Special Report on Global Warming of 1.5 °C

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https://en.wikipedia.org/wiki/Special_Report_on_Global_Warming_of_1.5_%C2%B0C 

Intergovernmental Panel on Climate Change
IPCC Assessment Reports:
First (1990)
1992 supplementary report
Second (1995)
Third (2001)
Fourth (2007)
Fifth (2014)
Sixth (2022)
IPCC Special Reports:
Emissions Scenarios (2000)
Renewable energy sources (2012)
Extreme events and disasters (2012)
Global Warming of 1.5 °C (2018)
Climate Change & Land (2019)
Ocean & Cryosphere (2019)
UNFCCC | WMO | UNEP

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

Cover of the Special Report on Global Warming of 1.5 °C

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 and 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 50% and 66% 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 Gt CO₂eq 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 year, 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.

(*) Non-CO₂ emissions included in this Report are all anthropogenic emissions other than CO₂ that result in radiative forcing. These include short-lived climate forcers, such as methane, some fluorinated gases, ozone precursors, aerosols or aerosol precursors, such as black carbon and sulphur dioxide, respectively, as well as long-lived greenhouse gases, such as nitrous oxide or some fluorinated gases. The radiative forcing associated with non-CO₂ emissions and changes in surface albedo is referred to as non-CO₂ radiative forcing.

Pathways to 1.5 °C

Various pathways are considered, describing scenarios for mitigation of global warming, including portfolios for energy supply and negative emission technologies (like afforestation or carbon dioxide removal).

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

P1	P2	P3	P4
A scenario with low energy demand (LED)	S1, based on SSP1	S2, based on SSP2	S5, based on SSP5
Grubler et al., 2018	Shared Socio-Economic Pathway 1 (SSP1: Sustainable development)	Shared Socio-Economic Pathway 2 (SSP2: Middle of the road)	Shared Socio-Economic Pathway 5 (SSP5: Fossil-fuelled development)

Carbon dioxide removal

The emission pathways that reach 1.5 °C contained in the report assume the use of carbon dioxide removal (CDR) to offset for remaining emissions. Pathways that overshoot the goal rely on CDR to remove carbon dioxide at a rate that exceeds 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. The report highlights a CDR technology called 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.

Solar radiation management

The report describes several proposals for solar radiation management (SRM). It concludes that SRMs have potential to limit warming, but "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." 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".

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 depleted ozone 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 Politics Andrew 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).

Other

The "Special Report on Global Warming of 1.5 °C" (SR15) is cited by Greta Thunberg in her speeches "Wherever I Go I Seem to Be Surrounded by Fairy Tales" (United States Congress, Washington DC, 18 September 2019) and "We Are the Change and Change Is Coming" (Week For Future, Climate Strike, Montreal, 27 September 2019), both published in the second edition of No One Is Too Small to Make a Difference.

At the 2019 World Economic Forum, the head of the International Monetary Fund, Kristalina Georgieva, said that: "The big eye opener [into climate change and its effects] was when last year I read [the SR15] IPCC report. I tell you, I could not sleep that night. [...] What have we done?".

IPCC Fifth Assessment Report

From Wikipedia, the free encyclopedia

Intergovernmental Panel on Climate Change
IPCC Assessment Reports:
First (1990)
1992 supplementary report
Second (1995)
Third (2001)
Fourth (2007)
Fifth (2014)
Sixth (2022)
IPCC Special Reports:
Emissions Scenarios (2000)
Renewable energy sources (2012)
Extreme events and disasters (2012)
Global Warming of 1.5 °C (2018)
Climate Change & Land (2019)
Ocean & Cryosphere (2019)
UNFCCC | WMO | UNEP

The Fifth Assessment Report (AR5) of the United Nations Intergovernmental Panel on Climate Change (IPCC) is the fifth in a series of such reports. The IPCC was established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess scientific, technical and socio-economic information concerning climate change, its potential effects and options for adaptation and mitigation.

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 Conference in Paris during late 2015.

Current status

Global Emissions by Economic Sector

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
• AR5 Synthesis Report (SYR) – 2 November 2014

The AR5 provides an update of knowledge on the scientific, technical and socio-economic aspects of climate change.

