What happens if the world warms beyond 1.5 degrees Celsius?

The planet’s average temperature is now 1.2 degrees Celsius warmer than it was before the industrial revolution in the late 1800s, according to the World Meteorological Organization. We are already seeing more intense heat waves, storms and other consequences. The goal of the international Paris climate accord is to prevent much worse, by limiting global warming to “well below” 2 degrees Celsius and ideally to 1.5 degrees Celsius.

In 2018, climate scientists convened by the United Nations published a report warning us of what is likely to happen beyond 1.5 degrees Celsius of warming. At 1.5 degrees warming, sea level is expected to rise by 10 to 30 inches (26 to 77 centimeters), putting 10 million more people at risk from coastal storms and flooding. Heat waves will continue to get worse, exposing 14 percent of the world population to extreme heat at least once every five years. Ecosystems will suffer, too. After 1.5 degrees Celsius of warming, up to 90 percent of all coral reefs could die out, and about 7 percent of Earth’s land area could shift into a new biome, with grasslands turning to desert, tundra turning to forest, etc.

At 2 degrees Celsius, some of these climate impacts will become twice as bad as they would be at 1.5 degrees. But these numbers shouldn’t be viewed as sudden cliffs. “Every half-degree matters,” Penn State University climate scientist Michael Mann told Inside Climate News in 2018. “A better analogy is a minefield. The further out on to that minefield we go, the more explosions we are likely to set off.”

After early heat waves across the northern hemisphere in the summer of 2021, some scientists think we are already setting off more explosions than expected. They warn that even 1.5 degrees Celsius may not be as safe, relatively speaking, as previously thought, and urge communities to start preparing and adapting. 

— Delger Erdenesanaa

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