the southern hemisphere. Precipitation in the tropics has likely
39 increased over the last decade, reversing the drying trend that occurred from the mid-1970s to mid-
40 1990s. {2.5.1, Figure 2.28}
41
42 • It is likely that, in a zonal mean sense, large-scale atmospheric circulation features have moved
43 poleward: since the 1970s the tropical belt has widened, storm tracks and jet streams have shifted
44 poleward, and the polar vortex has contracted. {2.7}.
45
46 Changes in many extreme weather and climate events have been observed, but the level of confidence in
47 these changes varies widely depending on type of extreme and regions considered. Overall the most robust
48 global changes are seen in measures of temperature {FAQ 2.2, 2.6} (see Table SPM.1).
5 In the WGI contribution to the AR5, uncertainty is quantified using 90% uncertainty intervals unless otherwise stated.
The 90% uncertainty interval, reported in square brackets, is expected to have a 90% likelihood of covering the value
that is being estimated. The upper endpoint of the uncertainty interval has a 95% likelihood of exceeding the value that
is being estimated and the lower endpoint has a 95% likelihood of being less than that value. A best estimate of that
value is also given where available. Uncertainty intervals are not necessarily symmetric about the corresponding best
estimate.
First Order Draft Summary for Policymakers IPCC WGI Fifth Assessment Report
Do Not Cite, Quote or Distribute SPM-4 Total pages: 26
1 • It is very likely that the overall number of cold days and nights has decreased and the overall number of
2 warm days and nights has increased on the global scale between 1951 and 2010. There is medium
3 confidence that the length of warm spells, including heat waves, has increased globally since the middle
4 of the 20th century (see Table SPM.1). {2.6.1}
5
6 • There have been statistically significant trends in the number of heavy precipitation events in some
7 regions. It is likely that the number of heavy precipitation events has increased in more regions than it
8 has decreased since 1950 (see Table SPM.1). {2.6.2}
9
10 • There is low confidence in observed large-scale trends in drought, due to lack of direct observations,
11 dependencies of inferred trends on the index choice, and geographical inconsistencies in the trends (see
12 Table SPM.1). {2.6.2}
13
14 • Tropical cyclone data provides low confidence that any reported long-term changes are robust, after
15 accounting for past changes in observing capabilities. This is a revision from previous IPCC
16 Assessments Reports, but consistent with the SREX. Over the satellite era, increases in the intensity of
17 the strongest storms in the Atlantic appear robust (see Table SPM.1). {2.6.3}
18
19
20 [INSERT TABLE SPM.1 HERE]
21 Table SPM.1: Recent trends, assessment of human influence on the trend, and projections for extreme weather and
22 climate events for which there is an observed late-20th century trend. Bold indicates a revised assessment since AR4
23 (2007), (*) indicates a revised assessment from the SREX (2012) and (#) indicates that an assessment was not provided
24 by either AR4 or SREX. {TS TFE9.1, 2.6, 11.3.2, 12.4.3, 12.4.4, 12.4.5}
25
26
27 Ocean Observations
28
29 Based on independent observational systems and datasets, and their agreement, it is virtually certain that the
30 upper ocean has warmed since 1971, and that ocean warming dominates the change in the global energy
31 content. {3.2.2, 3.2.3, Box 3.1, FAQ 3.1, Figure 3.1}
32
33 • Largest warming is found near the sea surface (>0.1°C per decade in the upper 75 m), decreasing to
34 about 0.015°C per decade by 700 m, for the time period 1971 to 2010. It is likely that the deep ocean
35 has warmed below 3000 m depth since the 1990s. The global ocean has warmed at a rate of <0.01°C
36 per decade below 4000 m over this time interval. It is very likely that the Southern Ocean has warmed
37 throughout the full ocean depth since the 1990s, at a rate of about 0.03°C per decade. {3.2, Figure 3.1,
38 Figure 3.3}
39
40 • Warming of the ocean accounts for more than 90% of the extra energy stored by the Earth between
41 1971 and 2010. Upper ocean (0–700 m) heat content very likely increased at a rate between 74 [43 to
42 105] °— 1012 W and 137 [120 to 154] °— 1012 W for the relatively well-sampled 40 year period from 1971
43 to 2010. Warming has also been observed globally below 4000 m and below 1000 m in the Southern
44 Ocean, in spite of sparse sampling (see Figure SPM.1). {3.2, Box 3.1, Figure 3.2, Figure 3.3}
45
46 • It is very likely that the mean regional pattern of sea surface salinity has been enhanced since the 1960s:
47 saline surface waters in the evaporation-dominated mid-latitudes have become more saline, while the
48 relatively fresh surface waters in rainfall-dominated tropical and polar regions have become fresher.
49 {3.3.2, Figure 3.4, FAQ 3.3}
50
51 • Recent observations have strengthened evidence for variability in major ocean circulation systems on
52 time scales from years to decades. It is very likely that the subtropical gyres in the North Pacific and
53 South Pacific have expanded and strengthened since 1993. There is no evidence for decadal trends in
54 the transports of the Atlantic Meridional Overturning Circulation (AMOC), and the Antarctic
55 Circumpolar Current. {3.6, Figure 3.10, Figure 3.11}
56
First Order Draft Summary for Policymakers IPCC WGI Fifth Assessment Report
Do Not Cite, Quote or Distribute SPM-5 Total pages: 26
1 Cryosphere Observations
2
3 More comprehensive and improved observations strengthen the evidence that the ice sheets are losing mass,
4 glaciers are shrinking globally, sea ice cover is reducing in the Arctic, and snow cover is decreasing and
5 permafrost is thawing in the Northern Hemisphere. Ice is being lost from many of the components of the
6 cryosphere, although there are significant regional differences in the rates of loss. {4.2–4.6, Table 4.1}
7
8 • There is very high confidence that globally, glaciers continue to shrink and lose mass, but there is less
9 agreement on the rates of mass loss. Recent estimates of global glacier mass loss based on independent
10 methods range from 210 [145 to 275] Gt yr–1 to 371 [321 to 421] Gt yr–1, based on different time
11 windows since 2003. {4.3, Table 4.5}.
12
13 • There is very high confidence that the Greenland Ice Sheet has lost mass since the early 1990s, and that
14 the rate of loss has increased. The average ice loss from Greenland was 123 [101 to 145] Gt yr–1 over
15 the period 1993–2010, and 228 [174 to 282] Gt yr–1 in the period 2005–2010. {4.4.2}
16
17 • There is high confidence that the Antarctic Ice Sheet is currently losing mass. The average ice loss from
18 Antarctica was 65 [32 to 98] Gt yr–1 over the period 1993–2010, and 112 [54 to 170] Gt yr–1 over the
19 period 2005–2010. The largest ice losses from Antarctica have occurred on the northern Antarctic
20 Peninsula and from the Amundsen Sea sector of West Antarctica. In the last two decades, East
21 Antarctica is likely to have experienced a small gain in mass. {4.4.2, FAQ 4.2}
22
23 • The average decadal extent of Arctic sea ice has decreased in every season since satellite observations
24 commenced in 1979. The overall decrease in sea ice extent over the period 1979–2011 has been 3.9 [3.7
25 to 4.1] % per decade with larger changes occurring in summer and autumn (see Figure SPM.1). There is
26 robust evidence of a decline in ice thickness, and in ice volume. The overall mean winter thickness has
27 about halved between 1980 and 2009. {4.2.2}
28
29 • Observations of Antarctic sea ice extent show a small but significant increase by 1.4 [1.2 to 1.6] % per
30 decade between 1979 and 2011. {4.2.3}
31
32 • Both satellite and in-situ observations show significant reductions in the Northern Hemisphere snow
33 cover extent over the past 90 years, with most reduction occurring in the 1980s (see Figure SPM.1).
