Cover of the Special Report on Global Warming of 1.5°C
The Special Report on Global Warming of 1.5°C (SR15) was published by the Intergovernmental Panel on Climate Change (IPCC) on 8 October 2018. The report, approved in Incheon, South Korea, includes over 6,000 scientific references, and was prepared by 91 authors from 40 countries. In December 2015, the 2015 United Nations Climate Change Conference called for the report.
The report was delivered at the United Nations' 48th session of the
IPCC to "deliver the authoritative, scientific guide for governments" to
deal with climate change.
Its key finding is that meeting a 1.5 °C (2.7 °F) target is possible but would require "deep emissions reductions" and "rapid, far-reaching and unprecedented changes in all aspects of society." Furthermore, the report finds that "limiting global warming to 1.5 °C compared with 2 °C would reduce challenging impacts on ecosystems, human health and well-being" and that a 2 °C temperature increase would exacerbate extreme weather, rising sea levels and diminishing Arctic sea ice, coral bleaching, and loss of ecosystems, among other impacts.
SR15 also has modelling that shows that, for global warming to be
limited to 1.5 °C, "Global net human-caused emissions of carbon dioxide
(CO2) would need to fall by about 45 percent from 2010 levels by 2030,
reaching 'net zero' around 2050." The reduction of emissions by 2030 and its associated changes and challenges, including rapid decarbonisation, was a key focus on much of the reporting which was repeated through the world.
Main statements
Global
warming will likely rise to 1.5 °C above pre-industrial levels between
2030 and 2052 if warming continues to increase at the current rate.
SR15 provides a summary of, on one hand, existing research on the impact
that a warming of 1.5 °C (equivalent to 2.7 °F) would have on the
planet, and on the other hand, the necessary steps to limit global
warming.
Even assuming full implementation of conditional and unconditional Nationally Determined Contributions submitted by nations
in the Paris Agreement, net emissions would increase compared to 2010, leading to a warming of about 3 °C by 2100, and more afterwards.
In contrast, limiting warming below or close to 1.5 °C would require to decrease net emissions by around 45% by 2030 and reach net zero by 2050 (i.e. keeping total cumulative emissions within a carbon budget).
Even just for limiting global warming to below 2 °C, CO2 emissions should decline by 25% by 2030 and by 100% by 2075.
Pathways (i.e. scenarios and portfolios of mitigation options) that would allow such reduction by 2050
describe a rapid transition towards producing electricity through
lower-emission methods, and increasing use of electricity instead of
other fuels in sectors such as transportation. On average, the pathways
describing the proportion of primary energy produced by renewables as
increasing to 60%, while the proportion produced by coal drops to 5% and
oil to 13%. Most pathways describe a larger role for nuclear energy and carbon capture and storage, and less usage of natural gas.
They also assume that other measures are simultaneously undertaken:
e.g. non-CO2 emissions (such as methane, black carbon, nitrous oxide)
are to be similarly reduced, energy demand is unchanged, reduced by even 30% or offsetted by an unprecedented scale of carbon dioxide removal methods yet to be developed, while new policies and research allows to improve efficiency in agriculture and industry.
Pathways
limiting global warming to 1.5 °C with no or limited overshoot would
require rapid and far-reaching transitions in energy, land, urban and
infrastructure (including transport and buildings), and industrial
systems. These systems transitions are unprecedented in terms of scale,
but not necessarily in terms of speed, and imply deep emissions
reductions in all sectors, a wide portfolio of mitigation options and a
significant upscaling of investments in those options. The rates of
system changes [...] have occurred in the past within specific sectors,
technologies and spatial contexts, but there is no documented historic
precedent for their scale.
— IPCC, SR15 Summary for policymakers, p. 17
Impact of 1.5 °C or 2 °C warming
According to the report, with global warming of 1.5 °C there would be
increased risks to "health, livelihoods, food security, water supply,
human security, and economic growth."
Impact vectors include reduction in crop yields and nutritional quality.
Livestock are also affected with rising temperatures through "changes in
feed quality, spread of diseases, and water resource availability."
"Risks from some vector-borne diseases, such as malaria and dengue
fever, are projected to increase."
"Limiting global warming to 1.5°C, compared with 2°C, could
reduce the number of people both exposed to climate-related risks and
susceptible to poverty by up to several hundred million by 2050."
Climate-related risks associated with increasing global warming depend
on geographic location, "levels of development and vulnerability", and
the speed and reach of climate mitigation and climate adaptation practices.
For example, "urban heat islands
amplify the impacts of heatwaves in cities."
In general, "countries in the tropics and Southern Hemisphere subtropics
are projected to experience the largest impacts on economic growth."
Weather, sea level, ice
Many
regions and seasons experience warming greater than the global annual
average, e.g. "2–3 times higher in the Arctic. Warming is generally
higher over
land than over the ocean," and it correlates with temperature extremes (which are projected to warm up to twice more on land than the global mean surface temperature) as well as precipitation extremes (both heavy rain and droughts).
The assessed levels of risk generally increased compared to the previous IPCC report.
The "global mean sea level
is projected rise (relative to 1986-2005) by 0.26 to 0.77 m by 2100 for
1.5 °C global warming" and about 0.1 m more for 2 °C. A difference of
0.1 m may correspond to 10 million more or fewer people exposed to
related risks.
"Sea level rise will continue beyond 2100 even if global warming is limited to 1.5 °C.
Around 1.5 °C to 2 °C of global warming," irreversible instabilities could be triggered in Antarctica and "Greenland ice sheet, resulting in multi-metre rise in sea level."
"An ice-free Arctic summer is projected once per century" (per decade) for 1.5 °C (respectively 2 °C).
"Limiting global warming to 1.5 °C rather than 2 °C is projected to
prevent the thawing over centuries of a permafrost area in the range of
1.5 to 2.5 million km2."
Ecosystems
"A
decrease in global annual catch for marine fisheries of about 1.5 or 3
million tonnes for 1.5 °C or 2 °C of global warming" is projected by one
global fishery model cited in the report.
Coral reefs are projected to decline by a further 70–90% at 1.5 °C, and even more than 99% at 2 °C.
"Of 105,000 species studied, 18% of insects, 16% of plants and 8% of
vertebrates fare projected to lose over half of their climatically
determined geographic range for global warming of 2 °C."
Approximately "4% or 13% of the global terrestrial land area is
projected to undergo a transformation of ecosystems from one type to
another" at 1 °C or 2 °C, respectively. "High-latitude tundra and boreal
forests are particularly at risk of climate change-induced
degradation and loss, with woody shrubs already encroaching into the
tundra and
will proceed with further warming."
Limiting the temperature increase
Human activities (anthropogenic greenhouse gas emissions) have already contributed 0.8–1.2 °C (1.4–2.2 °F) of warming.
Nevertheless, the gases which have been emitted so far are unlikely to
cause global temperature to rise to 1.5 °C alone, meaning a global
temperature rise to 1.5 °C above pre-industrial levels is avoidable,
assuming net zero emissions are reached soon.
Carbon budget
Limiting global warming to 1.5 °C requires staying within a total carbon budget, i.e. limiting total cumulative emissions of CO2.
In other words, if net anthropogenic CO2 emissions are kept above zero, a
global warming of 1.5 °C and more will eventually be reached.
The value of the total net anthropogenic CO2 budget since the pre-industrial era is not assessed in the report. Estimates of 400–800 GtCO2 (gigatonnes of CO2) for the remaining
budget are given (580 GtCO2 and 420 GtCO2 for a 66% and 50% probability
of limiting warming to 1.5 °C, using global mean surface air
temperature (GSAT);
or 770 and 570 GtCO2, for 50% and 66% probabilities, using global mean surface temperature (GMST)).
This is about 300 GtCO2 more compared to a previous IPCC report, due to updated understanding and further advances in methods.
Emissions around the time of the report were depleting this budget at 42±3 GtCO2
per year.
Anthropogenic emissions from the pre-industrial period to the end of
2017 are estimated to have reduced the budget for 1.5 °C by
approximately 2200±320 GtCO2.
The estimates for the budget come with significant uncertainties, associated with: climate response to CO2 and non-CO2 emissions (these contribute about ±400 GtCO2 in uncertainty),
the level of historic warming (±250 GtCO2), potential
additional carbon release from future permafrost thawing and methane
release from wetlands (reducing the budget by up to 100 GtCO2 over the century), and the level of future non-CO2 mitigation (±400 GtCO2).
Necessary emission reductions
Current nationally stated mitigation ambitions, as submitted under the Paris Agreement, would lead to global greenhouse gas
emissions of 52–58 GtCO2eq per year, by 2030.
"Pathways reflecting these ambitions would not limit global warming to 1.5 °C, even if supplemented by very challenging
increases in the scale and ambition of emissions reductions after 2030."
Instead, they are "broadly consistent" with a warming of about 3 °C by 2100, and more afterwards.
Limit global warming to 1.5 °C with no or limited overshoot would require reducing emissions to below 35 GtCO2eq per year in 2030, regardless of the modelling pathway chosen. Most fall within 25–30 GtCO2eq per yer, a 40–50% reduction from 2010 levels.
The report says that for limiting warming to below 1.5 C "global
net human-caused emissions of CO2 would need to fall by about 45% from
2010 levels by 2030, reaching net zero around 2050." Even just
for limiting global warming to below 2 °C, CO2 emissions should decline
by 25% by 2030 and by 100% by 2070.
