3 Degrees Celsius Global Warming Would Devastate Planet


Rob Dobi for BuzzFeed News

There’s a very real chance the planet will warm up an average of 3 degrees Celsius (5.4 degrees Fahrenheit) this century — and that would be disastrous.

In such a brutally hot world, scientists agree, deadly heat waves, massive wildfires, and damaging downpours will come far more often and hit much harder than they do today. The ocean will be hotter too and more acidic, causing fish declines and likely the end of coral reefs. In fact, a quarter or so of the Earth’s species may go extinct in such conditions or be headed that way. Our coastlines would be reshaped, as a consequence of sea levels rising foot after foot, century after century, drowning places like Charleston, South Carolina’s Market Street, downtown Providence, Rhode Island, and the Space Center in Houston.

All of this, as climate scientist Daniel Swain of the University of California, Los Angeles, put it, would be bad: “Bad for humans. Bad for ecosystems. Bad for the stability of the Earth systems that we humans depend on for everything.”

Experts can’t say exactly how likely this future is because that depends on what humankind does to mitigate the worsening climate crisis, especially over the coming decade. But for world leaders gathering this weekend in Glasgow for the 26th United Nations Climate Change Conference (COP26), this future may well become an inevitability if they don’t agree to more aggressive and measures to limit greenhouse gas emissions.

Bad for humans. Bad for ecosystems. Bad for the stability of the Earth systems that we humans depend on for everything.”

The collective global goal under the Paris climate agreement is to prevent global temperatures from increasing no more than rising than 2 degrees Celsius (3.6 Fahrenheit), with no more than 1.5 degrees (2.7 Fahrenheit) as ideal. But currently, we’re on track for almost double that — a potentially catastrophic 3 degrees.

“I fear that without science-based policy, and that most ambitious target being achieved, we will be facing a 3-degree-Celsius world by later this century,” Kim Cobb, a climate scientist at Georgia Tech and one of the authors on the latest Intergovernmental Panel on Climate Change (IPCC) report, told BuzzFeed News. “It’s almost unimaginable, frankly.”

So, what might 3 degrees Celsius of warming look like?

For one, our world will be much hotter than today.

George Rose / Getty Images

The water level at Lake Tahoe has fallen below its natural rim, dropping more than 3 feet and shutting off the flow of water down the Truckee River as seen on Oct. 17 in South Lake Tahoe, California.

The starting point for measuring future warming isn’t today — it’s the late 1800s, when reliable global temperature records started becoming available. More than a century later, the planet has already warmed a little more than 1 degree Celsius (1.8 degrees Fahrenheit) due to the accumulation of fossil fuel pollutants such as carbon dioxide and methane in the atmosphere. That’s an average, but some places have already gotten much warmer.

Adding 2 more degrees to the more than 1 degree we’ve already added would make our world much hotter and disproportionately hotter on land. Here’s why: About 70% of the planet is covered in water, and water warms more slowly than land.

“If the whole world is warmed by 3 degrees Celsius,” Swain explained, “all of the land area has to warm by a lot more than that.”

“It’s almost unimaginable, frankly.”

That would likely be about 1.5 degrees Celsius warmer on average over land, or collectively 4.5 degrees, according to Zeke Hausfather, a climate scientist and energy systems analyst at the Breakthrough Institute. And it will likely be even hotter in the Arctic, which is already warming roughly three times the rate of the rest of the planet.

One way to envision what this might look like in the places in which we live is to consider the projected number of days where the local temperature hits or exceeds 95 degrees Fahrenheit (35 degrees Celsius). Earlier this century, Arizona experienced roughly 116 days of such high temperatures, Texas experienced about 43 days, Georgia about 11 days, Montana approximately 6 days, and Massachusetts just 1 day, according to modeling by the Climate Impact Lab.

Were global temperatures to rise by an average of 3 degrees Celsius by 2100, those numbers would spike to an estimated range of 179 to 229 days of at least 95 degrees Fahrenheit days in Arizona, 135 to 186 days in Texas, 85 to 143 days in Georgia, 46 to 78 days in Montana, and 26 to 66 days in Massachusetts, per the same analysis.

Disasters will multiply.

Michael Hanson / AFP via Getty Images

A sign gives directions to a cooling center at Kellogg Middle School in Portland, Oregon, on Aug. 14.

Just this summer, the Northwest Pacific heat wave brought Death Valley–like temperatures to British Columbia, Oregon, and Washington, killing hundreds of people in an event that scientists agree would have been “virtually impossible” without climate change. Then a record-setting downpour dropped about 9 inches in the middle of Tennessee, killing about two dozen people. And last weekend, more than 5 inches dropped in a day in California’s capital city of Sacramento, setting a new record.

“What I think about is, what would the shocking event be in a 3-degree-warmer world?” Swain said.

It’s impossible to know the answer exactly. But the general contours of what it could look like are already clear: even more common and intense extreme heat events and similarly more frequent and intense downpours, even in places that are expected to get drier in such a world. This is true for almost anywhere on the planet.

