Summer temperatures are searing their way into the record books.
 
Last month was the hottest June on the planet since 1850, when global temperature tracking began, the National Oceanic and Atmospheric Administration reported on July 20. And August is predicted to be another history-making scorcher. 
 
Here atmospheric scientist Valentina Aquila, who teaches in AU’s Department of Environmental Science, explains why Earth is experiencing such a hot summer—and weather or not we can expect a mild winter.
 
Fact: Heat waves happen naturally—but this summer’s record-breaking temperatures are different. 
 
This heat wave is peculiar because it is practically a hemispheric heat wave, with three continents all experiencing very high temperatures. I am in Italy right now, and the temperatures here are also much warmer than usual. 
 
The Pacific Ocean is also currently transitioning from a La Niña phase to an El Niño phase. This natural oscillation, which happens every 5 to 10 years, has implications for the global climate, with La Niña generally cooling down the global mean temperature and El Niño warming it up. While El Niño is not causing this heat wave, it might be charging it by warming the baseline temperature.
 
Fact: This historic heat wave is a predictable consequence of climate change.
 
While a single event is not attributable to climate change, it increases the probability of events that would have been extremely rare otherwise. Climate change increases the base global mean temperature so that a warmer period more easily becomes a heat wave. Imagine adding a tablespoon of water to a half full glass: the water level increases, but no harm is done. Climate change is the equivalent of filling up the glass to the brim; a tablespoon more of water will make the water level go over the edge. 
 
Fiction: A scorching summer means we’ll have a warmer winter.
 
While we can expect heat waves to happen more frequently and to become more intense, the temperature in one season is generally not connected to the temperature in the text. We might have a milder winter—but not because the summer was hot.