In this post I draw together ideas developed in previous posts- Poles Apart, Pause Updates, Dig and Delve Parts I and II– in which I lamented the lack of tropospheric data for the regions of the northern and southern hemispheres from 20 to 60 degrees North and South. These regions between the Tropics and Polar regions I shall call Temperate regions, as that’s what I was taught in school.
A commenter of long standing, MikeR, who has always endeavoured to keep me on the straight and narrow, suggested a method of estimating temperature data for these regions using existing Polar and Extra-Tropical data. I’ve finally got around to checking, and can now present the results.
The correct formula is:
T (20 to 60 degrees) = 1.256 x TexT ( 20 to 90 degrees) – 0.256 X T pole(60 to 90 degrees).
This gives an approximation for these regions in lieu of UAH data specifically for them.
And the results are very, very interesting. Hello again, Pause.
All data are from the University of Alabama (Huntsville) (UAH) lower troposphere, V.6.0.
First of all, here are plots showing the Extra-Tropics (20-90), compared with the corresponding Temperate regions (20-60).
Fig. 1: Monthly UAH data for Northern Extra-Tropics (20-90N) and Estimate for Northern Temperate Region (20-60N)
Fig. 2: Monthly UAH data for Southern Extra-Tropics (20-90S) and Estimate for Southern Temperate Region (20-60S)
As expected, the result of very slight differences is a slight cooling of the Northern Extra Tropics trend, and a slight warming for the Southern. No surprise there.
The real surprise is in the Land and Ocean data. In the Northern Temperate region, CuSum analysis reveals a large regime change which occurred at the beginning of 1998. The following plots show trends in the data up to January 1998 and from February 1998 to December 2016.
Fig. 3: Estimated Northern Temperate data trends to January 1998 and from February 1998 to December 2016.
Fig. 4: Estimated Northern Temperate data trends to January 1998 and from February 1998 to December 2016: Ocean areas.
Fig. 5: Estimated Northern Temperate data trends to January 1998 and from February 1998 to December 2016: Land areas.
Say hello to the Pause again. Northern Temperate land areas- most of North America, Asia, Europe, and North Africa, containing the bulk of the world’s population, agriculture, industry, and CO2 emissions- has had zero trend for 18 years and 11 months. While the trend for the whole record is +1.8C per 100 years, the record is clearly made of two halves, the first with a much milder +0.7C trend, then after an abrupt step change, the second half is flat- in spite of the “super El Nino” and the “hottest year ever”.
Compare this with the Extra-Tropics data, 20-90N.
Fig. 6: Northern Extra-Tropics data (20-90N) trends to January 1998 and from February 1998 to December 2016: Land areas.
The step change is still there, but the trends are virtually unchanged- only 0.1C different +/- 0.1C.
Why the difference? Northern Extra Tropics data (20-90N) includes the North Polar data (60-90N). The major change in the North Polar region occurred in early 1995, as the next two figures show:
Fig. 7: Northern Polar data (60-90N) trends to February 1995 and from March 1995 to December 2016: Land areas.
Fig. 8: Northern Polar data (60-90N) trends to February 1995 and from March 1995 to December 2016: Ocean areas.
Massive changes in trend. Note the change apparently occurred in land data before ocean, which is peculiar, and both in the dead of winter. Polar regions, though much smaller, have a large impact on trends for the Extra-Tropics.
In the Southern part of the globe, once again say hello to the Pause.
Fig. 9: Estimated Southern Temperate data trends to January 1998 and from February 1998 to December 2016.
While the step change is much smaller, using the same dates the Pause is still undeniable.
Fig. 10: Estimated Southern Temperate data trends to January 1998 and from February 1998 to December 2016- Land areas.
Fig. 11: Estimated Southern Temperate data trends to January 1998 and from February 1998 to December 2016- Ocean areas.
Most of the Southern Hemisphere is ocean, so it follows that a Pause in the ocean leads to a Pause overall.
It is important to stress that the figures I show for Northern and Southern Temperate regions are estimates, not actual data from UAH. However, they are pretty good estimates, and until we have data from UAH, the best available.
Of the world’s regions, South Polar and Southern Temperate regions are paused, as is the Northern Temperate Land region, which is arguably the most important. The Tropics fluctuate with ENSO. Only the Arctic is strongly warming.
The Temperate regions are arguably the most important of the globe. Together they cover more than half the surface area, and contain the bulk of the world’s population, agriculture, industry, and emissions. I hope that Dr Spencer will be able to provide datasets for these regions as soon as possible.