Temperature Update - September 2018 - RSS

Data

According to the RSS Satellite data, September was 0.488°C warmer than the 1979 - 1998 average. This is cooler than recent Septembers but a smaller drop than UAH's data for September. It was the 9th coolest September since satellite records began, and the coolest since 2014. It was the 4th coolest monthly anomaly of the year. (Contrast with UAH which has this month as the coldest September in 10 years and the coldest anomaly this year.)

As with UAH the trend in September warming is stronger than overall warming. RSS has Septembers warming at the rate of 2.26°C / century, compared to an overall warming rate for all months of 1.96°C / century.

Predictions

The prediction for 2018 based on data up to September is 0.516 ± 0.059°C, compared with that from data up to August of 0.531 ± 0.07°C. For reference the average for the first 9 months of the year is 0.511°C.

This continues a downward trend in the predictions for RSS since the start of the year, with the current prediction being about 0.05°C lower than after January.

However the prediction is now even firmer that 2018 will finish 6th in the RSS data set, with close to a 95% confidence that it will finish between 2014 and 2015.

RSS 4.0

Rank	Year	Anomaly	Probability	Cumulative
1	2016	0.77	0.00%	0.00%
2	2017	0.65	0.00%	0.00%
3	2010	0.6	0.39%	0.40%
4	1998	0.58	1.34%	1.74%
5	2015	0.57	2.70%	4.43%
6	2014	0.44	94.75%	99.19%
7	2005	0.44	0.20%	99.38%
8	2003	0.4	0.61%	99.99%

The table suggests less than a 1% chance of finishing below 2014's 0.44°C. This would require the remaining three months to drop to an average of about 0.23°C. The last time temperatures were this cold was at the start of 2012.

My method suggests there is a small (~5%) of beating 2015's 0.57°C to finish 5th or even 4th, but this would require the rest of the year to average around 0.75°C. The only time there have been several months as war as this was during the strong El Niño of 2016, so whilst it might be technically possible given the statistical spread, I think in reality there is practically no chance of that happening in the next three months.

Therefore I am confidently predicting that unless something spectacular happens in October, RSS will have RSS as the 6th warmest year on record.