A few days ago, NASA released it’s GISS TEMP global surface temperature data showing that in that data set September was warm, with the same value as August (which was also warm). At least one science denier has told me that the fact that August and September were the same means that global warming was not real. What an idiot.
Anyway, it does depend on what data set you look at. If you look at ALL the data sets together on the same graph and stand back even a short distance you will see that they are all about the same. Global warming is real no matter how you measure it. But when we look at details we see some differences.
The venerable Japan Meteorological Agency has now released their data. Their data shows a huge increase in temperature globally for September, making it the warmest September on record.
This difference (between JMA and NASA GISS) is probably because the Japanese data reflect the effects of the ongoing El Nino more directly in the data set.
For the record, here are the JMA for annual global surface temperatures values over the entire record.
The annual value for 2015 is estimated by me by simply taking the average of all the months so far, though September. Normally that would be a reasonable estimate of global temperatures (there is not a huge seasonal variation across the year). However, this year, I’m confident this is a low-ball estimate. All indications are that October will be warmer than September in all the data sets, and since El Nino is cooking along nicely, the rest of the year (and the beginning of next year) may be extra warm as well.