Exhibit E: Water Vapor is by far the most significant Green House Gas (GHG)
When discussing global warming with a climate alarmist, be sure to always tie things back to how CO2 could be the cause. The only defined mechanism by which CO2 can affect climate change is by trapping outgoing radiation between the wavelengths of 13 and 18 microns.
- Incoming visible radiation has a wavelength between 0.4 and 0.7 microns and is consistent with a black body with a temperature around 5,525 degrees Celsius (the Sun). CO2 is transparent to those wavelengths. (See chart above/below)
- The earth emits IR mostly between 6.5 and 12.5 microns, with a peak near 9.5 microns. 9.5 microns is consistent with a black body of temperature 18 degrees Celsius. CO2 is mostly transparent to those wavelengths.
- CO2’s absorbs between 13 and 18 microns, with a peak near 15 microns. Those wavelengths are consistent with a black body of temperature -80 degrees Celsius. CO2’s signature would be to cause warming in Antarctica, which is a natural control for CO2. There has been no observed warming in Antarctica over the past 50 years.
- H2O is by far the most significant GHG, and absorbs across the IR Spectrum. Where there is water vapor in the atmosphere, there is warmth. The same can’t be said about CO2.
- CO2 absorbs a small fraction of the IR Spectrum having 3 narrow peaks at 2.7, 4.3 and 15 microns, all of which largely miss the peak outgoing IR radiance of the earth at 9.5 microns.
- H2O largely absorbs the same IR spectrum as CO2, and is at much higher concentrations in the atmosphere. H2O IR absorption usually makes CO2’s contribution to warming inconsequential. The following 2 charts demonstrate the impact on the lower 1.0 km of the earth’s atmosphere (the layer where all ground measurements are taken) from doubling CO2 from 400 ppm to 800 ppm. The W/M^2 remains UNCHANGED at 407.572.
- CO2 has changed from 0.0003 to 0.0004 over the past 100 years and absorbs a very very very small % of the outgoing radiation. H2O can change from 0.001 to 0.04 in a day and absorbs a vast majority of the outgoing IR spectrum. Neither H20 or CO2 have ever caused catastrophic warming of the globe, and CO2 has been as high at 7,000 ppm.
- Given that the GHG effect only slows cooling, and can never actually “warm” the atmosphere, the dynamics of the GHG effect is to put in a temperature floor. If you notice from the introductory graphic above, as the earth warms, it enters what is called an “atmospheric window” where little energy is trapped. As the earth cools, more and more of the outgoing wavelengths are trapped (note the near solid black to the right of 13 microns).
- Water vapor and temperature are almost indistinguishable in the atmosphere.