Peter Fawcett has a terrific paper in Nature this week on southwestern megadrought. I’ve been “upstream” (as the science journos like to say) for a while, having been along when Peter and others did some of their very first field work in the Valle Grande in Northern New Mexico back in 2003, and I’ve been talking to Peter (and occasionally writing about the project) ever since. So as a personal matter, this one has been fun on a lot of levels.
It’s also a fascinating paper, using lake sediments to recreate climate signal during Pleistocene. Peter and his colleagues found a couple of very important things:
- a tight correlation between warmer periods and epic droughts
- an apparent collapse in summer rains
They also tie their findings to Richard Seager’s 2007 Science paper on the possibility of huge droughts here as a result of climate change. Which is where, from an inner science perspective, this gets interesting to me. Because Seager told me and other reporters he thinks the connection between their work and his is small. From the story (sub/ad req):
A key to Fawcett’s research is evidence he says shows the region’s prolific summer rains shut down during the ancient megadroughts.
That led Columbia University’s Seager to caution that the new research sheds little light on what we can expect in a warming world, when rising greenhouse gases rather than orbital variations are driving climate changes.
“The thing is that the Fawcett megadroughts were … forced by orbital variations, not CO2, and are caused by drops in summer precipitation, not winter as for the projected future, so I think the relevance of the Fawcett paper to the future is slight,” Seager said in an e-mail.