2015’s record heat: It will soon be ‘normal’

In 2015, sweltering heat smashed temperature records around the globe. That year’s extreme heat, though, will soon be typical, says a new study. Today’s record heat, it suggests, soon will become the “new normal.”

Global temperatures are increasing in part because people are dumping greenhouse gases into the atmosphere. That has helped fuel global warming. The phrase the “new normal” is one that climate scientists have used to describe what will happen in the future. It is when hot days and nights that are rare today become common.

Sophie Lewis led the new study. She is a climate scientist at the Australian National University in Canberra. She and her colleagues started by giving the informal phrase a more formal definition: a time when at least half of the following 20 years surpass the record of the past. Then they applied their new definition to several computer simulations of future climate.

The outcome depends on how much more carbon dioxide, a main greenhouse gas, human activities (such as burning coal and oil) dump into the atmosphere. If humans keep pumping a lot of this CO₂ into the atmosphere, 2015 could become the “new normal” as soon as the 2020s. But even if there’s a sharp drop in CO₂ releases, 2015’s heat will seem typical by 2040. The team published its estimates online November 4 in the Bulletin of the American Meteorological Society.

When 2015’s record heat is common, 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, wildfires and other climate-related disasters.