34 Snow cover decreased most in spring when the average extent decreased by around 8% over the period
35 1970–2010 compared with the period 1922–1970. {4.5.2, Figure 4.19, Figure 4.20}
36
37 • There is high confidence that permafrost temperatures have increased by up to 3°C over major
38 permafrost regions of the Northern Hemisphere during the past three decades in response to increased
39 air temperature and changing snow cover. {4.6.2}
40
41
42 Sea Level Observations
43
44 It is unequivocal that global mean sea level is rising as is evident from tide gauge records and satellite data
45 (see Figure SPM.1).
46
47 • It is virtually certain that over the 20th century the mean rate of increase was between 1.4 to 2.0 mm
48 yr1, and between 2.7 and 3.7 mm yr–1 since 1993. It is likely that rates of increase were similar to the
49 latter between 1930 and 1950. {3.7.2, 3.7.3, Table 3.1, Figure 3.12, Figure 3.13}
50
51 • It is likely that extreme sea levels have increased since 1970, and this is mainly caused by rising mean
52 sea level. {3.7.5}
53
54
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1 Observation of Carbon and Other Biogeochemical Quantities
2
3 More than half of the total carbon emitted by human activities has been taken up by the ocean and the land
4 since 1750. The remainder has caused an increase in the atmospheric CO2 concentration by over 40% since
5 1750, and by about 10% since 1990. {6.3, Table 6.1, Figure 6.8}
6
7 • CO2 emissions from fossil fuel combustion and cement production estimated from energy statistics have
8 released 365 [335 to 395] PgC6 to the atmosphere, while deforestation and other land use change are
9 estimated to have released 180 [100 to 260] PgC since 1750. Of these 545 [460 to 630] PgC, only 240
10 [230 to 250] PgC have accumulated in the atmosphere and increased the atmospheric CO2 concentration
11 from 278 [273 to 283] ppm7 in 1750 to 390 ppm in 2011 (see Figure SPM.2). {6.3, Table 6.1, Figure
12 6.8}
13
14
15 [INSERT FIGURE SPM.2 HERE]
16 Figure SPM.2: Multiple observed indicators of a changing global carbon cycle. Measurements of atmospheric
17 concentrations of carbon dioxide (CO2) are from Mauna Loa and South Pole since 1958. Measurements of partial
18 pressure of CO2 at the ocean surface are shown from three stations from the Atlantic and the Pacific Oceans, along with
19 the measurement of in situ pH, a measure of the acidity of ocean water. These stations are the Hawaii Ocean Time20
series (HOT) from the station ALOHA, the Bermuda Atlantic Time-series Study (BATS), and the European Station for
21 Time series in the Ocean (ESTOC). Full details of the datasets shown here are provided in the underlying report.
22 {Figure 2.1, Figure 3.17}.
23
24
25 • It is virtually certain that the ocean is taking up anthropogenic carbon dioxide from the atmosphere.
26 There is very high confidence that the global ocean content of anthropogenic carbon increased from
27 1994 to 2010. Estimates range from 93–137 PgC in 1994 to 155 [125 to 185] PgC in 2010. {3.8.1,
28 Figure 3.15, Figure 3.16}
29
30 • There is very high confidence that oceanic uptake of anthropogenic CO2 has resulted in gradual
31 acidification of seawater evidenced by a decreasing pH in surface waters at a rate of between 0.015 and
32 0.024 per decade since the early 1980s (see Figure SPM.2). {3.8.2, Table 3.2, Box 3.2, FAQ 3.2, Figure
33 3.17, Figure 3.18}
34
35 • Natural terrestrial ecosystems not affected by land use change are estimated to have accumulated 150
36 [60 to 140] PgC since 1750. {6.3, Table 6.1, Figure 6.8}
37
38
39 Long-Term Perspective from Paleoclimatic Records
40
41 Analyses of a number of independent paleoclimatic archives provide a multi-century perspective of Northern
42 Hemisphere temperature and indicate that 1981–2010 was very likely the warmest 30-year period of the last
43 800 years. {5.3.5}
44
45 • There is medium confidence that in the Northern Hemisphere 1981–2010 was the warmest 30-year
46 period of the last 1300 years. There is high confidence that the Medieval Climate Anomaly, about 900
47 to 1400 CE, shows inconsistent temperature changes across seasons and regions, in contrast to the
48 widespread temperature increase of the late 20st century. {5.3.5, 5.5.1}
49
6 1 Petagram of carbon = 1 PgC = 1015 grams of carbon = 1 Gigatonne of carbon = 1 GtC. This corresponds to 3.67
GtCO2.
7 ppm (parts per million) or ppb (parts per billion, 1 billion = 1,000 million) is the ratio of the number of greenhouse
gas molecules to the total number of molecules of dry air. For example, 300 ppm means 300 molecules of a greenhouse
gas per million molecules of dry air.
First Order Draft Summary for Policymakers IPCC WGI Fifth Assessment Report
Do Not Cite, Quote or Distribute SPM-7 Total pages: 26
1 • There is medium confidence that the current near-global recession of glacier length is unusual in the
2 context of the last two millennia, consistent with reconstructed surface-temperature anomalies. There is
3 high confidence that retreating glaciers are still larger now than in the early-to-mid Holocene in most
4 regions, and that this is consistent with the astronomically driven trends of summer insolation and
5 temperatures in both hemispheres. {5.5.3}.
6
7 • There is medium confidence that the modern sea ice loss and increase of sea surface temperatures in the
8 Arctic are anomalous in the perspective of at least the last two millennia. Summer sea ice cover
9 between 8,000 and 6,500 years before the present was reduced compared to late 20th century levels
10 both in the Arctic Ocean and along East Greenland consistent with increased astronomically driven
11 summer insolation in the Northern Hemisphere. {5.5.2}
12
13 • There is high confidence that during the last interglacial period, global mean sea level was between 6
14 and 10 m higher than present. There is medium confidence that the rate of current global mean sea level
15 change is unusually high in the context of the past millennium. Paleo sea level data from many
16 locations around the globe indicate centennial to millennial variations of likely less than 25 cm (medium
17 confidence). Longer term trends of sea level change during the last few thousand years were about 10
18 times smaller than the trend during the 20th century. {3.7, 5.6, 13.2}
19
20
21
22 3. Drivers of Climate Change
23
24 Natural and anthropogenic drivers cause imbalances in the Earth's energy budget. The strongest
25 anthropogenic drivers are changes in greenhouse gas concentrations and aerosols. These can now be
26 quantified in more detail, but the uncertainties of the forcing associated with aerosols remain high.
