The world is busted. For decades, scientists have carefully accumulated data that confirms what we hoped wasn’t true: The greenhouse gas emissions that have steadily spewed from cars and planes and factories, the technologies that powered a massive period of economic growth, came at an enormous cost to the planet’s health. Today, we know that absent any change in our behavior, the average global temperature will rise as much as 4 degrees Celsius by the end of the century. Global sea levels will rise by up to 6 feet. Along with those shifts will come radical changes in weather patterns around the globe, leaving coastal communities and equatorial regions forever changed—and potentially uninhabitable.
Strike that. We are already seeing the effects of a dramatically changed climate, from extended wildfire seasons to worsening storm surges. Now, true, any individual weather anomaly is unlikely to be solely the result of industrial emissions, and maybe your particular part of the world has been spared so far. But that’s little solace when the historical trends are so terrifyingly real. (Oh, and while it used to take mathematicians months to calculate how the odds of specific extreme weather events were affected by humans, they’ve knocked that data-crunching time down to weeks.)
Thankfully, it seems most of the world’s nation-states are beyond quibbling over the if of climate change—they’re moving rapidly onto the what now? The 2015 Paris climate agreement marked a turning point in the conversation about planetary pragmatics. Renewable energy in the form of wind and solar is actually becoming competitive with fossil fuels. And the world’s biggest cities are driving sustainable policy choices in a way that rival the contributions of some countries. Scientists and policymakers are also beginning to explore a whole range of last-ditch efforts—we’re talking some serious sci-fi stuff here—to deliberately, directly manipulate the environment. To keep the climate livable, we may need to prepare for a new era of geoengineering.
How this Global Climate Shift Got Started
If we want to go all the way back to the beginning, we could take you to the Industrial Revolution—the point after which climate scientists start to see a global shift in temperature and atmospheric carbon dioxide levels. In the late 1700s, as coal-fired factories started churning out steel and textiles, the United States and other developed nations began pumping out its byproducts. Coal is a carbon-rich fuel, so when it combusts with oxygen, it produces heat along with another byproduct: carbon dioxide. Other carbon-based fuels, like natural gas, do the same in different proportions.
When those emissions entered the atmosphere, they acted like an insulating blanket, preventing the sun’s heat from escaping into space. Over the course of history, atmospheric carbon dioxide levels have varied—a lot. Models of ancient climate activity, hundreds of millions of years back, put carbon dioxide levels as high as several thousand parts per million. In the past half-million years or so, they’ve fluctuated between about 180 and 300 parts per million. But they haven’t fluctuated this fast. Today, atmospheric CO2 is at 407 ppm—roughly one and half times as high as it was just two centuries ago. And we know for certain that extra greenhouse gas is from humans; analysis of the carbon isotopes in the atmosphere show that the majority of the extra CO2 comes from fossil fuels.
The result: extreme weather. There’s global warming, of course; the Earth’s average temperature has increased 1.1 degrees Celsius since the late 19th century. But it goes further. As oceans absorb heat and polar ice sheets melt, hurricane seasons become more severe as warm water from the oceans kicks warm, moist air into the atmosphere. Sea levels rise—about 8 inches in the past century. Critically, the rate of these changes is increasing.
By the Numbers
The number of homes in the US that could end up underwater if sea levels rise 6 feet by 2100, as models suggest. The Miami area would be particularly devastated: Nearly 33,000 homes would end up underwater, at a total loss of $16 billion.
The decline in arctic sea ice per decade since 1980. Melting sea ice and land ice sheets causes a warming spiral: On account of being white, ice bounces light back into space, while exposed, darker land absorbs more of the sun’s energy.
The decrease in thickness of Alaska’s Muir Glacier between 1941 and 2004. During that same period, the front of the glacier retreated 7 miles.