This story is over 5 years old.


Three-Quarters of Extremely Hot Days Are Because of Climate Change, Say Scientists

While no single event can be attributed to climate change, the likelihood of an extremely hot day occurring is higher because of human greenhouse gas emissions — much like smoking increases a person's chance of contracting cancer.
Photo by Charlie Riedel/AP

VICE News is closely tracking global environmental change. Check out the Tipping Point blog here.

Seventy-five percent of extremely hot days and nearly a fifth of heavy rain or snow events are caused by climate change, according to a study published in Nature Climate Change.

Global average temperatures have risen about 0.8 Celsius since pre-industrial times, according to the UN Intergovernmental Panel on Climate Change. And, due to the inertia of the climate system and the total amount of carbon dioxide already emitted by humans, temperatures are likely to rise an additional 1 C.


The world's leaders will meet in Paris at the end of this year to hammer out an agreement on cutting greenhouse gas emissions and keep global temperature rise within 2 C of pre-industrial levels.

The researchers from the Swiss university ETH Zurich who conducted the study say as temperatures rise, the likelihood of extreme weather events rises non-linearly. "[T]he probability of hot extremes at 2 C, for example, is double that at 1.5 C global warming," the authors write.

If global temperature rise hits 2 C, say the authors, human-driven climate change will account for 40 percent of precipitation extremes and 96 percent of heat extremes.

The ETH Zurich researchers defined extreme events as ones that typically occur once every 1,000 days.

While they say no single extreme weather event can be attributed to climate change, human greenhouse gas emissions increase the likelihood of very hot days or extreme precipitation.

"In a broader context, the approach here is reminiscent of medical studies, where it is not possible to attribute a single fatality from lung cancer to smoking. Instead, a comparison of the lung-cancer-related mortality rate in smokers with the rate in non-smokers may allow attribution of the excess mortality to smoking," they write.

Related: Pope Francis is holding a climate change conference at the Vatican