Temperature Update - September 2018 - GISTEMP

According to NASA's GISTEMP the global surface temperature for September was 0.75°C above the 1951-1980 average. In contrast to the satellite data this is only slightly down on the anomaly in August of 0.77°C, and is the equal 6th warmest September on record. It ties with September 2005, and apart from this the last 6 Septembers have been the warmest 6 on record.

It continues the pattern of months that are slightly below the trend since 1970, of 1.81°C / century. The average of the last 12 months are almost exactly where you would expect them to be given a linear trend since 1970.

Predictions

The forecast for 2018 is now 0.814 ± 0.053°C, slightly down on the prediction from last month's data of 0.821 ± 0.067°C. For context the current average on anomalies for the 2018 is 0.806°C.

The history of predictions based on each month's data shows how little change there has been this year.

The current mid-point forecast of 0.814°C is nearly identical to the forecast I would have made based only on January data of 0.812°C. This, of course, has less to to with the power of my statistical method than with the fact that temperatures this year have been very flat and close to the trend.

There is even more certainty that 2018 in the GISTEMP record will be the 4th warmest (between 2014 and 2015), with around a 97.5% chance, that is my statistics suggest only a in 40 chance of being outside this ranking.

GISTEMP

Rank	Year	Anomaly	Probability	Cumulative
1	2016	0.99	0.00%	0.00%
2	2017	0.9	0.09%	0.09%
3	2015	0.87	2.13%	2.23%
4	2014	0.74	97.55%	99.78%
5	2010	0.7	0.22%	99.99%
6	2005	0.67	0.01%	100.00%

I'd still say the actual chance of being 3rd warmest is less than that. To beat 2015 would require the last three months to average over 1°C, temperatures only seen so far during the 2016 el Niño.

But if 2018 is the 4th warmest on record this will be astonishing, given the absence of serious el Niño. It would mean that the last 5 years have been the 5 warmest on record.