Greenhouse gases trapped in the upper atmosphere are acting like the natural climatic forces that made some ancient droughts last for 1,000 years, UCLA researchers say in a study released Thursday.
Global warming created by these gases could be making a more arid climate “the new normal,” like what California has seen in its current five-year drought, said UCLA geography professor Glen MacDonald, the study’s lead author, the San Gabriel Valley tribune reported.
The study in Scientific Reports found that carbon dioxide and methane emitted from the burning of fossil fuels may be mimicking the effects of some catastrophic environmental phenomena the planet has previously experienced, according to the newspaper.
The consequences of the buildup of greenhouse gases in the Earth’s atmosphere look a lot like the effects of storms on the surface of the sun, decreases in volcanic activity or wobbles in the Earth’s orbit. Events such as those precipitated 60-year periods of drought in the 12th century, MacDonald wrote. Some prehistoric droughts created by those phenomena lasted as long as 1,000 years.
Man-made activity causing the Earth’s temperature to rise may take the place of these natural phenomena — known as “radiative forcing” — in creating what scientists identify as extended arid periods, the study found.
“When you have arid periods that persist for 60 years, as we did in the 12th century, or for millennia, as we did from 6,000 to 1,000 B.C., that’s not really a ‘drought,’” MacDonald said in a statement cited by the Tribune. “That aridity is the new normal.”
While many scientists suspected that California had experienced extended dry periods in the ancient past, MacDonald’s study found new, decisive evidence of mega-droughts occurring before recorded history, according to the Tribune.
— City News Service
