Rebecca Hersher, Lauren Sommer
With just a few weeks left, 2020 is in a dead-heat tie for the hottest year on record. But whether it claims the top spot misses the point, climate scientists say. There is no shortage of disquieting statistics about what is happening to the Earth.
The hottest decade on record is coming to a close, with the last five years being the hottest since 1880. 2020 is just two-hundredths of a degree cooler than 2016, the hottest year ever recorded. The Earth is nearly 2 degrees Fahrenheit warmer now than it was in the 20th century, and greenhouse gas concentrations in the atmosphere are still rising.
The future will be even hotter, although humans, through the choices governments, corporations and individuals make, will decide exactly how much.
That means more years like 2020, with increasingly powerful hurricanes, more intense wildfires, less ice and longer heat waves. The average yearly number of $1 billion-dollar disasters in the U.S. has quadrupled in the last three decades. As of October 2020, there had been 16 climate-driven disasters that caused at least $1 billion in damage each.
"How many times can we say the word 'unprecedented'?" says Kristina Dahl, climate scientist at the Union of Concerned Scientists. "This is not just something theoretical that we're predicting. It's something that we are living through and that we're already beginning to see."
Climate-driven disasters — hurricanes, wildfires, heat waves, droughts and floods — affect every region of the U.S., but poor people and poor places suffer disproportionately. Around the world, climate change is exacerbating inequality.
As President-elect Joe Biden assembles a new administration that promises to reduce greenhouse gas emissions and help people across the country, and around the world, adapt to global warming, NPR's Climate Team asked climate scientists what lessons can be learned at the end of another hot year.
Dangerous heat waves that don't let up
Weather reports across the Southwest this year featured one number, over and over: 100 degrees.
That's because many cities endured lengthy stretches of relentless heat, breaking long-term temperature records. Phoenix, Arizona experienced a record-breaking 145 days above 100 degrees, the repeated, sustained heat waves made worse by a lack of rain. The city also had 15 days above 115 degrees, double the previous record.
"Basically almost everything set records," says Marvin Percha, meteorologist at the National Weather Service in Phoenix. "I've lived here a long time. I grew up here in the 70s and I've never seen anything quite like this."
Heat can have deadly consequences. Phoenix also broke the record for the number of heat-related deaths, with almost 300 people dying. Some were killed directly by the heat, while others suffered from cardiac and respiratory problems triggered by heat stress.
Cities, with their vast amounts of concrete, also experience higher temperatures than surrounding areas — what's known as the "urban heat island" effect. Nighttime temperatures are warming faster than daytime temperatures, which provides less respite from the heat. Other cities like Palm Springs and Sacramento, Calif. also broke their records for the number of days above 100 and 90 degrees, respectively.
Climate scientists say even small changes in average temperature translate to large increases in extremes. Drought and heat feed a vicious spiral, drying out soils and plants which then lead to hotter air temperatures around them.
"Certainly with the overall warmer Earth it makes it more likely to get these extremes temperatures," Percha says.
The Arctic is heating up fast. But exactly how fast?
Jackie Grebmeier has been traveling to the Arctic every summer for more than 30 years. A climate scientist at the University of Maryland, she studies how the oceans are changing, and what that means for people and animals.
This year the pandemic got in the way. It was October before Grebmeier and a pared down group of Arctic scientists made it to the Bering Strait near Alaska. Grebmeier expected much colder weather than she usually experiences during summer research trips, but was surprised by the warm conditions she found. "All the long johns we brought, we didn't need them," she says. "We saw not one piece of ice."
At one point, the scientists on the research vessel saw a container ship coming south through the Bering Strait. It had started in Canada and was headed for South Korea, via the Arctic Ocean. They also found evidence of a large algae bloom off the coast of northern Alaska. Usually, such blooms only occur in the summer.
The Arctic is warming twice as fast as the rest of the Earth, according to the federal government's 2020 Arctic Report Card. That means sea ice is melting earlier in the spring and freezing later in the fall. Permanently frozen ground is melting, and wildfires in boreal forests and Arctic shrublands are getting more frequent and severe. There was less Arctic sea ice this October than any previous October on record.
That comes as no surprise to many people who live in the Arctic. "You know, climate change for indigenous people is not anything new. It's maybe new for science to say, 'Yeah the Arctic is warming, there's a lack of sea ice,' " says Mellisa Johnson, the director of the Bering Sea Elders Group, which is made up of representatives from more than 40 communities on the Alaska coast.
Johnson says many indigenous people are already adapting hunting practices to accommodate for less sea ice, and the new ways of gathering traditional food are being passed down to younger generations.
But the climate models that scientists use to predict the future do not accurately predict how quickly ice in the Arctic is melting.