Non-CO2 emissions should decline in more or less similar ways.
This involves deep reductions in emissions of methane and black carbon:
at least 35% of both by 2050, relative to 2010, to limit warming near
1.5 °C.
Such measures could be undertaken in the energy sector and by reducing
nitrous oxide and methane from agriculture, methane from the waste
sector, and some other sources of black carbon and hydrofluorocarbons.
On timescales longer than tens of years, it may still be
necessary to sustain net negative CO2 emissions and/or further reduce
non-CO2 radiative forcing, in order to
prevent further warming (due to Earth system feedbacks), reverse ocean
acidification, and minimise sea level rise.
Examples of actions consistent with the 1.5 °C pathway include
"shifting to low- or zero-emission power generation, such as renewables;
changing food systems, such as diet changes away from land-intensive
animal products; electrifying transport and developing 'green
infrastructure', such as building green roofs, or improving energy
efficiency by smart urban planning, which will change the layout of many
cities."
As another example, an increase of forestation by 10,000,000 square kilometres (3,900,000 sq mi) by 2050 relative to 2010 would be required.
The pathways also assume an increase in annual investments in
low-carbon energy technologies and energy efficiency by roughly a factor
of four to ten by 2050 compared to 2015.
Model pathways with no or limited overshoot of 1.5 °C
The emission pathways that reach 1.5 °C contained in the report assume the use of negative emission technology to offset for remaining
emissions. Pathways that overshoot the goal rely on them to exceed remaining emissions in order to return to 1.5 °C.
However, understanding is still limited about the effectiveness of net
negative emissions to reduce temperatures after an overshoot.
Reversing an overshoot of 0.2 °C might not be achievable given
considerable implementation challenges.
There are two main groups of geoengineering types in the report, carbon dioxide removal (CDR) and solar radiation management (SRM).
For CDR the report highlights bioenergy with carbon capture and storage (BECCS). The report notes that apart from afforestation/reforestation
and ecosystem restoration, "the feasibility of massive-scale deployment
of many CDR technologies remains an open question", with areas of
uncertainty regarding technology upscaling, governance, ethical issues,
policy and carbon cycle.
The report notes that CDR technology is in its infancy and the
feasibility is an open question.
Estimates from recent literature are cited, giving a potential of up to 5
GtCO2 per year for BECCS and up to 3.6 GtCO2 per year for
afforestation.
An analysis of the geoengineering proposals published in Nature Communication
confirmed findings of the SR15, stating that "all are in early stages
of development, involve substantial uncertainties and risks, and raise
ethical and governance dilemmas. Based on present knowledge, climate
geoengineering techniques cannot be relied on to significantly
contribute to meeting the Paris Agreement temperature goals".
As for SRM, the report focuses on stratospheric aerosol injection, as it has the most available literature; however it is still an experimental technology. SRMs also "face large uncertainties and knowledge gaps as well as substantial risks, [...] and constraints";
"the impacts of SRM (both biophysical and societal), costs, technical
feasibility, governance and ethical issues associated need to be
carefully considered."
Process
There are three IPCC working groups: Working Group I (WG I), co-chaired by Valerie Masson-Delmotte and Panmao Zhai, covers the physical science of climate change. Working Group II (WG II), co-chaired by Hans-Otto Pörtner and Debra Roberts,
examines "impacts, adaptation and vulnerability". The "mitigation of
climate change" is dealt with by Working Group III (WG III), co-chaired
by Priyardarshi Shukla and Jim Skea.
The "Task Force on National Greenhouse Gas Inventories" "develops
methodologies for measuring emissions and removals". There are also
Technical Support Units that guide "the production of IPCC assessment
reports and other products".
Contributors
Researchers
from 40 countries, representing 91 authors and editors contributed to
the report, which includes over 6,000 scientific references.
Reactions
Researchers
In his 1 October 2018 opening statement at the 48th Session held in Incheon, Korea, Hoesung Lee, who has been Chair of the IPCC since 6 October 2015, described this IPCC meeting as "one of the most important" in its history.
Debra Roberts, IPCC contributor called it the "largest clarion bell
from the science community". Roberts hopes "it mobilises people and
dents the mood of complacency."
In a CBC interview, Paul Romer was asked if the Nobel Prize in economic sciences that he and William Nordhaus
received shortly before the SR15 was released, was timed as a message.
Romer said that he was optimistic that measures will be taken in time to
avert climate catastrophe. Romer compared the angst and lack of
political will in imposing a carbon tax to the initial angst surrounding
the chlorofluorocarbon (CFC) ban and the positive impact it had on restoring the depletedozone layer. In giving the Nobel to Nordhaus and Romer, the Royal Swedish Academy of Sciences
cited Nordhaus as saying "the most efficient remedy for problems caused
by greenhouse gases is a global scheme of universally imposed carbon
taxes".
Howard J. Herzog, a senior research engineer at the Massachusetts
Institute of Technology, said that carbon capture and storage
technologies, except reforestation, are problematic because of their impact on the environment, health and high cost.
In the article there is a link to another article that refers to a
study published in the scientific journal "Nature Energy". The study
says that we can limit warming to 1.5 degrees without carbon capture and storage, by technological innovation and changing lifestyle.
Politics
Australia
Prime Minister Scott Morrison emphasised that the report was not specifically for Australia but for the whole world. Energy Minister Angus Taylor
said the Government would "not be distracted" by the IPCC report saying
"A debate about climate change and generation technologies in 2050
won't bring down current power prices for Australian households and
small businesses." Environment Minister Melissa Price
said that scientists are "drawing a very long bow" to say coal should
be phased out by 2050 and supported new coal-fired power stations
pledging not to legislate the Paris targets.
Australia is not on track to meet the commitments under Paris agreement
according to modelling conducted by ClimateWorks Australia.
Canada
Canadian Environment Minister Catherine McKenna acknowledged that the SR15 report would say Canada is not "on track" for 1.5°C.
Canada will not be implementing new plans but it will continue to move
forward on a "national price on carbon, eliminating coal-fired power
plants, making homes and businesses more energy-efficient, and investing
in clean technologies and renewable energy". In response to a question
on the sense of urgency of the SR15 report during a 9 October interview
on CBC News's Power and PoliticsAndrew Scheer, the Leader of the Opposition,
promised that they are putting forward a "comprehensive plan to reduce
CO2 without imposing a carbon tax" which Scheer said "raised costs
without actually reducing emissions."
European Union
According to The New York Times, the European Union indicated it might add more ambitious reform goals centered around reducing emissions. On 9 October, the Council of the European Union presented their response to SR15 and their position for the Katowice Climate Change Conference of the Parties (COP 24) held in Poland in December 2018. Their environment ministers noted recent progress in legislation to reduce greenhouse gas emissions.
India
The Centre for Science and Environment said the repercussions for developing countries such as India, would be "catastrophic" at 2°C warming and that the impact even at 1.5°C described in SR15 is much greater than anticipated. Crop yields would decline and poverty would increase.
New Zealand
The Minister for Climate Change James Shaw
said that the Report "has laid out a strong case for countries to make
every effort to limit temperature rise to 1.5° Celsius above
pre-industrial levels. ... The good news is that the IPCC's report is
broadly in line with this Government's direction on climate change and
it's highly relevant to the work we are doing with the Zero Carbon
Bill."
United States
President Donald Trump said that he had received the report, but wanted to learn more about those who "drew it" before offering conclusions. In an interview with ABC's "This Week" the director of the National Economic Council, Larry Kudlow,
stated, "personally, I think the UN study is way too difficult," and
that the authors "overestimate" the likelihood for environmental
disasters. Since the publication Trump stated in an interview on 60 Minutes
that he didn't know that climate change is manmade and that "it'll
change back again", the scientists who say it's worse than ever have "a
very big political agenda" and that "we have scientists that disagree
with [manmade climate change]."
COP24
The
governments of four countries (the gas/oil-producers USA, Russia, Saudi
Arabia and Kuwait) blocked a proposal to welcome the Intergovernmental
Panel on Climate Change's (IPCC) Special Report on Global Warming of
1.5 °C at the 2018 United Nations Climate Change Conference (COP24).
The Fifth Assessment Report was finalized in 2014. As had been
the case in the past, the outline of the AR5 was developed through a
scoping process which involved climate change experts from all relevant
disciplines and users of IPCC reports, in particular representatives
from governments. Governments and organizations involved in the Fourth Report were asked to submit comments and observations in writing with the submissions analysed by the panel.
The report was delivered in stages, starting with Working Group I's
report on the physical science basis, based on 9,200 peer-reviewed
studies. The summaries for policy makers were released on 27 September 2013 for the first report, on 31 March 2014 for the second report entitled "Impacts, Adaptation, and Vulnerability", and on 14 April 2014 for the third report entitled "Mitigation of Climate Change". The Synthesis Report was released on 2 November 2014, in time to pave the way for negotiations on reducing carbon emissions at the UN Climate Change Conferencein Paris during late 2015.
Current status
The
Fifth Assessment Report (AR5) consists of three Working Group (WG)
Reports and a Synthesis Report. The first Working Group Report was
published in 2013 and the rest were completed in 2014.
WG I: The Physical Science Basis – 30 September 2013, Summary for Policymakers published 27 September 2013.
