This story is part of Fast Company‘s Climate Change Survival Plan package. As time runs out to prevent climate catastrophe, we’re looking at what we need to do now to safeguard our future. Click here to read the whole series.
We’re at a turning point: The choices that the world makes now will determine how livable the planet is later this century. We know what climate change looks like in 2021. This summer was the hottest on record; hundreds died in unprecedented heat in the Pacific Northwest, and there were widespread power outages in the Middle East, where temperatures topped 125 degrees Fahrenheit. In basements in New York City and subways in China, people were trapped by floods. Massive wildfires burned in Canada and Siberia and Greece. In Madagascar, after four years without rain, the country is facing the first famine caused entirely by climate change.
But this isn’t the “new normal.” As emissions keep growing, things can get much, much worse. The planet has heated up so far a little more than 1 degree Celsius. By the end of the century, we may have managed to limit warming to 1.5 degrees Celsius, the most ambitious goal in the Paris climate agreement. Or, if we’re slower to act, the average temperature may have soared up to 2 or 3 degrees Celsius, or more—differences that sound small, but in reality, will shape very different futures. (Consider the fact that 3 million years ago when the planet was hotter by 3 degrees Celsius, sea levels were as much as 50 feet higher, and giant camels lived in Arctic forests—not things that are going to happen this century but that illustrate the scale of what’s possible with a change of only a few degrees.)
Everything depends on how quickly businesses and governments and the rest of society change course this decade, and the next, and the next. “If we work around the edges of emissions reductions, kind of what we’re doing right now, let’s face it—we’ll definitely be into a 3-to-4-degree Celsius warming level [by the end of the century],” says Kim Cobb, a climate scientist at Georgia Tech. “If not more.” In a recent report, the United Nations warned that the plans countries have to cut emissions put the Earth on track to warm up more than 2.7 degrees Celsius by 2100, something the report emphasizes would be catastrophic—and that’s only if countries actually succeed in meeting those pledges. The numbers may seem abstract, but here’s a look at how they translate into impacts.
A 3-degree Celsius world
To imagine the planet after 3 degrees of warming, take the example of Australia, where catastrophic wildfires, fueled by ongoing drought and heat, burned an area larger than the state of Florida in late 2019 and early 2020—blanketing cities in smoke and killing or displacing 3 billion animals. Climate change has already increased the number of extreme fire risk days in the country. If the global temperature heats up by 3 degrees, something that’s plausible under the current path, the number of extreme fire risk days could double or even quadruple.
A recent report details other ways the country is likely to change. With 3 degrees of global warming, as many as 250,000 properties along the coast will risk flooding. Australia will also face more extreme heat. In Melbourne, the number of days hotter than 95 degrees Fahrenheit could double, from 11 to 24. In Darwin, in the country’s northern territory, the number of days hotter than 95 degrees Fahrenheit could jump from 11 to an average of 265 days.
Heat will impact daily life: Outdoor sports, for example, might have to move inside. Outdoor work will become more dangerous. But it will also impact larger systems. In the ocean, coral reefs will likely disappear; heat has already killed about half of the Great Barrier Reef. Hotter, more acidic oceans will impact fishing. Because of heat, drought, and the increasing numbers of pests, it will be harder to grow food; and yields of key crops could fall between 5% and 50%.
The rest of the world will face similar challenges, with the specific set of problems varying in each location. In low-lying Bangladesh, as sea levels rise, millions of people will likely be forced to relocate. Large swaths of major cities will flood, from Shanghai (where 17.5 million people may be displaced) to Alexandria, Egypt, to Miami; globally, hundreds of millions of people may have to relocate.
In some tropical countries, the combined levels of heat and humidity may grow so high during heat waves that it surpasses the limit of what human bodies can survive. (In India, this type of extreme heat stress may happen even at lower levels of climate change.) Droughts that are currently considered once-in-a-century events could happen every two to five years in much of the world, including parts of the U.S. As farms struggle with droughts, heat, and sometimes extreme rain, food prices will rise. The Amazon rainforest may not survive. Antarctic ice sheets will melt faster, pushing sea levels higher.
It’s very possible that the world will heat up even more, depending on both how slowly we act and how the natural world changes—rainforests, for example, which have played a critical role in absorbing carbon, are beginning to emit more carbon than they absorb. If the planet passes 4 degrees Celsius of warming, life will be considerably bleaker. The risk of extreme heat, hurricanes, fires, and other impacts will increase even more. Many of the glaciers that feed rivers in Asia will be lost. Much of Europe could become a desert. The area where people can live—and feasibly grow food—will significantly shrink. “A [4-degree Celsius] warmer world may well be survivable, but it would be eminently poorer than the one we currently enjoy,” journalist Gaia Vince writes in the Guardian.
A 2-degree Celsius world
At 2 degrees of global warming, the impacts the world will experience will still be extreme. Heat waves like the one in the Pacific Northwest this year will occur 14 times more often than they did historically. Severe droughts that used to happen once a decade will happen two to three times as often. Extreme rainfall will happen 70% more frequently. Coral reefs are likely to decline by 99%.
The Arctic Ocean, once a decade, could become ice free in the summer. The number of days with a high risk of wildfire will grow. “Compound” events, like heat waves that happen at the same time as droughts, will become more frequent. Yields of key crops, such as rice and wheat, are likely to decline, especially in sub-Saharan Africa, Southeast Asia, and South America.
For years, limiting global warming to 2 degrees Celsius was considered an important goal—though the number was suggested somewhat arbitrarily in the 1970s by an economist; and the more scientists study the likely impacts, the worse it appears. At the negotiations for the Paris climate agreement, island nations at high risk from rising sea levels lobbied for countries to push for a more ambitious goal of limiting warming to 1.5 degrees Celsius. Countries eventually agreed to limit warming to “well below” 2 degrees Celsius, and to aim for 1.5 degrees.
A 1.5 degree Celsius world
Limiting warming to 1.5 degrees still isn’t “safe.” But it’s substantially better than 2 degrees. Hundreds of millions of fewer people are likely to be exposed to extreme heat waves, for example. Still, heat will be a major problem: More than a billion people could be exposed to severe heat waves at least once every five years. Coral reefs are likely to decline by 70% to 90%—better than the scenario at 2 degrees of warming, when reefs aren’t likely to survive at all, but still a major problem both for marine life and for people who rely on seafood to eat. The global annual catch from marine fisheries may drop by 1.5 million metric tons. The sea level may rise, on average, as much as 2.5 feet. Around 4% of the land area on the planet—more than a billion acres—will transform into a different type of ecosystem (forests, for example, may change into shrublands). Many animals, including pollinators that are critical for the food system, could lose more than half of their range. (But, by comparison, the number of insects losing habitat would triple at 2 degrees Celsius of warming.)
Keeping warming under 1.5 degrees Celsius will require reaching “net zero” by 2050, meaning that most emissions are eliminated, and a huge amount of CO2 will have to be simultaneously pulled from the atmosphere by planting trees and using new technology like machines that suck up carbon in giant fans. When we hit net zero and warming stabilizes, we can go further. “We don’t think there’s much lag between a turnaround in atmospheric CO2 concentrations in the sky and the beginning of a decline in global temperatures,” says Cobb.
And the changes that are needed to reach the goal have other benefits. Shifting away from fossil fuels will also dramatically improve air quality and save lives. Planting trees in cities, which in turn will makes neighborhoods more walkable, will simultaneously cut CO2 and make cities better places to live. Installing new solar and wind plants and retrofitting houses for climate change will create jobs. The transition is necessary to be able to avoid the worst-case scenario—and it also can help now.