This decade, many people around the world woke up to a grim reality: Climate change is here, it’s happening now, and it could very easily get much, much worse.
These 10 years were punctuated by a series of deadly, dramatic, devastating events. Hurricanes like Sandy, Maria, and Harvey fundamentally changed the communities they barreled into, leaving behind scars that have yet to heal. Stronger and stronger heat waves forced communities across the country and world into dangerous swelter. Wildfires tore up hundreds of thousands of acres in a flash.
Climate records fell left and right. Hottest-ever year for the planet’s atmosphere? Check. Hottest-ever year for its oceans? Also check. Puny, unprecedentedly tiny stretches of Arctic sea ice? Check, check, check.
The underlying force beneath the changes is indisputable. Steadily increasing greenhouse gas concentrations in the atmosphere, caused primarily by humans burning fossil fuels, are trapping extra heat near Earth’s surface. That warms Earth as a whole. The outcome is both straightforward—a hotter planet—and incredibly complex, as changes cascade through the oceans, atmosphere, soil, rocks, trees, and every living thing on the planet.
“God, this was a terrible decade,” says Leah Stokes, a climate policy expert at the University of California, Santa Barbara. “Let’s make the next one less bad.”
We wrecked records large and small
The last decade was the hottest ever recorded, flashing a warning sign to anyone who was paying attention. On average, the annual temperatures over the years hover a little less than 1.8 degrees Fahrenheit (1 degree Celsius) higher now than they did from 1950 to 1980; the last five years alone was the hottest stretch ever recorded. So far, 2019 is shaping up to be the second hottest year ever, about 1.7 degrees F (0.94 degree C) above that long-term average.
That number might not sound like much, but its effects are large. Each little shift in the average increases the likelihood of extreme hot events. And just little shifts in the overall amount of heat stored in the oceans, air, and water can have huge effects on the planet.
For example, scientists think the planet was only about 10.8 degrees F colder (6 degrees C), on average, during the last ice age 20,000 or so years ago. But at that time a huge ice sheet covered North America, extending as far south as Long Island. The world looked very different, and there was only a small change in average temperature.
The hottest hot temperatures are also creeping higher—exactly what scientists would expect. As the average shifts upward, the likelihood of the extremely hot moments grows. Sure enough, “extreme” heat events have come with more frequency in the past decade, and that pattern is only expected to intensify.
There’s another important dimension to the overall warming, which is that it’s not happening evenly over the year or over distances. Winters are warming up faster than summers. The change in minimum temperatures between 2009 and 2018 (the last ten years that we have records for; 2019 records do not exist yet) was 1.34 degrees F. With milder winters come a whole host of unsettling, ecosystem-reshaping changes: Earlier springs cause a mismatch between pollinators and plant flowering times. More rain and less snow, and earlier-melting snow, affect water availability through the summer and fall. Unfrozen lakes, thawing permafrost, and open water appear where there should be ice.
Equally alarming and even more notable change is apparent in the oceans. While air temperatures tend to wobble around from year to year, responding to big patterns like El Niño—the periodic Pacific water-warming weather event—the ocean smooths out the signal, integrating all the warming that’s happened over past years. It responds more slowly and more steadily to changes happening above its surface, and what it’s telling us is clear.
The ocean has sucked up over 90 percent of all the extra heat trapped by human-caused climate change, and that signal is already apparent in its surface temperatures. Marine heat waves, like the heat waves we feel on land, and bigger changes—ones that could affect weather patterns around the entire planet—may be coming sooner than we think.
An icy tale tells us we’re in trouble
Earth’s ice served as the most obvious signpost of change over the past decade. The Arctic experienced about 1.8 F degrees (1 degree C) of warming in the past decade alone—compared to just under 1 degree C for the planet at large over the past 50 years. And its ice and frozen landscapes are responding just as sensitively as scientists predicted they would.
