We can now reconsider the criticisms by Singer and Avery (in italics), which represent other scientific global warming skeptics, who gave a list of things they claim the greenhouse gas theory does not explain.

Year

Observations

Models using only natural forces

Models using both natural and human forces

Figure 1.9 Comparison of observed global (land and sea) temperature with results simulated by models using natural and human radiative forcing. The lower (dark gray) band is the 5-95% range for 19 simulations from 5 climate models using only natural forcing. The upper (light gray) band is the 5-95% range for 58 simulations from 14 climate models using both natural and human radiative forcings. source: Reproduced by permission from Climate Change 2007:The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Figure SPM.4 (Cambridge: Cambridge University Press, 2007).

• CO2 changes do not account for the highly variable climate in the last 2,000 years. This is true, but scientists do not say that greenhouse gases are the only thing that affects climate.

• Greenhousegas theory does not explain recent temperature changes in the twentieth century. Increased production of greenhouse gases as a result of human activity is, in fact, the only way to account for the temperature changes in the last 50 years.

• CO2 increases have not led to planetary overheating. The results presented here clearly show that, in fact, the planet is overheating and the rate of warming is increasing steadily.

• Thepoles should warm the most, but they do not. The northern latitudes, and especially the Arctic, are in fact warming at a more rapid rate than elsewhere on the planet (24). West Antarctica is warming at the same rate as the rest of the earth.

• We should discount the “official” temperatures because of urban heat islands. scientists are well aware of this, and temperature records have been corrected for this phenomenon. Furthermore, ocean temperatures are also increasing.

• The earth’s surface has warmed more than the lower atmosphere up to 30,000feet, yet the theory says the lower atmosphere should warm first. Actually, temperatures measured by balloons (radiosonde) and satellites have increased in the middle troposphere (5,000 to 30,000 feet) very similar to

surface temperatures during 1958-2000 (0.12°C per decade for surface and 0.15°C per decade for mid-troposphere) and at an even higher rate since 1976 (0.17°C per decade in the mid-troposphere) (24, 46).

• CO2 has been a lagging indicator of temperature by 400 to 800yearsfor the last 250,000 years. This may have been true in the past, but as shown here, it is tightly linked to temperature changes over the last 50 years.

This is because we are artificially adding CO2 to the atmosphere at an unprecedented rate from fossil fuel use and destruction of forests.

• Greenhouse gas warming should increase water vapor, but there is no evidence that it is increasing. Water vapor actually has increased over the oceans at a rate of 1.2% per decade from 1988 to 2004 (24).

While there may be scientific quibbles with the finer points of issues related to global warming, the broad picture as presented here is extremely well supported by peer-reviewed scientific publications and is the scientific consensus.

As a final point to this discussion, it should be said that the physics showing that greenhouse gases in the atmosphere absorb infrared radiation emitted from the earth is very well established,9 and is the reason the earth is not cold like the moon. It is also unequivocal that the greenhouse gases are increasing dramati­cally. The onus, therefore, should be on the climate skeptics to explain how this would not lead to global warming.