27
28 Globally, CO2 is the strongest driver of climate change compared to other changes in the atmospheric
29 composition, and changes in surface conditions. Its relative contribution has further increased since the
30 1980s and by far outweighs the contributions from natural drivers. CO2 concentrations and rates of increase
31 are unprecedented in the last 800,000 years and at least 20,000 years, respectively. Other drivers also
32 influence climate on global and particularly regional scales. {5.2.2, 8.3.2, 8.5.1, Figure 8.6, Figure 8.17}
33
34 • Multiple lines of evidence confirm that the long-lived greenhouse gases CO2, CH4, N2O all have
35 increased substantially since 1750. There is very high confidence that they now exceed by 30%, 125%,
36 8%, respectively, the range of variability recorded in ice core records during past 800,000 years, noting
37 that ice cores typically produce values averaged over many years. {5.2.2, 6.3, Table 6.1, Figure 6.8}
38
39 • Since systematic measurements of CO2 began in 1958 annual mean concentrations have constantly
40 increased and are now 24% higher than at the start of the record (see Figure SPM.2). {6.3, Table 6.1,
41 Figure 6.8}
42
43 • It is virtually certain that atmospheric concentrations of long-lived greenhouse gases further increased
44 from 2005 to 2011. Annual increases in global mean CO2 and N2O mole fractions were at rates
45 comparable to those observed over the previous decade. Atmospheric CH4 began increasing again in
46 2007 after remaining nearly constant from 1999 to 2006. {2.2.1, Table 2.1}
47
48
49 [INSERT FIGURE SPM.3 HERE]
50 Figure SPM.3: Global average radiative forcing (RF) estimates and ranges for various drivers and three successive
51 time periods; 1750–1950, 1750–1980, 1750–2011. The anthropogenic drivers are carbon dioxide (CO2), other well52
mixed greenhouse gases (CH4, N2O, and others), ozone, land use change, statospheric water vapour, and aerosols, with
53 the sum of all contributions indicated. Assessed uncertainty ranges are given by black intervals. The RF of solar
54 irradiance, a natural driver, is also estimated for the three time periods. {Figure 8.17}
55
56
First Order Draft Summary for Policymakers IPCC WGI Fifth Assessment Report
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1 There is consistent evidence from observations of a net energy uptake of the Earth System due to an
2 imbalance in the energy budget. It is virtually certain that this is caused by human activities, primarily by the
3 increase in CO2 concentrations. There is very high confidence that natural forcing contributes only a small
4 fraction to this imbalance (see Figure SPM.3). {8.4.1, 8.5.1, 8.5.2, Figure 8.13, Figure 8.14, Figure 8.17,
5 Figure 8.19}
6
7 • The total anthropogenic RF has a best estimate of 2.40 [1.80 to 3.00] W m–2 (see Figure SPM.3) The
8 estimate of total anthropogenic RF is 50% higher compared to previous assessments due primarily to a
9 better understanding of aerosols which led to less negative estimates of aerosol RF, but also to
10 continued growth in greenhouse gas RF. {8.5.1, Figure 8.17}
11
12 • The RF of well-mixed greenhouse gases is 2.83 [2.55 to 3.11] W m–2. CO2 alone contributes 1.82 [1.64
13 to 2.00] W m–2 and is virtually certain to be the strongest component causing a positive RF (see Figure
14 SPM.3). {8.3.2, Figure 8.6}
15
16 • Short-lived greenhouse gases contribute substantially to RF. The total RF due to changes in ozone is
17 0.30 [0.10 to 0.50] W m–2, with RF due to tropospheric ozone of 0.40 [0.20 to 0.60] W m–2 and due to
18 stratospheric ozone of –0.10 [–0.25 to +0.05] W m–2 (see Figure SPM.3). {8.3.3, Figure 8.8}
19
20 • The total RF from aerosols is estimated to be –0.7 [–1.2 to –0.2] W m–2 (see Figure SPM.3). The
21 uncertainty in the aerosol contribution dominates the overall net uncertainty in RF, but there is high
22 confidence that aerosols have offset part of the forcing caused by the well-mixed greenhouse gases.
23 {8.3.4, 8.5.1, Figure 8.17}
24
25 • The RF of stratospheric aerosols is well understood and can have a large impact on the climate for years
26 to decades after volcanic eruptions. Several small eruptions have caused a RF of about –0.10 [–0.13 to –
27 0.07] W m–2 during the 2000 to 2010 period. {8.4.2, Figure 8.15, Figure 8.18}
28
29 • Persistent contrails from aviation contribute a RF of +0.02 [+0.01 to +0.03] W m–2. This forcing can be
30 much larger regionally but is very unlikely to produce observable regional effects on either the mean or
31 diurnal range of surface temperature. {7.2.5}
32
33 • Secular trends of total solar irradiance before the start of satellite observations rely on a number of
34 indirect proxies with a best RF estimate of +0.04 [–0.01 to +0.09] W m–2 since 1750 (see Figure
35 SPM.3). Satellite observations of total solar irradiance changes since 1978 spanning three solar cycle
36 minima show a change in RF of –0.04 [–0.06 to –0.02] W m–2 over the last three decades. This RF
37 estimate is substantially lower than previous estimates due to data of the latest solar cycle and
38 inconsistencies in how solar RF has been estimated in earlier assessments. {8.4.1, Figure 8.13, Figure
39 8.14}
40
41 • Cosmic rays enhance aerosol nucleation and cloud condensation nuclei production in the free
42 troposphere, but there is high confidence that the effect is too weak to have any significant climatic
43 influence during a solar cycle or over the last century. No robust association between changes in cosmic
44 rays and cloudiness has been identified. {7.3, 7.4.5}
45
46
47
48 4. Understanding the Climate System and its Recent Changes
49
50 Understanding of the climate system is based on the quantitative combination of observations, theoretical
51 studies of feedback processes, and model simulations. More detailed observations and improved climate
52 models now enable the attribution of detected changes to the increases in greenhouse gas concentrations in
53 a wider range of climate system components.
54
55
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1 Evaluation of Climate Models
2
3 Development of climate models has resulted in more realism in the representation of many quantities and
4 aspects of the climate system, including large scale precipitation, Arctic sea ice, ocean heat content, extreme
5 events, and the climate effects of stratospheric ozone. {9.4.1, 9.4.2, 9.4.3, 9.5.4, Figure 9.6, Figure 9.17}
6
7 • There is very high confidence that coupled climate models provide realistic responses to external
8 forcing. This is evident from simulations of the surface temperature on continental and larger scales,
9 and the global-scale surface temperature increase over the historical period, especially the last fifty
10 years. {9.4.1, Box 9.1, Figure 9.2, Figure 9.8, 10.2, 11.3, 12.2}
11
12 • The simulation of large-scale patterns of precipitation has improved since the AR4, but there is only
13 medium confidence that models simulate realistic amounts of precipitation increases in wet areas and
14 precipitation decreases in dry areas on large spatial scales during the past 50 years, based on high
15 agreement among models but only limited evidence that this has been detected in observed trends.
16 {9.4.1,10.3.2, 11.4.2, 12.4.5}
17
18 • There is very high confidence that climate models realistically simulate the annual cycle of Arctic sea19
ice extent, and there is high confidence that they realistically simulate the trend in Arctic sea ice extent
20 over the past decades. {9.4.3}.
21
22 • There is high confidence that many models simulate realistically the observed trend in ocean heat
23 content. {9.4.2, Figure 9.17, Box 13.1}.
24
25 • The combination of information from ocean warming and changes in glacier and ice sheet volume and
26 land water storage is now, within the uncertainties, in quantitative agreement with observations of total
27 sea level rise for the last four decades. This is a significant advance since the AR4 and strengthens the
28 confidence in the physical understanding and modelling of the causes of past global mean sea level
29 change. {4.3.1, 4.4.2, 13.3.6, Table 13.1, Figure 13.4, Figure 13.5, FAQ 3.1}
30
31 • There is high confidence that the global distribution of temperature extremes is represented well by
32 models. The observed warming trend of temperature extremes in the second half of the 20th century is
33 well simulated. There is medium confidence that CMIP5 models tend to simulate more intense and thus
34 more realistic precipitation extremes than CMIP3 models. {9.5.4}
35
36 • Since AR4, many climate models have been extended with biogeochemical cycles into Earth System
37 Models (ESMs). There is high confidence that most ESMs produce global land and ocean carbon sinks
38 over the latter part of the 20th century that are consistent with the range of observational estimates.
