Why is July the hottest month *worldwide*?
August 15, 2016 5:15 PM   Subscribe

I just read this article that says July 2016 was Earth's hottest month in recorded history. And the same article notes that: "NASA's five hottest months on record are July 2016, July 2011, July 2015, July 2009 and August 2014. Only July 2015 was during an El Nino. Records go back to 1880." The data relate to the global average temperature, not just the parts that are having summer in July. So why are the global averages being pulled up especially during the northern hemisphere's summer?

My guess is it's to do with the distribution of landmasses making the southern hemisphere's weather more mild generally, but part of me wonders if it's just a question of skewed data. Any insights and/or suggestions for further reading would be appreciated!
posted by nomis to Science & Nature (5 answers total) 4 users marked this as a favorite
Its to do with climate change. Summers are getting warmer but so are winters.
posted by fshgrl at 5:22 PM on August 15, 2016 [1 favorite]

Fshgrl, that's true, but doesn't explain why the opposite distribution (winter on the northern hemisphere and summer on the southern hemisphere) is not equally hot.
posted by papayaninja at 5:34 PM on August 15, 2016 [4 favorites]

A couple of factors that probably play into it:

-The northern hemisphere is a lot more populous, and highly populated areas tend to be hotter than the countryside.

-Very little of the southern hemisphere's landmass is at high latitude, so winter in the south is more mild.
posted by kevinbelt at 5:38 PM on August 15, 2016

Best answer: my first guess (before reading inside) is the same as yours. some googling turned up this article which argues that the north is actually getting warmer than the south and says
the greater amount of land mass in the north warms up faster than the ocean-dominated south
source paper.
posted by andrewcooke at 5:38 PM on August 15, 2016 [8 favorites]

Best answer: You are correct. Most years July is the hottest month on a global basis. This is indeed because the northern hemisphere has more land than the southern hemisphere. Air over land can heat up more than air over the ocean. Another way to think of it is that all that land in the northern hemisphere can get really cold in January compared to all that ocean in the southern hemisphere in July. So during the southern hemisphere summer (January), the extra cold northern hemisphere drags the global temperature down. The effect is big enough despite the fact that the Arctic (which is ocean) is much warmer during its winter (January) compared to Antarctica (land covered in ice) during its winter (July).
posted by Seymour Zamboni at 5:49 PM on August 15, 2016 [10 favorites]

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