WG II: Impacts, Adaptation and Vulnerability – 31 March 2014
WG III: Mitigation of Climate Change – 15 April 2014
More than 800 authors, selected from around 3,000 nominations,
were involved in writing the report. Lead authors' meetings and a number
of workshops and expert meetings, in support of the assessment process,
were held. A schedule of AR5 related meetings, review periods, and
other important dates was published.
On 14 December 2012, drafts of the Working Group 1 (WG1) report were leaked and posted on the Internet. The release of the summary for policymakers occurred on 27 September 2013. Halldór Thorgeirsson, a UN official, warned that, because big companies are known to fund the undermining of climate science,
scientists should be prepared for an increase in negative publicity at
the time. "Vested interests are paying for the discrediting of
scientists all the time. We need to be ready for that," he said.
Marking the finalization of the Physical Science Basis UN Secretary General Ban Ki-moon addressed the IPCC at Stockholm on 27 September 2013. He stated that "the heat is on. We must act". Jennifer Morgan, from the World Resources Institute, said "Hopefully the IPCC will inspire leadership, from the Mom to the business leader, to the mayor to the head of state." US Secretary of State John Kerry
responded to the report saying "This is yet another wakeup call: those
who deny the science or choose excuses over action are playing with
fire."
Authors and editors
In
March 2010, the IPCC received approximately 3,000 author nominations
from experts around the world. At the bureau session held in Geneva,
19–20 May 2010, the three working groups presented their selected
authors and review editors for the AR5. Each of the selected scientists,
specialists and experts was nominated in accordance with IPCC
procedures, by respective national IPCC focal-points, by approved
observer organizations, or by the bureau. The IPCC received 50% more
nominations of experts to participate in AR5 than it did for AR4.
A total of 559 authors and review editors had been selected for AR4
from 2,000 proposed nominees. On 23 June 2010 the IPCC announced the
release of the final list of selected coordinating lead authors,
comprising 831 experts who were drawn from fields including meteorology,
physics, oceanography, statistics, engineering, ecology, social
sciences and economics. In comparison to the Fourth Assessment Report
(AR4), participation from developing countries was increased, reflecting
the ongoing efforts to improve regional coverage in the AR5. About 30%
of authors came from developing countries or economies in transition.
More than 60% of the experts chosen were new to the IPCC process,
bringing fresh knowledge and perspectives.
Climate change 2013: report overview
On
23 June 2010, the IPCC announced the release of the final list of
selected coordinating lead authors, comprising 831 experts. The working
group reports would be published during 2013 and 2014. These experts
would also provide contributions to the Synthesis Report published in
late 2014.
The Fifth Assessment Report (Climate Change 2013) would be released in four distinct sections:
Working Group I Report (WGI): Focusing on the physical science basis and including 258 experts.
Working Group II Report (WGII): Assessing the impacts, adaptation
strategies and vulnerability related to climate change and involving 302
experts.
Working Group III Report (WGIII): Covering mitigation response
strategies in an integrated risk and uncertainty framework and its
assessments carried out by 271 experts.
The Synthesis Report (SYR): Final summary and overview.
Working group I contribution
The full text of Climate Change 2013: The Physical Science Basis
was released in an unedited form on Monday, 30 September 2013. It was
over 2,000 pages long and cited 9,200 scientific publications. The full, edited report was released online in January 2014 and published in physical form by Cambridge University Press later in the year.
Summary for Policymakers
A concise overview of Working Group I's findings was published as the Summary for Policymakers on 27 September 2013. The level of confidence in each finding was rated on a confidence scale, qualitatively from very low to very high and, where possible, quantitatively from exceptionally unlikely to virtually certain (determined based on statistical analysis and expert judgement).
Likelihood scale used in the report
Term
Likelihood of the outcome
Virtually certain
99–100 % probability
Extremely likely
95–100 % probability
Very likely
90–100 % probability
Likely
66–100 % probability
More likely than not
50–100 % probability
About as likely as not
33 to 66% probability
Unlikely
0–33 % probability
Very unlikely
0–10 % probability
Extremely unlikely
0–5 % probability
Exceptionally unlikely
0–1 % probability
The principal findings were:
General
Warming of the atmosphere and ocean system is unequivocal.
Many of the associated impacts such as sea level change (among other
metrics) have occurred since 1950 at rates unprecedented in the
historical record.
There is a clear human influence on the climate
It is extremely likely that human influence has been the
dominant cause of observed warming since 1950, with the level of
confidence having increased since the fourth report.
IPCC pointed out that the longer we wait to reduce our emissions, the more expensive it will become.
Historical climate metrics
It is likely (with medium confidence) that 1983–2013 was the warmest 30-year period for 1,400 years.
It is virtually certain the upper ocean warmed from 1971 to 2010. This ocean warming accounts, with high confidence, for 90% of the energy accumulation between 1971 and 2010.
It can be said with high confidence that the Greenland and Antarctic ice sheets have been losing mass in the last two decades and that Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.
There is high confidence that the sea level rise since the
middle of the 19th century has been larger than the mean sea level rise
of the prior two millennia.
Concentration of greenhouse gases in the atmosphere has increased to levels unprecedented on earth in 800,000 years.
Total radiative forcing of the earth system, relative to 1750, is positive and the most significant driver is the increase in CO 2's atmospheric concentration.
Models
AR5 relies on the Coupled Model Intercomparison Project Phase 5 (CMIP5), an international effort among the climate modeling community to coordinate climate change experiments. Most of the CMIP5 and Earth System Model (ESM) simulations for AR5 WRI were performed with prescribed CO 2 concentrations reaching 421 ppm (RCP2.6), 538 ppm (RCP4.5), 670 ppm (RCP6.0), and 936 ppm (RCP 8.5) by the year 2100. (IPCC AR5 WGI, page 22).
Climate models have improved since the prior report.
Model results, along with observations, provide confidence in the
magnitude of global warming in response to past and future forcing.
Projections
Further warming will continue if emissions of greenhouse gases continue.
The global surface temperature increase by the end of the 21st century is likely to exceed 1.5 °C relative to the 1850 to 1900 period for most scenarios, and is likely to exceed 2.0 °C for many scenarios
The global water cycle
will change, with increases in disparity between wet and dry regions,
as well as wet and dry seasons, with some regional exceptions.
The oceans will continue to warm, with heat extending to the deep ocean, affecting circulation patterns.
Decreases are very likely in Arctic sea ice cover, Northern Hemisphere spring snow cover, and global glacier volume
Global mean sea level will continue to rise at a rate very likely to exceed the rate of the past four decades
Changes in climate will cause an increase in the rate of CO 2 production. Increased uptake by the oceans will increase the acidification of the oceans.
Future surface temperatures will be largely determined by cumulative CO 2, which means climate change will continue even if CO 2 emissions are stopped.
The summary also detailed the range of forecasts for warming, and
climate impacts with different emission scenarios. Compared to the
previous report, the lower bounds for the sensitivity of the climate
system to emissions were slightly lowered, though the projections for
global mean temperature rise (compared to pre-industrial levels) by 2100
exceeded 1.5 °C in all scenarios.
Other
The 'Next Generation Earth System Models' (e.g. HadGEM2) can produce hundreds of terabytes to perhaps tens of petabytes of climate model data for analysis.
Climate model simulations in support of AR5 use a different
approach to account for increasing greenhouse gas concentrations than in
the previous report. Instead of the scenarios from the Special Report on Emissions Scenarios the models are performing simulations for various Representative Concentration Pathways.
Public debate after the publication of AR4 in 2009 put the IPCC
under scrutiny, with controversies over alleged bias and inaccuracy in
its reports. In 2010, this prompted U.N. Secretary-General Ban Ki-moon and IPCC chair Rajendra K. Pachauri to request that the InterAcademy Council
(IAC) review the IPCC and recommend ways to strengthen its processes
and procedures for the preparation of AR5. The IAC report made
recommendations to fortify IPCC's management structure, to further
develop its conflict-of-interest policy, to strengthen the review
process, to clarify the guidelines on the use of so-called gray literature,
to ensure consistency in the use of probabilities for the likelihood of
outcomes, and to improve its communications strategy especially
regarding transparency and rapidity of response.
The Climate and Development Knowledge Network
has produced region-specific toolkits for policy makers, practitioners,
journalists and teachers based on the findings in the Fifth Assessment
Report. They include summary reports which distill the key findings of
the IPCC report; as well as media materials such as infographics,
slideshow presentations and images which can be used for training,
educational and reporting purposes. The four toolkits that have been
developed are:
IPCC reports cover the "scientific, technical and socio-economic
information relevant to understanding the scientific basis of risk of
human-induced climate change, its potential impacts and options for adaptation and mitigation." The IPCC does not carry out original research, nor does it monitor climate or related phenomena itself. Rather, it assesses published literature, including peer-reviewed and non-peer-reviewed sources.
However, the IPCC can be said to stimulate research in climate science.
Chapters of IPCC reports often close with sections on limitations and
knowledge or research gaps, and the announcement of an IPCC special
report can catalyse research activity in that area.
Thousands of scientists and other experts contribute on a voluntary basis to writing and reviewing reports, which are then reviewed by governments. IPCC reports contain a "Summary for Policymakers",
which is subject to line-by-line approval by delegates from all
participating governments. Typically, this involves the governments of
more than 120 countries.
