Take a look at the CRU global temperature chart; you'll see a plateau until 1910 a rise until 1945 a plateau until 1975 and a rise until present now take a look at the models; solar and volcanic forcing until 1910 (12.6a) co2 and aerosol forcing from 1910 until present (12.6b) According to this model aerosol forcing diminished after 1975 due to environmental regulations, which explaines the rise after 1975. so far the models Now, there are several sources that claim that the observed deviation from a sraight line is caused by the north atlantic oscillation. In this case the oscillation would be natural and hence the forcing of co2 exagerrated. As can be seen in the summer data from de bilt and from the ice core data from greenland the oscillation is very persistant. If I consider the linear fit of the CRU northern hemisphere data, I get an average increase of 0.43 degrees per century:
The 0.43C is partly solar, partly co2 radiative, and partly due to land use change.
Forcing PhysicsThe co2 radiative effect is the Arrhenius law. dE=[alpha]ln([CO2]/[CO2}orig), where alpha is 5.35 (Myhre et al.) see IPCC TAR; dE is change in forcing using the derivative of Stefan-Boltzmann: dT/dE = 1/(4[sigma] T^3) gets: dT=[alpha]ln([CO2]/[CO2}orig)/(4[sigma] T^3) This is the equation without all feedbacks. Substituting the change in the 20th century 370-295.8 and substituting T= 15 degreesC = 288.16K dT=5.35*ln(370/295.8)/(4*5.6705E-08*(288.16^3)) =0.22 degrees
Fingerprinting De BiltIf I look at the De Bilt data (quote as: A van Engelen and Nellestijn, JW, 1996: Monthly, seasonal and annual means of air temperature in tenths of centigrades in De Bilt, Netherlands, 1706-1995. KNMI report from the Climatological Services Branch.) Download HERE LABRIJN.xls (permission granted by A van Engelen I see all aspects represented. The graph below shows a 30 year moving average of the De Bilt monthly values, and the theoretical CO2 effect based on Arrhenius-Myhre-Stefan-Boltzmann theory, combined with CO2 data from Mauna Loa (annual 1958-2000) and Law Dome Ice Core (5 year increment 1710-1955)
See also my IUGG 2003 abstract "EVIDENCE FOR A STEFAN-BOLTZMANN CLIMATE SENSITIVITY FROM THREE CENTURIES OF SUMMER TEMPERATURE OBSERVATIONS IN THE NETHERLANDS" at http://www.jamstec.go.jp/jamstec-e/iugg/htm/abstract/abst/mc07_p/021986-1.html There is a distinct CO2 trend in the summer months July/August which fits Arrhenius-Myhre-Stefan-Boltzmann. There apparently is no solar effect in these months, don't ask me why, I don''t know. There is a strong solar effect in the month of January, I have not tested the exact correlation yet. If I look at the winter months there is another big co2-like effect: IMHO this is due to two causes, urban sprawl and afforestation. Both effects show a trend that is similar to co2. But the effect works directly on winter albedo as can be seen from the following satellite image of the eastern netherlands You'll see that there is no snow cover on towns and forests, causing a direct albedo heating effect.
An albedo calculation exampleFor a lattitude of 52N on 4 january with fresh snow (albedo 0.8) the mid-day (clear sky) insolation is 68 W/m2 The albedo of a forest/town = 0.15 0% forest/town | winter albedo 0.8 | insolation 68 W/m2 10% forest/town | winter albedo 0.735 | insolation 90 W/m2 20% forest/town | winter albedo 0.67 | insolation 113 W/m2 30% forest/town | winter albedo 0.605 | insolation 135 W/m2 40% forest/town | winter albedo 0.54 | insolation 157 W/m2 50% forest/town | winter albedo 0.475 | insolation 179 W/m2 60% forest/town | winter albedo 0.41 | insolation 201 W/m2 70% forest/town | winter albedo 0.345 | insolation 223 W/m2 80% forest/town | winter albedo 0.28 | insolation 245 W/m2 90% forest/town | winter albedo 0.215 | insolation 268 W/m2 100% forest/town | winter albedo 0.15 | insolation 290 W/m2 Insolation data derived using the insolation calculator You see that change of landuse has a dramatic effect on the winter energy balance. Hans Erren
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