Cicadas are back, but climate change is messing with their body clocks

Billions of cicadas are emerging across about 16 states in the Southeast and Midwest. Periodical cicadas used to reliably emerge every 13 or 17 years, depending on their brood. But in a warming world where spring conditions arrive sooner, climate change is messing with the bugs' internal alarm clocks. 

Scientists believe that cicadas count years through the change in fluid flow in tree roots, and when their year to emerge arrives, they stay underground until the soil temperature reaches 64 degrees Fahrenheit. Spring-like conditions now occur earlier, with the season warming 2 degrees Fahrenheit across the U.S. since 1970, according to Climate Central, a nonprofit researching climate change. 

Spring arriving sooner means so are the cicadas. Last month, the cicadas' return started in Georgia nearly two weeks ahead of schedule before spreading north as far as the suburbs of Chicago. The Southwest has experienced the most spring warming, with locations in Nevada, Texas, and Arizona exceeding 6 degrees Fahrenheit of spring warming since 1970, according to Climate Central.