NASA Scientists Study Possible Future Droughts
NASA scientists, by comparing historical records of how changes in the sun’s output affected past climates with model projections of how rainfall patterns would change with warmer global temperatures, have found that a future warming of the Earth’s climate would likely produce droughts in the same areas as in ancient times, with the possibility of them being even more severe. Much evidence from the Mars data is being used to further this theory, along with data from other planets.
There is already evidence of changing patterns of rainfall, with much of the Mediterranean, North Africa, and the Middle East rapidly getting drier. Severe consequences in as little as twenty years could be expected if current trends continue, imposing serious water resource problems on the affected populations.
The NASA Goddard Institute for Space Studies climate model enabled researchers to determine that changes in solar output in the remote past increased surface temperatures leading to changes in atmospheric moisture and circulation. The result was severe droughts as confirmed by the records of tree rings, fire and lake sediment found across the U.S., Mexico, Peru, and the Yucatan Peninsula. These reliable records of historical climate conditions over the past 1,200 years confirm a significant increase in drought in those areas during times of increased solar activity. The amount of solar output is based on chemical isotopes produced in relation to the sun’s brightness. In areas of the tropics, ocean sediment data reflects changes in rainfall, and indicates increased precipitation.Increased solar output breaks up oxygen molecules which raises ozone concentrations in the upper atmosphere. The resulting increase in upper atmospheric temperatures causes changes in the circulation to the Earth’s surface, and, with surface temperatures warming, rainfall patterns are exaggerated. Areas receiving greater rainfall, such as the tropics, usually receive even more moisture, and dry areas become even drier, both because of less precipitation and higher temperatures drying out the soil’s existing moisture.
The computer model used by the researchers indicated that greenhouse gases warm the atmosphere similarly to changes in solar activity, showing that drier conditions could affect the subtropics. Areas such as the southwestern U.S., Mexico, areas of North Africa, the Middle East, and Australia, already experiencing water problems, could become drier, while the western Pacific, areas along the equator, and parts of southeast Asia could see increased rainfall.
Scientists think the past periods of drought confirmed by the new research affected ancient peoples such as the Pueblo dwellers of New Mexico and Arizona, who were apparently forced to abandon their homes in the fourteenth century. (http://www.amarsodyssey.com/2007/07/17/nasa-scientists-study-possible-future-droughts/)
