I was preparing a few graphs for a chapter of my upcoming book (current working title An Illustrated Guide to Global Warming and Skepticism), and I thought readers here would find them interesting because they display global warming in a different light. The changes in temperature are minuscule when we look at the annual temperatures at all latitudes of the planet. I believe most of us are aware of that fact, and often times, because we’re looking at anomalies, we lose sight of the big picture. (Those warming signals would be even smaller if we were to consider the seasonal cycles and daily variations in temperatures…but those additional variations are beyond the scope of this post.)
In this post, we’re going to be looking at global temperature data and a reanalysis of global temperatures in absolute form, on a latitude-average (zonal-mean) basis, for two decade-long periods: 1979 to 1988 and 2003 to 2012. The purpose of the little exercise is simply to show how minute the rise in global temperatures has been when we compare the average temperatures for those two periods, while looking at the temperatures in 5-degree latitude bands from the South Pole to the North Pole. Then we’ll take a look at the climate model simulations of global land+ocean surface air temperatures for 2003 to 2012 and the final decade of the CMIP5 RCP8.5 (IPCC AR5) worst-case scenario, 2091 to 2100.
I’ve included the GHCN-CAMS land surface reanalysis because there are no land surface temperature datasets available in absolute form through the KNMI Climate Explorer. I’ve downloaded the data through to the current month and would have presented the latter period as 2004 to 2013, but the GHCN-CAMS reanalysis is missing temperature estimates at high latitudes in the Antarctic in 2013 and I did not want to bias the data there by a seasonal component.
First, a couple of preliminary graphs and discussions:
Figure 1 contains three graphs where the data and reanalysis are presented as anomalies…the form we’re used to seeing. Each dataset (and model output in the case of the GHCN-CAMS reanalysis) covers the period of January 1979 to December 2012, and also shown are the period-average temperature anomalies for periods of 1979 through 1988 and of 2003 through 2012. Looking at the top graph, we can see that global sea surfaces (HADISST) were about 0.17 deg C warmer in 2003 to 2012 than they were in 1979 to 1988. Lower troposphere temperatures (RSS), center graph, were about 0.30 deg C higher in 2003 to 2012 than they were in 1979 to 1988. And in the bottom graph, we can see that land surface air temperatures (GHCN-CAMS reanalysis) were about 0.74 deg C higher in 2003 to 2012 than they were in 1979 to 1988.
As a reference for the GHCN-CAMS reanalysis, GISS Land-Ocean Temperature Index (LOTI) data with the oceans masked shows land surface air temperatures were about 0.64 deg C higher in 2003 to 2012 than they were in 1979 to 1988. See the graph here. The fact that the GHCN-CAMS reanalysis is biased warm is good for this presentation. Just keep that in mind, please.
Another preliminary graph: In Figure 2, the average temperatures (in absolute form) are presented on a zonal-mean (latitude-average) basis. They show the average temperatures for the period of 1979 to 2012 in 5-degree latitude bands. That is, the vertical axis (y-axis) is temperature in deg C. The horizontal axis (x-axis) is latitude. The South Pole is to the left, the North Pole to the right, and the equator is at 0-degree latitude in the center.
Looking at the dark-red curve, the land surface air temperatures are by far the coldest in the Antarctic, averaging almost 40 deg C below zero near the South Pole for the period of 1979 to 2012. The tropics are, of course, much warmer, reaching just over 27 deg C at 12.5 degrees north latitude. And, as one would expect, average land surface air temperatures for the period of 1979 to 2012 cool again gradually until they reach their coldest temperatures for the northern hemisphere near the North Pole. The sea surface temperature data in light blue are, logically, also warmest in the tropics and they cool toward the freezing temperature of sea water in the polar oceans. Sea surface temperatures are, for the most part, warmer than land surface air temperatures. Then across the latitudes sampled by RSS, the lower troposphere temperatures are consistently cooler than both sea surface temperatures and land surface air temperatures.
Figures 1 and 2 probably give you an idea of what you’re going to see…better said, not going to see…when we compare the average temperatures for the periods of 1979 to 1988 and 2003 to 2012.
As a reminder, the GHCN-CAMS curve is the output of a computer model, meaning it’s not data. See Fan, Y., and H. van den Dool (2008), A global monthly land surface air temperature analysis for 1948-present. But they use data as inputs to the reanalysis model and the model infills regions without data. One of the datasets used as input is GHCN, which is used by the three primary global temperature data suppliers for land surfaces. I would be happy to present data, not a reanalysis, if and when a land surface air temperature dataset in absolute form is available through the KNMI Climate Explorer.
Figure 3 includes the comparisons of global temperatures on a latitude-average basis, with the average temperatures for the period of 1979 to 1988 shown in blue and the average temperatures for 2003 to 2012 shown in red. Sea surface temperatures are in the top graph, lower troposphere temperatures in the center, and land surface temperatures in the bottom graph.
Looking at the land surface air temperatures in the bottom graph, there is about a 65 deg C temperature difference between the average temperatures at the South Pole and the equator, and the two curves overlap (by the breadth of the default line chosen by EXCEL) in the Southern Hemisphere, showing how insignificant the changes in temperature have been there. It’s only when we reach the high latitudes of the Northern Hemisphere that there is a noticeable difference between the two curves. At 82.5N, the period average temperature for 1979 to 1988 is about -17.2 deg C, and for 2003 to 2012 it’s -16 deg C…a whopping 1.2 degree rise in temperature between those two decade-long periods.
WHAT ABOUT THE CLIMATE MODELS USED BY THE IPCC?
We’ve already presented that CMIP5 (IPCC AR5) climate models are not capable of simulating surface temperatures over any timeframe. For examples, see the posts:
- Model-Data Comparison with Trend Maps: CMIP5 (IPCC AR5) Models vs New GISS Land-Ocean Temperature Index
- Will their Failure to Properly Simulate Multidecadal Variations In Surface Temperatures Be the Downfall of the IPCC?
- Maybe the IPCC’s Modelers Should Try to Simulate Earth’s Oceans
- Models Fail: Land versus Sea Surface Warming Rates
But as a reference…
We often see maps of future global surface temperatures, where the maps have been color-coded to show everything in red. Example: Refer to the maps in Figure 4. They’re from the BBC article IPCC climate report: humans ‘dominant cause’ of warming. The Arctic temperatures are forecasted to warm more than 11 deg C by the end of the century for the worst-case RCP8.5 scenario on the right.
What they fail to tell us is that average annual temperatures (2091 to 2100) in the Arctic are still below freezing, as they are in Antarctica. See Figure 6, which illustrates the multi-model ensemble-member mean of the climate models stored in the CMIP5 (IPCC AR5) archive, for the worst-case (RCP8.5) scenario. Shown are the simulated annual temperatures on a latitudinal basis for the period of 2003 to 2012 and for 2091 to 2100.
Now consider that there are seasonal variations in temperature every year and daily variations in temperature every day.
As the title of the post read, this was simply a different perspective of global warming.
Many people hear that global temperatures have warmed a specific amount over a certain time period and realize they personally would never have been able to sense that change. The only reason they’re aware of it is the constant propaganda from talking heads. Maybe that’s why global warming falls so far down on people’s priorities on the UN’s recent poll. See the MyWorld2015.org poll The United Nations Global Survey for a Better World.
The data, the reanalysis and the climate model outputs are available through the KNMI Climate Explorer.