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Darryll Pederson

The science of global warming is most easily understood by looking at the parts that make up the whole.

The sun is the ultimate heat source, which varies little in output over time. The suns radiation spectrum includes visible light, which makes up the rainbow; longer wavelengths, which generate heat; and shorter wavelengths, which cause sunburn. Sunlight striking the Earth is absorbed and converted into heat, which radiates as long wavelengths.

If the sun shines on snow, nearly all of the spectrum is reflected so little heating occurs. A car parked in the sun warms up because, while most of the sun's radiation spectrum can pass in through the windows and warms up the seats, etc., the longer wavelengths (heat) formed can’t pass out through the windows, the same as in greenhouses. More sunlight in summer means higher daytime temperatures than in winter.

Greenhouse gases in the atmosphere, especially carbon dioxide and methane, can absorb long wavelengths, including heat, before they radiate away from the Earth. As greenhouse gases warm up, the atmosphere around them is warmed up, leading to general warming of the atmosphere.

Clouds function the same way, as water is also a greenhouse gas. On clear nights, the atmosphere and ground cool rapidly, but, if there are clouds, there is much less cooling.

Greenhouse gases have the same net effect as car windows except, if the concentration of greenhouse gases increases, the atmosphere will warm up as more of the sun’s radiation is trapped.

In Earth’s history, there have been ice ages and interglacials caused by the periodic changing of the elliptical orbit of the Earth around the sun, the changing tilt of the Earth’s axis of rotation and the tilt of the axis with regard to the sun leading to periodic ice ages and interglacials.

Renowned astrophysicist Milutin Milankovitch worked out the mathematics of the cycles. The Earth should now be going into a new glacial cycle, but, instead is warming up, so a new factor is at work. Atmospheric concentration of carbon dioxide is increasing, much more rapidly than experienced in Earth history. Warming of polar regions is also causing increases of methane emissions as the permafrost thaws. This means accelerated warming will occur in the future.

The big question is why are carbon dioxide concentrations increasing? Man’s role can be demonstrated. There are two isotopes of carbon -- C12 and C14 (which is radioactive). The half-life of C14 is 5,730 years, meaning 50 percent of existing C14 (at any point in time) will decay back to nitrogen in 5,730 years.

The ratio of C12 vs. C14 on our planet was constant until the start of major burning of fossil fuels. Coal and oil -- sometimes called dead carbon -- have only C12 because the C14 in the original organic tissue, making up these deposits, has all radioactively decayed. The increase in atmospheric carbon dioxide is driven almost totally by dead carbon being released in the burning of fossil fuels, as shown by the changing ratio between C12 and C14.

The science is clear: Mankind is warming the atmosphere, more water is evaporated from the oceans and, with warming, patterns are modified. There is more heat energy in the atmosphere to form stronger storms plus more moisture. Everyone knows that a hot, humid, stagnant day suggests tornadoes. With higher temperatures, more evaporation of water on land occurs and dry areas become drier.

The concern of climate scientists is that a point will be reached where there is no return to the good old days. With warming, huge quantities of methane currently tied up in ice crystals will be released from the permafrost and ocean sediments. As methane is released, the additional warming effect causes more methane to be released; this is runaway global warming from which there is no returning.

The only perfect model of the Earth’s heat balance is the Earth itself. Climate models can project direction and likely rate of change but cannot reflect all the Earth processes involved in the heat balance. For this reason, climate models cannot predict the exact temperature change in the next 10 years, let alone dozens of years in the future -- but they can show clearly where we are heading.

The Earth model, using worldwide data collection, shows global warming is exceeding that predicted by models used by climatologists. Concentrations of greenhouse gases are increasing in the atmosphere and the true Earth model is showing the resulting global warming.

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Darryll Pederson is an emeritus professor of hydrogeology in the Earth and Atmospheric Sciences Department at the University of Nebraska-Lincoln.


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