I have been tracking the University of Maine (UM) Climate Change Institute (CCI) daily and monthly global temperature anomaly estimates based on reanalysis of the Global Forecast System (GFS) initialization data, also know as the Climate Forecast System Reanalysis (CFSR). Daily estimates through November are plotted in Figure 1 for 2015 so far and in Figure 2 for 2014 through 2015 so far.
These daily estimates show an overall flat trend through most of 2014 and 2015, with a sharp upward jump in October 2015 that continues high into November 2015. I suspect this jump is related at least in part to the peaking El Niño in the Pacific as it exerts influence on temperatures around the globe. These short-term changes are weather and not climate. It will be interesting to see how much longer this small upward spike lasts.
The UM CCI currently has final CFSR monthly estimates through June 2015 and daily estimates through October 2015. I compiled the final daily estimates into monthly estimates for July through October 2015 and compiled a preliminary November 2015 estimate from preliminary daily estimates. All of the UM CCI estimates presented here have been normalized to the most recent standard climatological reference period 1981 through 2010.
Figures 3 and 4 show the monthly global temperature anomaly trends for this century so far, 2001 through November 2015, and for the satellite era at the end of the last century 1979 through 2000 respectively.
The recent spike in global temperature anomaly has not significantly changed the downward slope for the 21st century so far, but has reduced the coefficient of determination, indicating a less certain trend. The indicated trend of -0.0012 degrees Celsius (C) per month corresponds to a trend of -1.44C per century if it continued through the remainder of this century, which is not likely. For comparison, the trend for the satellite era at the end of the 20th century, 1979 through 2000, is +0.0007C per month which corresponds to +0.84C per century if sustained.
Another way to view the CFSR estimate period is to break it at the intense 1997-1998 El Niño as shown in Figures 5 and 6. Figure 5 shows the most recent 1997 through November 2015 portion covering nearly 19 years and including the 1997-1998 El Niño . Figure 6 shows the previous 18 year period period for 1979 through 1996.
Both of these periods show essentially a flat trend with no overall increase or decrease, but with a higher step offset of about +0.3C for the most recent period. However, during this entire 37 year period, carbon dioxide (CO2) continued to increase steadily with no indication of a step trend. This data indicates that the relationship of CO2 to global temperature is not at all direct over this long of a time scale, which casts into serious doubt whether it has any significant effect at all.
For for the latest CFSR daily updates to key figures, see the Daily Updates page accessible from the menu bar at the top of this page.