No September update from RSS yet, which is unusual as satellite data usually gets updated in the first few days of the month, and the old RSS 3.3 was updated a couple of weeks ago. In the mean time we now have the first of the surface data released for September.
NASA's GISTEMP shows an anomaly of 0.8°C for September 2017 (compared with the base period of 1951 - 1980).
This is down by 0.04°C from August, and is the 4th warmest September in the record. The last 5 Septembers have been the 5 warmest Septembers on record.
The average for the year to date is now 0.909°C, compared to 0.923°C in August.
Forecast
My forecast 2017 is now 0.901 ± 0.054°C, compared with the forecast for data up to August of 0.906 ± 0.069°C.
It continues to look more likely that 2017 will be the 2nd warmest in the GISS record, but 3rd is still a distinct possibility.
| Rank | Year | Anomaly | Probability | Change |
|---|---|---|---|---|
| 1 | 2016 | 0.99 | 0.12% | -0.97% |
| 2 | 2015 | 0.87 | 88.15% | +3.63% |
| 3 | 2014 | 0.73 | 11.73% | -2.65% |
As always this forecast is based entirely on a simple statistical analysis of past years. In particular it does not take into account the possibility of a La Niña forming in the final months. Given forecasts that there is a reasonable likelyhood (55%-65%) of a La Niña forming soon, the probability of 2017 finishing 3rd warmest are going to be higher than my model suggests.
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