Earth is warming faster than previously thought, scientists say, and the window is closing to avoid catastrophic outcomes
Updated 0824 GMT (1624 HKT) August 9, 2021
(CNN)As the world battles historic droughts, landscape-altering wildfires and deadly floods, a landmark report from global scientists says the window is rapidly closing to cut our reliance on fossil fuels and avoid catastrophic changes that would transform life as we know it.
The state-of-the-science report from the United Nations' Intergovernmental Panel on Climate Change says the world has rapidly warmed 1.1 degrees Celsius higher than pre-industrial levels, and is now careening toward 1.5 degrees — a critical threshold that world leaders agreed warming should remain below to avoid worsening impacts.
Only by making deep cuts to greenhouse gas emissions, while also removing carbon dioxide from the atmosphere, can we halt the precipitous trend.
"Bottom line is that we have zero years left to avoid dangerous climate change, because it's here," Michael E. Mann, a lead author of the IPCC's 2001 report, told CNN.
Unlike previous assessments, Monday's report concludes it is "unequivocal" that humans have caused the climate crisis and confirms that "widespread and rapid changes" have already occurred, some of them irreversibly.
That is due in part to the breakneck pace at which the planet has been recently warming, faster than scientists have previously observed. Since 2018, when the panel published a special report on the significance of 1.5-degrees, greenhouse gas emissions have continued mostly unabated and have pushed global temperatures higher.
Even under the IPCC's most optimistic scenario, in which the world's emissions begin to drop sharply today and are reduced to net zero by 2050, global temperature will still peak above the 1.5-degree threshold before falling.
In a statement, UN Secretary-General António Guterres called the report "a code red for humanity," and noted the 1.5-degree threshold is "perilously close."
"The only way to prevent exceeding this threshold is by urgently stepping up our efforts, and pursuing the most ambitious path," Guterres said.
The IPCC report comes just three months before the UN-led international climate change talks, during which global leaders are expected to strengthen their commitments to cutting greenhouse gas emissions.
Though some countries have pledged stricter cuts since the 2015 Paris Agreement, many have missed deadlines to do so, and there is still a significant gap between what leaders are promising and what's needed by 2030.
"From a scientific perspective, every degree, every part of a degree, every half of a degree matters in terms of limiting the impacts that we will see from climate change," Ko Barrett, the former vice chair of the IPCC, told CNN. "So at whatever level countries decide is what they're aiming for, there are benefits and there are consequences to choosing those limits."
An evolution on climate change
With each IPCC report, the science has converged on what scientists now say is irrefutable: the climate crisis is caused by human greenhouse gas emissions.
1990 — "The unequivocal detection of the enhanced greenhouse effect ... is not likely for a decade or more."
1995 — The ability to connect climate change to human influence is "currently limited."
2001 — There is "new and stronger evidence" that warming is due to greenhouse gas emissions.
2007 — Global warming is unequivocal, and there is "high confidence" that human influence is to blame.
2013 — "Warming of the climate system is unequivocal," and "human influence on the climate system is clear."
2021 — "It is unequivocal that human influence has warmed the atmosphere, ocean and land."
Dave Reay, the director of the Edinburgh Climate Change Institute, said world leaders "must have the findings of this report seared into their minds" at the November conference and take urgent action.
"This is not just another scientific report," Reay said. "This is hell and highwater writ large."
As computing power increases, scientists are more confident than ever in connecting the dots between the climate crisis and extreme weather, which for some regions — even at 1.1 degrees of warming — is already becoming unbearable.
Michael Byrne, a climate researcher at the University of Oxford, said that's what's different about this report is "the effects of global warming are no longer in the distant future or in far-flung corners of the world."
"We knew what was coming and now it's here," Byrne said.
A heat wave that killed hundreds this summer in the US Northwest and British Columbia would have been "virtually impossible" without the climate crisis, researchers found. It made Hurricane Harvey's devastating rainfall roughly three times more likely to occur and 15% more intense, scientists said. Harvey dumped more than 19 trillion gallons of water on Texas and Louisiana in 2017, triggering devastating floods in the Houston area.
The IPCC says heavy rainfall that used to occur once every 10 years now occurs 30% more frequently.
JUST WATCHED
Nearly 200 people were killed in Germany and Belgium when more than an entire month's worth of rain fell in as little as 12 hours. Tens of thousands of people were unable to return to their homes left without access to power and drinking water.
