Even if humanity stops global warming in its tracks at two degrees Celsius, long seen as the guardrail for a climate-safe world, Arctic sea ice will still disappear in some years, scientists have warned.
Holding the line at 1.5 C (2.7 degrees Fahrenheit), however, would make a huge difference, according to two separate studies published Monday in the journal Nature Climate Change.
In a 2C (3.6F) world, the Arctic Ocean would be ice-free roughly one-in-four years, whereas if warming does not exceed 1.5C, the odds drop to one-in-40, the researchers concluded.
“I didn’t expect to find that half-a-degree Celsius would make a big difference, but it really does,” said Alexandra Jahn, author of one of the studies and an assistant professor at Colorado University in Boulder.
The 197-nation Paris climate pact enjoins the world to halt warming at “well under” 2C above mid-19th-century levels, and “pursue efforts” to cap the rise at 1.5C.
With one degree of warming so far, Earth has already seen a crescendo of droughts, heatwaves, and storms ramped up by rising seas.
The loss of Arctic sea ice is not only a consequence of global warming, but also an accelerant when millions of square kilometres of snow reflecting the Sun’s radiation back into space are replaced with dark blue ocean that absorbs it instead.
Recent studies have also fingered dwindling sea ice as a likely driver of topsy-turvy winter weather that has seen days when the North Pole is tens of degrees Celsius warmer than Europe and North America.