June 2015 was warm

Every month NASA GISS comes out with the new data for the prior month's global surface temperature, and I generally grab that data set and make a graph or two. In a way this is a futile effort because the actual global surface temperature month by month is not as important as the long term trend. But at the same time it is a worthy exercise because it is news, and especially lately, we seem to be breaking records of one kind or another every month.

This month I was out of town and actually traveling sans computer, when the NASA GISS data became available. So, for me to produce the graphs and report the news at this point is not that interesting. But, I do want to keep you updated.

June was, it turns out, a warm month. But also, there were corrections to the original data set this month that may cause some confusion. There are often, nearly monthly, but generally tiny corrections in the data, but this month the corrections were more extensive and involved changes in the way the monthly temperature anomalies are calculated.

June 2015 turns out to be the hottest June on record, at a whopping 0.80 degrees C above the 1951-1980 baseline used by NASA. That baseline is, of course, already well above the pre-industrial baseline. We are clearly above 1 full degree C above that.

Sou from Hot Whopper has produced a nice bullet list of results from the NASA GISS data as corrected, most of which I reproduce here:

  • No other month this year was hottest on record.
  • The highest anomaly this year is now March at 0.90°C, which makes it the third hottest March after March 2010, at 0.92°C and March 2002 at 0.91°C.
  • 2015 is still hottest on record so far. With the adoption of ERSST v4, some of the temperatures are higher. So are those of some other years, particularly in 2010, temperatures have been upped quite a bit. But all have changed.
  • April and May are still relatively cool, unlike in some other data sets. By cool I don't mean cold. May was 0.76C above the 1951-1980 mean. It's just that most people thought it would be among the hottest of Mays, particularly since ERSSTv4 was very high in May this year.
  • The lowest anomaly was in April this year, at 0.74°C above the 1951-1980 mean. 
  • The progressive year to date average up to and including June is 0.82°C above the 1951-1980 mean. In June 2010 it was 0.78°C above. (In June 2014, the hottest full year to date, it was 0.72°C above.)

Sou also has an update of her famous month to date chart, here. Go have a look.

The main change in the NASA GISS data is the use of ERSST v4 data for sea surface temperature. This changes all the NASA GISS data and requires that we throw out all our old graphs and make new ones. I'll do that eventually. NOAA has also made this change.

One of the most important features of the new, and improved, data is that the so called "pause" in global warming looks a lot less like a pause than it did before, and it didn't look much like a pause anyway. This of course has got the denialosphere all in a tizzy. And about that, we should really care not one bit. So that's all I'll say about it.

John Abraham, who has been making highly accurate predictions among his friends of what each month's NASA GISS data will look like (I occasionally help him with this) has some bad news about the ocean:

As I have said many times on this blog, if you want to know how much “global warming” is happening, you really have to be able to measure “ocean warming”. That is because more than 90% of the excess energy coming to the Earth from greenhouse gases goes into the ocean waters. My colleagues and I have a new publication, which better characterizes this heating and also compares climate model predictions with actual measurements. It turns out models have under-predicted ocean warming over the past few decades. ...

We separated the world’s oceans into the Atlantic, Pacific, and Indian. All three of these oceans are warming with the Atlantic warming the most. We also calculated the ocean heating by using 40 state-of-the-art climate models. Over the period from 1970, the climate models have under-predicted the warming by 15%.

I've put the graphic from that study above, and it has this caption:

(a) Upper (0–700 m) OHC, calculated using 40 CMIP5 models (gray lines; black line is the ensemble mean). The CMIP5 results are compared with the observation-based estimate using the strategies presented in this study (red line) and NODC mapping (dashed blue line). Two major volcanic eruptions are marked by the black arrows. (b) Annual global-averaged upper ocean warming rates from the CMIP5 model results (gray lines; red line is the ensemble mean) and from observations (blue line), computed from the first differences of OHC at 700 m (units: °C yr−1). Source: Institute of Atmospheric Physics.

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