Saturday, April 24, 2010

Albedo made me warm and cool.

While doing some research on the earth's albedo, I ran across a Cal Tech press release, which basically says that the experiment has been run--the experiment being a doubling of CO2. And guess what, we survived. The fear among the climate hysteriacs is that we will heat the earth. It isn't CO2 per se, but the heating effect of CO2 that is the worry. The heating is what they fear. So, have we had heating this century equivalent to doubling the CO2 content of the atmosphere? Yes.

By using a combination of earthshine observations and satellite data on cloud cover, the earthshine team has determined the following:

= Earth's average albedo is not constant from one year to the next; it also changes over decadal timescales. The computer models currently used to study the climate system do not show such large decadal-scale variability of the albedo.

= The annual average albedo declined very gradually from 1985 to 1995, and then declined sharply in 1995 and 1996. These observed declines are broadly consistent with previously known satellite measures of cloud amount.

= The low albedo during 1997-2001 increased solar heating of the globe at a rate more than twice that expected from a doubling of atmospheric carbon dioxide. This "dimming" of Earth, as it would be seen from space, is perhaps connected with the recent accelerated increase in mean global surface temperatures.

= 2001-2003 saw a reversal of the albedo to pre-1995 values; this "brightening" of the Earth is most likely attributable to the effect of increased cloud cover and thickness.


Now,greenhouse gases can be treated as if they are additional heat input to the earth. This is merely treating the greenhouse as if it was extra solar output.

The radiative forcings have been calculated for all the greenhouse gases as a function of their abundance. These calculations are done by computing the way the radiation at each wavelength is absorbed and reradiated at different layers in the atmosphere, until it escapes to space. The present radiative forcings of each greenhouse gas (compared to their greenhouse effects in pre-industrial times) are:
• Carbon dioxide: 1.5 Watts per square meter.
• Methane: 0.5 Watts per square meter.
• Nitrous oxide: 0.2 Watts per square meter.
• Halocarbons: 0.2 Watts per square meter.
• Total from all greenhouse gases: 2.4 Watts per square meter.
Hence, at present carbon dioxide is responsible for 60% of the anthropogenic greenhouse effect, methane is responsible for 20%, nitrous oxide for 10%, and halocarbons for 10%. The total radiative forcing of 2.4 Watts per square meter is equivalent to 1% of all the energy absorbed from sunlight in the surface and atmosphere of the Earth, at present, and it will increase as greenhouse gas abundances increase in the future. source

Below is a picture from the Palle et al article showing the changes in the Earth's albedo. I modified it to show what periods would be warming and cooling and the approximate warming due to greenhouse gas content of the atmosphere.

A one per cent change in the earth's albedo is a change of 13.6 watts per meter squared. From the chart one can see that the earth's albedo has changed by more than a percent just over the past 30 years. Yet the greenhouse gases will only change the radiative forcing by 2.4 watts per meter squared. This means that we have experienced more warming that the hysteriacs fear CO2 will bring us.

The problem with the global warming alarmists is that they focus on a single cause for the warming and proclaim (wrongly) that nothing else can affect the global climate. Data from satellites show that the earth's albedo is a bigger driver of warming than are the greenhouse gases.


  1. That 13.7 W/m^2 number you quote is the instantaneous reduction, but you have to divide by pi to get the 24-hour loss, which is what the 'greenhouse' 2.4W/m^2 is. Instead, 13.67/pi=4.35 W/m^2 is nearly twice the greenhouse amount. Since cloud albedo is not 100%, it takes more than 1% increase in clouds to get a 1% albedo increase. Also, cloud albedo is lower in the near IR, unlike ice and snow.

    An overlooked but perhaps more important effect of clouds than their higher albedo is that the unreflected energy is deposited in the clouds themselves, directly energizing weather, whereas sunlight hitting the ground must heat it up before air temp will rise, or ground water will evaporate. How much do we understand the different metereological effects of solar absorption by clouds (direct) vs surfaces (indirect)? Thus there could be global cooling AND stronger weather, because clouds would get more energetic, due to their absorbing 30% of sunlight. I bet none of this is in alarmists' precious supercomputer programs.

  2. Looking at the graph, it seems as though the albedo in 2007 was around the same as it was in 1985. However, global temperatures were significantly higher around 2007 than they were in 1985. Thus, it is not clear that albedo has any effect on the long-term trend.

    I would also point out that according to that graph it is in fact a two per cent change in albedo that causes a change of 13.6 watts. At no change in albedo, the watts are at 6.8. At 1 per cent change, they are 13.6.