1.5 degrees rise scenario: the worst heat waves will come 8 times in 50 years

IPCC Sixth Assessment Report (IPCC)

IPCC 6th Report Main Contents Disclosed

By 2040, in all scenarios, it is predicted that 1.5 degrees will exceed the target. Extreme heatwaves occurred frequently in the past 50 years. If the global average temperature rises more than 2 degrees, the heatwave frequency increases by 13.9 times. If we continue our greatest efforts, it is possible to recover the current level.. a glimmer of hope.

Through the Paris Climate Agreement adopted in December 2015, the international community agreed to limit the global average temperature from rising by more than 2°C above the pre-industrial level.

In addition, at the 48th General Assembly of the Intergovernmental Panel on Climate Change (IPCC) held in Songdo, Incheon, in October 2018, representatives from each country submitted a 'Global Warming 1.5℃ Special Report', which states that it is difficult to prevent catastrophe with 2℃ suppression.

The goal of the international community is to limit the increase in global temperature by 1.5 degrees Celsius. Accordingly, countries around the world are declaring ‘carbon neutrality’ to zero net greenhouse gas emissions from 2019 to 2050 in turn, and have been raising their greenhouse gas reduction targets for 2030 from last spring.

However, through the 'IPCC 6th Assessment Report (AR6) 1st Working Group (Scientific Base) Report' approved on the 6th and the 'summary' of this report published on the 9th, the PCC found that the average global surface temperature was 1.5℃ higher than before industrialization. It was predicted that it would be very difficult to tie it below.

1.5°C or higher before 2040

In particular, if the current trend of greenhouse gas emission continues, it is expected that the temperature will rise by 1.5°C between 2021 and 2040. This is 10 years earlier than the 2030-2052 predicted by the '1.5℃ Special Report' in 2018.

In addition, it is predicted that the temperature increase will exceed 1.5°C in 2050 even in the case of great efforts to reduce greenhouse gas emissions (minimum emission scenario). The IPCC did leave a glimmer of hope that the international community's goals could be achieved, adding that the global average temperature increase could be brought down to below 1.5°C again at the end of the 21st century depending on human efforts.

If so, is there still a chance to limit the rise in temperature to 1.5°C?

What will happen if the global temperature rises higher than 1.5°C?

It is difficult to achieve the target even in the lowest emission scenario

The IPCC used the newly introduced greenhouse gas emission pathway, the Shared Socio-economic Pathway (SSP) scenario, to forecast the temperature rise. This is an application of the future socio-economic aspects such as population, economy, land use, and energy use, which vary depending on the level of preparedness for future climate change.

The IPCC presented five scenarios.

Shared Socioeconomic Pathways (Wikipedia Commons)

The SP1-1.9 scenario thoroughly reduces greenhouse gas emissions to keep the global surface temperature rise below 1.5℃ by 2100, and sets the radiative forcing in 2100 (the amount of solar energy absorbed by greenhouse gases) of 1.9W per m2 (watts).

SSP1-2.6 is a case where it is assumed that the use of fossil fuels will be minimized and eco-friendly sustainable economic growth will be achieved through the development of renewable energy technology.

SSP2-4.5 assumes an intermediate level of climate change mitigation and socio-economic development.

SSP3-7.0 Assumes the social structure vulnerable to climate change due to the delay in technology development and passive in climate change mitigation policies.

SSP5-8.5 This is a scenario that assumes that the use of fossil fuels is high and urban-oriented indiscreet development will expand, focusing on the rapid development of industrial technology.

Even in the case of the SSP1-1.9 scenario, which is the most aggressive in reducing greenhouse gases, the IPCC predicted that the global temperature will rise by 1.5°C between 2021 and 2040 compared to pre-industrial levels. Also, in this scenario, the temperature increase is expected to reach 1.6℃ in the middle of the 21st century (2021-2060). Once within the achievable range, the 1.5℃ target will inevitably be exceeded no matter what efforts are made.

In the worst case, it rises by 5.7°C.

However, if greenhouse gas reduction efforts continue strongly as in the SSP1-1.9 scenario, it is expected that in the second half of the 21st century (2081~2100), the temperature will return to a level that has risen by 1.4 degrees (the most likely range is 1 to 1.8 degrees Celsius) compared to pre-industrial times. expected

In the best-case scenario, the best results can only be restored to the present level.

Even in the SSP1-2.6 scenario where mitigation efforts are actively made, the global temperature rises to 1.7°C in the middle of the 21st century, and the temperature rises by 1.8°C at the end of the 21st century.

In the case of the SSP2-4.5 scenario, it is predicted that the global temperature will rise by 2℃ in the middle of the 21st century and by 2.7℃ by the end of the 21st century.