“There are very few places on Earth that are not going to see an increase in the maximum precipitation intensity,” Swain said, adding that there are “very likely zero places that are not going to experience an increase in the most extreme hot days. ”

Pete Bannan / MediaNews Group via Getty Images

Warren Montgomery attempts to make his way across a road in Chadds Ford, Pennsylvania, following historic flooding from the storm system that was Hurricane Ida.

Statistics from the latest IPCC report support this. What was considered a 1-in-10-year extreme heat event, such as a heat wave, in the late 1880s would be more than 5.6 times likely to occur in a 3-degrees-warmer world. The outcome could be higher power costs due to an explosion of air-conditioning, which could trigger power supply problems. Those without access to cooling could suffer more heat sickness. And then there’s the issue of water shortages; together with ongoing heat waves, they could spur massive crop failures.

Likewise, what was previously considered a 1-in-10-year extreme precipitation event over land would be more than 1.7 times likely to occur. These types of disasters have historically caused washed-out roads, flooded homes and businesses, and knocked-out power lines.

Meanwhile, regional disasters will also increase in frequency and intensity. Think more prolonged droughts and bigger wildfires along the West Coast and more powerful hurricanes along the Gulf Coast and East Coast. Worse, a phenomenon called “compounding disasters” could mean such events hit in rapid succession or simultaneously. A recent example of this was Louisiana’s Lake Charles, which suffered through multiple federally declared disasters in a year: back-to-back hurricanes, including a devastating Category 4 storm, followed by a winter storm and then intense flooding.

Nickolay Lamm / Courtesy Climate Central

A rendering of the National Mall with 3 degrees of global warming

In a 3-degrees-warmer worldthe coastlines of today will largely be gone, endlessly reduced over the coming centuries by rising seas.

By the end of 2100, sea levels are expected to rise by about 2 feet on average. That would be near catastrophic for small island nations. Most of Maldives, large swaths of the Bermuda archipelago, and some of Seychelles island, including its airport, could be underwater. So, too, could large parts of Thailand’s capital of Bangkok, home to more than 5 million people; the Netherland’s Amsterdam, the Hague, and Rotterdam cities, which are, combined, home to about 2 million people; and much of the US Gulf Coast, including sections of big cities like New Orleans and Texas’s Galveston. These examples are based on mapping by the research group Climate Central, whose projections do not account for current or future defenses construction to rising counter water levels.

“An estimated 12% of the current global population living on land could be threatened.”

Water will continue rising next century and the one after. So jumping to 2,000 years in the future, Robert Kopp, a climate scientist at Rutgers University, expects water levels to be somewhere between 13 feet to more than 30 feet above current levels. That much water, assuming there are no defenses in place against the rising levels, would likely inundate parts of California’s Bay Area and Los Angeles and reconfigure much of the Texas, Louisiana, Mississippi, Alabama, and Florida coasts, according to Climate Central mapping.

“An estimated 12% of the current global population living on land could be threatened under long-term future sea level rise under the 3 degrees Celsius scenario,” said Scott Kulp, a principal computational scientist at Climate Central. “So that amounts to 810 million people.”

The projection to 2100 doesn’t account for the possibility of the world’s ice sheets rapidly melting, and even the longer-term estimates rapid collapse don’t assume a total, although it’s possible. “The more we push the system above 2 degrees Celsius — but we don’t know how much — the more chance we trigger ice sheet processes that could rapidly increase sea level rise,” Kopp explained in an email.

The terrifying unknown.

David Mcnew / Getty Images

A chaparral brush landscape is charred by the Alisal fire on Oct. 13 near Goleta, California.

Perhaps the most frightening thing about a 3-degrees-warmer world is an uncertainty about how it would impact the way our natural so-called carbon sinks — think plants and trees, soil, and even the ocean — regularly and consistently pull carbon dioxide out of the air . If any one of these sinks were to stop absorbing as much carbon, more carbon would linger in the atmosphere, fueling global warming.

“We certainly can’t rule out a 4-degree-warmer world.”

Or there’s a possibility that one of the more longer-term carbon sinks could simply vanish. Right now, for example, there’s a layer of frozen ground, called permafrost, spread across parts of the planet, including the poles. Collectively, all this permafrost stores more carbon than is currently in the atmosphere. As the planet warms, the permafrost layer will thaw, releasing some of that carbon into the atmosphere along the way and fueling more warming in a dangerous feedback loop.

“Half of our emissions right now are pulled back into the ground by natural carbon sinks that have been functioning decade in, decade out at the same service levels,” said Cobb of Georgia Tech. “So going forward, as a climate scientist, it is very concerning that we are beginning to understand that there’s a real risk that these natural carbon sinks could stop functioning as well at higher warming levels.”

As the Breakthrough Institute’s Hausfather put it: “The thing is, even if we think we’re on track for a 3-degree-warmer world under current policies, we certainly can’t rule out a 4-degree-warmer world.” ●


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