UN report: global warming should exceed the Parisian limit


Updated 13 minutes ago

Earth’s climate is getting so hot that temperatures within a decade or so will likely exceed a level of warming that world leaders have sought to prevent, according to a report released Monday that the United Nations is calling a “code red for humanity.”

“It’s just guaranteed to get worse,” said Linda Mearns, co-author of the report, senior climatologist at the US National Center for Atmospheric Research. “I don’t see any safe area … nowhere to run, nowhere to hide.”

But scientists have also quieted a little about the likelihood of absolute worst climate disasters.

The authoritative report of the Intergovernmental Panel on Climate Change (IPCC), which calls climate change clearly man-made and “unequivocal,” makes more accurate and warmer predictions for the 21st century than the last time it was released in 2013.

Each of the five scenarios for the future, based on reducing carbon emissions, exceeds the more stringent of the two thresholds set in the 2015 Paris climate agreement. World leaders then agreed to try to limit the warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) since the late 19th century, as problems worsen rapidly thereafter. The limit is only a few tenths of a degree higher than it is today, as the world has already warmed by almost 1.1 degrees Celsius (2 degrees Fahrenheit) over the past century and a half.

In each scenario, according to the report, the world will cross the 1.5 degree Celsius mark of warming in the 2030s, earlier than some past predictions. Warming has accelerated in recent years, data shows.

In three scenarios, the world will also likely exceed 2 degrees Celsius (3.6 degrees Fahrenheit) compared to pre-industrial times – the other, less strict Paris target – with heat waves, droughts and torrential downpours though. worse “unless deep carbon reductions in emissions of carbon dioxide and other greenhouse gases occur in the decades to come,” the report says.

“This report tells us that recent climate change is widespread, rapid and intensifying, unprecedented in thousands of years,” said IPCC Vice Chairman Ko Barrett, Senior Climate Advisor for the National Oceanic and Atmospheric Administration of the United States. “The changes we are experiencing will increase with further warming. “

The more than 3,000-page report by 234 scientists said that warming is already accelerating sea level rise, shrinking ice and worsening extremes such as heat waves, droughts, floods and storms. Tropical cyclones get stronger and wetter, as arctic sea ice decreases in summer and permafrost melts. All of these trends will get worse, according to the report.

For example, the type of heat wave that only happened once every 50 years now happens once a decade, and if the world warms another degree Celsius (1.8 degrees Fahrenheit), that will occur twice every seven years, according to the report.

As the planet warms, places will be more affected not only by extreme weather conditions, but also by multiple climate disasters happening simultaneously, according to the report. It’s like what’s happening in the western United States now, where heat waves, drought and wildfires are adding to the damage, Mearns said.

Some of the damage caused by climate change – shrinking ice caps, rising sea levels, and changes in the oceans as they lose oxygen and become more acidic – are “irreversible for centuries or even more. millennia, ”according to the report.

The world is “locked in” to 15 to 30 centimeters (6 to 12 inches) of sea level rise by the middle of the century, said report co-author Bob Kopp from Rutgers University.

Almost all of the warming that has occurred on Earth can be attributed to emissions of heat-trapping gases such as carbon dioxide and methane. At most, natural forces like the sun or mere chance can explain one or two tenths of a degree of warming, depending on the report.

The report describes five different future scenarios based on reducing global carbon emissions. They are: a future with incredibly large and rapid pollution reductions; another with intense but not so massive pollution reductions; a scenario with moderate emissions; a fourth scenario in which current plans to reduce pollution slightly continue; and a fifth possible future involving a continuing increase in carbon pollution.

In five previous reports, the world was on this latest hottest track, often dubbed “business as usual”. But this time around, the world falls somewhere between the moderate emissions trajectory and the scenario of small pollution reductions due to progress in curbing climate change, said report co-author Claudia Tebaldi, a scientist at the US Pacific Northwest National Lab.

In a way, the world may stay at the 1.5 degree threshold with extreme and rapid emission reductions, but even then the warming would reach 1.5 degrees in a decade, increase a bit and then come back down, said co-author Maisia ​​Rojas Corrada. , director of the Climate and Resilience Research Center in Chile.

While calling the report a “code red for humanity,” United Nations Secretary-General Antonio Guterres kept a silver lining that world leaders could still somehow prevent a 1.5 degree warming, which, according to him, is “dangerously close”.

“Anything we can do to limit, slow down, will pay off,” Tebaldi said. “And if we can’t get to 1.5, it’s probably going to be painful, but you better not give up. “

In the report’s worst-case scenario, the world could be about 3.3 degrees Celsius (5.9 degrees Fahrenheit) warmer than it is today by the turn of the century. But that scenario looks increasingly unlikely, said report co-author and climatologist Zeke Hausfather, director of climate change at the Breakthrough Institute. The two extremes seem less likely, he said.

“We’re much less likely to be lucky and end up with less warm-up than we thought. We will not be able to meet the goals of the Paris Agreement without rapid short-term reductions in our emissions, ”said Hausfather. “At the same time, the chances of ending up somewhere much worse than we expected if we cut our emissions are significantly lower.”

The report says ultra-catastrophic disasters, commonly referred to as “tipping points,” such as the collapse of the ice cap and the abrupt slowing of ocean currents, are “unlikely” but cannot be ruled out. The much-talked-about shutdown of Atlantic Ocean currents, which would trigger massive climate change, is something that’s unlikely to happen in this century, Kopp said.

The report “gives a strong sense of urgency to do even more,” said Jane Lubchenco, deputy White House science adviser.

In a new move, scientists have pointed out how reducing levels of methane in the air, a powerful but short-lived gas that has reached record levels, could help curb short-term warming.

More than 100 countries have informally pledged to achieve ‘net zero’ man-made carbon dioxide emissions by mid-century, which will be a key element in the climate negotiations this autumn in Scotland. The report said these commitments are essential.

“It is still possible to prevent many of the more serious impacts,” Barrett said.


Learn more about AP’s climate coverage at http://www.apnews.com/Climate


Follow Seth Borenstein on Twitter at @borenbears.


The Associated Press’s Department of Health and Science receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.


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