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Half a degree Celsius may not seem like much, but climate experts say a world that has warmed 1.5 degrees Celsius above 19th century levels compared to 2 C could be the difference between life and death.

A 2 C Earth would see the number of people facing extreme heat waves more than double. A quarter of a billion more people would face water shortages.

The Arctic Ocean will be ice-free not once in a century but once every 10 years.

Countries that signed the Paris Agreement vowed to cap the rise in global temperatures — already 1.1 C above the pre-industrial benchmark — at well below 2 C, and preferably at 1.5 C.

Humanity is still far off the mark: Even if fulfilled, current pledges to reduce emissions would still set the planet on course to warm by a “catastrophic” 2.7 C, according to the U.N.

Here’s what the U.N.’s Intergovernmental Panel on Climate Change (IPCC) says we can expect in a world that warms by 1.5 C, 2 C and beyond.

Heat waves

Maximum temperatures in some areas will increase by three degrees if the climate warms 1.5 C and four if global heating reaches the 2 C mark.

Heat waves that occur once-a-decade today will become four times more likely at 1.5 C and nearly six times more likely at 2 C.

The odds of extreme heat spells currently seen once every 50 years increase by nearly ninefold at 1.5 C, and fortyfold in a 4 C world.

More people will be affected as well: The percentage of humanity exposed to extreme heat waves at least once every five years jumps from 14% at 1.5 C to 37% with an extra half-a-degree.

Storms

Global warming will cause more rain at higher latitudes, north and south of the equator, as well as in the tropics and some monsoon zones.

Precipitation in subtropical zones will likely become rarer, raising the specter of drought.

Extreme precipitation events today are 1.3 times more likely and 7% more intense than before global warming kicked in.

At 1.5 degrees of warming, extreme rain, snowfall or other precipitation events will be 10% heavier and 1.5 times more likely.

Drought

In drought-prone regions, dry spells are twice as likely in a 1.5 C world, and four times more likely if temperatures climb 4 C.

Capping the rise in average global temperatures to 1.5 C rather than 2 C would prevent an additional 200 million to 250 million people from facing severe water shortages.

Limiting drought would also reduce the risk of related disasters such as wildfires.

Food

In a world that is two degrees warmer than pre-industrial levels, 7% to 10% of agricultural land will no longer be farmable.

Yields are also predicted to decrease, with corn harvests in tropical zones estimated to drop by 3% in a 1.5 C warmer world and 7% with a rise of 2 C.

Sea levels

If global warming is capped at 2 C, the ocean watermark will go up about half a meter over the 21st century. It will continue rising to nearly two meters by 2300 — twice the amount predicted by the IPCC in 2019.

Because of uncertainty over ice sheets, scientists cannot rule out a total rise of two meters by 2100 in a worst-case emissions scenario.

Limiting warming to 1.5 C would reduce rising sea levels by 10 about centimeters.

A destroyed school along the seaside fishing neighborhood of Guet N’Dar in Saint Louis is a reminder of the threat of rising seas, with hundreds of people from the village already displaced. | AFP-JIJI
A destroyed school along the seaside fishing neighborhood of Guet N’Dar in Saint Louis is a reminder of the threat of rising seas, with hundreds of people from the village already displaced. | AFP-JIJI

Species in peril

All these impacts affect the survival of plants and animals across the planet.

Global warming capped at 1.5 C negatively affects 7% of ecosystems. At 2 C, that figure nearly doubles.

An increase of 4 C would endanger half of the species on Earth.

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