39 {9.4}
40
41
42 Climate Processes and Feedbacks
43
44 Various feedbacks associated with water vapour can now be quantified, and together they are assessed to be
45 very likely positive and therefore to amplify climate changes. The net radiative feedback due to all cloud
46 types is likely positive. {7.2.4, Figures 7.8–7.10}
47
48 • The net “clear-sky” feedback from water vapour and lapse rate changes together is very likely positive
49 and estimated at +1.09 [0.91 to 1.27] W m−2 K−1, and the cloud feedback is very likely in the range of
50 −0.2 to 1.4 W m–2 K–1. {7.2.4, Figures 7.8–7.10}
51
52 • A limited number of modelling studies have quantified the aerosol-climate feedback as 0.0 [–0.2 to
53 +0.2] W m–2 K–1 although with low confidence. {7.3.4, 7.5.2}
54
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1 • Paleoclimate reconstructions and modelling indicate that there is a positive feedback between climate
2 and the carbon cycle on century to millennial time scales, i.e., when climate warms land and ocean
3 carbon storage are reduced. {6.3.2, 6.4}
4
5
6 Detection and Attribution of Climate Change
7
8 It is extremely likely that human activities have caused more than half of the observed increase in global
9 average surface temperature since the 1950s. There is high confidence that this has caused large-scale
10 changes in the ocean, in the cryosphere, and in sea level in the second half of the 20th century. Some
11 extreme events have changed as a result of anthropogenic influence. {10.3–10.6}
12
13
14 [INSERT FIGURE SPM.4 HERE]
15 Figure SPM.4: Comparison of observed and simulated climate change based on four large-scale indicators in the
16 atmosphere, cryosphere and the ocean. Indicators are time series of continental land surface air temperatures (1850–
17 2010, yellow padded panels), zonal mean precipitation in latitude bands (1950–2010, green padded panels), Arctic and
18 Antarctic sea ice (1950–2010, white padded panels), and ocean heat uptake in the major ocean basins (1950–2010, blue
19 padded panels). Global mean changes are also given. In all panels, black/grey curves indicate observation-based
20 estimates, blue curves and bands are multi-model mean and ensemble ranges based on simulations forced by natural
21 drivers only, and red curves and bands are for simulations forced by natural and anthropogenic drivers. The bands
22 indicate the 5 to 95% for temperature, and one standard deviation for precipitation, sea ice, and ocean heat content.
23 Model results are based on the ensemble of CMIP5. For sea ice extent the seven CMIP5 models are considered that
24 matched the mean minimum and seasonality with less than 20% error compared with observations. Full details are
25 provided in the Appendix of Chapter 10. {Figure 10.15, 10.20}
26
27
28 • The greenhouse gas contribution to the warming from 1951–2010 is in the range between 0.6 and
29 1.4°C. This is very likely greater than the total observed warming of approximately 0.6°C over the same
30 period. {10.3.1}
31
32 • Over every continent except Antarctica, anthropogenic influence has likely made a substantial
33 contribution to surface temperature increases since the mid-20th century (see Figure SPM.4). {10.3.1}
34
35 • It is very likely that early 20th century warming is due in part to external forcing, including greenhouse
36 gas concentrations, tropospheric aerosols, and solar variations. Climate model simulations that include
37 only natural forcings (volcanic eruptions and solar variations) can explain a substantial part of the pre38
industrial inter-decadal temperature variability since 1400 but fail to explain more recent warming since
39 1950 (see Figure SPM.4). {10.3.1, 10.7.2}
40
41 • It is very likely that more than half of the ocean warming observed since the 1970s is caused by external
42 forcing, mainly due to a combination of both anthropogenic forcing and volcanic eruptions (see Figure
43 SPM.4). It is extremely likely that this warming has resulted in global mean sea level rise due to thermal
44 expansion during this period. {10.4.1, 10.4.3}
45
46 New observations and their combination with climate model simulations now permit the attribution of some
47 changes in the water cycle since 1950 to anthropogenic influences. Taken together, these patterns are
48 consistent with an intensified global water cycle. {10.3.2}
49
50 • There is medium confidence for anthropogenic contributions to an increase in atmospheric moisture
51 content and tropospheric specific humidity, and to changes in zonal precipitation patterns over land with
52 reductions in low latitudes and increases in northern hemisphere mid to high latitudes since 1950 (see
53 Figure SPM.4).
54
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1 • It is likely that observed changes in ocean surface and sub-surface salinity are due in part to the changes
2 in the water cycle caused by anthropogenic increases in greenhouse gases. {10.3.2}
3
4 • It is likely that anthropogenic forcings have contributed to Arctic sea ice retreat since 1950. There is
5 medium confidence that the observed small net increase in Antarctic sea ice extent is consistent with
6 internal variability (see Figure SPM.4). Human influences are the likely cause for a substantial
7 reduction in glaciers since the 1960s (high confidence), and reductions in snow cover and permafrost
8 since the 1970s (medium confidence). {10.5.1, 10.5.2}
9
10 • It is likely that anthropogenic forcings have contributed to the increased surface melt of Greenland since
11 2000. There is only low confidence of a human contribution to the observed loss of Antarctic ice sheet
12 mass since 1990 due to limited scientific understanding of the processes involved. {10.5.1, 10.5.2}
13
14 • It is very likely that anthropogenic forcing has contributed to the observed changes in daily temperature
15 extremes since the mid-20th century. It is likely that human influence has substantially increased the
16 probability of some observed heatwaves. There is medium confidence that anthropogenic forcing has
17 contributed to an increase in the frequency of heavy precipitation events over the second half of the
18 20th century over land regions with sufficient observational coverage. {10.6}
19
20 • Consistent with SREX, there is low confidence in attribution of changes in tropical cyclone activity to
21 human influence due to insufficient observational evidence and low level of agreement between studies.
22 {10.6}.
23
24
25 Key Metrics Characterizing Anthropogenic Climate Change
26
27 • Equilibrium climate sensitivity is likely in the range 2°C–4.5°C, and very likely above 1.5°C. The most
28 likely value is near 3°C. Equilibrium climate sensitivity greater than about 6°C–7°C is very unlikely.
29 {Box 12.2}
30
31 • The total amount of anthropogenic emissions of long-lived greenhouse gases largely determines the
32 warming in the 21st century. The global mean warming per 1000 PgC is very likely between 0.8°C–
33 3°C. {12.5.4}
34
35 • Different metrics can be used to quantify the contributions to climate change of emissions of different
36 substances, and of emissions from regions/countries or sources/sectors. No single metric can accurately
37 compare all consequences of different emissions. The choice of metric therefore depends strongly on
38 the particular impact being investigated, and on the context in which it is applied. {8.7.1}
39
40
41
42 5. Projections of Global and Regional Climate Change
43
44 Projections of changes in the climate system are based on simulations using a hierarchy of climate models
45 ranging from simple climate models, to models of intermediate complexity, and comprehensive Earth System
46 Models. These models simulate changes based on a variety of scenarios of natural and anthropogenic
47 forcings.
48
49 • Projected climate change for the RCPs is similar to AR4 when accounting for scenario differences.
50 Uncertainties for the high RCPs are lower because carbon cycle uncertainties are not considered.
51 Simulated patterns of climate change in the CMIP5 models are very similar to CMIP3, despite
52 substantially increased model complexity, thus increasing the confidence in projections. {11.3.6, 12.3,
53 12.4, 12.4.9}
54
55
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1 • Projections of near-term climate change depend little on differences in greenhouse gas and aerosol
2 emissions within the range of the RCP scenarios. These scenarios assume that there are no major
3 volcanic eruptions and that anthropogenic aerosol emissions are rapidly reduced during the near term.
4 {11.3.2, 11.3.5}
5
6 Projections of many quantities on the near-term time horizon already provide an indication of changes later
7 in the 21st century. The confidence in these projections is often assessed to be lower for the near-term than
8 for later in the 21st century. {11.3.1, 11.3.6, Box 11.1, FAQ 11.1}
9
10
11 Near-Term Projections: Atmosphere
12
13 • The global mean surface air temperature change for the period 2016–2035 relative to the reference
14 period of 1986–20058, will likely be in the range 0.4°C–1.0°C (medium confidence) (see Figure SPM.5).
