Second hottest May on record

According to GISS NASA, the average global surface temperature anomaly for May was 0.88 °C, which is 0.05 °C less than the hottest May in 2016, making May 2017 the second hottest May in the record.

Here is a chart of the average of 12 months to May each year. The 12 months to May 2017 averaged 0.91 °C above the 1951-1980 mean, which was 0.10 °C cooler than the 12 months to May 2016. This makes it the second hottest May to May 12 month period on record.

Figure 1 | Global mean surface temperature anomaly for the 12 months to May each year. The base period is 1951-1980. Data source: GISS NASA

(Google has just made some changes to its charting program, and has yet to iron out some of the kinks. Let me know if you see any problems. I am having trouble seeing the values to the right of the charts. Hopefully it will get fixed soon.)

Below is a chart of the month of May only. This May was 0.88 °C above the 1951-1980 average and was the second hottest May on record. It was 0.05 °C cooler than May 2016 and just pipped the third hottest, which was 0.87 °C back in 2014. Hover over the chart to see the anomaly in any May:

Figure 2 | Global mean surface temperature anomaly for the the month of May only. The base period is 1951-1980. Data source: GISS NASA

ENSO year comparisons - another El Niño? Probably not.

In the chart below you can see the global mean temperature trend by month. It shows the strongest El Niño years since 1950, which were followed by a La Nina. I've included the 2015-17 period for comparison. The BoM ENSO update is now showing neutral, with a 50% chance of an El Nino later this year.

Of the seven very strong, strong and strong to moderate El Ninos since 1950, there were only three that were followed by a La Nina (not including 2015-17, which I don't count). The chart spans a three year period. That is, for the 2015-16 El Niño and subsequent, it goes from January 2015 to December 2017, or would if the data allowed. (For a more detailed explanation see the HW articles: El Niño to La Niña years with more detail here.)

Figure 3 | Global mean surface temperature for strong or moderate/strong El Nino years that were followed by a La Nina. Also includes the 2015/16 El Nino for comparison. Data source: GISS NASA

The Australian Bureau of Meteorology maintains an El Niño Watch in its ENSO wrap-up (see the HotWhopper sidebar). BoM gives a 50% chance of an El Nino, but it's ENSO wrap-up states that its own model indicates there'll not be an El Nino this year. This is from the BoM website on 6 June 2017:

...Virtually all models have reduced the extent of predicted ocean warming compared to earlier in the year, indicating that if El Niño forms, it is likely to be weak.

Where was it hot?

Last month it was very hot in much of Antarctica, and cooler up in the Arctic. This is in contrast to April (see below).

Figure 4 | Map showing mean surface temperature, anomalies for May, from the 1951-1980 mean. Source: GISS NASA

Below is the chart for April this year for comparison. The dark red blobs up north last month faded in May.

Figure 5 | Map showing mean surface temperature, anomalies for April, from the 1951-1980 mean. Source: GISS NASA

Year to date chart

For the record, here is the year to date progressive chart. You need to understand what it is to make sense of it. The chart below shows the average temperature for the year at each point on each separate line on the chart. The topmost line is last year (2016). At January, the point is just the anomaly for January. At February, the point is the average anomaly for January and February. At May, it's the average of January to May inclusive - all the way to December, which is the average for the whole year.

So the 2017 year shows that the average for the period January to May is 0.97 °C. This is 0.19 °C lower than the average for the year was this time last year during the massive El Nino. The average over the entire 2016 year is 0.98 °C (the point marked for December on the 2016 line) so although it's not impossible for this year to be another hottest year, the next few months would have to be very hot for that to happen.

Figure 6 | Global mean surface temperature anomaly by latitude for May 2017. The base period is 1951-1980. Data source: GISS NASA

The anomalies for the rest of the year would have to be more than 0.99 °C for 2017 to be hotter overall than last year. That's looking unlikely.