Sunday, May 13, 2007

 

The Great Global Warming Swindle Review: Part II

Unfortunately, it has been quite a while between part I and part II, but better late than never. This installment will deal with the assertion in the program that CO2 is an insignificant greenhouse gas. This argument (starting about 11 minutes in the show) takes a few forms, each of which we will examine:

1) CO2 is only a small part of the Earth’s atmosphere (13:31)
2) CO2 is not the most significant greenhouse gas, H20 is (14:10)
3) Humans contribute only a small part of the greenhouse gases (22:33)

Assertion #1 is undoubtedly true, but completely irrelevant. The vast majority of the Earth’s Atmosphere is N2 and O2, but these gases do not absorb infrared radiation, and are therefore not greenhouse gases. Since the program correctly states that the greenhouse effect is responsible for keeping the earth from being a frigid ball by trapping heat that would otherwise be reflected into space, it’s important to understand that without the greenhouse effect, the earth would be 25 degrees Celsius cooler than it currently is.

Assertion #2, that H20 is the most important greenhouse gas is also true. Although Tim Ball claims, "The atmosphere is made up of many gases. A small percentage of them, we call greenhouse gases, and of that very small percentage of greenhouse gases, 95% of it is water vapor, it's the most important greenhouse gas," the actual reality is that H20 is responsible for 36% to 70% percent of the greenhouse effect and CO2 is responsible for 9% to 26%. It is impossible to determine the exact percentages because of overlap, but Ball’s given number of 5% for everything but H2O is at least two times smaller than the most conservative measured estimate.

Just as a very, very rough generalization, skipping any feedback or feed-forward effects, let’s assume that the 9% contribution number is correct and that CO2 has grown by 23% since 1957. If we take the 25 degree Celsius number for the greenhouse effect, then we would expect a warming of 25*.09*.23 = .52 degrees Celsius of warming due to increases in atmospheric CO2. The amount of warming since 1957 is around .5 degrees Celsius. So, you can see that even if we take a conservative estimate of CO2's overall impact, it can have a noticable change on temperature with the current changes.

Before ending the H2O to CO2 comparison, there is another important distinction between the two. Changes in the levels of atmospheric CO2 are considered to be a force applied in the modelling of climate that will drive the temperature up. There are several other forces that act on the climate as well and change over time. H2O is not considered to be a force in the same way. Why? Because the mean level of H2O in the atmosphere is almost entirely a function of temperature. Introducing increased levels of H20 into the atmosphere will just cause them to quickly be rained out. Conversely, removing H2O from the atmosphere will be replaced in short order by evaporation. So, when people speak of H2O not being considered in the current climate models, it's not something that has been overlooked. It's just not something that drives climate due to independent changes in its concentration.

Finally, we get to assertion #3, humans contribute only a small part of the greenhouse gases. To quote John Christy, "Humans produce a small fraction, in the single digits, percentage wise, of the CO2 that is produced in the atmosphere." Human production of CO2 is about 24,000,000,000 metric tons per year as of 2002. This is about one tenth of the total production of CO2 in a given year by all natural sources. Of course, before the increased output of man, the natural production of CO2 and the natural sinks of CO2 were roughly aligned, so the overall level of CO2 in the atmosphere didn’t vary much from year to year. Increasing the output side by 10% has essentially overwhelmed the ability of the biosphere to absorb that excess CO2, so we get increased CO2 in the atmosphere year after year.

One other note on this subject as a closer. The program makes the bold (and completely false) claim at about 22:45 that, "Volcanoes produce more CO2 each year than all the factories and cars and planes and other sources of man-made carbon dioxide put together." The actual release of CO2 "from volcanoes, fumaroles, and hot springs and amounts to about (0.01 - 0.05) x 10^15 g C/year" compared to the burning of fossil fuels which releases about 5 x 10^15 g C/year, dwarfing the volcanoes output by a factor of at least 100. It is utter and complete falsehoods like this that make this show such a laughable endeavor.

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