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Factcheck: Is the Arctic 3-5C warming up now "locked"?



A a new UN report on the environment The Arctic was published last week, which covered a wide range of changes in the region, climate, environment, wildlife and epidemiology.

Following Press release focused on a part of the climate change report. He warned, "even if it is Paris Agreement goals are met, winter temperatures in the Arctic will increase by 3-5C by 2050 compared to the levels from 1986-2005.

The report is covered with numerous news, including news guardian, Vired, hill, CBC i the second. Media coverage focused on the idea – promoted in a press release – that a large amount of Arctic warming was "locked", "inevitable" or "inevitable."

However, the Carbon Brief investigation has found that part of the climate change report incorrectly combines the goal of the Paris Agreement – limiting heating to "Well below" 2C by the end of the century compared to pre-industrial levels – with a scenario that has a much more modest reduction in emissions that results in around 3C global warming.

In climatic models that use a scenario that limits global warming below 2C, the Arctic is still warming faster than the rest of the world. However, future winter heating in the Arctic will be about 0.5-5 ° C until the 2080s compared to the levels of 1986-2005, much lower than the 5-9C values ​​reported in the report.

This means that much of the future warming in the Arctic will depend on our shows in the 21st century, instead of being "locked", according to the report.

Incorrect paragraph

The UN Environment Report called "Global Connections: A Graphic View of the Variable Arctic". It provides a short, affordable and intensive view of the many different areas in which the Arctic has changed over the past decades and can change in the future.

Part of the report dealing with arctic temperatures – just two pages – is no new research. Instead, he summarizes the findings from several recent, more technical studies. Future temperature projections, which were in the focus of press releases and media coverage, are contained in one paragraph of the report:

"The warmer temperatures in the Arctic resulted in a record low in winter seaweed between 2015-2018.Overland et al., 2018). Indeed, according to the mid- or high-emission scenario, predicted temperature changes for the Arctic will follow the winter warming trend at least twice as high as for the northern hemisphere (AMAP 2017a). This means that even if countries manage to reduce greenhouse gas emissions to the goals set out in the Paris Agreement on Climate Change of 2015, winter temperatures in the Arctic will continue to be 3 to 5C higher by 2050 and 5 to 9C higher by 2080, compared to the 1986-2005 level. In fact, even if we stop all emissions overnight, winter temperatures in the Arctic will still increase by 4 to 5C compared to the end of the twentieth century. This increase is associated with the climate system already emitted GHG and ocean heat accumulation (AMAP 2017a). "

However, this paragraph contains a number of vague statements and mistakes that undermine the message that large amounts of future Arctic heating are "locked into the climate system".

Although the first two sentences are correct, the problems begin in the third, when the report claims that the fulfillment of the objectives of the Paris Agreement would continue to result in winter warming of the Arctic from 3-5C to 2050 and 5-9C to 2080, in relation to the levels of 1986-2005 .

The reference for these numbers is 2017 Report on the Arctic Monitoring and Assessment Program (AMAP). The AMAP report for 2017 states:

"Through the Arctic Ocean, which is in some ice-free models in early winters and is covered by thin sea ice during the late winter, warming is from 3 to 5 ° C until the middle of the century and 5-9 ° C until the end of the century under RCP4.5."

The UN Environment Report reduces references to the Arctic Ocean, citing these warming projections as "winter temperatures in the Arctic" – a much larger area of ​​the Earth than just an area above the Arctic Ocean. The actual heating in RCP4.5 for the entire Arctic (between 60N and 90N) in the AMAP report for 2017 is slightly lower: around 3.8-7.8C in the 2080s. There is another minor problem in which the new report gives specific years (2050 and 2080), while the report on AMAP 2017 actually uses the periods from 2050 to 2059 and 2080-2089.

Vocabulary

RCP4.5: RCPs (representative concentration paths) are scenarios of future concentrations of greenhouse gases and other sources of energy. RCP4.5 is a "stabilization scenario" in which policies are set up so that atmospheric levels of CO2 concentration … Read more

The biggest problem with the paragraph comes when linking the AMAP warm-up number 2017 – referring to the RCP4.5 scenario – with the "goals set out in the Paris Agreement on Climate Change of 2015".

In the Paris Agreement, countries have set themselves the goal of limiting heating "far below" 2C, with an aspiration target of limiting heating below 1.5C. However, the 2017 AMAP report examines only two scenarios of future emissions: the RCP8.5 very high-emission scenario, where the world experiences more than 4C warming; and RCP4.5 for the mid-emission, where the world experiences a 3C warming up compared to pre-industrial levels by the end of the century.

