Are years the appropriate units for such comparisons, though?
Anyway I give them their record, my main gripe is really the talk about averages. It's just plain misleading or at least not as informative as it could be.
Decades are a better unit, but new decades only come once every 10 years. Units less than a year are problematic because of seasons. For example, you could say that July was the hottest month on record this year, and that wouldn't really tell you anything interesting (except that maybe more humans live in the north hemisphere and we mostly take observations where humans live).
> For example, you could say that July was the hottest month on record this year, and that wouldn't really tell you anything interesting (except that maybe more humans live in the north hemisphere and we mostly take observations where humans live).
Water has a relatively large heat capacitance, which means that it is more resistant to changing temperature. As a result, places near large bodies of water tend to see lower highs and higher lows than places not near them. Compare the climate of, say, Mumbai (whose highs vary between 30 and 34C around the year) versus Nagpur (whose highs vary between 29 and 43C), both of which are at roughly the same latitude, but one is coastal and the other substantially more inland.
The southern hemisphere has very little land, especially in the temperate belt (between Tropic of Capricorn and Antarctic Circle)--that land is Argentina, Chile, Uruguay, a smallish part of Brazil, South Africa, half of Australia, New Zealand, and small fragments of a few more countries. There's no major landmasses to vary in temperature with the seasons like there is in the northern hemisphere, and hence the southern hemisphere has a much smaller role than the northern hemisphere in measuring global climatic fluctuations.
A better comparison would be to say "the hottest 10 days were all this July. There seems to be a trend here". Then it would be obvious that it was simply the hottest July, so of course all days were comparatively hot.
Just saying that there could be climate patterns that span more than a year, and "all the hottest Julies where in the last ten years" would be similar to saying "all the hottest days were in the last month".
Not saying it is the case, but also not saying that I automatically believe the fearmongering.