Tuesday, April 14, 2009

Global Warming Cure??

Obama Science Advisor John Holdren’s idea of injecting sulphur dioxide (SO2) into the atmosphere sounds like “we had to destroy the world in order to save it”. I decided to do some back of the envelope calculations to test the feasibility of his idea.

We know that volcanic eruptions have caused global cooling (volcanic winter) in the past so let’s look at them as a model for Dr. Holdren’s idea.

Volcanic eruptions are classified by their “Volcanic Explosivity Index” (VEI). This is a number between 1 and 8 that relates to the amount of material the volcano ejects. The amount of material ejected is measured in cubic kilometers. A cubic kilometer is a cube that is over a half mile on a side. An eruption with a VEI of 8 ejects 1,000 cubic kilometers of stuff. One with a VEI of 7 ejects 100 cubic kilometers of stuff, and so on by factors of 10. For comparison, let’s look at some well known eruptions.

Mount St. Helens in 1980 had a VEI of 5
Mount Pinatubo in 1991 was on the high end of 6
Mount Tambora in 1815 was on the high end of 7

(By the way, the USA has had a couple of 8s back in prehistoric times. Where? Yellowstone!)

Mount St. Helens didn’t seem to cause much of a volcanic winter. But Mount Pinatubo is known to have reduced global temperature by 1 degree F for about 2 years. Mount Tambora caused the year without a summer and widespread starvation. So, if we were to try to control global temperature, we’d probably like to start with a Mount Pinatubo sized event and go from there.

It is known that Mount Pinatubo put 20,000,000 tons of SO2 into the atmosphere to a height of 35 kilometers. We can estimate the amount of energy required to do that using high school physics. Multiply the mass in kilograms by the height in meters and the gravitational constant and you get the energy in Joules required to raise that weight to that elevation.

(18.16 x 10**9 Kg)(35 x 10**3 m)(9.8) = 6.23 x 10**15 Joules

(note that I use the double asterisk ** to indicate scientific notation)

Well, hell! I don’t have a clue what a Joule is so let’s get that into something we all can recognize.

It so happens that a kiloton on TNT yields 4.184 x 10**12 Joules. The Hiroshima atomic bomb was 12.5 kilotons. Therefore, if we wanted to inject an amount of SO2 equivalent to the Mount Pinatubo eruption, we would need to expend the energy equivalent to 119 Hiroshima atomic bombs.

If you prefer BTUs, we’d need 5.9 x 10**12 BTUs. That’s a lot of heat! I leave to the reader to convert that into units of your preference.

I know that this is a rather simplistic analysis but I think it makes the point that the energy required to attain even a modest, and temporary cooling of the earth is massive.

1 comment:

RobC said...

These Globull Warming experts are pretty cool... but lazy when it gets to the math...
Looking at your calculation the whole exercise is going to be pretty futile I would say...
Rather leave it up to nature I say... the sun and the cycles that have been changing weather over the ages has been rather good at sorting out a liveable average.