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IPCC warns some warming is locked in

The U.N. chief called a major new report on human-caused global warming ‘a code red for humanity’ though a brief window exists to avoid the worst.

San Francisco's Bay Bridge under an orange sky darkened by smoke from California wildfires
San Francisco's Bay Bridge under an orange sky darkened by smoke from California wildfires (AN/Christopher Michel)

GENEVA (AN) — Some extreme climate impacts are probably unavoidable due to baked-in effects from fossil fuel burning though humanity still has a brief window to avoid some of the most dire scenarios through swift greenhouse gas reductions, the U.N.'s panel of top climate experts warned in a major new report on Monday.

The Intergovernmental Panel on Climate Change offered five likely scenarios for what would happen when the world exceeds the 2015 Paris Agreement’s goal of preventing average global temperatures from rising more than 2 degrees Celsius above pre-industrial levels, or 1.5 degrees if possible. The world has already warmed by almost 1.1 degrees, since the effects from rising emissions of carbon and other gases take decades to alter.

Each scenario shows the world crossing the 1.5 degrees threshold in the 2030s, faster than earlier predicted, due to accelerating warming, according to the IPCC report, which reviews the most recent climate research including land and ocean temperatures, emissions, extreme weather, drought, wildfires and sea level rise.

“This report is a reality check,” said report co-chair and climate scientist Valerie Masson-Delmotte of France’s Laboratory of Climate and Environment Sciences at the University of Paris-Saclay. “It has been clear for decades that the Earth’s climate is changing, and the role of human influence on the climate system is undisputed."

The report, written by more than 200 scientists and approved by 195 governments last week, is the first of three that examine how the world is mitigating and adapting to climate change. It is part of IPCC's sixth major major assessment since 1990 — and the first to examine the science behind climate change since 2013.

Drafted ahead of the next major U.N. climate summit in Glasgow, Scotland, the report emphasizes that achieving net zero global emissions by 2050 would accomplish the Paris Agreement's goals.

'Code red for humanity'

Human-caused climate change is causing severe and widespread impacts such heatwaves, drought and flooding, and those impacts will dramatically worsen at 2 degrees, the report emphasized. It found melting ice sheets and ocean warming will likely cause sea level rise of five to 10 meters that will continue into the 22nd century.

Extreme heat waves are happening five times more often, IPCC reported, and will occur 14 times as often if the 2 degree threshold is breached. Droughts that occurred once-a-decade now happen 70% more often.

Many of the trends listed in the report are record-setting: oceans are heating up faster than scientists say has ever occurred in 11,000 years; glaciers are retreating at a rate not seen in at least 2,000 years; and Arctic sea ice in late summer is the thinnest it has been in at least 1,000 years.

That has led to scientists' scenarios that could involve some of the most extreme impacts such as rapid alterations in ocean circulation, collapse of ice sheets and huge losses of forestland. Still, the report adds, the worst-case scenarios could be prevented with immediate, sustained action.

The report is "a code red for humanity," said U.N. Secretary-General António Guterres.

"The alarm bells are deafening, and the evidence is irrefutable: greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk," he said. "Global heating is affecting every region on Earth, with many of the changes becoming irreversible. The internationally agreed threshold of 1.5 degrees Celsius is perilously close."