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

Play media

This video presents projections of 21st century temperature and precipitation patterns based on a buildup of greenhouse gases with a combined effect equivalent to 650ppm of atmospheric CO
2, a scenario the IPCC called "RCP4.5". The changes shown compare the model projections to the average temperature and precipitation benchmarks observed from 1971–2000.

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.

In August 2020 scientists reported that observed ice-sheet losses in Greenland and Antarctica track worst case scenarios of the IPCC Fifth Assessment Report's sea-level rise projections.

Other

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.

Current documents

• Working Group I: Landing page – Full report – Summary for Policymakers – Technical Summary – Headline Statements from the Summary for Policymakers
• Working Group II: Landing page – Full report, Part A, Full report, Part B – Summary for Policymakers – Technical Summary
• Working Group III: Landing page – Full report – Summary for Policymakers – Technical Summary
• Synthesis Report: Landing page – Full report – Summary for Policymakers – Headline statements from the Summary for Policymakers

Condensed versions

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:

• The IPCC's Fifth Assessment Report: What's in it for Small Islands Developing States?
• The IPCC's Fifth Assessment Report: What's in it for South Asia?
• The IPCC's Fifth Assessment Report: What's in it for Africa?
• The IPCC's Fifth Assessment Report: What's in it for Latin America?

Special Report on Global Warming of 1.5 °C

Main article: Special Report on Global Warming of 1.5 °C

The IPCC published their "Special Report on Global Warming of 1.5 °C" on October 8, 2018.

Paris Agreement

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Paris_Agreement 

Paris Agreement under the United Nations Framework Convention on Climate Change

State parties   Signatories   Parties also covered by European Union ratification   Agreement does not apply
Drafted	30 November – 12 December 2015 in Le Bourget, France
Signed	22 April 2016
Location	Paris, France
Effective	4 November 2016
Condition	Ratification and accession by 55 UNFCCC parties, accounting for 55% of global greenhouse gas emissions
Signatories	195
Parties	191
Depositary	Secretary-General of the United Nations
Languages	Arabic, Chinese, English, French, Russian, and Spanish

The Paris Agreement (French: l'accord de Paris) is an agreement within the United Nations Framework Convention on Climate Change (UNFCCC), on climate change mitigation, adaptation, and finance, signed in 2016. The agreement's language was negotiated by representatives of 196 state parties at the 21st Conference of the Parties of the UNFCCC in Le Bourget, near Paris, France, and adopted by consensus on 12 December 2015. As of March 2021, 191 members of the UNFCCC are parties to the agreement. Of the six UNFCCC member states which have not ratified the agreement, the only major emitters are Iran, Iraq and Turkey, though Iraq's president has approved that country's accession. The United States withdrew from the agreement in 2020, but rejoined in 2021.

The Paris Agreement's long-term temperature goal is to keep the rise in global average temperature to well below 2 °C (3.6 °F) above pre-industrial levels; and to pursue efforts to limit the increase to 1.5 °C (2.7 °F), recognizing that this would substantially reduce the risks and impacts of climate change. This should be done by reducing emissions as soon as possible, in order to "achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases" in the second half of the 21st century. It also aims to increase the ability of parties to adapt to the adverse impacts of climate change, and make "finance flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development."

Under the Paris Agreement, each country must determine, plan, and regularly report on the contribution that it undertakes to mitigate global warming. No mechanism forces a country to set a specific emissions target by a specific date, but each target should go beyond previously set targets. In contrast to the 1997 Kyoto Protocol, the distinction between developed and developing countries is blurred, so that the latter also have to submit plans for emission reductions.

History

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Paris Agreement negotiations

The Paris Agreement was opened for signature on 22 April 2016 (Earth Day) at a ceremony in New York. After the European Union ratified the agreement in October 2016, there were enough countries that had ratified the agreement that produce enough of the world's greenhouse gases for the agreement to enter into force. The agreement went into effect on 4 November 2016.

Lead-up

The Kyoto Protocol, adopted in 1997, regulated greenhouse gas reductions for a limited set of countries from 2008 to 2012. The protocol was extended until 2020 with the Doha Amendment in 2012. The United States decided not to ratify the Protocol, mainly because of its legally-binding nature. This, and distributional conflict, led to failures of subsequent international climate negotiations. The 2009 round of negotiations were intended to produce a successor treaty of Kyoto, but the resulting Copenhagen Accord was not legally binding and did not get adopted universally.

