‘Code red’: UN scientists warn of worsening global warming

The Earth is getting so hot that in about a decade, temperatures are likely to blow past a level of warming that world leaders have been trying to prevent, according to a report released Monday that the United Nations called a “code red for humanity.”

“It’s just guaranteed to get worse,” said report co-author Linda Mearns, a senior climate scientist at the U.S. National Center for Atmospheric Research. “Nowhere to run, nowhere to hide.”

But scientists also relaxed a bit about the likelihood of the absolute worst climate catastrophes.

The authoritative report from the Intergovernmental Panel on Climate Change (IPCC), which clearly calls climate change “unambiguous” and “an established fact”, makes more accurate and warmer predictions for the 21st century than when it was last published in 2013.

Each of the five future scenarios, based on how much carbon emissions are reduced, meets the stricter of two thresholds set out in the 2015 Paris climate agreement. World leaders then agreed to try to limit warming to 1.5 degrees. Celsius (2.7 degrees Fahrenheit) above the level at the end of the 19th century, as the problems rapidly increase after that. The world has since warmed nearly 1.1 degrees Celsius (2 degrees Fahrenheit).

According to the report, in any scenario, the world will cross the 1.5 degrees Celsius mark by the 2030s, earlier than some previous forecasts. Global warming has increased in recent years, data shows.

In three scenarios, the world is also likely to exceed 2 degrees Celsius (3.6 degrees Fahrenheit) in pre-industrial times — Paris’ less stringent target — with much worse heatwaves, droughts and floods triggering downpours unless deep emissions cuts are made. are, the report said.

“This report tells us that recent climate changes are widespread, rapid and more intense, unprecedented in thousands of years,” said IPCC Vice President Ko Barrett, senior climate adviser for the US National Oceanic and Atmospheric Administration.

With pivotal international climate negotiations in Scotland in November, world leaders said the report is prompting them to push harder to reduce carbon pollution. US Secretary of State Anthony Blinken called it “a grim memory.”

The 3,000-page report by 234 scientists said warming is already accelerating sea level rise and exacerbating extremes such as heat waves, droughts, floods and storms. Tropical cyclones become stronger and wetter, while Arctic sea ice recedes in summer and permafrost thaws. All of these trends are set to get worse, the report said.

The kind of heat wave that used to happen only once every 50 years now happens once every decade, and if the world warms one more degree Celsius, it will happen twice every seven years, the report said.

As the planet warms, places will be more affected not only by extreme weather, but also by multiple climate disasters at once, the report said. That’s like what’s happening in the western U.S., where heatwaves, droughts and wildfires amplify damage, Mearns said. Extreme heat is also causing massive fires in Greece and Turkey.

Some damage from climate change — dwindling ice sheets, rising sea levels and changes in the oceans as they lose oxygen and become more acidic — are “irreversible for centuries to millennia,” the report said.

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

Scientists have been bringing this message for more than three decades, but the world hasn’t listened, said Inger Andersen, executive director of the United Nations Environment Programme.

For the first time, the report provides an interactive atlas for people to see what has happened and could happen to where they live.

Nearly all of the warming that has occurred on Earth can be attributed to the release of heat-trapping gases such as carbon dioxide and methane. At most, natural forces or simple randomness can explain one or two-tenths of a degree of warming, the report said.

The report described five different future scenarios based on how much the world is reducing CO2 emissions. They are: a future with incredibly large and rapid pollution reductions; another with intense pollution reduction, but not as massive; a moderate emission reduction scenario; a fourth scenario in which current plans to implement a small reduction in pollution continue; and a fifth possible future with a continued increase in carbon pollution.

In five previous reports, the world was on that latest hottest path, often nicknamed “business as usual.” But this time, the world is somewhere between the temperate path and the small pollution reduction scenario because of progress to curb climate change, said study co-author Claudia Tebaldi, a scientist at the U.S. Pacific Northwest National Lab.

Calling the report “a code red for humanity,” UN Secretary-General Antonio Guterres held a glimmer of hope that world leaders could somehow still prevent 1.5 degrees of warming, which he says is “dangerously close.” “is.

Alok Sharma, the chair of Scotland’s upcoming climate negotiations, urged leaders to do more so they can “believe credibly that we’ve kept 1.5 degrees alive”.

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

In the report’s worst-case scenario, the world could be about 3.3 degrees Celsius (5.9 degrees Fahrenheit) hotter by the end of the century than it is today. But that scenario seems increasingly unlikely, said study co-author and climate scientist Zeke Hausfather, director of climate change at the Breakthrough Institute.

“We’re much less likely to get lucky and end up with less warming than we thought,” Hausfather said. “At the same time, if we reduce our emissions, the chances of us ending up in a much worse place than we expected are significantly lower.”

The report also said ultra-catastrophic disasters — commonly referred to as “tipping points,” such as the collapse of the ice sheet and the abrupt slowing of ocean currents — are “low probability” but cannot be ruled out. The much-discussed cessation of currents in the Atlantic, which would cause massive weather changes, is something that is unlikely to happen in this century, Kopp said.

A “great advance” in understanding how quickly the world is warming with every ton of carbon dioxide emitted allowed scientists to be much more accurate in the scenarios in this report, Mason-Delmotte said.

In a new step, scientists highlighted how reducing airborne methane levels — a potent but short-lived gas that has risen to record levels — could help curb short-term warming. Much of the methane in the atmosphere comes from leaks of natural gas, an important source of energy. Livestock also produces large amounts of gas, much of it in ranchers.

More than 100 countries have made informal commitments to reach man-made CO2 emissions sometime around the middle of the century, which will be a key part of negotiations in Scotland. According to the report, those commitments are essential.

“It’s still possible to prevent many of the most serious consequences,” Barrett said.


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


Follow Seth Borenstein on Twitter at @borenbears


The Associated Press Health and Science Department 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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