MUST WATCH
Nearly 200 people were killed in Germany and Belgium when more than an entire month's worth of rain fell in as little as 12 hours. Tens of thousands of people were unable to return to their homes left without access to power and drinking water. 01:21
Globally, droughts that may have occurred only once every 10 years or so now happen 70% more frequently, according to the report. The climate change connection is particularly strong in the Western United States, which is experiencing a historic, multiyear drought that has drained reservoirs and triggered water shortages.
Amid unrelenting drought and record heat, wildfire seasons are now longer and result in more destructive fires. Six of the top 10 largest fires in California have occurred in 2020 or 2021, according to CalFire.
"We're seeing truly frightening fire behavior. I don't know how to overstate that," said Chris Carlton, supervisor of California's Plumas National Forest supervisor in California, who called this year's wildfire season "uncharted territory."
Charles Koven, a lead author of the report's chapter on global carbon cycles, said California has already reached a tipping point on wildfires.
"I don't think we knew where that threshold was until we crossed it," he told CNN. "What the report makes clear is that the likelihood of crossing any of these tipping points is certainly going to increase the more warming that we see."
Photos: Wildfires raging in the West
The Alisal Fire burns near Goleta, California, on Tuesday, October 12.
Hide Caption
1 of 84
Photos: Wildfires raging in the West
A firefighter puts out a roadside fire in Goleta, California, on Wednesday, October 13.
Hide Caption
2 of 84
Photos: Wildfires raging in the West
An air tanker drops retardant on a wildfire in Goleta.
Hide Caption
3 of 84
Photos: Wildfires raging in the West
James Grooms looks through the remains of his home at the Rancho Marina Mobile Home & RV Park following the Brannan Fire in Sacramento County, California, on Tuesday, October 12.
Hide Caption
4 of 84
Photos: Wildfires raging in the West
Firefighter Tyler McManigal battles the Alisal Fire in Gaviota, California, on October 12.
Hide Caption
5 of 84
Photos: Wildfires raging in the West
A forest of ashen trees stands in the wake of the Windy Fire, south of California Hot Springs, on September 27.
Hide Caption
6 of 84
Photos: Wildfires raging in the West
A volunteer attempts to evacuate horses to safety as the Windy Fire expands in California's Sequoia National Forest on September 25.
Hide Caption
7 of 84
Photos: Wildfires raging in the West
Operations Section Chief Jon Wallace looks at the General Sherman giant sequoia tree at Sequoia National Park on September 22. The base of the tree, the world's largest by volume, was wrapped in an aluminum-based burn-resistant material to protect it from wildfires.
Hide Caption
8 of 84
Photos: Wildfires raging in the West
Firefighters spray water as flames from the Windy Fire push toward a road in California's Sequoia National Forest on September 22.
Hide Caption
9 of 84
Photos: Wildfires raging in the West
Firefighters battling the Windy Fire extinguish a spot fire in the Sequoia National Forest on September 19.
Hide Caption
10 of 84
Photos: Wildfires raging in the West
The Windy Fire burns in the Trail of 100 Giants grove in the Sequoia National Forest on September 19.
Hide Caption
11 of 84
Photos: Wildfires raging in the West
A helicopter drops water on the KNP Complex Fire burning in Sequoia National Park on September 15.
Hide Caption
12 of 84
Photos: Wildfires raging in the West
Flames from the KNP Complex Fire burn along a hillside in the Sequoia National Park on September 14.
Hide Caption
13 of 84
Photos: Wildfires raging in the West
This aerial photo, taken on September 4, shows the Dixie Fire on Horton Ridge in Plumas County, California.
Hide Caption
14 of 84
Photos: Wildfires raging in the West
Riley Cantrell cries while she and boyfriend, Bradley Fairbanks, view what's left of her mother's home in Greenville, California, on September 4. It was destroyed by the Dixie Fire.
Hide Caption
15 of 84
Photos: Wildfires raging in the West
A firefighter is seen as the Caldor Fire rages near California's Silver Lake on September 2.
Hide Caption
16 of 84
Photos: Wildfires raging in the West
A helicopter flies over Wrights Lake while battling the Caldor Fire in California's Eldorado National Forest.
Hide Caption
17 of 84
Photos: Wildfires raging in the West
Embers fly from a tree as the Caldor Fire burns along Highway 50 in California's Eldorado National Forest.
Hide Caption
18 of 84
Photos: Wildfires raging in the West
Veronica Foster, an evacuee from South Lake Tahoe, California, hugs her dog, Gracie, as she and her co-workers gather outside an evacuation center in Gardnerville, Nevada, on August 31. The governors of California and Nevada declared states of emergency as the fast-moving Caldor Fire prompted officials to tell everyone to get out of South Lake Tahoe.
