Yesterday evening (4 Sep 07) PBS ran a Nova on "Global Dimming." The thesis was that human-generated dust in the air has compensated for human-generated CO2 and held down the temperature rise, along with weaker solar output. This is nothing new, since the explanation for the 19401970 global cooling was a type of air pollution called sulfate aerosols.
The announcer spoke a climate shibboleth that the vast majority of climate scientists believed the human-generated "greenhouse gasses" caused global warming. The truth about this is the opposite; most scientists do not (Singer SF, Avery DT, Unstoppable Global Warming Every 1,500 Years, Lanham, MD: Roman and Little field, 2006, p. 134). The most active of the "greenhouse gasses" was never mentioned by name; it is, of course, water vapor (Joel M. Kauffman, Water in the Atmosphere, J. Chemical Education, 2004, B81(8), 12291230). CO2 can hardly have been the cause of warming because its level in air has been higher than it is now at least 3 times between 1812 and 1962 as shown by 90,000 direct chemical measurements (Beck, E.-G., 180 Years of Atmospheric CO2 Gas Analysis by Chemical Methods, Energy & Environment, 2007, 18(2), 259282). Further, there is no recent correlation between CO2 levels and atmospheric temps as you may see easily from a NOAA graph.
The "star witness" was Dr. James Hansen of NASA who said that global warming has been about 0.8 deg C in the last century, most in the last 30 years. The only parts of the globe with most warming in the last 30 years are big cities. For example, the least populated counties of CA gained 0.2 deg C from 1910 to 2000, while the most populated counties gained 2.3 deg C (Goodridge, J. D., Comments on Regional Simulation of Greenhouse Warming Including Natural Variability. Bulletin of the American Meteorological Society, 1996, 77(July), 34), as did New York City. With an allowance for such urban heat island effects, the global temp. rise from 19051940 was similar to the one from 19702003 (www.giss.nasa.gov). Dr. Hansen's flawed USA ground station temps from 20002006 needed a Y2K correction provided by the Canadian Steve McIntyre showing that 1934 was the warmest year of the last 100, not 1998 or 2006; see for yourself. Objective reporting would have meant showing how Dr. Hansen's runaway climate warnings since 1987 have been overdone by using a rebuttal witness.
A David Travis did a clever experiment on the contribution of jet contrails to warming. He compared the days before 9/11 and 4 days after with the 3 days when all aircraft were grounded. He found that the day/night temp. difference was 1 deg C more when jets were absent. The culprit was said to be dust in the jet exhaust that caused water droplets to form. First, the effect of humidity on day/night temp. difference was understood at least 100 years ago. In the narration this difference somehow became equated to an overall warming. Next, jet exhaust is equal in numbers of molecules of water and CO2. At stratospheric temps. water vapor would form white ice trails pretty fast.
A Prof. Ramanathan said that anything done to create energy causes atmospheric pollution. What a shock for proponents of hydro, wind, solar and nuclear power! His claim was that the particulate pollution over the northern Malidive Islands from India was absorbing 10% of solar energy. He failed to rule out water droplets in the wispy clouds shown in a satellite photo.
Repetitive photos of industrial plants of unknown type were shown to demonstrate dust pollution, a common ploy. But some or all of the plants were emitting steam, not smoke.
The sun's output was claimed to have dimmed in the last 20 years, but others note that the opposite is true (Prof. Lance Endersbee, Climate Change is Nothing New! New Concepts in Global Tectonics, no. 42, Mar 07, Singer & Avery, above, p1901).
PBS can atone most effectively by airing the 1-hour UKChannel 4 program: The Great Global Warming Swindle from March, 07.
September 7, 2007