In 2012, nearly the entire Greenland ice sheet turned to slush, gushing cascades of melt into its coastal waters. Then the softening happened again, and again. Arctic sea ice bottomed out at its lowest ever recorded extent in 2012 as well, and has hovered at historic lows ever since, distorting “normal” weather patterns that depend on Arctic cold.
West Antarctica’s towering glaciers, home to enough ice to raise sea levels by 10 feet or more if they melted, have begun an inexorable retreat. Almost every single glacier in Earth’s high mountains is shrinking now, reshaping life in those high elevation zones. It’s also hitting life far downstream, where billions of people depend on the water that has long been sourced from snow and ice in the high peaks above.
Both ocean-trapped heat and melting ice contributed to record-breaking sea levels across much of the planet. A warmer ocean expands, driving those levels higher, and simultaneously, melt from Greenland and Antarctica has added about 36 millimeters of extra fresh water to the world’s oceans in the past 10 years, and the rate is jacking up every year. The injection of fresh water is changing the composition of the ocean in the Far North, which is in turn slowing down the conveyor belt of current from north to south that controls the world’s weather, with uncertain—but not positive—effects.
Behind all of the change is one clear driver: atmospheric carbon dioxide. In 2009, atmospheric CO2 concentrations hovered around 390 parts per million. By 2014, the number blew past 400 parts per million. Today, we hover around 410 ppm. The planet hasn’t seen concentrations that high since at least 2.6 million years ago. And at that time, no ice sheet existed in the northern polar regions and forests grew on Antarctica, sea levels were likely more than 40 feet higher than today, and the planet as a whole operated under very different conditions.
“This last decade mattered a lot and it looked pretty bad,” says Kate Marvel, a climate scientist at Columbia University and NASA GISS. “We’ve just got to make it so the next one is different.”
How did people change attitudes around climate change?
The physical patterns of climate change are becoming clearer and clearer. Alongside those physical changes, attitudes are also shifting.
Throughout the 2000s, explains Anthony Leiserowitz, the director of the Yale Program on Climate Change Communication, Americans were engaged with the question of climate change. A 2007 IPCC report stoked conversation about how to deal with the issue, as did political communities. Scientists were speaking out.
But even the belief that climate was changing—let alone whether solutions should be pursued—dropped precipitously in the U.S. between 2008 and 2010, for a suite of political and social reasons. The first part of the decade, Leiserowitz says, was spent rebuilding attention to and interest in climate change as a major issue.
At the same time, scientists have developed new techniques to determine exactly how much more likely an event—from a hurricane to a heat wave to a wildfire—was because of climate change. They can link the wider patterns of change directly to a weather event. That kind of explicit linkage is changing the way people think about the broader issue, he says.
Climate change supercharged Hurricane Harvey, for example, adding an extra 20 percent of rain to what might have been expected. Clear messaging that links the science with the impact influences the way people understand the causes of such events.
In the past few years, public interest in and concern about climate change has increased dramatically. In 2010, 59 percent of the U.S. adults the Yale program surveyed thought global warming was happening; by this year, that number was up to 67 percent. In 2009, 31 percent of respondents thought global warming would harm them personally; by this year, that number was up to 42 percent.
And in the past year, activity has exploded amongst young people. Youth climate activists are gathering, millions deep, to bring attention to their stolen futures. Scientific teams are issuing stronger and stronger warnings. Global attention to the problem and the potential solutions is growing. But at the same time, the action that’s been taken so far is far from enough.
“A lot of people are starting to connect the dots,” says Leiserowitz. “Saying, oh my god, this event, is it climate change? And for a larger swath of the population, they’re starting to see it too, asking, ‘Huh, what’s going on with this record-setting event after record-setting event? Are these things connected?’”
“It was a very bad decade,” says Stokes. “I’d say we lost nine years of the decade, but we really started getting somewhere in the last 12 months. There’s a whole new energy and dynamism,” and that, she says, could signal that the next decade in climate might, hopefully, be different than the last.