It has been said that global warming has stopped over the last several years. Some say it has not been happening for 17 years, some say for ten years, some say for 12 years. Let’s test these hypotheses

Hypothesis: June, the most recent month with full data, was an average year, not a warm year.

Now that July is nearly over, we can look back at the data for June and see how warm or cool June was.

According to data from NOAA and NASA, summarized here,

June was one of the hottest such months on record globally…The month extended the unbroken string of warmer-than-average months to 340, or a stretch of more than 28 years. That means that no one under the age of 28 has ever experienced a month in which global average temperatures were cooler than average (based on the 20th century average)….Last month featured unusually wet conditions in the eastern U.S., and tragically wet conditions in northwest India, where rainfall that was 200 percent of average inundated parts of the state of Uttarakhand, killing nearly 6,000 and causing widespread destruction. Areas that experienced higher-than-average temperatures during the month include north-central Canada, most of Alaska — which had its third-warmest June on record — and the Western U.S., where about 80 percent of the region was in some stage of drought by the end of the month.

Huh.

Well, OK, so when we look at June we have to reject the hypothesis. But what about the entire year, so far, from January to June? If global warming has stopped, this should be an average year, right?

Hypothesis: Global warming has stopped, therefore this year is not warm.

Again, from NOAA and NASA, there is evidence that this year so far is the seventh warmest year on record so far. So, if this year is average for the last 14 years, than the last 14 years including this one are very, very warm. Sounds like global warming. However, the jury is still out on this one. There is evidence that certain climate effects that were keeping the atmosphere cooler than it otherwise might be are reversing or changing in a way that may make the rest of the year warmer. So, we are reasonably likely to rise from the 7th warmest year on record to a higher rank. But, in the meantime, here’s a nice graphic for you:

(Hat tip Paul Douglas)

But what about the Arctic? I’ve heard tell the sea ice melting started out average this year. Therefore, global warming is not real.

Arctic ice melt is average this year

There is really good data for a period of some 30 years or so in the Arctic. The first ten years of that period had ice melting at a certain rate, and the last ten years of those data had more ice melting, such that none of the last ten years were as icy as any of the first ten years. That suggests a trend. Last year the ice melted even more than ever observed, continuing the trend. But early this year, the ice seemed to be tracking average for the last 30 years, so everything is fine!!!!

But wait, over the last few weeks, the ice seems to have caught up, and it is now tracking right on the 98th percentile for all of the years, at the low (more melting, less ice) end. It is quite possible that this year’s ice will catch up to last year and we’ll have the most sea ice-free year recorded, but if not, we’ll probably have the second or third ice free year. So, well, that didn’t work out either.

It is true that a very rapid increase of sea surface and atmospheric temperatures that happened a decade ago was much greater than the rate of increase in heat in these areas over the last ten years, but the earth is still warming. More importantly, the deep ocean seems to be heating at a higher rate, and since 97% of the sun’s extra heat goes into the ocean anyway, we expect the atmospheric temperatures to fluctuate more randomly.

Also, if you live in the US, this has been an exceptionally warm period. Interestingly, US based denialists are screaming about how “global warming has stopped” while at the same time atmospheric warming is catching up in the US where in the past it was not as severe in some other areas of the world.

So, in the end, the evidence that global warming has stopped is … lacking.