The Divergence between Surface and Lower Troposphere Global Temperature Datasets and its Implications
<![CDATA[By Bob Tisdale I include a graph in my monthly global surface temperature and lower troposphere temperature anomaly updates that compares the average of the global surface land+ocean temperature anomaly products (from GISS, NCEI and UKMO) to the average of the global lower troposphere temperature anomaly products (from RSS and UAH). (See Figure 9 from the most recent August update for an example.) Because all of the suppliers use difference base years for their anomalies, I’ve recalculated the anomalies for all using the WMO-preferred reference period of 1981-2010. Figure 1 My Figure 1 is similar to Figure 9 from those updates, but in it, I’ve also shown the linear trends for the global surface and lower troposphere temperature anomaly products. The linear trend, the warming rate, presented by the average surface-based products is noticeably higher than the average lower troposphere products. This, of course, according to Dr. Gavin Schmidt (head of NASA GISS), is the opposite of what the anthropogenic global warming hypothesis tells us is supposed to happen, which is that the lower troposphere is supposed to warm at a faster rate than the surface. See Screen Cap 1. Screen Cap 1 (Click for full size) BUT WHEN DO THE SURFACE AND LOWER TROPOSPHERE PRODUCTS BEGIN TO DIVERGE? To determine this we need to look at the warming rates (linear trends) of the average surface and lower troposphere temperature data. With a start year of 1979 and working backwards in time from 2015 to 1989, I had EXCEL calculate the annual linear trends of the average surface temperature and average lower troposphere temperature anomaly data. Table 1 shows the lower troposphere and surface temperature trends from 1979 to the listed end years of 2015 to 1989. With the exception of a few end years from the late 1990s to the early 2000s, the average lower troposphere temperature data have noticeably lower warming rates than the average surface temperature products. The similarities in the trends from the late 1990s through to the early 2000s are likely caused by the excessive response of the global lower troposphere temperatures to the 1997/98 El Niño. Table 1 NOTE: For those new to the discussion, there are very fundamental reasons why the lower troposphere has an excessive response to a massive El Niño. The lower troposphere warms for two reasons during an El Nino. First, it warms because the Earth’s surface warms as a result of the El Nino. Second, the lower troposphere warms an additional amount because the El Niño’s higher sea surface temperatures in the tropical Pacific cause a tremendous amount of moisture to be evaporated from its surface and that moisture releases more heat to the troposphere after it rises into the atmosphere, condenses and forms clouds. [End note.] Plainly, the 1997/98 El Niño appears to have caused a temporary alignment of the trends of the average surface and average lower troposphere temperature products. Regardless, the trends of the two metrics align at the end year of 1999, so we’ll use that as our breakpoint in this discussion. See Figure 2. Figure 2 From 1979 to 1999, the trends of the two metrics are the same at 0.147 deg C/decade. WHAT ARE THE TRENDS AFTERWARDS? Figure 3 illustrates the linear trends of the average global surface temperature and the average global lower troposphere temperature products from January 2000 to now, August 2016. The average global surface temperature data almost double the warming rate of the average global lower troposphere temperature data during this period. Figure 3 But according to the hypothesis of manmade greenhouse gas-driven global warming, the opposite is supposed to happen…the lower troposphere is supposed to be warming faster than the surface. THREE POSSIBLE REASONS WHY DATA CONTRADICT HYPOTHESIS Of course, there are three possible reasons why the global lower troposphere and surface temperature products do not agree with the hypothesis of human-induced global warming:
- First, the global lower troposphere data are flawed, causing warming rates that are too low.
- Second, the surface temperature data are flawed, causing warming rates that are too high.
- Third, the hypothesis of human-induced global warming is flawed, along with the computer models that support it.