The Accord did lay the framework for bottom-up approach of what would become the Paris Agreement. Under the leadership of UNFCCC executive secretary Christiana Figueres, negotiation regained momentum after Copenhagen's failure. During the 2011 United Nations Climate Change Conference, the Durban Platform was established with the aim to negotiate a legal instrument governing climate change mitigation measures from 2020. The resulting agreement was to be adopted in 2015.

Adoption

Heads of delegations at the 2015 United Nations Climate Change Conference in Paris.

At the conclusion of COP21 (the 21st meeting of the Conference of the Parties, which guides the Conference), on 12 December 2015, the final wording of the Paris Agreement was adopted by consensus by all of the 195 UNFCCC participating member states and the European Union to reduce emissions as part of the method for reducing greenhouse gas. In the 12-page Agreement, the members promised to reduce their carbon output "as soon as possible" and to do their best to keep global warming "to well below 2 °C" [3.6 °F].

Signing and entry into force

The Paris Agreement was open for signature by states and regional economic integration organizations that are parties to the UNFCCC (the Convention) from 22 April 2016 to 21 April 2017 at the UN Headquarters in New York. Signing of the Agreement is the first step towards ratification , but it is possible to acceed to the agreement without signing. It binds parties to not act in contravention of the goal of the treaty. On 1 April 2016, the United States and China, which together represent almost 40% of global emissions, issued a joint statement confirming that both countries would sign the Paris Climate Agreement. The agreement was signed by 175 Parties (174 states and the European Union) on the first day it was opened for signature. As of March 2021, 194 states and the European Union have signed the Agreement.

Signing by John Kerry in United Nations General Assembly Hall for the United States

The agreement would enter into force (and thus become fully effective) if 55 countries that produce at least 55% of the world's greenhouse gas emissions (according to a list produced in 2015) ratify the treaty, by "acceptance, approval or accession". With ratification by the European Union, the Agreement obtained enough parties to enter into effect on 4 November 2016.

Both the EU and its member states are individually responsible for ratifying the Paris Agreement. A strong preference was reported that the EU and its 28 member states deposit their instruments of ratification at the same time to ensure that neither the EU nor its member states engage themselves to fulfilling obligations that strictly belong to the other, and there were fears that disagreement over each individual member state's share of the EU-wide reduction target, as well as Britain's vote to leave the EU might delay the Paris pact. However, the EU deposited its instruments of ratification on 5 October 2016, along with several individual EU member states.

Parties

The Indian Prime Minister, Narendra Modi greeting the President of Brazil, Dilma Rousseff, at the COP21 Summit on November 30, 2015

The EU and 190 states, have ratified or acceded to the Agreement, including China and India, the countries with the 1st and 3rd largest CO₂ emissions among UNFCCC members. As of January 2021 greenhouse gas emissions by Iran and by Turkey are both over 1% of the world total. Eritrea, Iraq, Libya and Yemen are the only other countries which have never ratified the agreement. Iraq is planning to ratify the Agreement after a parliamentary vote in favour in September 2020.

Article 28 of the agreement enables parties to withdraw from the agreement after sending a withdrawal notification to the depositary. Notice can be given no earlier than three years after the agreement goes into force for the country. Withdrawal is effective one year after the depositary is notified.

United States withdrawal and readmittance

On August 4, 2017, the Trump administration delivered an official notice to the United Nations that the United States, the second largest emitter of greenhouse gasses in the world, intends to withdraw from the Paris Agreement as soon as it was legally eligible to do so. The formal notice of withdrawal could not be submitted until the agreement was in force for three years for the US, on November 4, 2019. On November 4, 2019, the US government deposited the withdrawal notification with the Secretary General of the United Nations, the depositary of the agreement, and officially withdrew from the Paris climate accord one year later when the withdrawal became effective.

Joe Biden signed an executive order on his first day in office, January 20, 2021, to re-admit the United States into the Paris Agreement. Following the 30-day period set by Article 21.3, the US was readmitted to the Agreement on February 19, 2021. United States Climate Envoy John Kerry took part in virtual events, saying that the US would "earn its way back" into legitimacy in the Paris process. United Nations Secretary-General António Guterres welcomed the return of the United States as restoring the “missing link that weakened the whole."