In the SSP5-8.5 scenario without greenhouse gas reduction efforts, global temperature rise will exceed 1.5°C and rise 1.6°C before 2040, 2.4°C in the mid-21st century, and 4.4°C in the late 21st century (the likely range is 3.3°C). ~5.7℃) is expected to rise.

In the worst case scenario, the global temperature could rise as high as 5.7°C. This means that it will be difficult to achieve the 1.5℃ target unless countries around the world are more proactive in reducing greenhouse gas emissions in the near future.

If the temperature rises more than 2°C, the warming becomes more pronounced.

In this report, the IPCC predicted that global warming will become more widespread and more pronounced if the temperature rises by 2°C or higher. It is expected that the heat wave will increase in all regions compared to the 1.5℃ rise, and the permafrost, glaciers, and arctic ice will decrease further. The IPCC explains that extreme heat waves that occurred about once in 50 years from 1850 to 1900, before the appearance of human-induced climate change, are occurring about once every 10 years now that the temperature has risen by 1℃.

The IPCC report predicted that if the temperature rises by 1.5℃, the frequency of extreme heat waves at the same level will increase 8.6 times compared to pre-industrial times, 13.9 times when the temperature rises 2℃, and 39.2 times when the temperature rises 4℃.

When the temperature rises to 2°C or higher, it is expected that the range of changes in drought, heavy rainfall, and average precipitation will increase.

Regionally, tropical cyclones will become more intense, river flooding will increase, and wildfire-prone weather will become more frequent. In addition, when the temperature rises by 2°C or more, it is predicted that multiple extreme weather events will occur more frequently in different regions (such as crop production areas) at the same time.

Even if the global temperature rises by 1.5°C, the damage from climate change will appear, but if the temperature rises by 2°C or more, the situation could be much more serious. This is the reason why we have to work hard until the end to limit the increase in global temperature to 1.5℃.

Even if the temperature drops, the sea level will continue to rise

The bigger problem is that even if we succeed in reducing greenhouse gases in the future and the global temperature rises, the effects of climate change may continue due to the greenhouse gases emitted today and in the future. For example, stratification of the upper ocean, ocean acidification, and the formation of anoxic layers in the ocean are highly unlikely to recover on a time scale of hundreds or thousands of years.

In addition, alpine and polar glaciers will continue to melt for decades or hundreds of years, and the emission of greenhouse gases from the melting of permafrost in the polar regions is also projected to be irreversible for hundreds of years.

Even in the SSP1-1.9 scenario, which thoroughly reduces greenhouse gases, the sea level is expected to rise by 0.28 to 0.55 m by 2100 and by 0.37 to 0.86 m by 2150. The IPCC report predicted that the global average sea level will rise by 2~3m over the next 2000 years even if the temperature rise is restrained to 1.5℃.

Greenhouse gas absorption technology in the atmosphere is also required.

With the publication of this report, the rapid reduction of greenhouse gases has emerged as an urgent task. The IPCC proposes the amount of greenhouse gases that mankind can emit in the future with the concept of a “carbon budget” and ordered that it be matched.

Humans emitted 2390 gigatons (Gt) of carbon dioxide equivalent between 1850 and 2019, resulting in a global average temperature increase of 1.07°C (possible range 0.8-1.3°C) between 1850 and 2019. There is still 0.43°C left until the global temperature rise of 1.5°C. If an additional 500 gigatons are emitted in the future, the probability of achieving the 1.5°C target is 50%. The IPCC has urged the introduction of negative emission technology that absorbs and removes carbon dioxide from the atmosphere to reduce global greenhouse gas emissions.

Bioenergy-carbon capture and storage (BECCS) technology

Carbon dioxide emitted when bioenergy is used is captured and stored instead of released into the air, and as a result, carbon dioxide in the air is absorbed and removed. BECCS technology was presented in a 2018 IPCC special report as a necessary technology to achieve carbon neutrality in 2050 to keep global temperature rise below 1.5°C.

The IPCC predicted that the rate of greenhouse gas growth could be reduced by up to 10% through this report. However, in a paper published last month in the international scientific journal Nature Sustainability, a research team from the Climate Change Adaptation Center of the National Institute of Environment in Japan and the Potsdam Institute for Climate Impact Research in Germany stated, “Considering the sustainable supply of water resources, bioenergy cultivation through irrigation is Even if it is increased, carbon absorption will only increase by 5-6%.”

"Final Warning to Humanity"

In the end, the IPCC report concludes that only when greenhouse gas emissions are reduced as much as possible to the level that achieves carbon neutrality by 2050, the global temperature can be restored to 1.5℃ at the end of the 21st century and climate catastrophe can be reduced.

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