Kierra Waller, a 9-year-old girl from Baltimore, tries to beat the heat with a misting fan during an NFL football training camp practice in Virginia.

AP Photo/Alex Brandon

corching heat got you down? Better get used to it. A new NASA study reveals a "stunning increase" in the frequency of extremely hot summers over the past six decades. And even more sweltering days are on the horizon. Here's what you should know:

What happened in the study?
Analyzing yearly temperature data going back to the early 1950s, climatologists determined that the sheer likelihood of having a hotter-than-average summer is only getting higher. "Back in the 1950s, temperatures on any given summer day were as likely to be near average as they were to be unseasonably high or low," says Janet Raloff at Science News. Think of it this way: On any day you could roll a six-sided die with low, average, and above-normal temperatures each having equal odds, or two sides assigned to each. Researchers call this concept the "climate dice." 

Now what are the chances?
Since the '80s, that metaphorical die has become more heavily weighted toward hotter days. In fact, since the year 2000, the die has had 4.5 sides dedicated to above-normal temperatures, says Raloff. Before that, there was a "natural variability," says NASA climatologist James E. Hansen, who led the study. In an editorial for the Washington Post, Hansen says that we'll still see "cooler-than-normal summers or a typically cold winter." Charting the temperature data on a bell curve revealed that "the extremes of unusually cool and, even more, the extremes of unusually hot are being altered so they are becoming both more common and more severe."  

How hot is hotter?
The study didn't specify, but previous research has demonstrated that by the end of the century (2100), temperatures could rise as much as 6.3 degrees Fahrenheit. That would "bring a high risk of major extinctions, threats to food supplies, and the near-total collapse of the huge Greenland ice sheet," says The Guardian.

Is this really attributable to global warming?
The team made no attempt to attribute the underlying cause of warming directly to higher carbon dioxide levels or an increase in greenhouse gases, says Raloff. However, if the world is left unchanged, we'll have more events like the "2003 heat wave in Europe that killed more than 50,000 people, and the 2011 drought in Texas that caused more than $5 billion in damage," says Hansen. "The future is now. And it is hot."

Sources: The Guardian, Science News, Scientific American, The Washington Post