Content

Aims

The aim of the agreement, as described in its Article 2, is to have a stronger response to the danger of climate change; it seeks to enhance the implementation of the United Nations Framework Convention on Climate Change (UNFCCC) through:

(a) Holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change;

(b) Increasing the ability to adapt to the adverse impacts of climate change and foster climate resilience and low greenhouse gas emissions development, in a manner that does not threaten food production;

(c) Making finance flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development.

Countries furthermore aim to reach "global peaking of greenhouse gas emissions as soon as possible."

Nationally determined contributions

Since 2000, rising CO
2 emissions in China and the rest of world have surpassed the output of the United States and Europe.

 

Per person, the United States generates CO
2 at a far faster rate than other primary regions.

The contributions each country should make to achieve the worldwide goal are determined by that country and are therefore called nationally determined contributions (NDCs). Article 3 requires NDCs to be "ambitious efforts" towards "achieving the purpose of this Agreement" and to "represent a progression over time". The contributions should be set every five years and are to be registered by the UNFCCC Secretariat. Each further ambition should be more ambitious than the previous one, known as the principle of 'progression'. Countries can cooperate and pool their nationally determined contributions. The Intended Nationally Determined Contributions pledged during the 2015 Climate Change Conference are converted to NDCs when a country ratifies the Paris Agreement, unless they submit an update.

The Paris Agreement does not set in stone the nature of the NDCs. At a minimum, they should contain mitigation provisions, but they may also contain pledges on adaptation, finance, technology transfer, capacity building and transparency. Some of the pledges in the NDCs are unconditional, but parties have made other conditional on outside factors such as getting finance and technical support, the level of ambition from other parties or the details of rules of the Paris Agreement that are yet to be set. Most NDCs have a conditinal component.

While the NDCs themselves are not binding, the procedures surrounding them are (setting a more ambitious NDC every five years). There is no mechanism to force a country to set a target in their NDC by a specific date and no enforcement if a set target in an NDC is not met. There will be only a "name and shame" system or as János Pásztor, the U.N. assistant secretary-general on climate change, stated, a "name and encourage" plan. Reporting is called the "Enhanced Transparency Framework (ETF)" and parties to the agreement send their first Biennial Transparency Report (BTR), and greenhouse gas inventory figures in standard format, to the UNFCCC by 2024 and every two years after that (developed countries submit their first BTR in 2022 and inventories annually from that year).

Global stocktake

Under the Paris Agreement, countries must increase their ambition every five years. To facilitate this, the Agreement established the Global Stocktake, which assesses progress, with the first evaluation in 2023. The outcome is to be used as input for new nationally determined contributions of parties. The Talanoa Dialogue in 2018 was seen as an example for the global stocktake. After a year of discussion, a report was published and there was a call for action, but countries did not increase ambition afterwards.

The stocktake works as part of the Paris Agreement's effort to create a "ratcheting up" of ambition in emissions cuts. Because analysts agreed in 2014 that the NDCs would not limit rising temperatures below 2 degrees Celsius, the global stocktake reconvenes parties to assess how their new NDCs must evolve so that they continually reflect a country's "highest possible ambition". While ratcheting up the ambition of NDCs is a major aim of the global stocktake, it assesses efforts beyond mitigation. The 5-year reviews will also evaluate adaptation, climate finance provisions, and technology development and transfer.

Structure

The Paris Agreement has a 'bottom up' structure in contrast to most international environmental law treaties, which are 'top down', characterized by standards and targets set internationally, for states to implement. Unlike its predecessor, the Kyoto Protocol, which sets commitment targets that have legal force, the Paris Agreement, with its emphasis on consensus building, allows for voluntary and nationally determined targets. The specific climate goals are thus politically encouraged, rather than legally bound. Only the processes governing the reporting and review of these goals are mandated under international law. This structure is especially notable for the United States—because there are no legal mitigation or finance targets, the agreement is considered an "executive agreement rather than a treaty". Because the UNFCCC treaty of 1992 received the consent of the US Senate, this new agreement does not require further legislation from Congress.

