Most people don’t realize that global temperature has a seasonal pattern dominated by the Northern Hemisphere because of much more land in the Northern Hemisphere than in the Southern Hemisphere and land is where the largest seasonal temperature variations occur. Figure 1 shows the estimated average global temperature each month in 2015 and for the most recent climatic reference period 1981-2010 based on the University of Maine (UM) Climate Change Institute (CCI) Climate Forecast System Reanalysis (CFSR) data for comparison. The CFSR data are derived from all the inputs to the Global Forecast System (GFS) weather forecast model runs four times each day. For 2015 the largest monthly departures from the reference period were toward the end of the year, which also was the time that the latest El Niño was peaking, which could indicate a connection. Notice there is almost a four degree Celsius (C) range from the coldest month January to the warmest month July. The annual range in estimated global temperature dwarfs the individual monthly temperature anomalies relative to the reference period.
Figure 2 shows the UM CCI CFSR monthly global temperature estimates for 1979 through 2015. As can be seen in the graph, the annual variations are much larger than the overall trend for the period, which is 0.0012C per month corresponding to 1.44C per century if maintained. There also seems to be more variation from year to year at the low end of the annual range than at the high end.
Another interesting aspect of global temperatures is that trends for the average coldest month January and for the average warmest month July show some differences. Figure 2 shows the trend of UM CCI CFSR January global average temperature estimates for 1979 through 2015 (click on the graph to enlarge), including the average of the daily maximums for the month, the average for the month, and the average of the daily minimums for the month.
Similarly, Figure 3 shows the July temperature trends. Notice that for both January and July there is about a 4C difference between the monthly average minimum and maximum global temperature estimates. The trends over the entire period are small compared to the average range within each month.
The January trend is +0.0134C per year which corresponds to +1.34C per century if maintained, while the July trend is slightly lower at +0.010C per year which corresponds to +1.00C per century. The highest trend is +0.156C corresponding to +1.56C per century for the January average minimum global temperature estimates. The lowest trend is +0.0087C per year corresponding to +0.87C for the July average minimum global temperature estimates.
Figure 4 shows an update of the latest UM CCI daily global temperature anomaly estimates for 2014 through today (2016 January 26). The October 2015 through January 2016 period has been dominated by high spikes that may be related to the peaking El Niño event. It will be interesting to see how the rest of the year evolves.
For for the latest CFSR daily and monthly updates to key figures, see the Daily Updates and Monthly Trends pages accessible from the menu bar at the top of this page.