This Decade We Became Really, Really Sure Climate Change Is Real

In the past ten years, we lost hope in American politics, realized we were being watched on the internet, and finally broke the gender binary (kind of). So many of the beliefs we held to be true at the beginning of the decade have since been proven false—or at least, much more complicated than they once seemed. The Decade of Disillusion is a series that tracks how the hell we got here.

To climate scientist Kathie Dello, the clearest sign that the world had changed was the 2015 drought. As the associate director for the Oregon Climate Change Research Institute, Dello spent that year disseminating climate information to the public as historically warm weather melted mountain snowpack and dried out landscapes across the Pacific Northwest, triggering water scarcity, fueling historic wildfires, and offering a glimpse of what soon could be the new normal.

“To me, that was when I saw climate change unfold before my eyes,” Dello said. “This is what we were talking about happening decades in the future.”

Dello isn’t the only scientist for whom the potential consequences of life on a warming planet became all too real this past decade. It was a common theme in the recent conversations I had with nearly a dozen scientists to learn how our understanding of climate change has advanced over the last 10 years. While their specific responses were as diverse as the topics these researchers study, a consistent throughline is that while climate change is now manifesting all around us, whether through the mass coral reef die-offs or Greenland melting at rates unprecedented in the last 350 years.

“Everything we thought was happening [at the beginning of the decade] we’re much more confident is happening now,” said Gavin Schmidt, a climate scientist at NASA’s Goddard Institute for Space Studies. “That’s both good and bad.”

On the good side of the ledger, our understanding of climate change has advanced leaps and bounds. Through new satellite missions like the European Space Agency’s Earth-observing Sentinel array, airborne campaigns such as NASA’s cryosphere-monitoring Operation IceBridge, autonomous observatories like the Argo float network collecting oceanographic intel on the high seas, and field research campaigns from Alaska’s tundra to the Amazon rainforest, researchers have collected scores of data that shows how the effects of warming are rippling across diverse environments and ecosystems. Thanks to ongoing advancements in computing power, all of that data is being fed into increasingly sophisticated models to forecast our planet’s future. The big data revolution has also helped spawn a new field of attribution science, which allows researchers to say what kind of a role warming played in a heat wave, wildfire, hurricane, or other extreme event, often in near real-time.

“More and more, we’re able to say yes the following extreme event was influenced by climate change,” said Peter Gleick, a climate and water scientist and co-founder of the Pacific Institute. That, he said, is an advance that’s “absolutely of the last decade.”

But while scientific progress is a good thing, the picture all of this new data and computational capacity paints is a grim one.

The planet has only warmed around a degree so far, but already Arctic sea ice has retreated dramatically, its loss amplifying warming and helping tip parts of the north, like Arctic Alaska, into an entirely new climate state. All that warmth means Greenland is now shedding about 300 billion tons of frozen water into the sea each year, causing sea levels to rise at an accelerating rate. Ice losses across Antarctica are also contributing to that rise and could play a much bigger role in the future; research published this decade found that the Amundsen Sea sector of West Antarctica might have already entered a state of irreversible decline that will raise global sea levels by ten feet.

As low-lying communities glimpse a future of permanent inundation, offshore the buildup of heat is cooking ecosystems to death. From 2014 to 2017, the world’s shallow water coral reefs suffered a global bleaching event, losing the symbiotic algae that give them color and provide them with food thanks to heat stress. Between 2016 and 2017 half of all corals in the Great Barrier Reef died due to bleaching-induced starvation.

“One of the headline stories for this decade has been the pace at which coral reefs are succumbing to heat,” said Kim Cobb, a coral reef scientist who heads the Global Change Program at Georgia Tech. “This has been a very acute wake up call.”

Less headline-grabbing but equally alarming: Warmer ocean water holds less oxygen, a fact of physics that is beginning to manifest everywhere. In 2017, two studies pointed to an ongoing climate change-fueled depletion of oxygen in Earth’s surface oceans. While nobody is sure exactly how bad this will get, history doesn’t bode well: Research published last year suggests that global warming-fueled ocean anoxia might have been the chief culprit in the worst mass extinction event life on Earth ever experienced.

“This is a really serious problem,” said Matt Long, an oceanographer at the National Center for Atmospheric Research. “We’re fundamentally changing the metabolic status of the largest ecosystem on Earth, at a rate that’s not well-quantified.”