Another key difference between the Paris Agreement and the Kyoto Protocol is their scope. While the Kyoto Protocol differentiated between Annex-1 and non-Annex-1 countries, this division is blurred in the Paris Agreement, as all parties are required to submit emissions reductions plans. The Paris Agreement still emphasizes the principle of "Common but Differentiated Responsibility and Respective Capabilities"—the acknowledgement that different nations have different capacities and duties to climate action—but it does not provide a specific division between developed and developing nations.

Mitigation provisions and carbon markets

Article 6 has been flagged as containing some of the key provisions of the Paris Agreement. Broadly, it outlines the cooperative approaches that parties can take in achieving their nationally determined carbon emissions reductions. In doing so, it helps establish the Paris Agreement as a framework for a global carbon market. Article 6 is the last part of the Agreement that needs to be ironed out; negotiations in 2019 did not produce a result. The topic is now expected to be ironed out during the 2021 negotiations in Glasgow.

Linkage of carbon trading systems

Paragraphs 6.2 and 6.3 establish a framework to govern the international transfer of mitigation outcomes (ITMOs). The Agreement recognizes the rights of Parties to use emissions reductions outside of their own jurisdiction toward their NDC, in a system of carbon accounting and trading. This provision requires the "linkage" of various carbon emissions trading systems—because measured emissions reductions must avoid "double counting", transferred mitigation outcomes must be recorded as a gain of emission units for one party and a reduction of emission units for the other. Because the NDCs, and domestic carbon trading schemes, are heterogeneous, the ITMOs will provide a format for global linkage under the auspices of the UNFCCC. The provision thus also creates a pressure for countries to adopt emissions management systems—if a country wants to use more cost-effective cooperative approaches to achieve their NDCs, they will need to monitor carbon units for their economies.

Sustainable Development Mechanism

Paragraphs 6.4-6.7 establish a mechanism "to contribute to the mitigation of greenhouse gases and support sustainable development". Though there is no official name for the mechanism as yet, it has been referred to as the Sustainable Development Mechanism or SDM. The SDM is considered to be the successor to the Clean Development Mechanism, a mechanism under the Kyoto Protocol by which parties could collaboratively pursue emissions reductions.

In its basic aim, the SDM will largely resemble the Clean Development Mechanism, with the dual mission of contributing to global GHG emissions reductions and supporting sustainable development. Though the structure and processes governing the SDM are not yet determined, certain similarities and differences from the Clean Development Mechanisms can already be seen. Notably, the SDM, unlike the Clean Development Mechanism, will be available to all parties as opposed to only Annex-1 parties, making it much wider in scope.

The Clean Development Mechanism of the Kyoto Protocol was criticized for failing to produce either meaningful emissions reductions or sustainable development benefits in most instances. It has also suffered from the low price of Certified Emissions Reductions (CERs), creating less demand for projects. These criticisms have motivated the recommendations of various stakeholders, who have provided through working groups and reports, new elements they hope to see in SDM that will bolster its success.

Adaptation provisions

Adaptation issues garnered more focus in the formation of the Paris Agreement. Collective, long-term adaptation goals are included in the Agreement, and countries must report on their adaptation actions, making adaptation a parallel component of the agreement with mitigation. The adaptation goals focus on enhancing adaptive capacity, increasing resilience, and limiting vulnerability.

Ensuring finance

Pledges to the Green Climate Fund in 2018

At the Paris Conference in 2015 where the Agreement was negotiated, the developed countries reaffirmed the commitment to mobilize $100 billion a year in climate finance by 2020, and agreed to continue mobilizing finance at the level of $100 billion a year until 2025. The money is for supporting mitigation and adaptation in developing countries. The money includes funds for the Green Climate Fund, which is a part of the UNFCCC, but also a variety of other public and private pledges. The Paris Agreement states that a new commitment of at leas $100 billion per year has to be agreed before 2025.

Though both mitigation and adaptation require increased climate financing, adaptation has typically received lower levels of support and has mobilized less action from the private sector. A report by the OECD found that just 16 percent of global climate finance was directed toward climate adaptation in 2013–2014. The Paris Agreement called for a balance of climate finance between adaptation and mitigation, and specifically underscored the need to increase adaptation support for parties most vulnerable to the effects of climate change, including Least developed countries and Small Island Developing States. The agreement also reminds parties of the importance of public grants, because adaptation measures receive less investment from the public sector.

