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Home / Science / Factcheck: Are 3-5 ° C of Arctic warming now "locked up"?

Factcheck: Are 3-5 ° C of Arctic warming now "locked up"?



Last week a new UN environmental report on the Arctic was published, covering a wide range of changes in the climate, environment, wildlife and epidemiology of the region. The related press release focused on the section of the report on climate change. It warned that "even if the goals of the Paris Agreement of 19659002 are achieved, temperatures in the Arctic will increase by 2050 by 2050 by 2050 compared to the values ​​of 1986-2005," and by 2080 to 5 9C will heat up.

The report has been covered by a number of news agencies, including Guardian Wired Hill CBC and and others ]. Media coverage focused on the idea promoted in the press release that large Arctic warming is "locked in," "inevitable," or "inevitable."

An investigation by Carbon Brief has revealed, however, that the Climate Change Report brings the goal of the Paris Agreement that warming up to the end of the century compared to pre-industrial levels "well below" 2C [1

9659002]combined with a scenario that has a much lower emission reductions, which lead to a global warming of about 3 ° C.

In climate model scenarios that limit global warming below 2 ° C, the Arctic is still warming faster than the rest of the world. Future winter warming in the Arctic will be around 0.5 to 5 ° C in the 2080s, compared to the years 1986-2005, which is much lower than the report's reported 5 to 9 ° C over our emissions in the year 21st century, instead of being "locked up" as the report claims.

Incorrect Paragraph

The UN Environmental Report is titled "Global Connections: A Graphical View of the Changing Arctic." It provides a concise, accessible, and infographic-rich insight into a number of different areas, including The Arctic has changed in recent decades and may change in the future.

The two-page section of the Arctic Temperature Report contains no recent research, but rather summarizes the results of a series of recent, more technical studies Future temperature forecasts, which were the focus of the press release and related media coverage, are contained in a single section of the report:

"Arctic warmer temperatures in 2015 led to a record low in the winter sea ice extent -2018 ([19659002] Overland et al., 2018 [19659026]). In a medium or high emission scenario, the expected temperature changes for the Arctic will follow a winter warming trend that is at least twice that of the northern hemisphere (AMAP 2017a). This means that winter temperatures in the Arctic will be 3 to 5 ° C higher by 2050 and 5 to 9 ° C by 2080 than in countries where countries manage to reduce their greenhouse gas emissions to those specified in the Paris Climate Change Agreement 2015 targets. 2005 levels. Even if we have stopped all emissions overnight, winter temperatures in the Arctic will still rise by 4 to 5 ° C compared to the end of the 20th century. This increase is linked to the climate system through the emission of greenhouse gases and the storage of heat storage in the ocean (AMAP 2017a). "

However, this paragraph contains a number of unclear statements and errors that undermine the claim that future Arctic warming will be large amounts. Included in the climate system.

While the first two sentences are correct, the problems in the third sentence begin when the report argues that the achievement of the objectives of the Paris Agreement still leads to an Arctic warming of 3-5 ° C by 2050 and by 5 9 ° C would result in 2080, compared to the levels of 1986-2005.

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

"Over the Arctic Ocean, which is ice-free in some models in early winter and covered in thin sea ice in late winter, mid-century warming is 3-5 ° C and 5 -9 ° C at the end of the last century under RCP4.5. "

The UN Environmental Report drops its reference to the Arctic Ocean, referring to these warming projections as" winter temperatures in the Arctic "- a much larger area of ​​the Earth than just the region above the Arctic Ocean. The actual warming in RCP4.5 for the entire Arctic (between 60N and 90N) in the 2017 AMAP report is slightly lower: it was 3.8-7.8 ° C in the 2080s new year (2050 and 2080), while the AMAP 2017 report actually uses the periods 2050-2059 and 2080-2089.

Glossary

RCP4.5: Representative Concentration Pathways (RCPs) are scenarios of future concentrations of greenhouse gases and other fuels. RCP4.5 is a "stabilization scenario" that establishes guidelines for determining CO2 levels in the atmosphere. Read more

The main problem with this paragraph is that it indicates the 2017 AMAP warming figures – which refer to the RCP4.5 scenario – with "those in the Paris Convention targets set for climate change in 2015 ".

In the Paris MOU, states have set a target to limit warming to well below 2 ° C, with the aim of limiting warming below 1.5 ° C. However, the AMAP 2017 report only takes into account two future emission scenarios: a very high-emission RCP8.5 scenario where the world experiences a warming in excess of 4 ° C; and a medium-emission RCP4.5 scenario, where the world experiences 3 ° C warming towards the pre-industrial level towards the end of the century.