Hide Caption
19 of 84
Photos: Wildfires raging in the West
Jason Marone of the Roseville Fire Department hoses down a hot spot in Meyers, California, on August 31.
Hide Caption
20 of 84
Photos: Wildfires raging in the West
A tree burns in a blackened forest at dawn on August 30 after the Caldor Fire tore through Twin Bridges, California.
Hide Caption
21 of 84
Photos: Wildfires raging in the West
A firefighter winds up hose at a spot fire near Meyers, California, on August 30.
Hide Caption
22 of 84
Photos: Wildfires raging in the West
The Caldor Fire burns homes along a ridge near South Lake Tahoe on August 30.
Hide Caption
23 of 84
Photos: Wildfires raging in the West
South Lake Tahoe residents are stuck in gridlock while attempting to evacuate the city on August 30.
Hide Caption
24 of 84
Photos: Wildfires raging in the West
A tanker makes a fire-retardant drop near Lytle Creek, California, on August 26 as efforts continued to stop the South Fire.
Hide Caption
25 of 84
Photos: Wildfires raging in the West
A firefighter tries to extinguish flames at a burning house as the South Fire burned in Lytle Creek, California, on August 25.
Hide Caption
26 of 84
Photos: Wildfires raging in the West
From left, Astrid Covarrubias, Jose Lamas and Maria Covarrubias walk through smoke after visiting their burned-out home in Lytle Creek on August 25.
Hide Caption
27 of 84
Photos: Wildfires raging in the West
The French Fire continues to spread near Wofford Heights, California, on August 25.
Hide Caption
28 of 84
Photos: Wildfires raging in the West
Firefighters are seen behind the flames of a backfire they were setting to battle the French Fire near Wofford Heights.
Hide Caption
29 of 84
Photos: Wildfires raging in the West
Crews battle California's Caldor Fire as it moved east toward Lake Tahoe on August 23.
Hide Caption
30 of 84
Photos: Wildfires raging in the West
This aerial photo, taken on August 19, shows burned homes at the Creekside Mobile Home Park a day after they were destroyed by the Cache Fire in Clearlake, California.
Hide Caption
31 of 84
Photos: Wildfires raging in the West
Firefighters dig a containment line on the Caldor Fire near Pollock Pines, California, on August 18.
Hide Caption
32 of 84
Photos: Wildfires raging in the West
Smoke and haze from wildfires obscure the Golden Gate Bridge and the San Francisco skyline on August 18.
Hide Caption
33 of 84
Photos: Wildfires raging in the West
In this long-exposure photo, embers light up hillsides as the Dixie Fire burns near Milford, California, on August 17.
Hide Caption
34 of 84
Photos: Wildfires raging in the West
Destiney Barnard holds Raymond William Goetchius while stranded at a gas station in Doyle, California, on August 17. Barnard's car broke down as she was helping Raymond and his family flee the Dixie Fire.
Hide Caption
35 of 84
Photos: Wildfires raging in the West
Destroyed property is seen August 17 after the Caldor Fire passed through Grizzly Flats, California.
Hide Caption
36 of 84
Photos: Wildfires raging in the West
Firefighters spray water on trees being burned by the Dixie Fire near Janesville, California, on August 17.
Hide Caption
37 of 84
Photos: Wildfires raging in the West
As the KNP Complex Fire approaches, Forest Service firefighters Armando Flores, right, and Heron Hilbach-Barger clear vegetation around structures at the Ash Mountain headquarters in Sequoia National Park, Calif., on Sept. 15, 2021. The blaze is burning near the Giant Forest, home to more than 2,000 giant sequoias.
Hide Caption
38 of 84
Photos: Wildfires raging in the West
A firefighting helicopter flies in front of the sun, which was shrouded in thick wildfire smoke near Lakeview, Oregon, on August 15.
Hide Caption
39 of 84
Photos: Wildfires raging in the West
Wind blows smoke away for a moment, revealing damage from the Parleys Canyon Fire in Utah on August 14.
Hide Caption
40 of 84
Photos: Wildfires raging in the West
Crews battle a fire in Newhall, California, on August 12.
Hide Caption
41 of 84
Photos: Wildfires raging in the West
A table and chairs sit in front of a destroyed home in Greenville, California, on August 12.
Hide Caption
42 of 84
Photos: Wildfires raging in the West
A firefighter battles the Dixie Fire near Taylorsville, California, on August 10.
Hide Caption
43 of 84
Photos: Wildfires raging in the West
Smoke plumes rise from the Kwis Fire near Eugene, Oregon, on August 10.
Hide Caption
44 of 84
Photos: Wildfires raging in the West
A firefighter works to extinguish a controlled burn, a preventative measure, to protect a home in Greenville, California, on August 9.