Some specific outcomes of the elevated attention to adaptation financing in Paris include the G7 countries' announcement to provide US$420 million for climate risk insurance, and the launching of a Climate Risk and Early Warning Systems (CREWS) Initiative. The largest donors to multilateral climate funds, which includes the Green Climate Fund, are the Unites States, the United Kingdom, Japan, Germany, France and Sweden.

Loss and damage

A new issue that emerged as a focal point in the Paris negotiations rose from the fact that many of the worst effects of climate change will be too severe or come too quickly to be avoided by adaptation measures. The Paris Agreement specifically acknowledges the need to address loss and damage of this kind, and aims to find appropriate responses. It specifies that loss and damage can take various forms—both as immediate impacts from extreme weather events, and slow-onset impacts, such as the loss of land to sea level rise for low-lying islands.

The push to address loss and damage as a distinct issue in the Paris Agreement came from the Alliance of Small Island States and the Least Developed Countries, whose economies and livelihoods are most vulnerable to the negative impacts of climate change. The Warsaw Mechanism, established two years earlier, categorized loss and damage as a subset of adaptation, which was unpopular with many countries. It was recognized as a separate pillar within the Paris Agreement. The United States argued against this, possibly worried that classifying the issue as separate from adaptation would create yet another climate finance provision.

In the end, all parties acknowledged the need for "averting, minimizing, and addressing loss and damage" but the text specifies that it cannot be used as the basis for liability. The agreement also adopts the Warsaw International Mechanism, an institution that will attempt to address questions about how to classify, address, and share responsibility for loss.

Enhanced transparency framework

While each Party's NDC is not legally binding, the Parties are legally bound to have their progress tracked by technical expert review to assess achievement toward the NDC, and to determine ways to strengthen ambition. Article 13 of the Paris Agreement articulates an "enhanced transparency framework for action and support" that establishes harmonized monitoring, reporting, and verification (MRV) requirements. Thus, both developed and developing nations must report every two years on their mitigation efforts, and all parties will be subject to both technical and peer review.

While the enhanced transparency framework is universal, along with the global stocktaking to occur every 5 years, the framework is meant to provide "built-in flexibility" to distinguish between developed and developing countries' capacities. In conjunction with this, the Paris Agreement has provisions for an enhanced framework for capacity building. The agreement recognizes the varying circumstances of some countries, and specifically notes that the technical expert review for each country consider that country's specific capacity for reporting. The agreement also develops a Capacity-Building Initiative for Transparency to assist developing countries in building the necessary institutions and processes for complying with the transparency framework.

There are several ways that flexibility mechanisms can be incorporated into the enhanced transparency framework. The scope, level of detail, or frequency of reporting may all be adjusted and tiered based on a country's capacity. The requirement for in-country technical reviews could be lifted for some less developed or small island developing countries. Ways to assess capacity include financial and human resources in a country necessary for NDC review.

Implementation and effectiveness

The process of translating the Paris Agreement into national agendas and implementation has started. One example is the commitment of the least developed countries (LDCs). The LDC Renewable Energy and Energy Efficiency Initiative for Sustainable Development, known as LDC REEEI, is set to bring sustainable, clean energy to millions of energy-starved people in LDCs, facilitating improved energy access, the creation of jobs and contributing to the achievement of the Sustainable Development Goals.

There are various barriers to implementing the Agreement. Some countries struggle to attract the finance often considered necessary for investments in decarbonisation. Climate finance is fragmented, further complicating investments. Another issue is the lack of capabilities within government and other institutions to implement policy. Clean technology and knowledge is often not transferred to countries or places that need it. In December 2020, the former chair of the COP 21, Laurent Fabius, argued that the implementation of the Paris Agreement could be bolstered by the adoption of a Global Pact for the Environment. The latter would define the environmental rights and duties of States, individuals and businesses. This project is currently under discussion at the United Nations.

In 2021, a study using a fully statistical probabilistic model concluded that the rates of emissions reductions need to increase by 80% beyond NDCs to likely meet the 2 °C upper target range of Earth's Paris Agreement, that the probabilities of major emitters meeting their NDCs without such an increase is very low, estimating that with current trends the probability of staying below 2 °C of warming is 5% – and if NDCs were met and continued post-2030 by all signatory systems 26%.