Glossary

RCP2.6: Representative Concentration Pathways (RCPs) are scenarios of future concentrations of greenhouse gases and other fuels. RCP2.6 (sometimes referred to as "RCP3-PD") is a scenario of "peak and decline" in which severe mitigation … Read more

When countries reach the goal of In limiting warming to "well below" 2C, global emissions would actually follow an RCP2.6 scenario (or reduce emissions even faster to limit warming to 1.5C) , While RCP2.6 still has additional warming in the Arctic, it is much smaller than the number in the report.

The following figure shows winter warming in the Arctic of all CMIP5 climate models in the Intergovernmental Panel on Climate Change (IPCC) fifth assessment report for the RCP2.6 scenario. The black lines show the average of all models, the dark area shows the area where two-thirds of the models fall (the one-sigma area ), and the bright area shows the 95% range. the model runs (the two-sigma area ).

The RCP2.6 climate model runs from CMIP5 for the region between 60N and 90N for the winter months (December, January and February) for the 32 different climate models with RCP2.6 runs (one run per model). Model data obtained from KNMI Climate Explorer.

In a scenario in which the goal of the Paris Agreement is achieved, the winter warming planned for the Arctic is 0.8-4.5 ° C in the 2050s and 0.5-5C in the 2080s compared to 1986- 2005 levels (according to the AMAP approach used in 2017 to set one-sigma bandwidths). The mean of the multiple model shows a warming of 2.8 ° C in both the 2050s and 2080s, as the decline in global emissions after the middle of the century limits further warming in the Arctic compared to the end of the 20th century. Still rising by 4 to 5 ° C in the 20th century, "is puzzling, as it is nowhere to be found in the 2017 AMAP report.

Confusingly, the UN Environmental Report claims that emissions are reduced zero would immediately lead to higher levels of warming than climate models with the RCP2.6 scenario – a scenario where emissions will only reach zero by 2080 . Carbon Brief turned to a number of climate researchers who were all confused as to what could be the basis for this assertion. Carbon Brief asked UN Environment and the authors of the report for an answer, but did not receive an answer before publishing it. (This article is updated with each answer.)

According to an analysis included in the recent IPCC Special Report on 1.5C all human greenhouse gas emissions and emissions are reduced to zero aerosols would immediately lead to a moderate short-term increase in temperature around 0.15 ° C, as earth-cooling aerosols disappear, followed by a decline. About 20 years after emissions dropped to zero, global temperatures dropped below their current levels and cooled by about 0.25 ° C by 2100. While the reduction of aerosols in the Arctic could have a greater impact on warming than in other regions, additional long-term warming from 4 ° C to 5 ° C appears unlikely.

Not "Caged"

Why could the report link a global warming scenario of 3C (RCP4.5) to the Paris Agreement (RCP2.6)? The real commitments that countries have made in the Paris Agreement – Nationally Defined Contributions (NDCs) – – are far behind what would be required to achieve the Paris goal. If countries only take these measures – and not improve their commitments after the end of the Paris Commitment Period in 2030 – studies indicate that the world would have [3,959,002] a little more than 3C warming ] Also, how much of the assumptions related to emissions between 2030 and 2100 depends.

However, the report should also mean "the warming that results from the Paris Commitments" and not the "Paris targets", the press release and the following media coverage is still misleading. Unless the authors argue that the world as a whole is already bound to the warming of 3C – and there are a variety of scenarios that global warming is below 2 ° C or even at 1.5 ° C – The amount of future The warming that will occur in the Arctic during the 21st century will depend in large part on our future emissions.

The following figure shows the Arctic winter warming compared to 1986-2005 from the average of all IPCC-CMIP5 climate models for each future RCP emission scenario. There is a wide range of potential future warming, from 2.7 ° C in 2100 in RCP2.6 to 12 ° C in RCP8.5. Which of these future warming scenarios will occur depends largely on our greenhouse gas emissions in the remaining 21st century.

CMIP5 Multimodel means for each RCP scenario for the region between 60N and 90N for the winter months (December, January and February)). Model data from KNMI Climate Explorer.

If the world actually reaches the Paris goal of limiting warming to below 2 ° C, future Arctic winter warming will be 0.5-5 ° C, much lower than the 5-9 ° reported in the report C.

There are still many possible outcomes for the region. Consequently, any claim that massive future warming is "locked up" in the region is misleading.

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