Dec 14, 2018 | Updated: 09:51 PM EST

Extremely Hot Days—Why One Study Is Saying that Global Warming is to Blame

Apr 28, 2015 06:00 PM EDT


Climate change is already causing heat waves and other extreme weather events around the world.  Now, a new study has confirmed that these types of extreme events will only get worse and as much as 75 percent of the planet's "moderate daily hot extremes" can be tied to climate change.

This figure means that heat events in a world without climate change would only occur in one out of every 1,000 days, or about once every three years.  However, because of climate change, these events will now occur in about four or five out of every 1,000 days, said the study's lead author, Erich Fischer.  Essentially, climate change has increased the odds of these events occurring.

The percentage of extreme precipitation events since the Industrial Revolution that can be linked to climate change is lower, or about 18 percent, according the report.  However, if the planet does reach 2°C of warming, that figure could rise to 40 percent.  Additionally, if the planet temperatures do rise by 2°C, 95 percent of the planet's daily heat extremes will be connected to climate change.  Currently, the planet is on track to warm by 2°C my the middle of the century, and is expected to warm by 4°C by 2100.

"This new study helps get the actual probability or odds of human influence," University of Arizona climate scientist Jonathan Overpeck, who wasn't part of the research, said. "This is key: If you don't like hot temperature extremes that we're getting, you now know how you can reduce the odds of such events by reducing greenhouse gas emissions."

While the study based its conclusions on what will occur over the entire globe, it did note that Africa and South America would have the highest percentages of hot days connected to climate change, at 89 and 88 percent respectively.  North America and Europe, on the other hand, have a much lower amount, at 67 and 63 percent respectively.

Tying one weather event to climate change isn't easy compared to determining whether or not an event was made more likely by climate change.  So, when scientists do tie extreme events to climate change, they do so by looking at how much more likely it is that event will occur today than before the warming period began.

"Climate change doesn't 'cause' any single weather event in a deterministic sense," Erich Fischer, a Swiss climate scientist and the study's lead author said. "But a warmer and moister atmosphere does clearly favor more frequent hot and wet extremes."

Many studies have illustrated the link between climate change and extreme weather events.  For example, a 2013 study from the National Oceanic and Atmospheric Administration found that extra moisture in the air from climate change will drive a 20 to 30 percent increase in precipitation in the Northern Hemisphere by 2099.

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