Climate change is changing the earth in ways that have been “unprecedented” for thousands of years – and in some cases hundreds of thousands of years – according to a United Nations report released Monday.
The sobering assessment also revealed that some of the changes that are already taking place, such as ocean warming and sea level rise, are “irreversible for centuries to millennia.”
The report is the most comprehensive assessment by the UN Intergovernmental Panel on Climate Change (IPCC) since 2013 and provides the strongest evidence to date of human-caused global warming.
The report also found that climate change is intensifying, accelerating, and already affecting all regions of the planet.
“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,” Valérie Masson-Delmotte, co-chair of IPCC Working Group I, said in a statement.
Ko Barrett, vice chairman of the IPCC and chief climate advisor for the National Oceanic and Atmospheric Administration, told NBC News that the report shows that regardless of what people do in the future, the future will be hotter than it is now.
“It can be kind of demoralizing or depressing to think that there are so many things that are somehow irreversible for a long period of time,” Barrett said. “But the good news is that these irreversible changes can be slowed down by reducing greenhouse gas emissions quickly, strongly and sustainably.”
Founded in the late 1980s, the IPCC consists of thousands of scientists from 195 member governments who review the latest published and peer-reviewed research on global warming and compile the results in a report on the current state of the climate. The assessment, which includes a look at the future risks and impacts of climate change, typically represents a consensus within the scientific community. More than 230 authors contributed to the current report.
The assessment will be made less than three months before the meeting of the world leaders from October 31st to November 12th in Glasgow, Scotland, for the UN Climate Conference 2021. Countries are expected to set ambitious targets to reduce emissions by 2030, and the results of the IPCC are likely to play an important role in the discussions.
The report says that greenhouse gas emissions from human activity have caused global warming at a rate not seen in at least 2,000 years. It is estimated that man-made climate change has been responsible for about 1.1 degrees Celsius of warming since 1850-1900, the earliest time with reliable measurements of global surface temperatures, the authors wrote.
Additionally, the report noted that global temperatures are expected to exceed 2 degrees Celsius this century, “unless that [carbon dioxide] and other greenhouse gas emissions will occur in the coming decades. “
“This report is a reality check,” said Masson-Delmotte in the statement. “We now have a much clearer picture of past, present and future climates, which is essential to understanding where we are going, what can be done and how we can prepare.”
Climate scientists have warned against limiting the rise in global mean temperatures to below 2 degrees Celsius in order to avoid the most devastating effects of global warming. The 2-degree benchmark was set by climate negotiators in Copenhagen in 2009, but studies have increasingly shown that the target may already be out of reach.
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The new IPCC assessment goes further than any of the group’s previous reports by linking man-made climate change to the increase in extreme weather events around the world.
“It’s almost certain that hot extremes (including heat waves) have become more common and intense in most land regions since the 1950s, while cold extremes (including cold waves) have become rarer and less severe, “the authors wrote, adding that is man-made global warming the “main driver” of these changes.
The report also describes how rising ocean and surface temperatures in different regions of the world will lead to myriad physical changes in climate – including drought, heat waves, torrential rain, and coastal flooding.
The assessment is part of the IPCC’s latest summary on climate change, known as the Sixth Assessment Report, or AR6, which will be released next year. The full report consists of four sections: the Working Group I report on the science of climate change; Working Group II report on vulnerabilities and socio-economic impact; the report of Working Group III on possible ways to mitigate climate change; and the synthesis report, which reviews the results of all working groups and integrates relevant information for policy makers.
Josh Lederman contributed.