"Many models seem to have difficulties in reproducing what we're seeing in the Arctic," says Jens Hesselbjerg Christensen, a climate scientist at the University of Copenhagen.
Faced with obviously rapid Arctic warming, scientists are trying to figure out why that is. Climate models are particularly crucial in the Arctic because there is less directly observed data available.
In a 2020 study, Hesselbjerg Christensen and his colleagues analyzed how quickly the Arctic is warming now compared to dramatic temperature changes in the distant past, such as when the last Ice Age ended, and found that what's happening now is comparably fast. "The amount of warming that's taking place is quite comparable to what happened at the top of Greenland like 30,000 years ago," he says. "This is almost as abrupt as anything gets."
Now, scientists like Hesselbjerg Christensen are trying to understand what that means for the future, and whether the past could help them design climate models that reflect what's actually happening in the Arctic.
"It's not about what happens this year," Hesselbjerg Christensen says. "It's about what happens next year and the year after and the year after that."
Wildfires shattered records across the West
The West is no stranger to fires, but this year's blazes seemed relentless. More than nine million acres burned and 17,000 homes and buildings were destroyed. Three states experienced the largest wildfires in their recorded history: California, Oregon and Colorado.
The pattern was unsettlingly similar across those states: extreme hot weather and high winds created explosive infernos that sent people fleeing their homes with just minutes to spare. As multiple fires burned, fire-fighting crews were stretched thin with little relief. No state could spare extra personnel to help their Western neighbors. Millions of people inhaled unhealthy air for weeks, as the smoke spread to places far and wide that had not had wildfires.
Extreme fires can have many causes that lead to their destructiveness. Many ecosystems are overgrown with brush, after years of land management practices that focused on extinguishing fires rather than letting them clear out vegetation when safe to do so. At the same time, millions of people have moved into fire-prone landscapes where fires are a regular part of the ecology.
But climate scientists say the warming climate set the stage for fires to get out of hand. California experienced the hottest October on record. Many parts of the Southwest had the driest late summer ever recorded.
That created an extremely "thirsty" atmosphere — a key metric that scientists track to measure fire danger. When the air is hot and dry, it acts like a sponge, drawing moisture out of soils and plants. That dry vegetation is highly flammable, creating the conditions for explosive fires.
Climate scientists say as temperatures continue to rise, the West will see more and more days with high fire danger due to a "thirstier" atmosphere.
"That's what we saw this year," says Dan McEvoy, climatologist with the Western Regional Climate Center and Desert Research Institute. "We saw a record high and it was almost double compared to the previous record. So we're seeing this play out in real time."
With the potential for catastrophic fires only increasing, fire experts say Western communities must reduce the risk where they can. That means changing their relationship with fire by using it as a tool. Setting controlled burns in the winter season can help reduce overgrown fuels, as Native American tribes have done for millennia.
Making homes and buildings more resistant to fire with better building materials gives them a chance to survive wildfires or at least slow them down. While that's required in risky areas in California, many Western states have failed to institute wildfire building codes.
Given the speed of wildfires this past year, evacuation plans are more critical than ever.
"Fire on the landscape in the West is normal," McEvoy says. "We need that fire. But the thing that's changing is the rate that they spread and how quickly they become these large mega-fires."
Hotter ocean water is bad news in so many ways
Ocean warming was also on full display in 2020, and it was messy.
Sections of the Indian Ocean, the Pacific and the Caribbean all had their hottest years ever. Most of the Earth's ocean area was much warmer than average.
Hotter water meant more powerful storms. Warm water on the ocean surface helps storms gain energy as they form, which leads to more destructive wind and storm surge. Hot ocean water also endows some storms with enormous amounts of moisture that falls as rain when the storm hits land.
Record-breaking heat in the Bay of Bengal helped power a devastating cyclone that hit India and Bangladesh in May. By the time the Atlantic Hurricane season began in June, the water in the Gulf of Mexico was also heating up.
That helped fuel a record-breaking number of rapidly intensifying hurricanes whose wind speeds got about 35 miles per hour faster in 24 hours or less. Wind speed indicates how powerful a hurricane is, so the 10 storms that rapidly intensified in 2020 all gained a lot of power very quickly, which made it more difficult for people in their path to prepare.
Climate scientists expected hotter water to lead to more rapidly intensifying storms, but 2020 was still surprisingly prolific. "This season has just been something that no one could have believed," says Rebecca Morss, a scientist at the National Center for Atmospheric Research. "Watching those hurricanes rapidly intensify in the Gulf [of Mexico] is just crazy."
The hot water was also bad news for fisheries. Fish and other marine creatures are moving farther and farther to find water that is the appropriate temperature for them, according to a study by scientists at the National Oceanic and Atmospheric Administration published this year. That's disruptive for the migrating animals themselves, and for humans and other animals that prey on marine species.
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