What if July Beats Records The Way March Just Did?

Last month I wrote about how global warming might not be so bad after all. Not for me, anyway. Sure, sea level is rising, threatening millions of Americans and many more millions of people around the world. Sure, glaciers are melting and winter snowpack is disappearing in the West (and again, in other parts of the world), putting summer water supplies at risk. Sure, extreme weather is on the rise, almost certainly as a result of human-triggered climate change.

But February, which normally alternates between cold and bitterly cold in Princeton, N.J., where Climate Central is headquartered, was unusually mild. Call me selfish, but I kind of liked it. I didn’t realize at the time that March would be even warmer, and I really liked that. The average high here in central New Jersey is 50°F in March, but this month we went over 60° no fewer than 15 times (the forecast says we might do it once more before April begins). We topped 70° eight times. We hit 78° twice, and once we got all the way up to 79° — fully 29° above normal.

All of that was really nice. But then I began thinking about summer . . . and thinking about how it gets kind of hot. The average high for July, the hottest month, is 85°, and of course there are plenty of days that get hotter than that. Then I thought: what would it be like around here if this coming July resembled the month just ending in term of beating the average. And I began to sweat.

Credit: flickr/rachel a. k.

If July temperatures beat the averages by the same amount March temperatures did, we should see 15 or 16 days above 95°. Eight of those would top 105°. And we’d have two days at 113° and one at 114°. For comparison, the all-time high ever recorded in New Jersey is 110°.

Ouch.

There’s no reason to think that this will happen, I realize. This past winter has been unusually warm in the Midwest and Northeast due to an unusual weather pattern, not because global warming has actually raised temperatures this dramatically (although it has probably played an indirect role). There’s no reason to think a warm winter will be followed by a warm summer—and in fact, there doesn’t seem to be much of a correlation between the two historically.

Beyond that, it’s easier for winter to be a lot warmer than normal than it is for summer. During the coldest season of the year, there’s warmer air not too far away — in the Gulf of Mexico, for example — which can be diverted northward to heat things up. During the summer, air from the Gulf is warmer, but not that much warmer.

As global warming drives up temperatures around the planet, however, even a normal summer will be warmer than it is today. In Philadelphia, the closest major city to Princeton, projections show that by 2050, the number of July days above 90° will increase by nearly 25% — before you count in the inevitable heat wave.

So while my summer scenario is somewhat farfetched, it’s still a useful and sobering reminder that while global warming will make life easier for some people, it’s not really something to wish for.