JACKSON, Tenn. -- The subject of global warming has received much press in the last few years. With the change in leadership in Congress, we should expect to hear much more about this subject in days to come. Recently, Union University hosted an illuminating debate on this subject between Dr. David P. Gushee (principle author of the Evangelical Climate Initiative, ECI) and Dr. E. Calvin Beisner (one of four co-authors of the response to the ECI by the Interfaith Stewardship Alliance, ISA).

The principal issue in global warming is whether the observed warming in the Northern Hemisphere (the Southern Hemisphere has not been warming) is manmade or natural. Much of the evidence offered for manmade warming relies on the work of the United Nations’ Intergovernmental Panel on Climate Change (IPCC), which rests the cause of the Northern Hemisphere warming from 1979 through 1998 on human emissions of carbon dioxide into the atmosphere.

The IPCC’s report then names various biological and physical changes on the earth (the number and intensity of storms, global sea level, Arctic ice thickness, longer growing seasons, plant and animal migration) that its authors think are manmade. It is often this type of evidence – citing a broad scientific agreement or consensus – that is appealed to for governmental involvement.

It should be considered, though, that the warming from 1979 through 1998 is not new. Surface temperature is a dynamic property that cycles through highs and lows, e.g., from the Medieval Warm Period (1,000-1,100 A.D., with the same level of warming seen in the 20th century), to the Little Ice Age (1,500-1,600 AD), to the recent warming period. Furthermore, temperature is a logarithmic function of carbon dioxide concentration. That is, each new unit of CO2 added to the atmosphere causes less warming than the last. Furthermore, carbon dioxide concentration tends to follow increases in temperature rather than precede them, which is exceedingly difficult to reconcile with human cause. Also, the Third Assessment Report of the IPCC attributes .5 degrees Celcius warming in the first half of the 20th century to solar variability. Since there has only been an increase of .6 degrees Celcius over the whole 20th century, the oft-cited proof for manmade global warming only attributes a maximum of 17 percent to possible human causes. In fact, new research is showing that surface temperature variation has more to do with cloud formation dynamics dependent on cosmic rays.

An analogy might help us evaluate the credibility and significance of claims of consensus. How many pastors and lay-leaders would say there is a theological consensus on the relationship between the supernatural and human component in the doctrine of Scripture or, say, redemption? How much more then will there not be a scientific consensus regarding the natural and human component of global warming, where nature is not nearly as perspicuous as Scripture, scientists do not have the common bond of Christ, and advanced climate studies are only a few decades old, compared with biblical and theological studies that have been under way for nearly 2,000 years? Evangelicals appealing to broad consensus on global warming should know better.

Considering a few of the effects of Northern Hemisphere warming, it is not true that warmer surface temperatures yield an increase in the number or intensity of storms. These storms depend on the temperature gradient between tropical and polar regions, among other things. Historical evidence has shown a larger number of more ferocious storms occurred during the Little Ice Age than during the Medieval Warm Period. The IPCC's 2007 draft report estimates sea level rise through the remainder of this century at only 0.06 to 0.18 inches per year (6 to 18 inches per century), which, for the higher figure, is a 52 percent reduction from the 2001 report. The International Union for Quaternary Research estimates only 0.082 inches per year (8.2 inches per century). Adapting to such slow sea level rise is both technically practical and economically affordable -- unlike trying to prevent it by reducing carbon dioxide emissions, which would have little to no effect on temperature and almost certainly no effect on sea level rise but would cost the global economy hundreds of billions of dollars per year. Furthermore, newly published research shows the Antarctic ice sheet expanding, not shrinking, thus diminishing rather than adding to sea level rise. The effect of temperature increases and rising CO2 concentration on agricultural production is actually the opposite of what alarmists would suppose, as agricultural yield increases with both temperature and CO2 concentration.