Unprecedented efforts are needed to end global warming at 1.5 ° C: the IPCC

A new major study of the Intergovernmental Panel on Climate Change (IPCC) estimates that it is still possible to prevent the global temperature from rising more than 1.5 ° C pre-industrial values ​​and limit the devastating effects of climate change. However, this would require a vast unprecedented global effort.

Otherwise, the carbon dioxide will have to be extracted from the atmosphere more and more massive. Failure to achieve this goal would result in sea level rise of up to 6 feet, critical crop loss and near-eradication of coral reefs worldwide, among other serious consequences.

"It will not be possible to avoid overruns and dependence on the future large-scale deployment of carbon dioxide removal (CDR) if global CO2 emissions start to decline well. before 2030, "said the study published Monday after the members of the study had made final revisions. at an IPCC meeting in Incheon, South Korea.

Staying in the 1.5 ° C threshold will also require significant reductions in emissions of methane, black carbon and nitrous oxide, the report says.

"Limiting warming to 1.5 ° C is possible in the laws of chemistry and physics, but that would require unprecedented changes," said Jim Skea, Co-Chair of IPCC Working Group III, which focuses on reducing climate change (mitigation).

A unique ambitious goal

Since the late 1800s, global average temperature has risen by about 1 ° C, bringing the planet back to about two-thirds of the 1.5 ° C threshold.

The increased use of fossil fuels has pushed atmospheric levels of carbon dioxide above 405 parts per million, more than 30% above pre-industrial values. Carbon dioxide is the most prevalent greenhouse gas produced by humans that warms the climate.

Carbon dioxide emissions from energy use were virtually stable from 2014 to 2016, even as the global economy grew.

However, emissions have increased by 1.4% in 2017, according to the International Energy Agency. The agency attributed this increase to increased energy demand and reduced progress in energy efficiency.

The Paris Agreement of 2015 called on the nations of the world to keep global warming well below 2 ° C, with efforts to stay within 1.5 ° C. All countries of the Earth have acceded to the World Health Agreement. Paris, although the United States has announced its intention in 2017 to withdraw from the agreement.

National commitments submitted to date under the agreement are not sufficient to avoid more than 1.5 ° C warming, the IPCC noted.

A table of very confident conclusions

Many of the effects of climate change already observed will intensify further if warming reaches 2 ° C, or exceeds 1.5 ° C and then returns to that point, instead of stopping at 1.5 ° C.

For example, the highest daily records already exceed the lowest records in many areas. The IPCC report predicts that the number of hot days will increase faster for a global warming of 2 ° C against 1.5 ° C.

Heavy rains and snowfalls have become stronger in many parts of the world in recent decades, as global warming allows more water vapor to enter the atmosphere. The commission noted that the risk of extreme precipitation would be even higher with a warming of 2 ° C compared to 1.5 ° C in several parts of the northern hemisphere, including East Asia and the Middle East. East of North America.

The IPCC report assessed its conclusions in terms of trust, with many findings at "medium" or "high" confidence levels. Among the high confidence results:

– If the warming is between 1.5 and 2.0 ° C, this may result in instabilities in the ice sheet over Antarctica and / or irreversible loss of the Greenland Ice Sheet. The result could be a sea level rise of more than six feet over hundreds or even thousands of years.

– 70 to 90% of the coral reefs would perish with a warming of 1.5 ° C, but more than 99% of the reefs would be lost at 2 ° C.

– The frequency of an ice-free Arctic Ocean in summer would pass about once a century with a warming of 1.5 ° C to about once a decade, with a warming of 2 ° C.

– Limiting global warming to 1.5 ° C would reduce the net loss of yields of cereal crops and help stem the loss of nutritional quality of rice and wheat.

What should happen?

According to the new report, technologies are underway to limit global warming to 1.5 ° C, such as renewable energies. The main challenge is to use them quickly and massively, depending on the desires of decision-makers and the public.

"These system transitions are unprecedented in scale, but not necessarily in terms of speed," the report says.

The reductions in emissions needed to stay below 1.5 ° C of warming would require keeping large amounts of known fossil fuel reserves in the soil.

Most of the approaches examined by the expert group included at least some use of carbon capture and storage (preventing carbon from entering the air of fossil fuels or biofuels) and afforestation (planting). new forests that extract carbon dioxide through photosynthesis).

Carbon capture and storage would become increasingly important if the target of 1.5 ° is exceeded and if large amounts of carbon are to be removed from the air, the commission said.

Achieving the goal of 1.5 ° C could help achieve goals that go beyond reducing climate change, the study revealed. For example, reducing the number of tiny particles released into the air by burning fossil fuels would have significant health benefits.

The reduced impact of warming by 1.5 ° C compared to 2.0 ° C would help societies adapt to climate change while meeting other goals aimed at improving human well-being and preserving climate change. environment, says the report.

The IPCC report involved 91 authors from 40 countries, drawing on more than 6,000 published studies. The authors finalized the report after reviewing more than 42,000 comments on the draft versions of the report.