15 There is robust evidence that collectively the RCPs represent the low end of future emissions scenarios
16 for aerosols and other short-lived reactive gases. Therefore, it is more likely than not that actual
17 warming will be closer to the lower bound of 0.4°C than the upper bound of 1.0°C (medium
18 confidence). {11.3.2, Figure 11.33}
19
20 • A future volcanic eruption similar in size to the 1991 eruption of Mount Pinatubo would cause a rapid
21 drop in global mean surface air temperature of several tenths of 1°C in the following year, with
22 recovery over the next few years. Possible future reductions in solar irradiance would reduce global
23 mean surface air temperature, but such cooling is unlikely to exceed –0.1°C by 2050 (medium
24 confidence). {11.3.6}
25
26 • It is more likely than not that over the next few decades there will be increases in mean precipitation in
27 regions and seasons that are relatively wet during 1986–2005, and decreases in regions and seasons that
28 are relatively dry during 1986-2005. However, it is likely that these changes from 1986–2005 will only
29 be significant, relative to natural internal variability, on the largest spatial scales, e.g., zonal and global
30 means (see Figure SPM.5). {11.3.2, Figure 11.16}
31
32 • Over the next few decades increases in near-surface specific humidity are very likely. Models project
33 increases in evaporation in most regions. There is low confidence in projected changes in soil moisture
34 and surface run off. Natural internal variability will continue to have a major influence on all aspects of
35 the water cycle. {11.3.2, Figure 11.18}
36
37 • It is very likely that in the next decades the frequency of warm days and warm nights will increase,
38 while the frequency of cold days and cold nights will decrease at the global scale. Models also project
39 increases in the duration, intensity and spatial extent of heat-waves and warm spells for the near term.
40 {11.3.2, Figure 11.22, Figure 11.23}
41
42 • In the near term, it is likely that the frequency and intensity of heavy precipitation events will increase at
43 the global scale and at high latitudes. Regional-scale changes are strongly affected by natural variability
44 and also depend upon the future aerosol emissions, volcanic forcing and land use changes.{11.3.2,
45 Figure 11.22, Figure 11.23}
46
47
48 Near-Term Projections: Ocean
49
50 • It is virtually certain that globally-averaged surface and upper ocean (top 700 m) temperatures averaged
51 over 2016–2035 will be warmer than those averaged over 1986–2005. {11.3.3}
52
8 In this WGI Summary for Policymakers, projections of future climate change are generally compared to the standard
reference period of 1986–2005, unless otherwise stated.
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Do Not Cite, Quote or Distribute SPM-13 Total pages: 26
1 • Overall, it is likely that there will be some decline in the AMOC by 2050. However, the rate and
2 magnitude of weakening is very uncertain, and decades when this circulation increases are also to be
3 expected {11.3.3}.
4
5
6 Near-Term Projections: Cryosphere
7
8 • It is very likely that there will be continued loss of sea ice extent in the Arctic, decreases of snow cover,
9 and reductions of permafrost at high latitudes of the Northern Hemisphere by 2016–2035. Using
10 RCP4.5, Arctic sea ice area is projected to decrease by 28% for September and 6% for February;
11 Northern Hemisphere snow cover area is projected to decrease by 4.0 [2.1 to 5.9] % (one standard
12 deviation) for a March-April average; annual mean near-surface permafrost is projected to decrease by
13 18%. {11.3.4}
14
15
16 [INSERT FIGURE SPM.5 HERE]
17 Figure SPM.5: CMIP5 multi-model simulated time series. Panel (a) provides the radiative forcing reconstructed for the
18 historical time period and projected for the future. Other panels provide mean changes (relative to 1986–2005) of (b),
19 global annual mean surface air temperature, (c), global annual mean precipitation, (d), Northern Hemisphere sea-ice
20 extent anomaly in September, and (e), global mean ocean surface pH from CMIP5 climate model simulations from
21 1850 to 2100. Projections are shown for emissions scenarios RCP2.6 (blue) and RCP8.5 (red) for the multi-model mean
22 (solid lines) and ±1 standard deviation across the distribution of individual model simulations (shading). Black (grey
23 shading) is the modelled historical evolution using historical reconstructed forcings. For pH, a subset of the CMIP5
24 models is chosen which simulate the global carbon cycle and which are driven by prescribed atmospheric CO2
25 concentrations. The number of CMIP5 models to calculate the multi-model mean is indicated for each time
26 period/scenario. {Figure 12.5, Figure 12.28, Figure 6.28}
27
28
29 [INSERT FIGURE SPM.6 HERE]
30 Figure SPM.6: Maps of multi-model results in 2081–2100 (relative to 1986–2005) of (a), surface air temperature
31 change, (b), average percent change in mean precipitation, (c), Northern Hemisphere sea ice concentration, and (d)
32 change in global ocean surface pH. The two emissions scenarios RCP2.6, and RCP8.5 are considered. The number of
33 CMIP5 models to calculate the multi-model mean is indicated in the upper right corner of each panel. The pink lines in
34 panels (c) show the observed 15% sea ice concentration limits averaged over 1986–2005 for comparison. {Figure
35 12.11, Figure 12.22, Figure 12.29, Figure 6.28}. [PLACEDHOLDER FOR SECOND ORDER DRAFT: Information on
36 robustness and model agreement to be considered.]
37
38
39 [INSERT TABLE SPM.2 HERE]
40 Table SPM.2: Projected change in global average surface air temperature (SAT) and sea level rise (SLR) for three time
41 horizons during the 21st century. {Table 12.2, Table 13.5, 12.4.1, 11.3.2}
42
43
44 Long-Term Projections: Temperature
45
46 By mid-21st century, the rate of global warming begins to be more strongly dependent on the scenario. For
47 RCP4.5, 6.0 and 8.5, global mean surface air temperatures are projected to at least likely exceed 2°C
48 warming with respect to preindustrial by 2100, and about as likely as not to be above 2°C warming for
49 RCP2.6 (see Figure SPM.5). {12.3.1, 12.4.1, Figure 12.2, Figure 12.5}
50
51 • Global-mean surface temperatures for 2081–2100 (relative to 1986–2005) for the CO2 concentration
52 driven RCPs will likely be in the 5–95% range of the CMIP5 climate models, i.e., 0.2°C–1.8°C
53 (RCP2.6), 1.0°C–2.6°C (RCP4.5), 1.3°C–3.2°C (RCP6.0), 2.6°C–4.8°C (RCP8.5) (see Figure SPM.5,
54 Table SPM.2). {8.5.3, Figure 8.20, Figure 8.21, 12.4.1, Figure 12.8}
55
56
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1 • There is very high confidence that future changes in global land surface air temperature will exceed
2 changes in global average ocean-area surface air temperature by a factor of 1.5 [1.3 to 1.7] (one
3 standard deviation). There is very high confidence that the Arctic region will warm most rapidly (see
4 Figure SPM.6). {12.4.3}
5
6 • It is virtually certain that, in most places, there will be more hot and fewer cold temperature extremes as
7 global temperature increases. These changes are expected for events defined as extremes on both daily
8 and seasonal time scales. Although increases in the frequency, duration and magnitude of hot extremes
9 are expected, occasional cold winter extremes will continue to occur. {12.4.3}
10
11 • Under RCP8.5 it is likely that, in most regions, what is currently a 20-year maximum temperature event
12 will at least double its frequency, but in many regions becoming 10 to 20 times more frequent, i.e., a 2-
13 year to annual event, and that what is currently a 20-year minimum temperature event will become
14 exceedingly rare by the end of the 21st century. {12.4.3}
15
16
17 Long-Term Projections: Atmospheric Circulation
18
19 • There is generally low confidence in basin-scale projections of trends in tropical cyclone frequency and
20 intensity to the mid-21st century. Projections for the end of the 21st century indicate that it is likely that
21 the global frequency of tropical cyclones will either decrease or remain essentially unchanged,
22 concurrent with a likely increase in both global mean tropical cyclone maximum wind speed and rainfall
23 rates. The frequency of the most intense tropical cyclones is projected to more likely than not increase
24 substantially in some basins {11.3.2, Box 14.2}.
