A new United Nations climate report released on Monday morning lays out in stark terms how climate change is already wreaking havoc on the world, warning that any additional warming will only fuel more extreme disasters.
“It is unequivocal that human influence has warmed the atmosphere, ocean and land,” according to a summary distilling the report’s findings for policymakers. “Human-induced climate change is already affecting many weather and climate extremes in every region across the globe.”
The highly anticipated report is part of the sixth climate assessment released by the UN’s Intergovernmental Panel on Climate Change, which provides the most comprehensive scientific overview of the impacts of the climate crisis so far and an analysis of how bad it could still get.
The latest report stands apart from previous versions for explicitly pointing to the cause of the climate crisis: human-induced climate pollution. Without humans curbing their release of carbon dioxide, methane, and other greenhouse gases, the report warns, deadly heat waves, heavy rains, droughts, and other disasters will get more intense and more frequent.
Hundreds of scientists worldwide contributed to the report and its key findings, which are spelled out in the policymaker summary. Additional reports will come out in the next year and a half: A second report will dig into who is most vulnerable to ongoing climate impacts and how to best prepare for them, while a third will focus on how to prevent more warming.
The declaration that human activity definitively is to blame is “the strongest statement the IPCC has ever made,” said Ko Barrett, IPCC vice chair and a senior advisor for climate at the US National Oceanic and Atmospheric Administration, on a Sunday press call.
The new report’s findings will likely add to the pressure facing world leaders who will be meeting in Glasgow in November as part of their ongoing participation in the Paris climate agreement.
If countries of the world come together and collectively cut their release of greenhouse gases to net-zero emissions by 2050 — the stated goal of the Paris climate agreement — global temperature rise and some other climate impacts could slow and even reverse, per the report.
Acting aggressively now can ensure that “these next two decades of warming may be some of our last,” said Kim Cobb, another report coauthor and a climate professor at Georgia Tech, on the press call. “That’s really to me what is important to keep in mind here.”
The summer has been one long series of disasters. A record-shattering heat wave killed hundreds in the Pacific Northwest and Canada. Extreme flooding in Germany killed more than 100 people and left hundreds more missing. Thousands were displaced by flooding in China. Meanwhile, ongoing wildfires are raging across the globe, from California to Greece to Siberia.
Disasters are hitting more frequently and more intensely, just one of the ways the IPCC report says the planet has transformed due to climate change:
Global surface temperatures have so far increased by about 1.1 degrees Celsius since preindustrial times. This rate of human-induced warming is unprecedented in at least 2,000 years.
Heat waves and precipitation events have become more frequent and more intense worldwide.
Droughts are also intensifying.
The upper levels of the ocean have also warmed, ocean acidification has increased, and there’s been a drop in Arctic sea ice.
Marine heat waves have about doubled in frequency since the 1980s.
Global sea levels have already risen by about half a foot, and the rate of sea rise is increasing, a result of melting glaciers and ocean waters expanding with heat. The rate of sea level rise observed since 1900 is the fastest it has been in at least 3,000 years.
And the simultaneous shrinking of so many glaciers globally is unprecedented in at least the last 2,000 years of Earth’s history.
And what’s around the corner if humans don’t stop emitting greenhouse gases into the atmosphere is much worse.
“With every additional increment of global warming, changes in extremes continue to become larger,” according to the summary report. Extreme heat events, such as heat waves, that occurred once every 10 years on average in a world without human-made climate change now likely occur roughly 2.8 times a decade.
And if the planet continues to warm, such deadly events will become even more likely. With 1.5 degrees Celsius of warming, extreme heat waves and other events could occur 4.1 times a decade, per the report, while 2 degrees of warming could increase the frequency to 5.6 times. The most alarming scenario, 4 degrees of warming, would have deadly heat events happening roughly every year.
And it’s not just heat extremes. For every additional 0.5 degree Celsius of warming, the IPCC report warns there will be an expected increase in the frequency and intensity of heavy rain events, as well as agricultural and ecological droughts. More warming also brings the increasing chance of concurrent disasters, such as heat waves and droughts occurring at the same time.
But as bad as things can get, the report stresses that swift and aggressive action on climate change can even reverse some of its effects. A rapid effort to not just stop emitting greenhouse gases but also pull them out of the air, achieving negative emissions, would spur a reversal in surface temperatures and surface ocean acidification.
Unfortunately, not all climate impacts can be stopped. For example, some global sea level rise is now unavoidable. “Sea level change through the middle of the century, around 2050, has largely been locked in,” said summary report coauthor Bob Kopp. “Regardless of how quickly we get our emissions down, we’re likely looking at about 15 to 30 centimeters, or about 6 to 12 inches, of global sea level rise.”
Beyond this point, he added, “sea level projections become increasingly sensitive to the emission choices we are making today.” Under 2 degrees of warming, sea levels will rise about 1.5 feet by 2100; under 4 degrees, water levels could rise more than 2 feet within this century.
“It is possible to forestall many of the dire impacts, but it really requires unprecedented transformational change,” Barrett said. “The idea that there is still a path forward, I think, is a point that should give us some hope.”