As 1.5 Degrees Looms, Scientists See Growing Risk of Runaway Warming, Urgent Need to Slash Emissions

A firefighter confronts a blaze near Galice, Oregon.

A firefighter confronts a blaze near Galice, Oregon. Lance Cheung / U.S. Forest Service via Flickr

As the planet rapidly approaches 1.5 degrees C of warming, scientists warn that rising temperatures are degrading the Earth’s ability to soak up carbon dioxide, threatening to further exacerbate climate change. To keep warming in check, they stress, countries must make steep cuts to emissions in the next few years.

Research highlighted in Hot Science, a project of the Bezos Earth Fund and World Resources Institute, underscores the urgent need to draw down emissions, which hit a record high last year as the global economy recovered from the pandemic slowdown. Ocean warming also hit a new high in 2022, with scientists warning that the “global long-term warming trend is so steady and robust that annual records continue to be set with each new year.”

If emissions stay at their current level, the world could hit 1.5 degrees C of warming in just nine years, scientists estimate, breaching the target set in the Paris Agreement.

While governments and the private sector are investing unprecedented sums in clean energy, it is growing increasingly difficult to curb climate change, as degraded lands and waters take up less and less carbon dioxide. Over the last decade, carbon uptake by oceans has fallen 4 percent, while uptake by land has fallen 17 percent, research shows. And the challenge is likely to grow more severe.

Scientists say that surpassing 1.5 degrees C could trigger a cascade of tipping points, which would irreversibly alter the global climate system and further exacerbate warming. The collapse of the Greenland Ice Sheet, for instance, would alter ocean currents, shifting the distribution of heat around the planet, which could lead to mass die-offs in the Amazon. If warming reaches 2 degrees C, even temporarily, scientists calculate that there is a roughly one-third chance of triggering one or more tipping points.

A shift in Atlantic currents, which draw nutrient-rich waters up from the deep, would impact plankton near the surface, inhibiting their ability to soak up carbon dioxide, a recent study finds.

In the Amazon, the degradation of the rainforest threatens to further drive up emissions. While scientists have tended to focus on the wholesale clearing of forest, even minor disturbances — such as fires, drought, or small-scale logging — can release massive amounts of carbon. Over the last two decades, emissions from such degradation have roughly equaled emissions from deforestation, a study finds, and rapid warming would fuel even more severe drought and fire, leading to greater decay.

In the Arctic, increasingly severe fires are unleashing carbon stored in peatlands, and as temperatures rise, the problem could get much worse. A recent study found that even small increases in temperature could lead to “exponential increases in the area burned.”

Climate change also threatens the world’s largest tropical peatland, which lies in the Congo Basin. Longer dry seasons could desiccate the region, causing its forested swamps to decompose. Recent research shows that swamps in the Congo Basin “may be more vulnerable to future climate change than most other tropical peatlands.”

To keep warming in check, it’s not sufficient for countries to zero out emissions by mid-century, researchers say. Nations need to make deep cuts to their emissions in the near term, a study shows. Current policies put the world on track for more than 2 degrees C of warming, but if countries ratchet up their 2030 targets, slashing emissions by another 30 percent, they could limit peak warming to roughly 1.7 degrees C.

“Let’s face it. We are going to breach the 1.5 degrees limit in the next couple of decades,” Haewon McJeon, a scientist at the Pacific Northwest National Laboratory and coauthor of the study, said in a statement. After warming peaks, he said, “we’ll need to bring it back down to 1.5. But how fast we can bring it down is key.”


As Climate Change Worsens, A Cascade of Tipping Points Looms