Second hottest April on record

According to GISS NASA, the average global surface temperature anomaly for April was 0.88 °C, which is 0.18 °C lower than the hottest April in 2016, making April 2017 the second hottest April in the record.

Here is a chart of the average of 12 months to April each year. The 12 months to April 2017 averaged 0.91 °C above the 1951-1980 mean, which was 0.07 °C cooler than the 12 months to April 2016,. This makes it the second hottest April to April 12 month period on record.

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

Below is a chart of the month of April only. This April was 0.88 °C above the 1951-1980 average and was the second hottest April on record. It was 0.18 °C cooler than April 2016 and just pipped the third hottest, which was 0.87 °C back in 2010. Hover over the chart to see the anomaly in any April:

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

ENSO year comparisons - another El Niño? Probably not.

There was no La Niña after the recent El Niño, or not according to the Australian Bureau of Meteorology (by NOAA criteria there was a weak one). 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

Looking at the chart above for 2015-17, you can see that if there was a La Niña, it wasn't just very weak, it was also very short and hot. 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 9 May 2017:

...five of eight surveyed models indicating El Niño is likely to form by spring. However, the Bureau's climate model POAMA predicts that the Pacific will begin to cool in winter and remain neutral for the rest of the year.

Where was it hot?

Last month it was very hot in much of the high northern latitudes, with some cool patches. There was a very cold patch down in Antarctica.

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

Below is the chart for March this year for comparison.

Figure 5 | Map showing mean surface temperature, anomalies for March, 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. What the chart below shows is 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 April, it's the average of January to April 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 April is 0.99 °C. This is 0.2 °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 this year could still be another hottest year, though the next few months would have to be quite hot for that to happen.

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

The anomalies for the rest of the year would have to remain high for 2017 to be hotter overall than last year, an average of 0.97 °C.