If you thought 2015 was hot, just wait

The sweltering heat that smashed temperature records in 2015 will soon be par for the course.

Depending on how much more carbon dioxide humans dump into the atmosphere, 2015 could become the “new normal” for global temperatures as soon as the 2020s, researchers estimate online November 4 in the Bulletin of the American Meteorological Society. Even if there’s a sharp reduction in CO₂ emissions, the record-setting year (SN: 2/20/16, p. 13) will seem typical by 2040.

Those predictions are based on defining “new normal” — previously an informal term — as a point in time when at least half of the following 20 years surpass the record. Climate scientist Sophie Lewis of Australian National University in Canberra and colleagues applied their new definition to several simulations of future climate.

When 2015’s record heat is the new normal, extremely hot years will be beyond anything humans have encountered so far, the researchers predict. That extreme heat could lead to more deadly heat waves (SN: 9/3/16, p. 5), wildfires (SN Online: 7/15/15) and other climate-related disasters.