The IPCC provides an internationally accepted authority on climate change, producing reports that have the agreement of leading climate scientists and consensus from participating governments. The 2007 Nobel Peace Prize was shared between the IPCC and Al Gore.
Following the election of a new Bureau in 2015, the IPCC embarked
on its sixth assessment cycle. Besides the Sixth Assessment Report, to
be completed in 2022, the IPCC released the Special Report on Global Warming of 1.5 °C
in October 2018, released an update to its 2006 Guidelines for National
Greenhouse Gas Inventories—the 2019 Refinement—in May 2019, and
delivered two further special reports in 2019: the Special Report on Climate Change and Land (SRCCL), published online on August 7, and the Special Report on the Ocean and Cryosphere in a Changing Climate
(SROCC), released on September 25, 2019. This makes the sixth
assessment cycle the most ambitious in the IPCC's 30-year history. The IPCC also decided to prepare a special report on cities and climate change in the seventh assessment cycle and held a conference in March 2018 to stimulate research in this area.
Origins and aims
The IPCC developed from an international scientific body, the Advisory Group on Greenhouse Gases set up in 1985 by the International Council of Scientific Unions, the United Nations Environment Programme (UNEP), and the World Meteorological Organization
(WMO) to provide recommendations based on current research. This small
group of scientists lacked the resources to cover the increasingly
complex interdisciplinary nature of climate science. The United States Environmental Protection Agency and State Department wanted an international convention to agree restrictions on greenhouse gases, and the conservativeReagan Administration
was concerned about unrestrained influence from independent scientists
or from United Nations bodies including UNEP and the WMO. The U.S.
government was the main force in forming the IPCC as an autonomous
intergovernmental body in which scientists took part both as experts on
the science and as official representatives of their governments, to
produce reports which had the firm backing of all the leading scientists
worldwide researching the topic, and which then had to gain consensus
agreement from every one of the participating governments. In this way,
it was formed as a hybrid between a scientific body and an
intergovernmental political organisation.
The United Nations formally edorsed the creation of the IPCC in
1988. Some of the reasons the UN stated in its resolution include
"[C]ertain human activities could change global climate
patterns, threatening present and future generations with potentially
severe economic and social consequences"
"[C]ontinued growth in atmospheric concentrations of
"greenhouse" gases could produce global warming with an eventual rise in
sea levels, the effects of which could be disastrous for mankind if
timely steps are not taken at all levels."
The IPCC was tasked with reviewing peer-reviewed scientific
literature and other relevant publications to provide information on the
state of knowledge about climate change.
Organization
The
IPCC does not conduct its own original research. It produces
comprehensive assessments, reports on special topics, and methodologies.
The assessments build on previous reports, highlighting the latest
knowledge. For example, the wording of the reports from the first to the
fifth assessment reflects the growing evidence for a changing climate
caused by human activity.
The IPCC has adopted and published "Principles Governing IPCC Work", which states that the IPCC will assess:
This document also states that IPCC will do this work by assessing
"on a comprehensive, objective, open and transparent basis the
scientific, technical and socio-economic information relevant to
understanding the scientific basis" of these topics. The Principles also
state that "IPCC reports should be neutral with respect to policy,
although they may need to deal objectively with scientific, technical
and socio-economic factors relevant to the application of particular
policies."
Korean economist Hoesung Lee has been the chair of the IPCC since 8 October 2015, with the election of the new IPCC Bureau.
Before this election, the IPCC was led by Vice-Chair Ismail El Gizouli, who was designated acting Chair after the resignation of Rajendra K. Pachauri in February 2015. The previous chairs were Rajendra K. Pachauri, elected in May 2002; Robert Watson in 1997; and Bert Bolin in 1988. The chair is assisted by an elected bureau including vice-chairs and working group co-chairs, and by a secretariat.
The Panel itself is composed of representatives appointed by
governments. Participation of delegates with appropriate expertise is
encouraged. Plenary sessions of the IPCC and IPCC Working Groups are held at the level of government representatives. Non-Governmental and Intergovernmental Organizations admitted as observer organizations may also attend. Sessions of the Panel, IPCC Bureau, workshops, expert and lead authors meetings are by invitation only.
About 500 people from 130 countries attended the 48th Session of the
Panel in Incheon, Republic of Korea, in October 2018, including 290
government officials and 60 representatives of observer organizations.
The opening ceremonies of sessions of the Panel and of Lead Author
Meetings are open to media, but otherwise IPCC meetings are closed.
There are several major groups:
IPCC Panel: Meets in plenary session
about once a year. It controls the organization's structure,
procedures, and work programme, and accepts and approves IPCC reports.
The Panel is the IPCC corporate entity.
Chair: Elected by the Panel.
Secretariat: Oversees and manages all activities. Supported by UNEP and WMO.
Bureau: Elected by the Panel. Chaired by the Chair. 34 members
include IPCC Vice-Chairs, Co-Chairs of Working Groups and the Task
Force, and Vice-Chairs of the Working Groups. It provides guidance to the Panel on the scientific and technical aspects of its work.
Working Groups: Each has two Co-Chairs, one from the developed and
one from developing world, and a technical support unit. Sessions of the
Working Group approve the Summary for Policymakers of special reports
and working group contributions to an assessment report. Each Working
Group has a Bureau comprising its Co-Chairs and Vice-Chairs, who are
also members of the IPCC Bureau.
Working Group I: Assesses scientific aspects of the climate system and climate change. Co-Chairs: Valérie Masson-Delmotte and Panmao Zhai
Working Group II: Assesses vulnerability of socio-economic and
natural systems to climate change, consequences, and adaptation options.
Co-Chairs: Hans-Otto Pörtner and Debra Roberts
Working Group III: Assesses options for limiting greenhouse gas
emissions and otherwise mitigating climate change. Co-Chairs:
Priyadarshi R. Shukla and Jim Skea
Task Force on National Greenhouse Gas Inventories. Co-Chairs: Kiyoto Tanabe and Eduardo Calvo Buendía
Task Force Bureau: Comprises the two Co-Chairs, who are also members of the IPCC Bureau, and 12 members.
Executive Committee: Comprises the Chair, IPCC Vice-Chairs and the
Co-Chairs of the Working Groups and Task Force. Its role includes
addressing urgent issues that arise between sessions of the Panel.
The IPCC receives funding through the IPCC Trust Fund, established in 1989 by the United Nations Environment Programme (UNEP) and the World Meteorological Organization
(WMO), Costs of the Secretary and of housing the secretariat are
provided by the WMO, while UNEP meets the cost of the Depute Secretary.
Annual cash contributions to the Trust Fund are made by the WMO, by
UNEP, and by IPCC Members. Payments and their size are voluntary. The
Panel is responsible for considering and adopting by consensus the
annual budget. The organization is required to comply with the Financial
Regulations and Rules of the WMO.
Assessment reports
The IPCC has published five comprehensive assessment reports reviewing the latest climate science,
as well as a number of special reports on particular topics. These
reports are prepared by teams of relevant researchers selected by the
Bureau from government nominations. Expert reviewers from a wide range
of governments, IPCC observer organizations and other organizations are
invited at different
stages to comment on various aspects of the drafts.
Each assessment report is in three volumes, corresponding to
Working Groups I, II, and III. It is completed by a synthesis report
that integrates the working group contributions and any special reports
produced in that assessment cycle.
Scope and preparation of the reports
The
IPCC does not carry out research nor does it monitor climate related
data. Lead authors of IPCC reports assess the available information
about climate change based on published sources. According to IPCC guidelines, authors should give priority to peer-reviewed sources. Authors may refer to non-peer-reviewed sources (the "grey literature"), provided that they are of sufficient quality.
Examples of non-peer-reviewed sources include model results, reports
from government agencies and non-governmental organizations, and
industry journals.
Each subsequent IPCC report notes areas where the science has improved
since the previous report and also notes areas where further research is
required.
There are generally three stages in the review process:
Expert review (6–8 weeks)
Government/expert review
Government review of:
Summaries for Policymakers
Overview Chapters
Synthesis Report
Review comments are in an open archive for at least five years.
There are several types of endorsement which documents receive:
Approval. Material has been subjected to detailed, line by line discussion and agreement.
Working Group Summaries for Policymakers are approved by their Working Groups.
Synthesis Report Summary for Policymakers is approved by Panel.
Adoption. Endorsed section by section (and not line by line).
Panel adopts Overview Chapters of Methodology Reports.
Panel adopts IPCC Synthesis Report.
Acceptance. Not been subject to line by line discussion and
agreement, but presents a comprehensive, objective, and balanced view of
the subject matter.
Working Groups accept their reports.
Task Force Reports are accepted by the Panel.
Working Group Summaries for Policymakers are accepted by the Panel after group approval.
The Panel is responsible for the IPCC and its endorsement of Reports allows it to ensure they meet IPCC standards.
There have been a range of commentaries on the IPCC's procedures,
examples of which are discussed later in the article (see also IPCC Summary for Policymakers). Some of these comments have been supportive, while others have been critical. Some commentators have suggested changes to the IPCC's procedures.
