One issue with the IPCC's anthropogenic global warming hypothesis has been the post WWII cooling period. The 1945-1975 period is only one period in question. Other than the lack of warming since 2002, we also have another 30 year cooling period from about 1885-1915. Using HadCRUT data, the world warmed for about 30 years (1855-1885), then cooled for about 30 years (1885-1915) then warmed for about 30 years (1915-1945), then cooled for about 30 years (1945-1975), then warmed for about 30 years (1975-2005). It is no longer warming. The 1945-1975 cooling period is just of special mention since the CO2 levels started to skyrocket around 1945. In light of these oscillations within the temperature record, suggesting that all of the 1980's and 1990's warming is from CO2 does not make sense.

Indeed, a paper in a spring 2008 volume of Nature suggested that the oceans would prevent us from warming until at least 2015. The oceanic cycles' noise in the temperature signal must be filtered out, so climate must be at least 60 if not 120 years instead of the IPCC's 30 years. What happens when that noise is removed?

Let's look at the background trend instead. Taking the mid point of each warming period from the HadCRUT June 18, 2008 data I estimate this:

1870 -0.3
1930 -0.2
1990 0.2

Graphed data: http://users.vianet.ca/paulak2r/AGW/HadCRUT20080618.JPG
Current data: http://hadobs.metoffice.com/hadcrut3/diagnostics/global/nh+sh/monthly
(the second column is the global anomoly in Celsius)

Estimating off a graph is not accurate enough for me. I put the data from 1850 to 2007 into a database and calculated both the 5 year average and the 10 year average. That data was extrapolated to 2127. That is, I chose to add two sixty year periods to the data. I also found the average global temperature for each warming period:

Avg and thePeriod
-0.3341 Yr >= 1855 and <= 1885
-0.1925 Yr >= 1915 and <= 1945
0.1726 Yr >= 1975 and <= 2005

These averages gave the rise in temperature from the middle of one warming period to the next:

The 1870 to 1930 rise: -0.1925 + 0.3341 = 0.1416 C
The 1930 to 1990 rise: 0.1726 + 0.1925 = 0.3651 C

Here are the key data and a graph:

http://users.vianet.ca/paulak2r/AGW/MyModel.jpg

Note: The rate of increase for each year was 0.002359902 for the first cycle and 0.006085932 for the second cycle. The Bkg1 data are based on the assumption that we will return to the warming of the first cycle. The red Bkg4 data assume we are going to remain at the higher trend of the second cycle.

I admit it. This is a very poor sample of only three points, but it is just for discussion due to the short period of direct temperature measurements. I chose to only use HadCRUT and ignored proxy data from other sources, like ice cores, due to data resolution issues.

The trend seems to have increased from 0.14 C to about 0.37 C every 60 years. If the 0.37 C trend holds, by 2110 we would be about 0.74 C warmer than the 1990 average. This is much less than the IPCC TAR's lowest case scenario. It would also be near the top end of the AR4 idealised constant composition commitment scenario for which we don't qualify. Of course, this assumes that the trend will continue at the 1930 to 1990 pace.

Back to that wiki page ( http://en.wikipedia.org/wiki/Solar_variation ) it says "[t]he level of solar activity during the past 70 years is exceptional — the last period of similar magnitude occurred over 8,000 years ago." I will not quibble over the 70 year value. That page also quotes Sami Solanki saying 60 years. Others have mentioned that this increased solar activity fell back down to 'normal' about 10 years ago. Perhaps that is where the 70 comes from. Regardless, it has been suggested that the increase in solar output would only increase our surface temperatures by 0.15C.

If I take the 1930 to 1990 trend of 0.37 C per sixty years and subtract out the natural warming of the previous period, I get this:

Trend increase = 0.37 - 0.14 = 0.23 C per sixty years.

If 0.15 C of that was solar, then that leaves ( 0.23 - 0.15 = ) 0.08 C of warming to be attributed to other causes like decreased volcanic activity and CO2 warming.

John M Reynolds

Finally, here is a link I don't want to lose: CO2 does seem to not drive temperature

2010/08/01: Girma Orssengo, MASc, PhD performed a similar calculation. My calculations were off by 5 years as compared to Dr. Orssengo's