Decelerating Global Warming !

Shown below is an updated version of the 2007 IPCC graph which formed the basis for the claim that AGW was accelerating. The same  analysis repeated in 2012  now shows a deceleration in warming, which  demonstrates just how dubious the original claim was.

FIG1. The same fits as Fig 2 but done in 2012 (plus one extra for the last 13 years)


The 2007 AR4 report claimed was that global warming was accelerating. This was all based on a novel interpretation of calculus for deriving the second derivative to global temperature data. The end point was fixed but a series of half time intervals were then used to show that the slope of HADCRUT3 temperature anomaly data was increasing with time – see figure 2. The original graph can be found in chapter 3 of  the WG1 AR4 report. To quote from the IPCC report:

“Linear trend fits to the last 25 (yellow), 50 (orange), 100 (purple) and 150 years (red) are shown, and correspond to 1981 to 2005, 1956 to 2005, 1906 to 2005, and 1856 to 2005, respectively. Note that for shorter recent periods, the slope is greater, indicating accelerated warming.”

Fig2: Original fits from AR4

I have now redone these same  fits to include new data up to 2012 as shown in Fig 1. The linear fits to the same half periods as before are now as follows.

   Period(years)      Rate deg.C per decade
       14                 -0.046
       25                  0.120
       50                  0.135
      100                  0.074
      150                  0.044

Therefore using the IPCC method of measuring the second derivative, there would now apear to be a deceleration in warming  over the last 25 years ! In fact the sharpest increase in warming throughout the measured data  occurred between 1910 and 1945 with a fitted rate of  0.148 deg.C/decade.

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2 Responses to Decelerating Global Warming !

  1. Bryan says:

    Will they repeat this graph for AR5

  2. Werner Brozek says:

    The following also verify that global warming is not accelerating.

    2012 in perspective so far

    With the UAH anomaly for May at 0.289, the average for the first five months of the year is (-0.089 -0.111 + 0.111 + 0.299 + 0.289)/5 = 0.0998. If the average stayed this way for the rest of the year, its ranking would be 12th. This compares with the anomaly in 2011 at 0.153 to rank it 9th for that year. (1998 was the warmest at 0.428. The highest ever monthly anomalies were in February and April of 1998 when it reached 0.66.)

    With the RSS anomaly for May at 0.233, the average for the first five months of the year is (-0.058 -0.121 + 0.074 + 0.333 + 0.233)/5 = 0.0922. If the average stayed this way for the rest of the year, its ranking would be 16th. This compares with the anomaly in 2011 at 0.147 to rank it 12th for that year. (1998 was the warmest at 0.55. The highest ever monthly anomaly was in April of 1998 when it reached 0.857.)

    With the GISS anomaly for May at 0.65, the average for the first five months of the year is (0.34 + 0.41 + 0.47 + 0.55 + 0.65)/5 = 0.484. If the average stayed this way for the rest of the year, its ranking would be 10th. This compares with the anomaly in 2011 at 0.514 to rank it 9th for that year. (2010 was the warmest at 0.63. The highest ever monthly anomalies were in March of 2002 and January of 2007 when it reached 0.88.)

    With the Hadcrut3 anomaly for April at 0.482, the average for the first four months of the year is (0.217 + 0.194 + 0.305 + 0.482)/4 = 0.2995. If the average stayed this way for the rest of the year, its ranking would be 14th. This compares with the anomaly in 2011 at 0.34 to rank it 12th for that year. (1998 was the warmest at 0.548. The highest ever monthly anomaly was in February of 1998 when it reached 0.756.)

    With the sea surface anomaly for April at 0.292, the average for the first four months of the year is (0.203 + 0.230 + 0.242 + 0.292)/4 = 0.242. If the average stayed this way for the rest of the year, its ranking would be 14th. This compares with the anomaly in 2011 at 0.273 to rank it 12th for that year. (1998 was the warmest at 0.451. The highest ever monthly anomaly was in August of 1998 when it reached 0.555.)

    So on all five of the above data sets, for their latest anomaly average, the 2012 average is colder than their 2011 average value.

    On all data sets, the different times for a slope that is flat for all practical purposes range from 10 years and 8 months to 15 years and 7 months. Following is the longest period of time (above 10 years) where each of the data sets is more or less flat. (For any positive slope, the exponent is no larger than 10^-5, except UAH which was 0.00103655 per year or 0.10/century, so while it is not significant, it could be questioned whether it can be considered to be flat.)

    1. RSS: since November 1996 or 15 years, 7 months (goes to May)
    2. HadCrut3: since January 1997 or 15 years, 3 months (goes to March)
    3. GISS: since May 2001 or 11 years, 1 month (goes to May)
    4. UAH: since October 2001 or 10 years, 8 months (goes to May)
    5. Combination of the above 4: since October 2000 or 11 years, 6 months (goes to March)
    6. Sea surface temperatures: since January 1997 or 15 years, 4 months (goes to April)
    7. Hadcrut4: since December 2000 or 11 years, 6 months (goes to May using GISS. See below.)

    See the graph below to show it all for #1 to #6.

    http://www.woodfortrees.org/plot/hadcrut3gl/from:1997/trend/plot/gistemp/from:2001.33/trend/plot/rss/from:1996.83/trend/plot/wti/from:2000.75/trend/plot/hadsst2gl/from:1997/trend/plot/uah/from:2001.75/trend

    For #7: Hadcrut4 only goes to December 2010 so what I did was get the slope of GISS from December 2000 to the end of December 2010. Then I got the slope of GISS from December 2000 to the present. The DIFFERENCE in slope was that the slope was 0.0046 lower for the total period. The positive slope for Hadcrut4 was 0.0041 from December 2000. So IF Hadcrut4 were totally up to date, and IF it then were to trend like GISS, I conclude it would show no slope for at least 11 years and 6 months going back to December 2000. (By the way, doing the same thing with Hadcrut3 gives the same end result, but GISS comes out much sooner each month.) See:

    http://www.woodfortrees.org/plot/hadcrut4gl/from:2000/to/plot/hadcrut4gl/from:2000.9/trend/plot/gistemp/from:2000/plot/gistemp/from:2000.9/to:2011/trend/plot/gistemp/from:2000.9/trend

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