25
26 • It is unlikely that the global number of extra-tropical cyclones will decrease by more than a few percent
27 due to global warming. {12.4.4}
28
29
30 Long-Term Projections: Water Cycle
31
32 Changes in precipitation in a warming world will not be uniform. The high latitudes are very likely to
33 experience larger amounts of precipitation. Many regions in the mid-latitudes that are arid and semi-arid will
34 likely experience less precipitation, while those that are moist will likely receive more precipitation. While
35 there is high confidence in patterns of these changes, there is only low confidence in the magnitude (see
36 Figure SPM.6). {12.4.5}
37
38 • It is virtually certain that global precipitation will increase with global mean surface temperature (see
39 Figure SPM.5). It is likely that the rate of increase of precipitation with temperature will be in the range
40 1–3% K–1, for scenarios other than RCP2.6. For RCP2.6 the range of sensitivities in the CMIP5 models
41 is 0.5–4.0% K–1 at the end of the 21st century. {12.4.1, Figure 12.6}
42
43 • Regional to global-scale projections of soil moisture and drought remain relatively uncertain compared
44 to other aspects of the hydrological cycle. Surface drying in the Mediterranean, southwestern North
45 America and southern African regions is likely when global temperatures increase. {12.4.5}
46
47 • The frequency distribution of precipitation events is projected to very likely undergo changes as global
48 temperatures increase. For short-duration events, a shift to more intense individual storms and fewer
49 weak storms is likely. In moist and some arid and semi-arid regions, extreme precipitation events will
50 very likely be more intense and more frequent. {12.4.5}
51
52
53
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1 Long-Term Projections: Climate Phenomena
2
3 Climate phenomena exhibit large natural variations both in amplitude and spatial patterns. While they are
4 increasingly well simulated by climate models, there still remain uncertainties in the physical understanding.
5 This results in overall low confidence in projections in many aspects of these climate phenomena, although
6 some projections are assessed to be robust. {9.5.3, 14.2–14.6}
7
8 • In high emission scenarios, global monsoon area and global monsoon total precipitation are very likely
9 to increase by the end of the 21st century. Monsoon onset dates are likely to become earlier or not to
10 change much, and the monsoon retreat dates are very likely to become later, resulting in lengthening of
11 the monsoon season. {14.2}
12
13 • The El Niño-Southern Oscillation very likely remains the dominant mode of interannual variability in
14 the future in the tropical Pacific. It is likely that the intensity of the central Pacific warming will
15 increase, but there is low confidence that the central Pacific type of El Niño will become more frequent
16 in a warmer climate. {14.4}
17
18 • It is likely that both El Niño and La Niña-induced teleconnection patterns over the extra-tropical
19 Northern Hemisphere will move eastwards in the future. {14.4}
20
21
22 Long-Term Projections: Ocean
23
24 • It is very likely that the AMOC will weaken over the 21st century with a best estimate decrease in 2100
25 of about 20–30% for the RCP4.5 scenario and 36–44% for the RCP8.5 scenario. It is very unlikely that
26 the AMOC will undergo an abrupt transition or collapse in the 21st century, and it is unlikely that the
27 AMOC will collapse beyond the 21st century for the scenarios considered. {12.5.5}
28
29 • The climate model projections suggest that regions with high sea surface salinity in the subtropics that
30 are dominated by net evaporation will typically become more saline; regions with lower sea surface
31 salinity at high latitudes will typically become fresher. {12.4.7, Figure 12.34}
32
33 • On multidecadal timescales, the rate of ocean heat uptake is projected to increase while the radiative
34 forcing increases. Because the ocean integrates the surface heat flux, projections of changes in ocean
35 heat content following different scenarios do not significantly diverge for several decades {13.4.1,
36 13.5.1}.
37
38
39 Long-Term Projections: Cryosphere
40
41 It is very likely that the Arctic sea ice cover will continue to shrink and thin in the course of the 21st century
42 as global temperature rises. There is high confidence that an increase in annual mean global surface
43 temperature greater than 2°C above present will eventually lead to a nearly ice-free Arctic Ocean in late
44 summer (see Figures SPM.5 and SPM.6). {12.4.6, Figure 12.28}
45
46 • Reductions in Arctic sea ice are projected for all scenarios and year-round, with reductions in sea ice
47 extent ranging from 39% for RCP2.6 to 94% for RCP8.5 in September and from 9% to 35% in
48 February by the end of the century (see Figures SPM.5 and SPM.6). {12.4.6, Figure 12.28}
49
50 • For RCP8.5 it is very likely that the September Arctic sea ice will nearly vanish, i.e., the extent will fall
51 below 106km2, before the end of the century (see Figures SPM.5 and SPM.6). {12.4.6, Figure 12.28}
52
53 • There is low confidence in model projections of Southern Hemisphere sea ice extent for the end of the
54 21st century. {12.4.6, Figure 12.28}
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1 • It is very likely that Northern Hemisphere snow cover will decrease as global temperatures increase.
2 Projections of the reduction in the area of spring snow cover in the Northern Hemisphere by the end of
3 the 21st century vary between 7% (RCP2.6) and 25% (RCP8.5). {12.4.6}
4
5 • A reduction in permafrost extent with rising global temperatures is virtually certain. Near-surface
6 permafrost area is projected to decrease by between 37% (RCP2.6) and 81% (RCP8.5) by the end of the
7 21st century. {12.4.6}
8
9
10 Long-Term Projections: Sea Level
11
12 It is very likely that the rate of global mean sea level rise during the 21st century will exceed the rate
13 observed during 1971–2010 for all RCP scenarios. Together, ocean thermal expansion and glaciers are very
14 likely to make the largest contributions during the 21st century (see Figure SPM.7). {13.5.1, Table 13.5,
15 Figure 13.8, Figure 13.9}
16
17
18 [INSERT FIGURE SPM.7 HERE]
19 Figure SPM.7: Projections of total global mean (top) and regional mean (bottom) sea level change from 2000 to 2100
20 for the two emissions scenarios RCP2.6, and RCP8.5. The total sea level change results from various contributions
21 whose estimated ranges are given over the period 2081–2100. The scenario-dependent contributions of thermal
22 expansion are derived from CMIP5 model simulations, glaciers and surface mass balances from the Greenland and
23 Antarctic ice sheets are estimated from CMIP5 results using parametrised schemes based on recent studies.
24 Contributions from ice-sheet dynamical changes and anthropogenic land water storage are also included; they are
25 independent of scenario, and are treated as having uniform probability distributions. The maps of projected regional
26 mean sea level change include a correction for glacial isostatic adjustment for the period 2081–2100 compared to 1986–
27 2005. See Appendix 13.A for methods. {Figure 13.8, Figure 13.9, Figure 13.15} [PLACEHOLDER FOR SECOND
28 ORDER DRAFT: Information on robustness and model agreement to be considered.]
29
30
31 • For the period 2081 to 2100, compared to 1986 to 2005, global mean sea level rise is likely (medium
32 confidence) to be in the range 0.29–0.55 m for RCP2.6, 0.36–0.63 m for RCP4.5, 0.37–0.64 m for
33 RCP6.0, and 0.48–0.82 m (0.56–0.96 m by 2100 with a rate of rise 8 to 15 mm yr–1 over the last decade
34 of the 21st century) for RCP8.5 (see Figure SPM.7, Table SPM.2). {13.5.1, Table 13.5, Figure 13.8,
35 Figure 13.9}
36
37 • These projections include estimates of dynamical ice loss from Greenland and Antarctica (see Figure
38 SPM.7). However, there is low confidence in models of ice sheet dynamics, and there is no consensus
39 about the reliability of semi-empirical models that give higher projections than process-based models.