Vocabulary

RCP2.6: RCPs (representative concentration paths) are scenarios of future concentrations of greenhouse gases and other sources of energy. RCP2.6 (sometimes referred to as "RCP3-PD") is a scenario of "climax and decline" in which strict mitigation … Read More

In order for countries to meet the goal of the Paris Heat Restructuring Agreement to "significantly below" 2C, global emissions would in fact follow the RCP2.6 scenario (or reduce emissions) even faster to limit heating to 1.5C). Although RCP2.6 still sees some additional warming of the Arctic, it is much smaller than the number in the report.

The picture below shows winter warming in the Arctic of all CMIP5 climate models used in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report for the RCP2.6 script. Black lines show the average of all models, the dark area shows a range in which two thirds of the model falls ( one sigma range), and the light region shows a range covering 95% of the model model ( two-sigma range).

The RCP2.6 climatic model ranges from CMIP5 to the region between 60N and 90N for winter months (December, January and February) for 32 different climate models that provide RCP2.6 (one run per model). Data on the model obtained from the KNMI Climate Explorer.

In the scenario where the goal of the Paris Agreement was reached, the actual winter heating projected for the Arctic is 0.8-4.5C of the 2050s and 0.5-5C 2080s relative to the levels 1986-2005 (the next approach used in the AMAP report for 2017 one sigma range). Multiple models show 2.8C warming up in the 2050s and 2080s, as the decline in global emissions limits further warming after mid-century.

A statement in the report that "even if we stop all emissions overnight, the winter temperatures in the Arctic will still increase by 4C to 5C compared to the end of the twentieth century" is confusing because they do not appear anywhere in the 2017 AMAP report cites.

Confusingly, the UN Environment Report argues that reducing emissions to zero will immediately lead to more warming than it does in climatic models using the RCP2.6 scenario – a zero-emission scenario around 2080. Carbon Brief spoke to numerous climatologists, all of whom expressed confusion over what could be the basis for this claim. Carbon Brief requested a response from the UN Environment and Reporting Authority, but did not receive any messages before publication. (This article will be updated to include any response.)

According on analysis contained in the newer one IPCC Special Report on 1.5CReducing all emissions of greenhouse gases and aerosols to zero would immediately result in a modest short-term drop in global temperatures of about 0.15C, as the Earth's cooling airs would disappear, followed by a fall. About 20 years after the emissions went to zero, global temperatures would fall below current levels and then cooled by about 0.25 ° C to 2100. While the reduction in aerosols could have a greater impact on warming in the Arctic compared to other regions, additional long-term heating from 4C to 5C seems unlikely.

It's not locked

Why could the report link the 3C global warming scenario (RCP4.5) with the aim of the Paris Agreement (RCP2.6)? The real obligations that countries have signed in the Paris Agreement – nationally determined contributions (NDCs) – they fall short what would be needed to fulfill the Paris goal. If the countries just take these actions – and not ratchet up their obligations after the completion of the Paris Binding Period by 2030 – studies indicate that the world will be on its way slightly more than 3C heating, but to a large extent it depends on the assumptions about emissions between 2030 and 2100.

However, even if the report wants to say "warming that imply existing obligations from Paris" and not "Paris targets," the press release and subsequent media coverage are still misleading. Unless the authors claim that the world as a whole has already been closed in 3C warming – and there are many scenarios which will maintain a global warming below 2C, or even 1.5C warming – the amount of future warming that will occur in the Arctic during the 21st century will largely depend on our future emissions.

The lower figure shows the Arctic winter warming compared to 1986-2005 from the average of all climate models of the IPCC CMIP5 for each future RCP emission scenario. There is a wide range of potential future warming, from just 2.7C to 2100 in RCP2.6 to as much as 12C in RCP8.5. Which of these future heating scenarios will largely depend on our emissions of greenhouse gases in the rest of the 21st century.

CMIP5 Multimodel means for each RCP scenario for a region between 60N and 90N for winter months (December, January and February). Data on the model obtained from the KNMI Climate Explorer.

If the world actually fulfills the Paris target limit of heating below 2C, the future winter warming of the Arctic will be about 0.5-5C, which is much less than 5-9C values ​​reported in the report.

There is still a wide range of possible outcomes for the region. As a result, any claim that huge amounts of future heating for the region are "locked" is wrong.

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