Thursday, April 19, 2012
What the Flux!
hat is a busy chart comparing the Mauna Loa CO2 concentration change estimated forcing to the University of Alabama (UAH) Microwave Sounding Unit (MSU) middle tropospheric temperature data. The light blue line burried in the noise is the calculated forcing of CO2 based on the formula 5.35ln(Cf/co) were Co is 280 Parts Per Million PPM. Cf is the monthly average from the Mauna Loa observatory CO2 measurements. Since the UAH data is in anomalies, I converted the CO2 forcing estimate to Anomalies by subtracting the average of the period of the satellite data series.
Low and behold, the CO2 forcing is nearly a perfect fit of the UAH land temperature data series. Both the global and the ocean series are below the land series.
This chart is just the land data and the estimated CO2 forcing. Pretty close match. If you extend the regressions out to the year 2100, it is about 0.8 C greater than the start in 1979. Now here is a little bit of a shocker, CO2 is causing most of that warming. But why is it only a good match over land?
The average surface temperature of the Earth is often listed as 288K degrees with a outgoing energy flux of 390Wm-2. Average temperature, average flux right? The average temperature of the oceans, 70% of the global surface is about 294K degrees and the average temperature of the land area is about 273K degrees. The energy flux at 294K degrees is about 423.6Wm-2 and the flux at 273.15 is about 315.6Wm-2. .7*294+.3*273.15=287.7 and .7*423.6+.3*315.6=391.2 the temperature is a touch lower and the flux a touch higher. Small errors right?
If you add 3.7Wm-2 of forcing to a 273.13K surface it would increase to 273.9K. Add 3.7Wm-2 of forcing to a surface at 294K and it would increase the temperature to 294.6K, only 80% of the increase. If you estimate the increase in forcing based on an average of temperatures instead of an average of fluxes, you get a slightly high bias in your estimate. Then if you apply the slightly high estimate to an average of temperatures you would get a slightly low response. This is exactly what appears to have happened to the climate change projections.
This does not explain all of the discrepancies, but since the oceans appear to also have a negative water vapor feedback, it should explain a large percentage of the error.