40 As a result, larger values of sea level rise cannot be excluded, but current scientific understanding is
41 insufficient for evaluating the probability of higher values. {13.4.4, 13.5.1, Table 13.5, Figure 13.8,
42 Figure 13.9}
43
44 • Global mean sea level rise will very likely continue beyond 2100, with ocean thermosteric sea level rise
45 to continue for centuries to millennia, unless global temperatures decline. The few available model
46 results indicate global mean sea level rise by 2300 likely to be less than 1 m for greenhouse gas
47 concentrations below 500 ppm CO2-equivalent scenario but rise as much as 1–3 m for concentrations
48 above 700 ppm CO2-equivalent{13.5.2, Figure 13.10, Figure 13.11}.
49
50
51 Long-Term Projections: Carbon and Other Biogeochemical Cycles
52
53 • It is very likely that the global ocean will be a net carbon sink in all RCP scenarios. It is very likely that
54 global land will be a net carbon sink for scenarios with decreasing areas of anthropogenic land-use
55 (RCP4.5, RCP6.0). For scenarios with increasing areas of land-use (RCP2.6, RCP8.5), a net land sink is
56 likely, but some models project a source by 2100. {6.4, Figures 6.19–6.22, Figure 6.24}
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1 Based on coupled carbon cycle - climate models it is very likely that the feedback between climate and the
2 carbon cycle is positive in the 21st century and beyond. These models indicate a loss of carbon of 59 [20 to
3 98] PgC and 17 [13 to 21] PgC per °C warming from the land and the ocean, respectively. {6.4.2.1, Figure
4 6.20}
5
6 • For RCP2.6, large reductions in CO2 emissions relative to present day are projected. It is about as likely
7 as not that sustained globally negative emissions will be required for this scenario. {6.4, Figure 6.25,
8 Figure 6.26}
9
10 • Anthropogenic ocean acidification, evidenced by a decrease in pH, is projected to continue worldwide
11 over the 21st century in all RCPs (see Figure SPM.5). The largest decrease in pH is projected to occur
12 in the warmer low and mid-latitudes. It is likely that surface waters in the Southern Ocean become
13 corrosive for a less stable form of calcium carbonate by 2100, and even before in the Arctic Ocean (see
14 Figure SPM.6). {6.4, Box 6.5, Figure 6.28}
15
16 • There is medium confidence on the magnitude of carbon losses through CO2 or CH4 emissions to the
17 atmosphere from thawing permafrost. Projections for 2100 range from 33 to over 400 PgC for RCP8.5.
18 {6.4.3}
19
20
21 Long-Term Projections: Climate Stabilization, Commitment and Irreversibility
22
23 Many aspects of climate change will persist for centuries even if concentrations of greenhouse gases are
24 stabilised. This represents a substantial multi-century commitment created by human activities today.
25 {12.5.4}
26
27 • Emission pathways that likely limit warming below 2°C above pre-industrial by 2100 indicate that CO2-
28 equivalent emissions cannot exceed 8.5–12.6 PgC yr–1 by 2020, and 4.6–6.3 PgC yr–1 by 2050. Median
29 2010 emissions are 13.1 PgC yr–1. The 2°C temperature target implies cumulative carbon emissions by
30 2100 to be below about 1000–1300 PgC in the set of scenarios considered, of which about 545 [460 to
31 630] PgC were already emitted by 2011. {12.5.4}
32
33 • Continuing greenhouse gas emissions beyond 2100 as in the RCP8.5 extension induces a total radiative
34 forcing above 12 W m–2 by 2300 that leads to a warming of 8.7 [5.0–11.6] °C by 2300 relative to 1986–
35 2005. Substantial sustained reductions of emissions beyond 2100 could keep the total radiative forcing
36 below 2 W m–2 by 2300, as for example in the RCP2.6 extension, which reduces the warming to 0.6
37 [0.3–1.0] °C by 2300. {12.3.1, 12.5.1}
38
39 • For scenarios driven by carbon dioxide alone, global average temperature is projected to remain
40 approximately constant for many centuries following a complete cessation of emissions. Thus a large
41 fraction of climate change is largely irreversible on human time scales, except if net anthropogenic
42 greenhouse gas emissions were strongly negative over a sustained period. {12.5.5}
43
44 • Surface melting of the Greenland ice sheet is projected to exceed accumulation for global mean surface
45 air temperature over 3.1 [1.9–4.6] °C above preindustrial, leading to ongoing decay of the ice sheet. The
46 loss of the Greenland ice sheet is not inevitable, because surface melting has long time scales and it
47 might re-grow to most of its original volume if global temperatures decline. However, a significant
48 decay of the ice sheet may be irreversible. {13.3.3, 13.4.3, 13.4.4, Figure 13.11}
49
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1 Tables
2
3 Table SPM.1: Recent trends, assessment of human influence on the trend, and projections for extreme weather and
4 climate events for which there is an observed late-20th century trend. Bold indicates a revised assessment since AR4
5 (2007), (*) indicates a revised assessment from the SREX (2012) and (#) indicates that an assessment was not provided
6 by either AR4 or SREX. {TS TFE9.1, 2.6, 11.3.2, 12.4.3, 12.4.4, 12.4.5}
7
Phenomenon and
direction of trend
Likelihood that trend
occurred in late 20th
century (typically
post 1950)
Likelihood of a
human contribution
to observed trend
Likelihood of future
trends based on
projections for the
next few decades#
Likelihood of future
trends based on
projections for 21st
century using RCP
scenarios
Warmer and fewer cold
days and nights over
most land areas
Very likely Very likely*a Very likely Virtually certain
Warmer and more
frequent hot days and
nights over most land
areas
Very likely Very likely*a Very likely Virtually certain
Warm spells/heat waves.
Frequency increases over
most land areas
Medium confidence Likelyb Likely Very likely
Heavy precipitation
events. Frequency (or
proportion of total
rainfall from heavy falls)
increases over more
areas than decreases
Likely Medium confidence Likely Very likely*c
Increases in frequency
and/or intensity of
droughtd
Low confidence*d Low confidence*d Not assessed Likely in some
regions*d
Intense tropical cyclone
activity increases
Low confidencee Low confidencee Low confidence Medium confidence
8 Notes:
9 (a) SREX assessed likely anthropogenic influence on trends at the global scale.
10 (b) SREX did not provide an explicit attribution of warm spells/heat waves to human contributions.
11 (c) SREX assessed a likely increase in the frequency of heavy precipitation events or increase in the proportion of total
12 rainfall from heavy falls over many areas of the globe, in particular in high latitudes and tropical regions.
13 (d) AR4 assessed the overall area affected by drought. SREX assessed with medium confidence that some regions of the
14 world had experienced more intense and longer droughts, and medium confidence that anthropogenic influence had
15 contributed to some observed changes in drought pattern. There was also medium confidence in a projected increase in
16 duration and intensity of droughts in some regions of the world.
17 (e) Assessments of 50-year global trends limited by data uncertainties. Higher confidence of increased activity in some
18 regions linked to anthropogenic aerosol forcing.
