Global Warming, Another Look

In the ongoing debate over global warming media attention has focused on a growing chorus of alarming predictions coming from the scientific and environmental communities and denials by the economic and political sectors founded on lack of firm proof. Proponents point to growing evidence of increasing temperature and point out that waiting for unequivocal proof will leave it too late to avoid catastrophe. Opponents claim that the economic costs of greenhouse gas reduction would be too high to bear without clear evidence of necessity.

While the media chooses to concentrate on controversy and threats of calamity there is a significant and credible minority opinion in science that presents a quite different perspective. In this view the purported warming has been exaggerated.  The extent to which it does exist is largely due to natural causes, and it is more likely to be beneficial than detrimental. Many geologists in particular adhere to this persuasion but it receives little notice from the media.

Geologists now have powerful tools for looking at past climate records preserved in sediments and ice cores. They have clear evidence that the recent epoch of glacial cycles involves over a hundred glacial periods spanning the past several million years. Looking at such records we are now nearing the end of a warm interglacial period when temperature peaks, just before the plunge into a new glacial cycle.

These cycles correspond to cycles in the Earth’s orbit that affect how much sunlight the planet receives. Superimposed on this pattern are shorter term cycles of solar activity that also effect climate on a shorter time scale. These latter cycles correspond to sunspot activity and they are recorded in the formation of the isotope Beryllium10 which can be read in ice and sediment cores. Comparing temperature and sunspot activity over the past 1000 years we find that the record high temperatures of the past decade corresponds to a record high level of solar activity.

The general consensus among those knowledgeable in this area is that certainly most of the recently observed temperature increase is attributable to natural cycles and any contribution from increased greenhouse gases must be minor.  It also means that contrary to the global warming scenario we are probably close to entering another ice age. Whether "close" in this sense means decades or centuries is uncertain but one piece of evidence indicates it may begin sooner rather than later.

Ice age sediments from the Arctic Ocean contain abundant remains of open water plankton. Contrary to what one might expect, the Artic Ocean is mostly open water during glacial periods. This is not as unreasonable as it may seem. The ice covered Artic is now a polar desert in terms of atmospheric moisture. An open water Arctic Ocean would greatly increase moisture and snowfall leading to greatly increased ice buildup on land and accelerated cooling by reflection of solar radiation from ice, snow, and clouds. This could only maintain of course, if the sea remained open and this could only happen with an inflow of warmer water. This in turn would most likely involve a diversion of a portion of the Gulf Stream into the Artic Ocean. Thinning of Arctic Ocean ice and increasing ice free areas in summer has been noticeable in recent decades.  If continued for another decade or two this will result in much of the sea being open in summer. It seems reasonable that some point in this process may be the threshold for a shift in current patterns and the turning point into the next glacial cycle.

In the meantime another study just released has found evidence of past bleaching events in coral cores over the last 1000 years so the recently observed bleaching events are not unprecedented but may also just be something that occasionally happens in our dynamic world.

How all of this may play out in the real world will probably be argued until actuality settles it. We have neither the will to change ourselves nor the means to change the world and only a very limited ability to predict it. We can however enjoy the ride. It should be a most interesting one.

 Walter Starck