Authors
Each chapter has a number of authors who are responsible for writing
and editing the material. A chapter typically has two "coordinating lead
authors", ten to fifteen "lead authors", and a somewhat larger number
of "contributing authors". The coordinating lead authors are responsible
for assembling the contributions of the other authors, ensuring that
they meet stylistic and formatting requirements, and reporting to the
Working Group chairs. Lead authors are responsible for writing sections
of chapters. Contributing authors prepare text, graphs or data for
inclusion by the lead authors.
Authors for the IPCC reports are chosen from a list of
researchers prepared by governments and participating organisations, and
by the Working Group/Task Force Bureaux, as well as other experts known
through their published work. The choice of authors aims for a range of
views, expertise and geographical representation, ensuring
representation of experts from developing and developed countries and
countries with economies in transition.
First assessment report
The IPCC First Assessment Report (FAR) was completed in 1990, and served as the basis of the UNFCCC.
The executive summary of the WG I Summary for Policymakers report
says they are certain that emissions resulting from human activities
are substantially increasing the atmospheric concentrations of the greenhouse gases, resulting on average in an additional warming of the Earth's surface. They calculate with confidence that CO2
has been responsible for over half the enhanced greenhouse effect. They
predict that under a "business as usual" (BAU) scenario, global mean
temperature will increase by about 0.3 °C per decade during the [21st]
century. They judge that global mean surface air temperature has
increased by 0.3 to 0.6 °C over the last 100 years, broadly consistent
with prediction of climate models, but also of the same magnitude as
natural climate variability. The unequivocal detection of the enhanced
greenhouse effect is not likely for a decade or more.
Supplementary report of 1992
The 1992 supplementary report was an update, requested in the context of the negotiations on the UNFCCC at the Earth Summit (United Nations Conference on Environment and Development) in Rio de Janeiro in 1992.
The major conclusion was that research since 1990 did "not affect
our fundamental understanding of the science of the greenhouse effect
and either confirm or do not justify alteration of the major conclusions
of the first IPCC scientific assessment". It noted that transient
(time-dependent) simulations, which had been very preliminary in the
FAR, were now improved, but did not include aerosol or ozone changes.
Second assessment report
Climate Change 1995, the IPCC Second Assessment Report (SAR), was finished in 1996. It is split into four parts:
A synthesis to help interpret UNFCCC article 2.
The Science of Climate Change (WG I)
Impacts, Adaptations and Mitigation of Climate Change (WG II)
Economic and Social Dimensions of Climate Change (WG III)
Each of the last three parts was completed by a separate Working
Group (WG), and each has a Summary for Policymakers (SPM) that
represents a consensus of national representatives. The SPM of the WG I
report contains headings:
Greenhouse gas concentrations have continued to increase
Anthropogenic aerosols tend to produce negative radiative forcings
Climate has changed over the past century (air temperature has
increased by between 0.3 and 0.6 °C since the late 19th century; this
estimate has not significantly changed since the 1990 report).
The balance of evidence suggests a discernible human influence on
global climate (considerable progress since the 1990 report in
distinguishing between natural and anthropogenic influences on climate,
because of: including aerosols; coupled models; pattern-based studies)
Climate is expected to continue to change in the future (increasing realism of simulations increases confidence; important uncertainties remain but are taken into account in the range of model projections)
There are still many uncertainties (estimates of future emissions
and biogeochemical cycling; models; instrument data for model testing,
assessment of variability, and detection studies)
Third assessment report
The Third Assessment Report (TAR) was completed in 2001 and consists of four reports, three of them from its Working Groups:
Working Group I: The Scientific Basis
Working Group II: Impacts, Adaptation and Vulnerability
Working Group III: Mitigation
Synthesis Report
A number of the TAR's conclusions are given quantitative estimates of
how probable it is that they are correct, e.g., greater than 66%
probability of being correct. These are "Bayesian" probabilities, which are based on an expert assessment of all the available evidence.
"Robust findings" of the TAR Synthesis Report include:
"Observations show Earth's surface is warming. Globally, 1990s very likely warmest decade in instrumental record". Atmospheric concentrations of anthropogenic (i.e., human-emitted) greenhouse gases have increased substantially.
Since the mid-20th century, most of the observed warming is "likely" (greater than 66% probability, based on expert judgement) due to human activities.
Projections based on the Special Report on Emissions Scenarios suggest warming over the 21st century at a more rapid rate than that experienced for at least the last 10,000 years.
"Projected climate change will have beneficial and adverse effects
on both environmental and socio-economic systems, but the larger the
changes and the rate of change in climate, the more the adverse effects
predominate."
"Ecosystems and species
are vulnerable to climate change and other stresses (as illustrated by
observed impacts of recent regional temperature changes) and some will
be irreversibly damaged or lost."
"Greenhouse gas emission reduction (mitigation) actions would lessen the pressures on natural and human systems from climate change."
"Adaptation [to the effects of climate change] has the potential to reduce adverse effects of climate change and can often produce immediate ancillary benefits, but will not prevent all damages." An example of adaptation to climate change is building levees in response to sea level rise.
In 2001, the US National Research Council (US NRC) produced a report that assessed Working Group I's (WGI) contribution to the TAR. US NRC (2001)
"generally agrees" with the WGI assessment, and describes the full WGI
report as an "admirable summary of research activities in climate
science".
IPCC author Richard Lindzen has made a number of criticisms of the TAR.
Among his criticisms, Lindzen has stated that the WGI Summary for
Policymakers (SPM) does not faithfully summarize the full WGI report. For example, Lindzen states that the SPM understates the uncertainty associated with climate models. John Houghton, who was a co-chair of TAR WGI, has responded to Lindzen's criticisms of the SPM.
Houghton has stressed that the SPM is agreed upon by delegates from
many of the world's governments, and that any changes to the SPM must be
supported by scientific evidence.
IPCC author Kevin Trenberth has also commented on the WGI SPM.
Trenberth has stated that during the drafting of the WGI SPM, some
government delegations attempted to "blunt, and perhaps obfuscate, the
messages in the report". However, Trenberth concludes that the SPM is a "reasonably balanced summary".
US NRC (2001) concluded that the WGI SPM and Technical Summary are "consistent" with the full WGI report. US NRC (2001) stated:
[...] the full [WGI] report is adequately summarized in
the Technical Summary. The full WGI report and its Technical Summary are
not specifically directed at policy. The Summary for Policymakers
reflects less emphasis on communicating the basis for uncertainty and a
stronger emphasis on areas of major concern associated with
human-induced climate change. This change in emphasis appears to be the
result of a summary process in which scientists work with policy makers
on the document. Written responses from U.S. coordinating and lead
scientific authors to the committee indicate, however, that (a) no
changes were made without the consent of the convening lead authors
(this group represents a fraction of the lead and contributing authors)
and (b) most changes that did occur lacked significant impact.
Fourth assessment report
The Fourth Assessment Report (AR4) was published in 2007. Like previous assessment reports, it consists of four reports:
Working Group I: The Physical Science Basis
Working Group II: Impacts, Adaptation and Vulnerability
Working Group III: Mitigation
Synthesis Report
People from over 130 countries contributed to the IPCC Fourth Assessment Report, which took 6 years to produce.
Contributors to AR4 included more than 2500 scientific expert
reviewers, more than 800 contributing authors, and more than 450 lead
authors.
"Robust findings" of the Synthesis report include:
"Warming of the climate system is unequivocal, as is now evident
from observations of increases in global average air and ocean
temperatures, widespread melting of snow and ice and rising global
average sea level".
Most of the global average warming over the past 50 years is "very
likely" (greater than 90% probability, based on expert judgement) due to human activities.
"Impacts [of climate change] will very likely increase due to
increased frequencies and intensities of some extreme weather events".
"Anthropogenic warming and sea level rise would continue for
centuries even if GHG emissions were to be reduced sufficiently for GHG
concentrations to stabilise, due to the time scales associated with
climate processes and feedbacks". Stabilization of atmospheric greenhouse gas concentrations is discussed in climate change mitigation.
"Some planned adaptation (of human activities) is occurring now;
more extensive adaptation is required to reduce vulnerability to climate
change".
"Unmitigated climate change would, in the long term, be likely to
exceed the capacity of natural, managed and human systems to adapt".
"Many impacts [of climate change] can be reduced, delayed or avoided by mitigation".
Global warming projections from AR4
are shown below. The projections apply to the end of the 21st century
(2090–99), relative to temperatures at the end of the 20th century
(1980–99). Add 0.7 °C to projections to make them relative to
pre-industrial levels instead of 1980–99. (UK Royal Society, 2010, p=10. Descriptions of the greenhouse gas emissions scenarios can be found in Special Report on Emissions Scenarios.
AR4 global warming projections
Emissions scenario
Best estimate (°C)
"Likely" range (°C)
B1
1.8
1.1 – 2.9
A1T
2.4
1.4 – 3.8
B2
2.4
1.4 – 3.8
A1B
2.8
1.7 – 4.4
A2
3.4
2.0 – 5.4
A1FI
4.0
2.4 – 6.4
"Likely" means greater than 66% probability of being correct, based on expert judgement.
Response to AR4
Several science academies have referred to and/or reiterated some of the conclusions of AR4. These include:
Joint-statements made in 2007, 2008, and 2009 by the science academies of Brazil, China, India, Mexico, South Africa and the G8 nations (the "G8+5").
A statement made in 2010 by the Inter Academy Medical Panel This statement has been signed by 43 scientific academies.