Hide Caption
45 of 84
Photos: Wildfires raging in the West
Firefighters battling the Dixie Fire clear a fallen tree from a roadway in Plumas County, California, on August 6.
Hide Caption
46 of 84
Photos: Wildfires raging in the West
Flames from the Dixie Fire consume a pickup truck on Highway 89, south of Greenville, California, on August 5.
Hide Caption
47 of 84
Photos: Wildfires raging in the West
Operations Chief Jay Walter passes the historic Sierra Lodge as the Dixie Fire burns through Greenville, California, on August 4. The fire leveled multiple historic buildings and dozens of homes in central Greenville.
Hide Caption
48 of 84
Photos: Wildfires raging in the West
Firefighters work at a Greenville home that was engulfed by the Dixie Fire on August 4.
Hide Caption
49 of 84
Photos: Wildfires raging in the West
The Dixie Fire burns near Taylorsville, California, on July 29.
Hide Caption
50 of 84
Photos: Wildfires raging in the West
California Gov. Gavin Newsom, left, and Nevada Gov. Steve Sisolak tour an area destroyed by the Tamarack Fire in Gardnerville, Nevada, on July 28.
Hide Caption
51 of 84
Photos: Wildfires raging in the West
Firefighter Brentt Call walks through a burned-over area of the Bootleg Fire near Klamath Falls, Oregon, on July 27.
Hide Caption
52 of 84
Photos: Wildfires raging in the West
Cal Fire Capts. Tristan Gale, left, and Derek Leong monitor a firing operation in California's Lassen National Forest on July 26. Crews had set a ground fire to stop the Dixie Fire from spreading.
Hide Caption
53 of 84
Photos: Wildfires raging in the West
Firefighters try to reach a fire site in Quincy, California, on July 25.
Hide Caption
54 of 84
Photos: Wildfires raging in the West
Volunteers sort clothing at a donation shelter for those affected by the Bootleg Fire in Bly, Oregon.
Hide Caption
55 of 84
Photos: Wildfires raging in the West
Scott Griffin surveys his property, which was destroyed by the Bootleg Fire in Sycan Estates, Oregon.
Hide Caption
56 of 84
Photos: Wildfires raging in the West
Flames consume a home as the Dixie Fire tears through the Indian Falls community of Plumas County, California, on July 24.
Hide Caption
57 of 84
Photos: Wildfires raging in the West
People stand behind the fire line as flames from the Steptoe Canyon Fire spread through dry grass in Colton, Washington, on July 22.
Hide Caption
58 of 84
Photos: Wildfires raging in the West
Plumes of smoke from the Dixie Fire rise above California's Plumas National Forest, near the Pacific Gas and Electric Rock Creek Power House, on July 21.
Hide Caption
59 of 84
Photos: Wildfires raging in the West
Firefighters walk near a wildfire in Topanga, California, on July 19.
Hide Caption
60 of 84
Photos: Wildfires raging in the West
A firefighter does mop-up work in the Fremont-Winema National Forest, which has been struggling with the Bootleg Fire in Oregon.
Hide Caption
61 of 84
Photos: Wildfires raging in the West
A car is charred by the Bootleg Fire along a mountain road near Bly, Oregon.
Hide Caption
62 of 84
Photos: Wildfires raging in the West
Nicolas Bey, 11, hugs his father, Sayyid, near a donated trailer they are using after their home was burned in the Bootleg Fire near Beatty, Oregon.
Hide Caption
63 of 84
Photos: Wildfires raging in the West
Firefighters extinguish hot spots in an area affected by the Bootleg Fire near Bly, Oregon.
Hide Caption
64 of 84
Photos: Wildfires raging in the West
A bear cub clings to a tree after being spotted by a safety officer at the Bootleg Fire in Oregon.
Hide Caption
65 of 84
Photos: Wildfires raging in the West
Firefighters work to protect Markleeville, California, from the Tamarack Fire on July 17. The Tamarack Fire was started by a lightning strike.
Hide Caption
66 of 84
Photos: Wildfires raging in the West
The Tamarack Fire burns in Markleeville, near the California-Nevada border, on July 17.
Hide Caption
67 of 84
Photos: Wildfires raging in the West
A member of the Northwest Incident Management Team 12 holds a map of the Chuweah Creek Fire as wildfires devastated Nespelem, Washington, on July 16.
Hide Caption
68 of 84
Photos: Wildfires raging in the West
A cloud from the Bootleg Fire drifts into the air near Bly, Oregon, on July 16.
