Image Credit: WoodForTrees.org
Guest Post By Werner Brozek, Edited By Just The Facts
In reference to my previous article RSS Reaches Santer’s 17 Years, and taking into account the good work already done in analyzing Cowtan and Way by Steve McIntyre, Judith Curry, Bob Tisdale, David Whitehouse, and Christopher Monckton, I will focus on one of Cowtan and Way’s methods, which used UAH satellite data to infill missing HadCRUT4 data.
In a nutshell, what Cowtan and Way have done is use the HadCRUT4 data, which covers 84% of the globe, and combine it with UAH data which covers much more of the globe. They have attempted to show what HadCRUT4 would show as a slope if a greater part of the globe could be accounted for by HadCRUT4. Their conclusion was that the warming over the last 16 years would be 2.5 times larger with more extensive global coverage. The main areas where HadCRUT4 is weak is the polar areas and parts of Africa. However it seems as if they did not have many issues with the African coverage nor with the Antarctic coverage. But it seems as if it is in the Arctic where they perceive the problems to lie. Apparently the Arctic has warmed up eight times faster than the rest of the globe over the last 16 years and HadCRUT4 does not reflect that.
What does all this have to do with RSS? Since it is the Arctic that is the issue, I will focus on how well RSS covers this area. RSS covers up to latitude 82.5 degrees. With the circumference of Earth being about 40,000 km, the distance from 82.5 to 90 would be 7.5/90 x 10,000 = 830 km. So the area in the north NOT covered is pir^2 = 2.16 x 10^6 km2. Dividing this by the area of the earth, 5.1 x 10^8 km2, we get about 0.42% NOT covered by RSS for the portion relevant to our discussion. As a fraction, this is about 1/230 of the area of the earth. So for argument sake, let us assume that this 1/230 warmed up more than other parts over the last 17 years. How would that change the length of The Pause according to RSS?
The slope for RSS over the last 17.0 years is -0.00012/year. So over the last 17 years, the rest of the globe would have cooled by 0.00012 x 17 = 0.0020 degrees C. And if that portion of the Arctic not covered by RSS were to make up for this, it would have had to warm by 0.0020 x 230 = 0.46 C. Is this possible? I do not think we can rule it out.
If we take the RSS slope for shorter times than 17 years, the slope gets more negative with each passing month for a year. What happens if we use the slope for 16 years and 11 months? That slope is -0.000444/year. In 16 years and 11 months, that amounts to a decrease of 0.0075 C. If the area north of latitude 82.5 were to make up for this, it would have had to warm up by 0.0075 x 230 = 1.7 C over this time period. I could be wrong, but I do not think this could have happened.
My conclusion is that even if we had accurate data to the north pole, it may have pushed the 17.0 years back a month, or possibly two months at the very most. When we get the RSS data for November, it may well show a pause of 17 years and one or two months. If that is the case, then Cowtan and Way will have negligible implications for RSS. Furthermore, it will make the discrepancy between HadCRUT4 and RSS become larger that it already is.
Now I will provide an explanation of the four trend lines in the graph at the head of this article. The slightly downward sloping line is the trend for RSS since 1997. The slightly upward sloping line is the trend line for HadCRUT4 since 1997. The steeply upward sloping blue line is the trend line one gets by applying the analysis of Cowtan and Way to the HadCRUT4 data. The yellow trend line is for UAH since 1997.
GISS and HadCRUT4 treat missing data in opposite ways, yet both have very similar times for a pause in the warming: GISS is at 12 years and 6 months and HadCRUT4 is at 12 years and 10 months. If Cowtan and Way are correct, I would have expected the difference between GISS and HadCRUT4 to have been much larger.
In the sections below, we will present you with the latest facts. The information will be presented in two sections. The first section will show for how long there has been no warming on several data sets. The second section will show for how long there has been no statistically significant warming on several data sets.
This analysis uses the latest month for which data is available on WoodForTrees.com (WFT). All of the data on WFT is also available at the specific sources as outlined below. We start with the present date and go to the furthest month in the past where the slope is a least slightly negative. So if the slope from September is 4 x 10^-4 but it is – 4 x 10^-4 from October, we give the time from October so no one can accuse us of being less than honest if we say the slope is flat from a certain month.
On all data sets below, the different times for a slope that is at least very slightly negative ranges from 5 years and 5 months to an even 17 years.
1. For GISS, the slope is flat since May 2001 or 12 years, 6 months. (goes to October)
2. For Hadcrut3, the slope is flat since May 1997 or 16 years, 5 months. (goes to September)
3. For a combination of GISS, Hadcrut3, UAH and RSS, the slope is flat since December 2000 or 12 years, 11 months. (goes to October)
4. For Hadcrut4, the slope is flat since December 2000 or 12 years, 10 months. (goes to September)
5. For Hadsst3, the slope is flat since November 2000 or an even 13 years. (goes to October)
6. For UAH, the slope is flat since June 2008 or 5 years, 5 months. (goes to October using version 5.5)
7. For RSS, the slope is flat since November 1996 or an even 17 years. (goes to October) RSS has reached Ben Santer’s 17 years.
The next graph shows just the lines to illustrate the above for what can be shown. Think of it as a sideways bar graph where the lengths of the lines indicate the relative times where the slope is 0. In addition, the sloped wiggly line shows how CO2 has increased over this period.
When two things are plotted as I have done, the left only shows a temperature anomaly.
The actual numbers are meaningless since all slopes are essentially zero and the position of each line is merely a reflection of the base period from which anomalies are taken for each set. No numbers are given for CO2. Some have asked that the log of the concentration of CO2 be plotted. However WFT does not give this option. The upward sloping CO2 line only shows that while CO2 has been going up over the last 17 years, the temperatures have been flat for varying periods on various data sets.
The next graph shows the above, but this time, the actual plotted points are shown along with the slope lines and the CO2 is omitted.
For this analysis, data was retrieved from Nick Stokes moyhu.blogspot.com. This analysis indicates for how long there has not been statistically significant warming according to Nick’s criteria. Data go to their latest update for each set. In every case, note that the lower error bar is negative so a slope of 0 cannot be ruled out from the month indicated.
On several different data sets, there has been no statistically significant warming for between 16 and 20 years.
The details for several sets are below.
For UAH: Since November 1995: CI from -0.001 to 2.500
For RSS: Since December 1992: CI from -0.011 to 1.950
For Hadcrut4: Since August 1996: CI from -0.006 to 1.358
For Hadsst3: Since March 1994: CI from -0.020 to 1.711
For GISS: Since June 1997: CI from -0.032 to 1.283
Due to the extensive coverage that RSS already has in the Arctic, a similar analysis of Cowtan and Way on RSS would have little impact on the length of the pause as shown by RSS. However it does make the discrepancy between RSS and HadCRUT4 even wider than it is at the present time. On the other hand, the new trend line gets closer to UAH. What would have happened if they had used RSS instead of UAH?