The Netherlands Environmental Assessment Agency (PBL, et al., 2009; 2010) has carried out two reviews of AR4. These reviews are generally supportive of AR4's conclusions. PBL (2010)
make some recommendations to improve the IPCC process. A literature
assessment by the US National Research Council (US NRC, 2010) concludes:
Climate
change is occurring, is caused largely by human activities, and poses
significant risks for—and in many cases is already affecting—a broad
range of human and natural systems [emphasis in original text].
[...] This conclusion is based on a substantial array of scientific
evidence, including recent work, and is consistent with the conclusions
of recent assessments by the U.S. Global Change Research Program [...],
the Intergovernmental Panel on Climate Change’s Fourth Assessment Report
[...], and other assessments of the state of scientific knowledge on
climate change.
Some errors have been found in the IPCC AR4 Working Group II report. Two errors include the melting of Himalayanglaciers, and Dutch land area that is below sea level.
Fifth assessment report
The IPCC's Fifth Assessment Report (AR5) was completed in 2014. AR5 followed the same general format as of AR4, with three Working Group reports and a Synthesis report. The Working Group I report (WG1) was published in September 2013.
Conclusions of AR5 are summarized below:
Working Group I
"Warming of the climate system is unequivocal, and since the
1950s, many of the observed changes are unprecedented over decades to
millennia".
"Atmospheric concentrations of carbon dioxide, methane, and nitrous
oxide have increased to levels unprecedented in at least the last
800,000 years".
Human influence on the climate system is clear. It is extremely likely (95-100% probability) that human influence was the dominant cause of global warming between 1951-2010.
Working Group II
"Increasing magnitudes of [global] warming increase the likelihood of severe, pervasive, and irreversible impacts"
"A first step towards adaptation to future climate change is reducing vulnerability and exposure to present climate variability"
"The overall risks of climate change impacts can be reduced by limiting the rate and magnitude of climate change"
Working Group III
Without new policies to mitigate climate change, projections suggest an increase in global mean temperature in 2100 of 3.7 to 4.8 °C, relative to pre-industrial levels (median values; the range is 2.5 to 7.8 °C including climate uncertainty).
The current trajectory of global greenhouse gas emissions is not
consistent with limiting global warming to below 1.5 or 2 °C, relative
to pre-industrial levels. Pledges made as part of the Cancún Agreements
are broadly consistent with cost-effective scenarios that give a
"likely" chance (66-100% probability) of limiting global warming (in
2100) to below 3 °C, relative to pre-industrial levels.
Representative Concentration Pathways
Projections in AR5 are based on "Representative Concentration Pathways" (RCPs).[86]
The RCPs are consistent with a wide range of possible changes in future
anthropogenic greenhouse gas emissions. Projected changes in global
mean surface temperature and sea level are given in the main RCP article.
Special reports
In
addition to climate assessment reports, the IPCC publishes Special
Reports on specific topics. The preparation and approval process for all
IPCC Special Reports follows the same procedures as for IPCC Assessment
Reports. In the year 2011 two IPCC Special Report were finalized, the
Special Report on Renewable Energy Sources and Climate Change Mitigation
(SRREN) and the Special Report on Managing Risks of Extreme Events and
Disasters to Advance Climate Change Adaptation (SREX). Both Special
Reports were requested by governments.
Special Report on Emissions Scenarios (SRES)
The Special Report on Emissions Scenarios (SRES) is a report by the IPCC which was published in 2000. The SRES contains "scenarios" of future changes in emissions of greenhouse gases and sulfur dioxide.
One of the uses of the SRES scenarios is to project future changes in
climate, e.g., changes in global mean temperature. The SRES scenarios
were used in the IPCC's Third and Fourth Assessment Reports.
The SRES scenarios are "baseline" (or "reference") scenarios,
which means that they do not take into account any current or future
measures to limit greenhouse gas (GHG) emissions (e.g., the Kyoto Protocol to the United Nations Framework Convention on Climate Change).
SRES emissions projections are broadly comparable in range to the
baseline projections that have been developed by the scientific
community.
Comments on the SRES
There have been a number of comments on the SRES. Parson et al. (2007)
stated that the SRES represented "a substantial advance from prior
scenarios". At the same time, there have been criticisms of the SRES.
The most prominently publicized criticism of SRES focused on the
fact that all but one of the participating models compared gross
domestic product (GDP) across regions using market exchange rates (MER), instead of the more correct purchasing-power parity (PPP) approach. This criticism is discussed in the main SRES article.
Special report on renewable energy sources and climate change mitigation (SRREN)
This report assesses existing literature on renewable energy commercialisation
for the mitigation of climate change. It was published in 2012 and
covers the six most important renewable energy technologies, as well as
their integration into present and future energy systems. It also takes
into consideration the environmental and social consequences associated
with these technologies, the cost and strategies to overcome technical
as well as non-technical obstacles to their application and diffusion.
The full report in PDF form is found here.
More than 130 authors from all over the world contributed to the
preparation of IPCC Special Report on Renewable Energy Sources and
Climate Change Mitigation (SRREN) on a voluntary basis – not to mention
more than 100 scientists, who served as contributing authors.
Special Report on managing the risks of extreme events and disasters to advance climate change adaptation (SREX)
The report
was published in 2012. It assesses the effect that climate change has
on the threat of natural disasters and how nations can better manage an
expected change in the frequency of occurrence and intensity of severe
weather patterns. It aims to become a resource for decision-makers to
prepare more effectively for managing the risks of these events. A
potentially important area for consideration is also the detection of
trends in extreme events and the attribution of these trends to human
influence. The full report, 594 pages in length, may be found here in PDF form.
More than 80 authors, 19 review editors, and more than 100
contributing authors from all over the world contributed to the
preparation of SREX.
Special Report on Global Warming of 1.5 °C (SR15)
When the Paris Agreement was adopted, the UNFCCC
invited the Intergovernmental Panel on Climate Change to write a
special report on "How can humanity prevent the global temperature rise
more than 1.5 degrees above pre-industrial level". The completed report, Special Report on Global Warming of 1.5 °C
(SR15), was released on October 8, 2018. Its full title is "Global
Warming of 1.5 °C, an IPCC special report on the impacts of global
warming of 1.5 °C above pre-industrial levels and related global
greenhouse gas emission pathways, in the context of strengthening the
global response to the threat of climate change, sustainable
development, and efforts to eradicate poverty".
The finished report summarizes the findings of scientists,
showing that maintaining a temperature rise to below 1.5 °C remains
possible, but only through "rapid and far-reaching transitions in
energy, land, urban and infrastructure..., and industrial systems". Meeting the Paris target of 1.5 °C (2.7 °F) is possible but would require "deep emissions reductions", "rapid", "far-reaching and unprecedented changes in all aspects of society".
In order to achieve the 1.5 °C target, CO2 emissions must decline by
45% (relative to 2010 levels) by 2030, reaching net zero by around 2050.
Deep reductions in non-CO2 emissions (such as nitrous oxide and
methane) will also be required to limit warming to 1.5 °C. Under the
pledges of the countries entering the Paris Accord, a sharp rise of 3.1
to 3.7 °C is still expected to occur by 2100. Holding this rise to
1.5 °C avoids the worst effects of a rise by even 2 °C. However, a
warming of even 1.5 degrees will still result in large-scale drought,
famine, heat stress, species die-off, loss of entire ecosystems, and
loss of habitable land, throwing more than 100 Million into poverty.
Effects will be most drastic in arid regions including the Middle East and the Sahel
in Africa, where fresh water will remain in some areas following a
1.5 °C rise in temperatures but are expected to dry up completely if the
rise reaches 2 °C.
Special Report on climate change and land (SRCCL)
The final draft of the "Special Report on climate change and land"
(SRCCL)—with the full title, "Special Report on climate change,
desertification, land degradation, sustainable land management, food
security, and greenhouse gas fluxes in terrestrial ecosystems" was
published online on August 7, 2019.
The SRCCL consists of seven chapters, Chapter 1: Framing and Context,
Chapter 2: Land-Climate Interactions, Chapter 3: Desertification,
Chapter 4: Land Degradation, Chapter 5: Food Security, Chapter 5
Supplementary Material, Chapter 6: Interlinkages between
desertification, land degradation, food security and GHG fluxes:
Synergies, trade-offs and Integrated Response Options, and Chapter 7:
Risk management and decision making in relation to sustainable
development.
Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC)
The "Special Report on the Ocean and Cryosphere in a Changing Climate" (SROCC) was approved on September 25, 2019 in Monaco.
Among other findings, the report concluded that sea level rises could
be up to two feet higher by the year 2100, even if efforts to reduce
greenhouse gas emissions and to limit global warming are successful;
coastal cities across the world could see so-called "storm[s] of the
century" at least once a year.
to develop and refine an internationally agreed methodology and
software for the calculation and reporting of national greenhouse gas
emissions and removals; and
to encourage the widespread use of this methodology by countries participating in the IPCC and by signatories of the UNFCCC.
Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories
The
1996 Guidelines for National Greenhouse Gas Investories provide the
methodological basis for the estimation of national greenhouse gas emissions inventories. Over time these guidelines have been completed with good practice reports: Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories and Good Practice Guidance for Land Use, Land-Use Change and Forestry.
The 1996 guidelines and the two good practice reports are to be used by parties to the UNFCCC and to the Kyoto Protocol in their annual submissions of national greenhouse gas inventories.