Hide Caption
69 of 84
Photos: Wildfires raging in the West
Firefighters spray water from the Union Pacific Railroad's fire train while battling the Dixie Fire in California's Plumas National Forest on July 16.
Hide Caption
70 of 84
Photos: Wildfires raging in the West
Horses climb a hillside that was burned by the Chuweah Creek Fire in eastern Washington.
Hide Caption
71 of 84
Photos: Wildfires raging in the West
Fire from the Bootleg Fire illuminates smoke near Bly, Oregon, on the night of July 16.
Hide Caption
72 of 84
Photos: Wildfires raging in the West
A firefighter battles the Bootleg Fire in the Fremont-Winema National Forest, along the Oregon and California border, on July 15.
Hide Caption
73 of 84
Photos: Wildfires raging in the West
A firefighting aircraft drops flame retardant on the Bootleg Fire in Bly, Oregon, on July 15.
Hide Caption
74 of 84
Photos: Wildfires raging in the West
Firefighters dig away at hot spots underneath stumps and brush after flames from the Snake River Complex Fire swept through the area south of Lewiston, Idaho, on July 15.
Hide Caption
75 of 84
Photos: Wildfires raging in the West
Burned cars sit outside a home that was destroyed by the Chuweah Creek Fire in Nespelem, Washington.
Hide Caption
76 of 84
Photos: Wildfires raging in the West
Evacuee Dee McCarley hugs her cat Bunny at a Red Cross center in Klamath Falls, Oregon, on July 14.
Hide Caption
77 of 84
Photos: Wildfires raging in the West
An airplane drops fire retardant on the Chuweah Creek Fire in Washington on July 14.
Hide Caption
78 of 84
Photos: Wildfires raging in the West
Operations Section Chief Bert Thayer examines a map of the Bootleg Fire in Chiloquin, Oregon, on July 13.
Hide Caption
79 of 84
Photos: Wildfires raging in the West
Fire consumes a home as the Sugar Fire, part of the Beckwourth Complex Fire, tears through Doyle, California, on July 10. It's the second time in less than a year that the small town has been ravaged by a wildfire.
Hide Caption
80 of 84
Photos: Wildfires raging in the West
Men hug a member of the Red Cross at a Bootleg Fire evacuation center in Klamath Falls, Oregon.
Hide Caption
81 of 84
Photos: Wildfires raging in the West
Embers blow across a field as the Sugar Fire burns in Doyle, California, on July 9.
Hide Caption
82 of 84
Photos: Wildfires raging in the West
Firefighters monitor the Sugar Fire in Doyle, California, on July 9.
Hide Caption
83 of 84
Photos: Wildfires raging in the West
In this long-exposure photograph, taken early on July 2, flames surround a drought-stricken Shasta Lake during the Salt Fire in Lakehead, California.
Hide Caption
84 of 84
With every fraction of a degree of warming, the effects worsen. Even limiting warming to 1.5 degrees, which countries in the Paris Agreement determined was ideal to stave off the worst impacts, the kinds of extreme weather the world has experienced this summer will become more severe and more frequent.
Beyond 1.5 degrees, scientists say the climate system could begin to look unrecognizable.
Andrew Watson, a scientist at the University of Exeter, said the climate models used in the report don't capture the risk of "low probability, high impact" events that become more likely as global temperature increases.
"These are events such as ice sheet collapse, sudden changes in ocean circulation, or catastrophic wildfires," Watson said. "These 'known unknowns' are scarier still."
The roughly 3,500-page report is a culmination of nearly a decade of climate research by scientists around the world. And although the IPCC is considered the ultimate source on climate change, it tends to be conservative in its findings because of the way it's developed — by having hundreds of scientists come to a consensus not only on the research but the language describing it.
Yet Monday's report uses the strongest wording to date in describing the climate crisis. Ice sheets are melting and will continue to melt; extreme flooding from higher sea level will continue to get more frequent; and sea level itself will continue to rise well into the 22nd century, simply because of the amount of heat the oceans have already trapped.
At the same time scientists are sounding the alarm, the International Energy Agency says human carbon emissions "are on course to surge by 1.5 billion tonnes in 2021 — the second-largest increase in history — reversing most of last year's decline caused by the Covid-19 pandemic."
The IPCC report is clear that global leaders must cut greenhouse gas emissions now, before deadly and costly weather extremes get even worse. But Barrett said a key message in the report is that it's still possible to prevent the most dire impacts.
"It really requires unprecedented transformational change, rapid and immediate reduction of greenhouse gas emissions to net zero by 2050," said Barrett. "The idea that there is still a pathway forward is a point that should give us some hope."