19
20
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Table SPM.2: Projected change in global average 1 surface air temperature (SAT) and sea level rise (SLR) for three time
2 horizons during the 21st century. {Table 12.2, Table 13.5, 12.4.1, 11.3.2}
3
Variable Scenario 2016–2035** Level of
Confidence* 2046–2065 Level of
Confidence* 2081–2100 Level of
Confidence*
ΔSATa
[°C]
RCP2.6 0.7 [n/a] n/a 1.0 [n/a] n/a 1.0 [0.2–1.8] high
RCP4.5 0.7 [n/a] n/a 1.4 [n/a] n/a 1.8 [1.0–2.6] high
RCP6.0 0.7 [n/a] n/a 1.3 [n/a] n/a 2.3 [1.3–3.2] high
RCP8.5 0.8 [n/a] n/a 2.0 [n/a] n/a 3.7 [2.6–4.8] high
Total
SLRb
[m]
RCP2.6 0.11 [0.08–0.14] medium 0.25 [0.19–0.33] medium 0.42 [0.29–0.55] medium
RCP4.5 0.11 [0.08–0.14] medium 0.27 [0.20–0.35] medium 0.49 [0.36–0.63] medium
RCP6.0 0.11 [0.07–0.14] medium 0.26 [0.19–0.34] medium 0.50 [0.37–0.64] medium
RCP8.5 0.12 [0.08–0.15] medium 0.31 [0.23–0.39] medium 0.64 [0.48–0.82] medium
4 Notes:
5 (a) CMIP5 ensemble; anomalies calculated with respect to 1986–2005; Numbers are in the format: mean [likely range]
6 (b) 21 CMIP5 models; anomalies calculated with respect to 1986–2005. Where CMIP5 results were not available for a
7 particular AOGCM and scenario, they were estimated as explained in Chapter 13, Table 13.5. The contributions from
8 ice sheet dynamical change and anthropogenic land water storage are treated as independent of scenario, since scenario
9 dependence cannot be evaluated on the basis of existing literature, and as having uniform probability distributions,
10 uncorrelated with the magnitude of global climate change. Numbers are in the format: mean [likely range]
11 * [PLACEHOLDER FOR SECOND ORDER DRAFT: Level of confidence to be updated]
12 ** [PLACEHOLDER FOR SECOND ORDER DRAFT: Near-term values and ranges to be updated]
13
14
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1 Figures
2
3
4
5 Figure SPM.1: Multiple observed indicators of a changing global climate. Each line represents an independently
6 derived estimate of change in various large-scale quantities from the atmosphere, the cryosphere, the land, and the
7 ocean. In panels where individual datasets overlap, the datasets have been normalized to a common period of record.
8 Anomalies are relative to the mean of 1981–2000 (panels a and b), 1971–2000 (panel c), 1961–1990 (panels e and f),
9 and the year 1971 (panel h). Panel c provides the 13-year running mean of the March-April Snow Cover Extent (SCE)
10 anomaly for the full observational record, and June SCE (x’s) for the satellite period only. Full details of the datasets
11 shown here are provided in the Supplementary Material to Chapters 2 and Chapter 4. Where available, uncertainties in
12 the observations are indicated by a shaded range. {Figure 2.15, Figure 2.19, Figure 2.24, Figure 3.2, Figure 3.13, Figure
13 4.3, Figure 4.19}.
14
15
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1
2
3 Figure SPM.2: Multiple observed indicators of a changing global carbon cycle. Measurements of atmospheric
4 concentrations of carbon dioxide (CO2) are from Mauna Loa and South Pole since 1958. Measurements of partial
5 pressure of CO2 at the ocean surface are shown from three stations from the Atlantic and the Pacific Oceans, along with
6 the measurement of in situ pH, a measure of the acidity of ocean water. These stations are the Hawaii Ocean Time7
series (HOT) from the station ALOHA, the Bermuda Atlantic Time-series Study (BATS), and the European Station for
8 Time series in the Ocean (ESTOC). Full details of the datasets shown here are provided in the underlying report.
9 {Figure 2.1, Figure 3.17}.
10
11
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1
2
3 Figure SPM.3: Global average radiative forcing (RF) estimates and ranges for various drivers and three successive
4 time periods; 1750–1950, 1750–1980, 1750–2011. The anthropogenic drivers are carbon dioxide (CO2), other well5
mixed greenhouse gases (CH4, N2O, and others), ozone, land use change, statospheric water vapour, and aerosols, with
6 the sum of all contributions indicated. Assessed uncertainty ranges are given by black intervals. The RF of solar
7 irradiance, a natural driver, is also estimated for the three time periods. {Figure 8.17}
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1
2
3 Figure SPM.4: Comparison of observed and simulated climate change based on four large-scale indicators in the atmosphere, cryosphere and the ocean. Indicators are time series of
4 continental land surface air temperatures (1850–2010, yellow padded panels), zonal mean precipitation in latitude bands (1950–2010, green padded panels), Arctic and Antarctic sea
5 ice (1950–2010, white padded panels), and ocean heat uptake in the major ocean basins (1950–2010, blue padded panels). Global mean changes are also given. In all panels,
6 black/grey curves indicate observation-based estimates, blue curves and bands are multi-model mean and ensemble ranges based on simulations forced by natural drivers only, and
7 red curves and bands are for simulations forced by natural and anthropogenic drivers. The bands indicate the 5 to 95% for temperature, and one standard deviation for precipitation,
8 sea ice, and ocean heat content. Model results are based on the ensemble of CMIP5. For sea ice extent the seven CMIP5 models are considered that matched the mean minimum and
9 seasonality with less than 20% error compared with observations. Full details are provided in the Appendix of Chapter 10. {Figure 10.15, 10.20}
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1
2
3 Figure SPM.5: CMIP5 multi-model simulated time series. Panel (a) provides the radiative forcing reconstructed for the
4 historical time period and projected for the future. Other panels provide mean changes (relative to 1986–2005) of (b),
5 global annual mean surface air temperature, (c), global annual mean precipitation, (d), Northern Hemisphere sea-ice
6 extent anomaly in September, and (e), global mean ocean surface pH from CMIP5 climate model simulations from
7 1850 to 2100. Projections are shown for emissions scenarios RCP2.6 (blue) and RCP8.5 (red) for the multi-model mean
8 (solid lines) and ±1 standard deviation across the distribution of individual model simulations (shading). Black (grey
9 shading) is the modelled historical evolution using historical reconstructed forcings. For pH, a subset of the CMIP5
10 models is chosen which simulate the global carbon cycle and which are driven by prescribed atmospheric CO2
11 concentrations. The number of CMIP5 models to calculate the multi-model mean is indicated for each time
12 period/scenario. {Figure 12.5, Figure 12.28, Figure 6.28}
13
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1
2
3 Figure SPM.6: Maps of multi-model results in 2081–2100 (relative to 1986–2005) of (a), surface air temperature
4 change, (b), average percent change in mean precipitation, (c), Northern Hemisphere sea ice concentration, and (d)
5 change in global ocean surface pH. The two emissions scenarios RCP2.6, and RCP8.5 are considered. The number of
6 CMIP5 models to calculate the multi-model mean is indicated in the upper right corner of each panel. The pink lines in
7 panels (c) show the observed 15% sea ice concentration limits averaged over 1986–2005 for comparison. {Figure
8 12.11, Figure 12.22, Figure 12.29, Figure 6.28}. [PLACEDHOLDER FOR SECOND ORDER DRAFT: Information on
9 robustness and model agreement to be considered.]
10
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1
2
3 Figure SPM.7: Projections of total global mean (top) and regional mean (bottom) sea level change from 2000 to 2100
4 for the two emissions scenarios RCP2.6, and RCP8.5. The total sea level change results from various contributions
5 whose estimated ranges are given over the period 2081–2100. The scenario-dependent contributions of thermal
6 expansion are derived from CMIP5 model simulations, glaciers and surface mass balances from the Greenland and
7 Antarctic ice sheets are estimated from CMIP5 results using parametrised schemes based on recent studies.
8 Contributions from ice-sheet dynamical changes and anthropogenic land water storage are also included; they are
9 independent of scenario, and are treated as having uniform probability distributions. The maps of projected regional
10 mean sea level change include a correction for glacial isostatic adjustment for the period 2081–2100 compared to 1986–
11 2005. See Appendix 13.A for methods. {Figure 13.8, Figure 13.9, Figure 13.15} [PLACEHOLDER FOR SECOND
12 ORDER DRAFT: Information on robustness and model agreement to be considered.]
13

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