The scientists involved in this study have found these persistent dry periods were different in nature from even the most severe decades-long droughts of the past two millenia, including the 1930s “Dust Bowl.” And they determined that these millennial droughts occurred at times when Earth’s mean annual temperature was similar to or slightly higher than what it is now. The droughts from the last two centuries were classified as being shorter and climatically different from future permanent ‘dust-bowl-like’ conditions lasting much longer. They used molecular palaeotemperature proxies to reconstruct the mean annual temperature (MAT) in ground sediments from the Valles Caldera in New Mexico, and determined that the driest conditions in the region correlated directly to the warmest phases of interglacials, and when the MAT was similar to or higher than the current MAT. They also analyzed these samples for signs of drought, and in the process developed a technique to determine temperatures from the past by looking at signs left by soil bacteria, and concluded that the fats in the walls of the bacteria change their internal structures in correlation to temperature changes, so they are, in essence, a recording device for temperatures from the past.
These findings predictably coincide with similar projections by the U.N. Intergovernmental Panel on Climate Change and others, according to study author Peter Fawcett of the University of New Mexico. The results of this study are published and can be found in the current edition of the Nature Journal.
The American Southwest has seen above average population growth over the last century, with population increasing by 1,500 percent from 1900 to 1990, according to the U.S. Geological Survey. The total U.S. population grew 225 percent over the same period. The relocation of people to this region. as with all human migrations, depends on access to water. There would clearly be much less water available in a megadrought. With everyone flocking to this region, which is already somewhat arid to begin with, it could spell disaster in the near future as water demands increase and supplies dwindle.
Previously recorded Ancient Megadroughts were caused by subtle changes in the Earth’s orbit around the Sun, which also can account for shifts in climate from megadroughts and warmers temperatures to ice ages. If these orbital changes were the only influence on the planet’s climate, then the planet should be heading into a cool period according to Fawcett.
Current temperature models and statistical data collected over the last century indicate that this is not at all true however, as it should be. The last decade has been the hottest on record since modern record-keeping began in the early 1880’s. And as we follow the temperature records, 1991 to 2000 was the second warmest decade, and respectively, 1981 to 1990 was the third warmest decade on record, so this does not fit the pattern that the orbital shift models suggest should be happening. This natural cooling cycle which is part of the natural orbital cycle probably is being altered by the release of carbon burning emissions, or greenhouse gases into the atmosphere.