2006 IPCC Guidelines for National Greenhouse Gas Inventories
The 2006 IPCC Guidelines for National Greenhouse Gas Inventories is the latest version of these emission estimation methodologies, including a large number of default emission factors.
Although the IPCC prepared this new version of the guidelines on
request of the parties to the UNFCCC, the methods have not yet been
officially accepted for use in national greenhouse gas emissions
reporting under the UNFCCC and the Kyoto Protocol.
Activities
The
IPCC concentrates its activities on the tasks allotted to it by the
relevant WMO Executive Council and UNEP Governing Council resolutions
and decisions as well as on actions in support of the UNFCCC process.
While the preparation of the assessment reports is a major IPCC
function, it also supports other activities, such as the Data
Distribution Centre and the National Greenhouse Gas Inventories Programme, required under the UNFCCC. This involves publishing default emission factors, which are factors used to derive emissions estimates based on the levels of fuel consumption, industrial production and so on.
The IPCC also often answers inquiries from the UNFCCC Subsidiary Body for Scientific and Technological Advice (SBSTA).
Nobel Peace Prize
In December 2007, the IPCC was awarded the Nobel Peace Prize
"for their efforts to build up and disseminate greater knowledge about
man-made climate change, and to lay the foundations for the measures
that are needed to counteract such change". The award is shared with
Former U.S. Vice-President Al Gore for his work on climate change and the documentary An Inconvenient Truth.
Criticisms
There is widespread support for the IPCC in the scientific community, which is reflected in publications by other scientific bodies and experts. However, criticisms of the IPCC have been made.
Since 2010 the IPCC has come under yet unparalleled public and political scrutiny. The global IPCC consensus approach has been challenged internally and externally, for example, during the 2009 Climatic Research Unit email controversy ("Climategate"). It is contested by some as an information monopoly with results for both the quality and the impact of the IPCC work as such.
Projected date of melting of Himalayan glaciers
A paragraph in the 2007 Working Group II report ("Impacts, Adaptation
and Vulnerability"), chapter 10 included a projection that Himalayan
glaciers could disappear by 2035.
Glaciers in the Himalaya are receding faster than in any
other part of the world (see Table 10.9) and, if the present rate
continues, the likelihood of them disappearing by the year 2035 and
perhaps sooner is very high if the Earth keeps warming at the current
rate. Its total area will likely shrink from the present 500,000 to
100,000 km2 by the year 2035 (WWF, 2005).
This projection was not included in the final summary for
policymakers. The IPCC has since acknowledged that the date is
incorrect, while reaffirming that the conclusion in the final summary
was robust. They expressed regret for "the poor application of
well-established IPCC procedures in this instance". The date of 2035 has
been correctly quoted by the IPCC from the WWF report, which has
misquoted its own source, an ICSI report "Variations of Snow and Ice in the past and at present on a Global and Regional Scale"
Former IPCC chairman Robert Watson
said, regarding the Himalayan glaciers estimation, "The mistakes all
appear to have gone in the direction of making it seem like climate
change is more serious by overstating the impact. That is worrying. The
IPCC needs to look at this trend in the errors and ask why it happened". Martin Parry, a climate expert
who had been co-chair of the IPCC working group II, said that "What
began with a single unfortunate error over Himalayan glaciers has become
a clamour without substance" and the IPCC had investigated the other
alleged mistakes, which were "generally unfounded and also marginal to
the assessment".
Emphasis of the "hockey stick" graph
IPCC WG1 Co-chair Sir John T. Houghton showing the IPCC fig. 2.20 hockey stick graph at a climate conference in 2005
The original northern hemisphere hockey stick graph of Mann, Bradley & Hughes 1999,
smoothed curve shown in blue with its uncertainty range in light blue,
overlaid with green dots showing the 30-year global average of the PAGES 2k Consortium 2013 reconstruction. The red curve shows measured global mean temperature, according to HadCRUT4 data from 1850 to 2013.
Comparison of MBH99 40-year average from proxy records, as used in IPCC TAR 2001 (blue), with IPCC 1990
schematic Figure 7.1.c (red) [based on Lamb 1965 extrapolating from
central England temperatures and other historical records]; central
England temperatures to 2007 shown from Jones et al. 2009 (green dashed line). Also shown, Moberg et al. 2005 low frequency signal (black).
The third assessment report (TAR) prominently featured a graph labeled "Millennial Northern Hemisphere temperature reconstruction" based on a 1999 paper by Michael E. Mann, Raymond S. Bradley and Malcolm K. Hughes (MBH99), which has been referred to as the "hockey stick graph". This graph extended the similar graph in Figure 3.20 from the IPCC Second Assessment Report of 1995, and differed from a schematic in the first assessment report
that lacked temperature units, but appeared to depict larger global
temperature variations over the past 1000 years, and higher temperatures
during the Medieval Warm Period
than the mid 20th century. The schematic was not an actual plot of
data, and was based on a diagram of temperatures in central England,
with temperatures increased on the basis of documentary evidence of
Medieval vineyards in England.
Even with this increase, the maximum it showed for the Medieval Warm
Period did not reach temperatures recorded in central England in 2007. The MBH99 finding was supported by cited reconstructions by Jones et al. 1998, Pollack, Huang & Shen 1998, Crowley & Lowery 2000 and Briffa 2000,
using differing data and methods. The Jones et al. and Briffa
reconstructions were overlaid with the MBH99 reconstruction in Figure
2.21 of the IPCC report.
These studies were widely presented as demonstrating that the
current warming period is exceptional in comparison to temperatures
between 1000 and 1900, and the MBH99 based graph featured in publicity.
Even at the draft stage, this finding was disputed by contrarians: in
May 2000 Fred Singer's Science and Environmental Policy Project held a press event on Capitol Hill, Washington, D.C., featuring comments on the graph Wibjörn Karlén and Singer argued against the graph at a United States Senate Committee on Commerce, Science and Transportation hearing on 18 July 2000. Contrarian John Lawrence Daly
featured a modified version of the IPCC 1990 schematic, which he
mis-identified as appearing in the IPCC 1995 report, and argued that
"Overturning its own previous view in the 1995 report, the IPCC
presented the 'Hockey Stick' as the new orthodoxy with hardly an apology
or explanation for the abrupt U-turn since its 1995 report". Criticism of the MBH99 reconstruction in a review paper, which was quickly discredited in the Soon and Baliunas controversy, was picked up by the Bush administration, and a Senate speech by US Republican senator James Inhofe
alleged that "manmade global warming is the greatest hoax ever
perpetrated on the American people". The data and methodology used to
produce the "hockey stick graph" was criticized in papers by Stephen McIntyre and Ross McKitrick, and in turn the criticisms in these papers were examined by other studies and comprehensively refuted by Wahl & Ammann 2007, which showed errors in the methods used by McIntyre and McKitrick.
On 23 June 2005, Rep. Joe Barton, chairman of the House Committee on Energy and Commerce wrote joint letters with Ed Whitfield, chairman of the Subcommittee on Oversight and Investigations
demanding full records on climate research, as well as personal
information about their finances and careers, from Mann, Bradley and
Hughes. Sherwood Boehlert, chairman of the House Science Committee,
said this was a "misguided and illegitimate investigation" apparently
aimed at intimidating scientists, and at his request the U.S. National Academy of Sciences arranged for its National Research Council to set up a special investigation.
The National Research Council's report agreed that there were some
statistical failings, but these had little effect on the graph, which
was generally correct. In a 2006 letter to Nature,
Mann, Bradley, and Hughes pointed out that their original article had
said that "more widespread high-resolution data are needed before more
confident conclusions can be reached" and that the uncertainties were
"the point of the article".
The IPCC Fourth Assessment Report
(AR4) published in 2007 featured a graph showing 12 proxy based
temperature reconstructions, including the three highlighted in the 2001
Third Assessment Report (TAR); Mann, Bradley & Hughes 1999 as before, Jones et al. 1998 and Briffa 2000 had both been calibrated by newer studies. In addition, analysis of the Medieval Warm Period cited reconstructions by Crowley & Lowery 2000 (as cited in the TAR) and Osborn & Briffa 2006.
Ten of these 14 reconstructions covered 1,000 years or longer. Most
reconstructions shared some data series, particularly tree ring data,
but newer reconstructions used additional data and covered a wider area,
using a variety of statistical methods. The section discussed the divergence problem affecting certain tree ring data.
Conservative nature of IPCC reports
Some critics have contended that the IPCC reports tend to be conservative by consistently underestimating the pace and impacts of global warming, and report only the "lowest common denominator" findings.
On the eve of the publication of IPCC's Fourth Assessment Report
in 2007 another study was published suggesting that temperatures and
sea levels have been rising at or above the maximum rates proposed
during IPCC's 2001 Third Assessment Report.
The study compared IPCC 2001 projections on temperature and sea level
change with observations. Over the six years studied, the actual
temperature rise was near the top end of the range given by IPCC's 2001
projection, and the actual sea level rise was above the top of the range
of the IPCC projection.
Another example of scientific research which suggests that
previous estimates by the IPCC, far from overstating dangers and risks,
have actually understated them is a study on projected rises in sea
levels. When the researchers' analysis was "applied to the possible
scenarios outlined by the Intergovernmental Panel on Climate Change
(IPCC), the researchers found that in 2100 sea levels would be 0.5–1.4 m
[50–140 cm] above 1990 levels. These values are much greater than the
9–88 cm as projected by the IPCC itself in its Third Assessment Report,
published in 2001". This may have been due, in part, to the expanding
human understanding of climate.
