Nighttime temperatures are on the rise in Jacksonville and across the state, and climate change is to blame, scientists say.
The expected overnight low for Tuesday, July 5, is 78 degrees in Downtown Jacksonville, according to the National Weather Service. That’s about 5 degrees above the date’s average low temperature and just 1 degree shy of the record 79 degrees. Similar conditions are expected on Wednesday with an overnight low of 79 degrees, which ties the date’s record and sits 6 degrees higher than the average.
Andrew Pershing, the director of climate science for the nonprofit research group Climate Central, says a few degrees of difference may not sound like a lot, but it can have serious implications.
“Because the range of temperatures overnight is really low in your region, about 10 degrees Fahrenheit, a 2 degree shift in the baseline is actually really significant. And what we’re showing is that those temperatures are five times more likely due to climate change,” he said.
Climate Central uses a tool they’re calling the Climate Shift Index — or CSI — which builds on a decade's worth of research on climate change attribution science to show how climate change is affecting air temperature. Climate change attribution is a relatively new field of research that can be used to determine if climate change made a weather event more severe or more likely to occur, and if so, by how much.
A CSI above zero means that human-caused climate change has made a temperature more common or likely, while a CSI below zero means climate change has made that temperature less common. This week’s anticipated nighttime temperatures around Jacksonville are at level 5, which is the highest number on the CSI scale. That means climate change has made these conditions more than five times as likely. In other words, this level of heat would be nearly impossible without carbon pollution, according to Pershing.
Higher overnight temperatures can cause health issues, especially for people who work outside and those with underlying health conditions. In homes without air conditioning, warmer nights mean people will have more trouble cooling off and recovering from hot days. Those rising temperatures can also lead to higher utility bills as people crank up their air conditioning and have to use it more often. A study from 2019 found that warmer nights can even make it harder to get a good night’s sleep.
When it comes to things like rising temperatures, scientists are extremely confident that climate change is playing a significant role, Pershing says.
“Nighttime temperatures, high temperatures during the day … we have really high certainty and we can make those calculations really well,” he explained. “We know that carbon dioxide puts this heat trapping blanket around the planet and warms things up, and we know from physics that has to be true.”
