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2°C warming limit? More like 3°C and hotter, leading climate scientists say

  • About two-thirds of climate scientists surveyed said they don’t think the Paris Agreement’s target of limiting global warming to 2°C (3.6°F) above pre-industrial levels by 2100 is achievable.
  • Of the 92 scientists surveyed by the journal Nature, a majority said we are facing at least 3°C (5.4°F) of temperature rise by the end of this century.
  • The survey did not consider scientific results but asked for the opinions of the researchers who serve as experts with the IPCC, the U.N.’s top body on climate science.
  • The U.N. climate negotiations underway in Glasgow, Scotland, have nonetheless given some reason for cheer, with the return of the U.S., one of the biggest emitters, and more than 100 leaders vowing to rein in deforestation, a significant source of carbon emissions.

As delegates from around the world convened in Glasgow, Scotland, for the COP26 climate summit, most top climatologists say the threshold for reining in global warming is already out of reach.

About two-thirds of the scientists who took part in the Nature survey expect the world to warm by at least 3° Celsius (5.4° Fahrenheit) above pre-industrial levels by 2100. That exceeds the 2°C (3.6°F) limit under the Paris Agreement seen as crucial for staving off the worst impacts of a changing climate.

The survey was limited to 92 scientists who also serve as experts in the Intergovernmental Panel on Climate Change (IPCC), who are the most familiar with the scale of the challenge facing the human species.

The latest summit is taking place six years after COP22 in Paris. Despite the commitments made back then, greenhouse gas emissions have continued to rise, and many doubt the latest round of talks will prompt action at the scale needed to cap emissions below that limit.

“Right now, governments are just at the stage of providing green promises, but so far we have not seen any actions to curb greenhouse-gas emissions,” Mouhamadou Bamba Sylla, a climate modeler at the African Institute for Mathematical Sciences in Kigali, Rwanda, said in a Nature article.

Sylla is one of the experts contributing to the climate assessments from the IPCC, the U.N.’s top scientific body on climate change. It releases periodic assessments of the state of the climate and its repercussions. In the sixth edition of the IPCC report, the agency warned of “unprecedented planetary changes.” Major assessments, including the IPCC report released this year, suggest we’re on track to breach the 2°C mark.

Building on the expected changes in average temperatures, researchers are now helping people envision what this would mean for them. Modelers at Vrije Universiteit Brussel have developed a climate “crystal ball” accessible at My Climate Future. It captures the increased risk of extreme events like crop failures, droughts and heat waves in people’s lifetimes.

On average, global temperatures are already 1.2°C (2.2°F) hotter than in the 19th century. Even if nations meet their current pledges under the Paris accord, we could still see around 2.5°C (4.5°F) of warming by 2100. This could swell to as much as 4°C (7.2°F) without any actions — an unprecedented spike in recorded climate history.

Because extreme events are increasing in intensity and frequency, younger people are expected to face more climate calamities in their lifetimes. With warming of 2.4°C (4.3°F), a person born in 1991 will face 18 times more heat waves over their lifetime than in a world without climate change. In sub-Saharan Africa, the risk of heat waves increases to nearly 26 times in this scenario.

Someone born in 2001 will face 24 times as many heat waves in their lifetime under this scenario, a risk that increases to 34 times for those in sub-Saharan Africa.

The Nature survey involved sending questionnaires and eliciting opinions, and some of the scientists expressed discomfort at sharing their views rather than scientific results. However, the despair pervading sections of the scientific community is evident even in social media discussions around climate change.

However, not everybody is giving up on the collective goal. A fifth of the researchers surveyed thought the 2°C goal was still achievable. However, less than 5% believed the global community would meet the more ambitious goal of limiting warming to 1.5°C (2.7°F).

There were some signs of hope emerging from the first days of the Glasgow meeting. More than 100 world leaders vowed to put a stop to deforestation by 2030.

While the U.S., China, the EU and India, the biggest polluters, emit greenhouse gases through their use of dirty fossil fuels, others like Brazil and Indonesia release most of their carbon by clearing forests and peatlands.

The biggest emitters haven’t committed to net-zero emissions even by 2050. India announced on Nov. 1 that it would reach the net-zero goal by 2070, while China has set itself a deadline of 2060.

Tracking the realities of a changing climate has spurred some respondents to reorient their own lives, from how they travel to whether they have children. If the general public appreciates the true nature of the “crisis,” they could follow suit.

Charles Koven, a climate scientist at Lawrence Berkeley National Laboratory in California, said changing public opinion has given him hope.

“Fundamentally, I believe that the majority of people really do care about the future,” he said in the Nature news feature, “and that it is possible for governments to coordinate and avoid the worst climate outcomes.”

Citations:

Tollefson, J. (2021). Top climate scientists are sceptical that nations will rein in global warming. Nature, 599(7883), 22-24. doi:10.1038/d41586-021-02990-w

Thiery, W., Lange, S., Rogelj, J., Schleussner, C., Gudmundsson, L., Seneviratne, S. I., . . . Wada, Y. (2021). Intergenerational inequities in exposure to climate extremes. Science, 374(6564), 158-160. doi:10.1126/science.abi7339

(Banner Image of baobab trees at sunset in western Madagascar. Image by Rhett A. Butler/Mongabay.)