Watching the global thermometer - year to date GISTemp with June 2015

NOTE: GISS has announced corrections and thanked Nick Stokes (see comments below). Refer to the updated version of this article.


Every month since March, I've posted a chart of the progressive year-to-date global average surface temperature, from GISS. This is the update with June included. I'll repeat the explanation with each update and add what seem to be things to watch.

Note: I made a mistake with the June YTD in the original, which I've now fixed. (Sou 9:00 am)

Update: I've added a chart of annual temps for GISTemp, comparing the version put out in June with the version put out in July. That's so that you can see what difference the shift to ERSST v4 makes.

Sou 12:18 pm Thursday 16 July 2015

Worth noting

• June was an average of 0.76°C above the 1951-1980 mean and is equal hottest June on record, with June 1998.
• The only other month this year that's been hottest on record is February with an anomaly of 0.89°C.
• The highest anomaly this year is now March at 0.91°C, which makes it the second hottest March after March 2010, at 0.92°C.
• 2015 is still hottest on record so far, equal with 2010. 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.
• May is still relatively cool, unlike in some other data sets. By cool I don't mean cold. It was 0.73C above the 1951-1980 mean. It's just that most people thought it would be among the hottest of Mays.
• The lowest anomaly was in April this year, at 0.71°C above the 1951-1980 mean. 
• The progressive year to date average up to and including June is 0.8°C above the 1951-1980 mean. In June 2010 it was also 0.8°C above.

Explaining the chart

The chart is a progressive year to date average for all years from 1995 to the present. (Thanks to JCH for the tip.) What that means is for January each year, it just shows the anomaly for January. For February it shows the average of January and February for each year. For March, its the average of the monthly anomaly from January to March.

If you look at December, each year shows the annual average temperature for the full year. For November, each year has the average for the year up to November, not including December. (As before, I've made it extra large because of all the fine detail.)

Data Source: NASA GISS

2015 is now equal with 2010. The years to watch are 2014, 2010 and 2005. I've plotted them with slightly thicker lines so they stand out more easily.

The coldest year of the lot was 1996, which still ended up more than 0.3°C above the 1950 to 1981 average.  The next time someone tries to tell you that "it hasn't warmed since 1996" then show them this chart :)

GISTemp changes with ERSST v4

Now that GISTemp is using ERSST v4, the temperature data has changed some over all years. Below is a chart showing the annual average for the June version and this latest July version, which uses ERSST v4. I've also plotted the difference between the two versions. It's really piddly in the whole scheme of things as you can see.

Data Source: NASA GISS

Points to note:

• The 2015 temperature for both series is year to date average to May (not including June), so they can be compared.
• The "difference" is the June version minus the July version. Negative means the July version is higher than the June version.
• As you can see, mostly it's almost zilch. The biggest difference is 1943, which is 0.09 so still less than 0.1C difference. Most years it's +/- 0.01C to 0.03C. 
• The July version is higher than the June version at both ends. There's barely any difference in the middle of last century.
• There's that questionable peak around 1940 that someone will undoubtedly be able to sort out one of these days. (Probably because something different happened on war vessels to how the temps were usually taken.)

Related updates

• YTD including March
• YTD including April
• YTD including May

I'll add a link to the table shortly. Here is the link to the table for the top Year to Date chart.