Effect on temperatures

Scenarios of global greenhouse gas emissions. If all countries achieve their current Paris Agreement pledges, average warming by 2100 would still significantly exceed the maximum 2°C target set by the Agreement.

The negotiators of the agreement stated that the "Intended Nationally Determined Contributions" (as NDCs were referred to at the time of the negotiations) presented at the time of the Paris Conference were insufficient, noting "with concern that the estimated aggregate greenhouse gas emission levels in 2025 and 2030 resulting from the intended nationally determined contributions do not fall within least-cost 2 °C scenarios but rather lead to a projected level of 55 gigatonnes in 2030", and recognizing furthermore "that much greater emission reduction efforts will be required in order to hold the increase in the global average temperature to below 2 °C by reducing emissions to 40 gigatonnes or to 1.5 °C."

In July 2020 the World Meteorological Organisation (WMO) announced that it assesses the chance of exceeding 1.5 °C around 20% in at least one year between 2020 and 2024.

An April 2020 study showed that implementation of current policies leaves a median emission gap of 22.4 to 28.2 GtCO₂eq by 2030 with the "optimal" pathways to implement the well below 2 °C and 1.5 °C Paris goals. If Nationally Determined Contributions were to be fully implemented, this gap would be reduced by a third. The countries evaluated were found to not achieve their pledged contributions with implemented policies (implementation gap), or to have an ambition gap with optimal pathways towards well below 2 °C. The study showed that all countries would need to accelerate the implementation of policies for renewable technologies, while efficiency improvements are especially important in emerging countries and fossil-fuel-dependent countries.

None of the major industrialized emitters meet target

How well each individual country is on track to achieving its Paris agreement commitments is monitored through the Climate Change Performance Index, Climate Action Tracker and the Climate Clock.

A pair of studies in Nature found that as of 2017 none of the major industrialized nations were implementing the policies they had pledged, and none met their pledged emission reduction targets, and even if they had, the sum of all member pledges (as of 2016) would not keep global temperature rise "well below 2 °C".

According to the 2020 United Nations Environment Programme (UNEP), with the current climate commitments of the Paris Agreement, global mean temperatures will likely rise by more than 3 °C by the end of the 21st century. Newer net-zero commitments were not included in the NDCs, and may bring down temperatures a further 1.5 °C. To limit global temperature rise to 1.5 °C, a global emission reduction of 7.6% is needed every year between 2020 and 2030.

The four top emitters of greenhouse gasses, in decreasing order of annual emissions China, United States, EU27 and India, contributed over 55% of the world's total emissions over the last decade, excluding emissions from land-use change such as deforestation. Among these top four emitters, some have actually increased their annual emissions: China's emissions grew 1.6% in 2018 to reach a high of 13.7 Gt of CO2 equivalent. The U.S., which is responsible for 13% of global emissions, saw emissions rise by 2.5% in 2018. To meet the 1.5C target, by 2030 the U.S. would have to reduce its greenhouse gas emissions by at least 57–63% below 2005 levels, according to a report by Climate Change Tracker. The European Union emits 8.5% of global emissions, and has seen its emissions decline 1% every year across the last decade. EU emissions declined 1.3% in 2018. India's 7% of global emissions grew 5.5% in 2018.

International response

The agreement was lauded by many, including French President François Hollande and UN Secretary General Ban Ki-moon, but criticism has also surfaced. For example, James Hansen, a former NASA scientist and a climate change expert, voiced anger that most of the agreement consists of "promises" or aims and not firm commitments. He called the Paris talks a fraud with 'no action, just promises' and feels that only an across the board tax on CO
2 emissions, something not part of the Paris Agreement, would force CO
2 emissions down fast enough to avoid the worst effects of global warming. Institutional asset owners associations and think-tanks have also observed that the stated objectives of the Paris Agreement have also questioned whether pollutors will voluntarily control emissions.

When the agreement achieved enough signatures to cross the threshold on 5 October 2016, US President Barack Obama said that "Even if we meet every target ... we will only get to part of where we need to go." He also said that "this agreement will help delay or avoid some of the worst consequences of climate change. It will help other nations ratchet down their emissions over time, and set bolder targets as technology advances, all under a strong system of transparency that allows each nation to evaluate the progress of all other nations." The president of Brazil, Dilma Rousseff, called the agreement "balanced and long-lasting".