Greg Holland from the National Center for Atmospheric Research, who reviewed a multi-meter sea level rise study by Jim Hansen, noted “There
is no doubt that the sea level rise, within the IPCC, is a very
conservative number, so the truth lies somewhere between IPCC and Jim.”
In reporting criticism by some scientists that IPCC's
then-impending January 2007 report understates certain risks,
particularly sea level rises, an AP story quoted Stefan Rahmstorf,
professor of physics and oceanography at Potsdam University as saying
"In a way, it is one of the strengths of the IPCC to be very
conservative and cautious and not overstate any climate change risk".
In his December 2006 book, Hell and High Water: Global Warming, and in an interview on Fox News on 31 January 2007, energy expert Joseph Romm noted that the IPCC Fourth Assessment Report
is already out of date and omits recent observations and factors
contributing to global warming, such as the release of greenhouse gases
from thawing tundra.
Political influence on the IPCC has been documented by the
release of a memo by ExxonMobil to the Bush administration, and its
effects on the IPCC's leadership. The memo led to strong Bush
administration lobbying, evidently at the behest of ExxonMobil, to oust Robert Watson,
a climate scientist, from the IPCC chairmanship, and to have him
replaced by Pachauri, who was seen at the time as more mild-mannered and
industry-friendly.
IPCC processes
Michael Oppenheimer, a long-time participant in the IPCC and coordinating lead author of the Fifth Assessment Report conceded in Science Magazine's State of the Planet 2008–2009
some limitations of the IPCC consensus approach and asks for
concurring, smaller assessments of special problems instead of the large
scale approach as in the previous IPCC assessment reports. It has become more important to provide a broader exploration of uncertainties.
Others see as well mixed blessings of the drive for consensus within
the IPCC process and ask to include dissenting or minority positions or to improve statements about uncertainties.
The IPCC process on climate change and its efficiency and success
has been compared with dealings with other environmental challenges. In case of the Ozone depletion, global regulation based on the Montreal Protocol has been successful. In case of Climate Change, the Kyoto Protocol failed. The Ozone case was used to assess the efficiency of the IPCC process.
The lockstep situation of the IPCC is having built a broad science
consensus while states and governments still follow different, if not
opposing goals. The underlying linear model of policy-making of the more knowledge we have, the better the political response will be is being doubted.
According to Sheldon Ungar's comparison with global warming, the
actors in the ozone depletion case had a better understanding of
scientific ignorance and uncertainties. The ozone case communicated to lay persons "with easy-to-understand bridging metaphors derived from the popular culture" and related to "immediate risks with everyday relevance", while the public opinion on climate change sees no imminent danger.
The stepwise mitigation of the ozone layer challenge was based as well
on successfully reducing regional burden sharing conflicts.
In case of the IPCC conclusions and the failure of the Kyoto Protocol,
varying regional cost-benefit analysis and burden-sharing conflicts with
regard to the distribution of emission reductions remain an unsolved
problem.
In the UK, a report for a House of Lords committee asked to urge the
IPCC to involve better assessments of costs and benefits of climate
change, but the Stern Review, ordered by the UK government, made a stronger argument in favor to combat human-made climate change.
Outdatedness of reports
Since
the IPCC does not carry out its own research, it operates on the basis
of scientific papers and independently documented results from other
scientific bodies, and its schedule for producing reports requires a
deadline for submissions prior to the report's final release. In
principle, this means that any significant new evidence or events that
change our understanding of climate science between this deadline and
publication of an IPCC report cannot be included. In an area of science
where our scientific understanding is rapidly changing, this has been
raised as a serious shortcoming in a body which is widely regarded as
the ultimate authority on the science. However, there has generally been a steady evolution of key findings and levels of scientific confidence from one assessment report to the next.
The submission deadlines for the Fourth Assessment Report (AR4)
differed for the reports of each Working Group. Deadlines for the
Working Group I report were adjusted during the drafting and review
process in order to ensure that reviewers had access to unpublished
material being cited by the authors. The final deadline for cited
publications was 24 July 2006. The final WG I report was released on 30 April 2007 and the final AR4 Synthesis Report was released on 17 November 2007.Rajendra Pachauri,
the IPCC chair, admitted at the launch of this report that since the
IPCC began work on it, scientists have recorded "much stronger trends in
climate change", like the unforeseen dramatic melting of polar ice in
the summer of 2007, and added, "that means you better start with intervention much earlier".
Burden on participating scientists
Scientists
who participate in the IPCC assessment process do so without any
compensation other than the normal salaries they receive from their home
institutions. The process is labor-intensive, diverting time and
resources from participating scientists' research programs.
Concerns have been raised that the large uncompensated time commitment
and disruption to their own research may discourage qualified scientists
from participating.
Lack of error correction after publication
In
May 2010, Pachauri noted that the IPCC currently had no process for
responding to errors or flaws once it issued a report. The problem,
according to Pachauri, was that once a report was issued the panels of
scientists producing the reports were disbanded.
Proposed organizational overhaul
In February 2010, in response to controversies regarding claims in the Fourth Assessment Report, five climate scientists – all contributing or lead IPCC report authors – wrote in the journal Nature
calling for changes to the IPCC. They suggested a range of new
organizational options, from tightening the selection of lead authors
and contributors, to dumping it in favor of a small permanent body, or
even turning the whole climate science assessment process into a moderated "living" Wikipedia-IPCC.
Other recommendations included that the panel employ a full-time staff
and remove government oversight from its processes to avoid political
interference.
In March 2010, at the invitation of the United Nations secretary-general and the chair of the IPCC, the InterAcademy Council (IAC) was asked to review the IPCC's processes for developing its reports. The IAC panel, chaired by Harold Tafler Shapiro, convened on 14 May 2010 and released its report on 1 September 2010.
The IAC found that, "The IPCC assessment process has been
successful overall". The panel, however, made seven formal
recommendations for improving the IPCC's assessment process, including:
establish an executive committee;
elect an executive director whose term would only last for one assessment;
encourage review editors to ensure that all reviewer comments are
adequately considered and genuine controversies are adequately reflected
in the assessment reports;
adopt a better process for responding to reviewer comments;
working groups should use a qualitative level-of-understanding scale in the Summary for Policy Makers and Technical Summary;
"Quantitative probabilities (as in the likelihood scale) should be
used to describe the probability of well-defined outcomes only when
there is sufficient evidence"; and
implement a communications plan that emphasizes transparency and
establish guidelines for who can speak on behalf of the organization.
The panel also advised that the IPCC avoid appearing to advocate specific policies in response to its scientific conclusions. Commenting on the IAC report, Nature News
noted that "The proposals were met with a largely favourable response
from climate researchers who are eager to move on after the media
scandals and credibility challenges that have rocked the United Nations
body during the past nine months".
Archiving
Papers
and electronic files of certain working groups of the IPCC, including
reviews and comments on drafts of their Assessment Reports, are archived
at the Environmental Science and Public Policy Archives in the Harvard Library.
Endorsements of the IPCC
Various scientific bodies have issued official statements endorsing and concurring with the findings of the IPCC.
Joint science academies' statement of 2001. "The work of the Intergovernmental Panel on Climate Change (IPCC) represents the consensus of the international scientific community
on climate change science. We recognise IPCC as the world's most
reliable source of information on climate change and its causes, and we
endorse its method of achieving this consensus".
Canadian Foundation for Climate and Atmospheric Sciences.
"We concur with the climate science assessment of the Intergovernmental
Panel on Climate Change (IPCC) in 2001 ... We endorse the conclusions
of the IPCC assessment..."
Canadian Meteorological and Oceanographic Society.
"CMOS endorses the process of periodic climate science assessment
carried out by the Intergovernmental Panel on Climate Change and
supports the conclusion, in its Third Assessment Report, which states that the balance of evidence suggests a discernible human influence on global climate."
European Geosciences Union.
"The Intergovernmental Panel on Climate Change [...] is the main
representative of the global scientific community [...][The] IPCC third
assessment report [...] represents the state-of-the-art of climate
science supported by the major science academies around the world and by
the vast majority of scientific researchers and investigations as
documented by the peer-reviewed scientific literature".
International Council for Science (ICSU). "...the IPCC 4th Assessment Report
represents the most comprehensive international scientific assessment
ever conducted. This assessment reflects the current collective
knowledge on the climate system, its evolution to date, and its
anticipated future development".
National Oceanic and Atmospheric Administration
(USA). "Internationally, the Intergovernmental Panel on Climate Change
(IPCC)... is the most senior and authoritative body providing scientific
advice to global policy makers".
United States National Research Council. "The IPCC Third Assessment Report']
conclusion that most of the observed warming of the last 50 years is
likely to have been due to the increase in greenhouse gas concentrations
accurately reflects the current thinking of the scientific community on
this issue".
Network of African Science Academies.
"The IPCC should be congratulated for the contribution it has made to
public understanding of the nexus that exists between energy, climate
and sustainability".
Stratigraphy Commission of the Geological Society of London.
"The most authoritative assessment of climate change in the near future
is provided by the Inter-Governmental Panel for Climate Change".
