Every month since March, I've posted a chart of the progressive year-to-date global average surface temperature, from GISS. This is the update with September included. I'll repeat the explanation with each update and add what seem to be things to watch.
Worth noting: Second Hottest September on Record
- 2015 is still hottest on record so far, and not showing any sign of dropping behind.
- The progressive year to date average up to and including September is 0.81 °C above the 1951-1980 mean.
- September was an average of 0.81 °C above the 1951-1980 mean and is the second hottest September on record, after September last year (0.90 °C).
- June this year was the hottest June on record. After late additions to the data, July dropped to being the second hottest July on record after July 2011.
- The highest anomaly this year is still March, now at 0.90 °C, which now makes it the third hottest March after March 2010 at 0.93 °C, and March 2002 at 0.91 °C.
- The lowest anomalies this year so far were April, now 0.74 °C, and July now 0.73 °C above the 1951-1980 mean.
- To drop below the hottest year on record, 2014 (0.75 °C), the average anomaly for the next three months would need to be around 0.58 °C, which seems unlikely. Especially given the El Niño and the fact that the lowest anomaly so far this year was 0.73 °C.
Explaining the chart
The chart is a progressive year to date average, or running mean, for all years from 1995 to the present. What that means is for January each year, it just shows the anomaly for January. For February it shows the average of January and February for each year. For March, its the average of the monthly anomaly from January to March.
If you look at December, each year shows the annual average temperature for the full year. For November, each year has the average for the year up to November, not including December. (As before, I've made it extra large because of all the fine detail.)
|Data Source: NASA GISS - GHCN-v3 1880-09/2015 + SST: ERSST v4 1880-09/2015|
2015 is tracking above all other years, and not showing any sign of dropping (yet). The years to watch are 2014, 2010 and 2005. I've plotted them with slightly thicker lines so they stand out more easily.
The coldest year of the lot was 1996, which still ended up being 0.35°C above the 1950 to 1981 average. The next time someone tries to tell you that "it hasn't warmed since 1996" then show them this chart :)
- YTD including March
- YTD including April
- YTD including May
- YTD including June
- YTD including July
- YTD including August
Some charts showing how temperatures evolved in previous El Niño years can be seen in this article: Why Christopher Monckton is getting nervous about global temperature.
Here is the link to the table for the Year to Date chart.