Explainer

Four Key Takeaways From the IPCC Climate Report

The future is bleak—unless policymakers take aggressive actions now to cut global emissions.

By , an editorial fellow at Foreign Policy.
Serbian firefighters use a water hose to extinguish the burning blaze of a forest fire in the Greek village Glatsona on Evia (Euboea) island on Aug. 9.
Serbian firefighters use a water hose to extinguish the burning blaze of a forest fire in the Greek village Glatsona on Evia (Euboea) island on Aug. 9. ANGELOS TZORTZINIS/AFP via Getty Images

The catastrophic impacts of human-induced climate change have perhaps never been clearer than they are this summer, as searing heat waves, record droughts, and deadly floods tear across the world.

It’s just the start of what experts forecast to be a worsening situation, according to the first new assessment in seven years by the U.N.-affiliated Intergovernmental Panel on Climate Change, or IPCC. The report, released on Monday, is a stark compilation of the latest climate-change research. It details how profoundly humans have altered the climate and what the future could look like if harmful carbon emissions continue on their current trajectory. But the report also outlines a brighter future, where political will to create a low-emissions future could check runaway temperatures and limit the worst of the damaging impacts.

The report “is a code red for humanity,” U.N. Secretary-General António Guterres declared in a statement. “Global heating is affecting every region on Earth, with many of the changes becoming irreversible."

The catastrophic impacts of human-induced climate change have perhaps never been clearer than they are this summer, as searing heat waves, record droughts, and deadly floods tear across the world.

It’s just the start of what experts forecast to be a worsening situation, according to the first new assessment in seven years by the U.N.-affiliated Intergovernmental Panel on Climate Change, or IPCC. The report, released on Monday, is a stark compilation of the latest climate-change research. It details how profoundly humans have altered the climate and what the future could look like if harmful carbon emissions continue on their current trajectory. But the report also outlines a brighter future, where political will to create a low-emissions future could check runaway temperatures and limit the worst of the damaging impacts.

The report “is a code red for humanity,” U.N. Secretary-General António Guterres declared in a statement. “Global heating is affecting every region on Earth, with many of the changes becoming irreversible.”

Here are some of Foreign Policy’s key takeaways from the IPCC’s latest assessment.


The planet is experiencing nearly unprecedented rising temperatures and carbon concentration levels, and human activity is the “unequivocal” driver.

Blistering temperatures in the Arctic, southern Europe, and American West are just signs of a stark global trend: Humans are warming the climate at a rate unprecedented over the last 2,000 years, according to the report. Finding the last two periods of high temperatures like those of the last decade requires going back 6,500 and 125,000 years.

That’s mostly a function of huge amounts of carbon dioxide in the atmosphere, beginning with the Industrial Revolution but really ramping up in the latter 20th century: Carbon dioxide concentrations are higher than at any time in the last 2 million years, the report found. And that’s driving all sorts of impacts, and not just on land: Global sea level rise since 1900 is higher than any century in the last 3,000 years, and oceans are warming faster than anytime in the last 11,000 years.

Toward Deep Decarbonization

Toward Deep Decarbonization: Some 70 percent of today’s CO2 emissions belong to countries with net-zero commitments, but tangible policy action to those ends continues to fall short. Batteries and hydrogen have emerged as two promising technologies for enabling this next level of economy-wide deep decarbonization. This FP Analytics’ Special Report examines the state of the technology, investment trends, and strategic collaborations that are driving decarbonization in some of the hardest-to-abate sectors. Read the report.

At current rates of greenhouse gas emissions, the world will exceed a global temperature increase of 1.5°C—the ostensible target of the Paris climate agreement—during this century. It will even surpass 2°C unless steps are quickly taken to zero-out emissions. The impacts from that half a degree are big, the IPCC notes: At 2°C, “compound” events, such as deadly heatwaves and killer droughts at the same time in the same location, are more likely.

Some worst-case scenarios outlined by the IPCC point to even higher temperature increases of 3°C to 5°C. But even the middle-of-the-road projections are off the charts for human civilization: the last time temperatures were 2.5°C above normal was likely 3 million years ago.


Even if the world takes drastic actions to reduce emissions, a lot of the worst impacts are likely already baked in.

Glaciers will continue to shrink for decades or centuries, regardless of the steps that are taken now. The thaw of Arctic permafrost, which itself releases loads of carbon and methane, “is irreversible at centennial timescales,” according to the report. Sea levels will almost certainly continue to rise for the rest of the century, with a mid-range estimate of between 1.4 and 2.5 feet—bad news for coastal cities, which often bear the brunt of rising sea levels, especially with regard to infrastructure. Eight of the world’s 10 biggest cities are near the coast, and in the United States, almost 40 percent of people reside in coastal areas where rising sea levels can influence flooding and shoreline erosion. Weather events that in the past came once a century will now likely be annual episodes in many coastal locations.

And no matter what steps are taken now to rein in emissions, huge future sea level rises are all but guaranteed. “In the longer term, sea level is committed to rise for centuries to millennia due to continuing deep ocean warming and ice sheet melt, and will remain elevated for thousands of years,” the IPCC report found. 


There are some real black swans out there.

Most of the negative effects of rising temperatures can be more or less projected, depending on how aggressive the planet is about cutting emissions. But there could be nasty surprises, too—and more of them the warmer it gets. “The probability of low-likelihood, high impact outcomes increases with higher global warming levels,” the IPCC report found. 

Those outcomes include things like massive ice sheet loss, the collapse of forests, or even the breakdown of the circulatory system in the Atlantic Ocean that regulates much of the Northern Hemisphere’s weather and climate. Even without disaster-movie scenarios, it’s likely that warmer temperatures will still lead to combinations of extreme events that are harsher, longer-lasting, and more widespread ​​than anything “in the observational record,” according to the report.


Despite the gloom, all is not lost.

Since there’s a near-linear relationship between carbon in the atmosphere and rising temperatures, aggressive action now to cut global emissions to the bone over the next few decades could limit the temperature increase to about 1.5°C. That would also minimize the worst expected impacts, such as torrential rain and flooding and deadly heat waves, later in the century, according to the report.

Listen to Heat of the Moment: The climate change crisis can feel so formidable, so daunting, that instead of mobilizing people to action, it engenders paralysis. What could we mortals possibly do to prevent the calamity? A fair bit, it turns out. On Heat of the Moment, a 12-part podcast by FP Studios, in partnership with the Climate Investment Funds, we focus on ordinary people across the globe who have found ways to fight back.

Listen to Heat of the Moment: The climate change crisis can feel so formidable, so daunting, that instead of mobilizing people to action, it engenders paralysis. What could we mortals possibly do to prevent the calamity? A fair bit, it turns out. On Heat of the Moment, a 12-part podcast by FP Studios, in partnership with the Climate Investment Funds, we focus on ordinary people across the globe who have found ways to fight back.

“The IPCC report underscores the overwhelming urgency of this moment,” John Kerry, the U.S. special presidential envoy for climate, told Politico. “The world must come together before the ability to limit global warming to 1.5 degrees Celsius is out of reach.”

And if the most advanced technologies come into widespread use—such as sucking carbon out of the atmosphere and burying it—some of that temperature increase, though not the sea level rise or ice melt, could actually be reversed by the end of the century. 

“This report is a reality check,” said Valérie Masson-Delmotte, co-chair of Working Group I at the IPCC. “We now have a much clearer picture of the past, present and future climate.

“If we reduce emissions to #NetZero by 2050, we can keep temperatures close to 1.5C.”

Christina Lu is an editorial fellow at Foreign Policy. Twitter: @christinafei

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