But it’s on land where the consequences of rapid climate change are becoming most apparent to humans, whether it’s the fires of unprecedented size and intensity tearing across the western U.S. and Australia, the historic downpours from Houston to Bangladesh, vanishing snowpack in the Sierra Nevada, or deadly heat waves in Europe and India. In the high Arctic, the very ground communities have built their homes on is crumbling as once-stable permafrost turns to mush.

To Miami University fire scientist Jessica McCarty, last month’s wildfire near Santa Barbara, California crystallizes how climate change can amplify the threat of disasters: The blaze, which tore across a landscape dried out by intense late-summer heat, was quickly followed by “bomb cyclone” that brought heavy rain and raised the risk of mudslides. In the 2000s, McCarty says, “there was a kind of theorized loop of drought and then these bombogenesis storms that would release a lot of water that would cause landslide risk. Now we just see it—it’s this known thing that we expect.”

There’s plenty of research left to be done. To better project future sea level rise, we need to improve our understanding of how ice sheets melt at their base and how warmer ocean waters eat away at their edges, said Ruth Mottram, a climate scientist and glaciologist at the Danish Meteorological Institute. We also need to get better at modeling clouds, which Mottram described as a “climate scientist’s absolute nightmare” but which play a critical role in how much sunlight reaches the Arctic in the summer. And there are feedback loops and tipping points we’re still uncertain about, like how much future warming we could see due to the slow release of carbon from thawing permafrost or a massive, drought-fueled dieback of the Amazon rainforest.

As a commentary published last month in Nature pointed out, those two feedbacks alone could “all but erase” the carbon budget humanity has left in order to maintain a good chance of capping global warming at the “safe” level of 1.5 degrees Celsius.

“Even if we stopped warming today, that spin up of permafrost thaw is going to contribute” to future emissions, said Merritt Turetsky, an ecosystem ecologist at the University of Guelph in Canada. “Our investments in mitigation today help us scale back these climate tipping points.”

There are also fundamental questions about how much warming future carbon emissions will cause. Worryingly, Schmidt of NASA Goddard says, a number of new flagship climate models are “running hot,” suggesting the climate system may be far more sensitive to increased CO2 than previously thought. As we enter the 2020s, he said, climate science faces a strange contrast of more observations, better attribution science, and “greater uncertainty about what’s going to happen in the future.”

But while there will always be more knowledge to gather and uncertainties to rectify, the scientists I spoke with were clear that puzzling out the details of all the planetary chaos we’re creating won’t change the basic picture, which has been pretty much the same since Exxon was doing climate research in the 1970s.

“We don’t need more information on how critical the situation is,” said Adriane Esquivel-Muelbert, a research fellow studying global change and forests at the University of Birmingham in the UK. “We need to start acting.”

Schmidt thinks it’s unlikely that we’ll be able to bring carbon emission down quickly enough to cap global warming at 1.5 degrees. As the U.N. noted in a recent report noted, to do so we’ll need to cut carbon emissions an unprecedented 7.6 percent every year of the 2020s. (In the 2010s, emissions rose 1.5 percent a year, per the U.N.) At the same time, he and most other scientists I spoke felt more hopeful about climate action today than they did at the beginning of the decade. Despite seemingly endless stalling and entrenched climate denial at the highest levels of government, there’s been a revolution in public awareness and concern over the last few years as the dire effects of warming become impossible to ignore.

Cobb called the U.N.’s 1.5 degree Celsius report last year—which alerted the world that we have about a decade left to slash emissions in order to keep global warming within safe boundaries—“one of the most important advances of the decade” because of how it galvanized the public. And while the progress we’ve made cutting emissions hasn’t kept pace with increasingly loud calls for action, we’re now at least discussing radical decarbonization strategies commensurate with the scale of the problem.

“I feel more positive today about the number of people who are concerned [about climate change], understand that it’s human caused, and that human action will dictate our future,” said Twila Moon, a glaciologist at the National Snow and Ice Data Center in Colorado. But, she added, she’d like to see the conversation move “very strongly” toward figuring out how to meaningfully reduce emissions.

After all, it’s not too late to keep climate change from metastasizing into something far worse. If the 2010s were the decade where warming got real, the 2020s could go down in history as the moment humanity started dial the planetary thermostat down.

Either that, or we’re about to see how bad things can really get.