By Andy May
This post was updated August 25, 2015 to clarify the text on sea surface temperatures, provide a correlation coefficient between the two warming periods and to discuss the Planck parameter.
Many writers, including Professor Richard Lindzen and Ed Caryl have noticed the remarkable similarity in global warming observed from around 1910 to 1944 and 1975 to 2009. The similarity in slopes exists in all global surface temperature datasets. Figure 1 shows the HadCRUT version 4 dataset and the NASA GISS land (GHCN v3) and ocean (ERSST v4) temperature dataset. We’ve identified the two periods of interest on the figure. All datasets also show some cooling between 1945 and 1975.
Figure 2 shows the two periods overlain with data from the HadCRUT version 4 dataset. This display is scaled to actual average temperature. Unlike Figure one this figure uses monthly smoothed data. In that way, we can see some of the variation within each year.
The left side of Figure 2 represents 1910 for the blue line and 1975 for the orange line. On average the earlier blue line is 0.36°C cooler than the later line. The later line also has a steeper slope, the earlier represents 0.144°C of warming per decade and the later line shows 0.192°C warming per decade. Figure 3 shows the yearly HadCRUT v4 anomalies from the mean with the two means forced to be the same.
Overlay of the two 20th century HadCRUT warming periods
Now we can easily see the similarity in the two warming periods. The linear correlation coefficient (also called the Pearson product moment correlation coefficient) between the two periods is 0.81, so they are highly correlated. Yet the IPCC in their AR5 Summary for Policy Makers states on page 17:
“It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together.”
On page 14 of the Summary for Policy Makers they provide a description of the anthropogenic “radiative forcing” from man’s emissions and other actions. This is shown in Figure 4.
By Andy May
In previous posts (here and here), I’ve compared historical events to the Alley and Kobashi
GISP2 Central Greenland Temperature reconstructions for the past 4,000 years. Unfortunately, these two reconstructions are very different. Recently Steve McIntyre has suggested a third reconstruction by Bo Vinther. Vinther’s data can be found here. Unfortunately, Vinther is often significantly different from the other two. The Alley data has been smoothed, but the details of the smoothing algorithm are unknown. So the other datasets have been smoothed so they visually have the same resolution as the Alley dataset. Both datasets (Kobashi and Vinther) were first smoothed with a 100 year moving average filter. Then 20 year averages of the smoothed data were taken from the one year Kobashi dataset to match the Vinther 20 year samples. The Alley data is irregularly sampled, but I manually averaged 20 year averages where the data existed. If a gap greater than 20 years was found that sample was skipped (given a null value).
All three reconstructions are shown in Figure 1. There is no reason to prefer one of the three reconstructions over the other two, so I simply averaged them. The average is the blue line. I’m not presenting this average as a new or better reconstruction, it is merely a vehicle for comparing the three reconstructions to one another and to other temperature reconstructions. This is an attempt to display the variability in common temperature reconstructions for the past 2,000 to 4,000 years.
Mark Steyn has written a wonderful new book on Dr. Michael Mann’s hockey stick and the controversy surrounding it. It is difficult to overstate the significance or impact of Mann’s Hockey Stick (Mann, Bradley, Hughes (23 April 1998), “Global-scale temperature patterns and climate forcing over the past six centuries” (PDF), Nature 392 (6678): 779–787, Figure 5, the paper is often abbreviated as “MBH”). The Hockey Stick appeared in Figure 1 of the Summary for Policymakers of the third IPCC Assessment Report (called “TAR” published in 2001) and it was prominently displayed in Al Gore’s movie “An Inconvenient Truth.” As the book clearly shows, both the graph and the movie have been thoroughly discredited by hundreds of scientists who have attempted and failed to reproduce Michael Mann’s hockey stick using his data and other proxy data.
#a-disgrace-to-the-profession, #climate-change, #hide-the-decline, #hockey-stick, #ipcc, #mark-steyn, #mikes-nature-trick, #scientific-fraud