Guest essay by Sheldon Walker
Most people have probably seen the SkepticalScience graph called “The Escalator”. If you haven’t seen it yet, then you can view it here:
SkepticalScience claims that “Contrarians” inappropriately “cherrypick” short time periods that show a cooling trend.
But SkepticalScience uses a linear regression over the full date range (1970 to December 2014), to determine the “long-term global surface air warming trend of 0.16 °C per decade”.
We can create a global warming contour map, that shows the SkepticalScience view of the warming rate. Here it is:
Because SkepticalScience uses a linear regression over the full date range, they can only get a single straight line, with a single fixed slope, as seen in part 2 of their escalator animation:
It is impossible for them to show a slowdown or a speedup, if one existed. The method that SkepticalScience uses, guarantees that the global warming contour map of their results, will always be a triangle of a single colour.
We can also create a global warming contour map that shows what the warming rate actually did. Note that this contour map uses the same Gistemp global land and ocean temperature series that SkepticalScience uses. Here it is:
Note that the SkepticalScience view of the warming rate agrees with what the warming rate actually did, when the trend length is greater than 26 years. However, when the trend length is less than 26 years, the SkepticalScience view of the warming rate looks completely bland, and is definitely wrong. Where are the El Nino’s and La Nina’s? Where are the slowdowns and speedups. Do they expect us to believe that global warming proceeds at a uniform constant rate?
I will take this opportunity to point out the recent slowdown in global warming. Look at Graph 2, between 2005 and 2010 on the X-axis, and between trend length 5 and 15 on the Y-axis. The large light-green area is the slowdown. Light-green means that the warming rate was between 0.0 and +1.0 degrees Celsius per century. The average warming rate for the whole graph, is the colour at the top of the triangle, which is yellow. Yellow means a warming rate between +1.0 and +2.0 degrees Celsius per century. So light-green is a slowdown compared to yellow.
This global warming contour map not only shows the slowdown, but it also suggests a possible reason for the slowdown. Look at the light-green areas above 1974, 1983, 1992, 1999 (this is a small one that looks as if it didn’t develop fully), and 2007-2008 (the recent slowdown).
It appears that there is a slowdown approximately every 9 or 10 years. This sounds like it could be a natural ocean cycle, like the PDO or AMO. I have read articles by scientists suggesting that the recent slowdown was caused by natural ocean cycles, and this global warming contour map certainly supports that view.
For anybody who would like to view more global warming contour maps, the website “mta-graphs.com” has 27 UAH contour maps, and 18 Gistemp contour maps. The UAH contour maps all cover 1980 to 2016 (because the UAH satellite series only started in 1979).
The Gistemp contour maps cover 1880 to 2016 (the big picture), 1970 to 2016 (the time of fairly constant global warming), and 1980 to 2016 (to match the date range of UAH).
For anybody who would like some general information about global warming contour maps, there is an article at: