Something else to worry about over the weekend:

As the southern tier of the USA suffers through a drought that stretches from Arizona to Virginia – a distance of some 2,000 miles – new research this week finds that "megadroughts" used to be a common feature of the southwestern USA, and may be again, thanks to our favorite villain, climate change.

These "megadroughts" lasted for, um, millennia, which I think is a long, long time.

The authors, in a study published this week in the British journal Nature, say that "megadroughts" were a regular feature of Pleistocene interglacial periods in the Southwest, which were some 370,000 to 550,000 years ago. The study suggests that if it wasn't for man-made climate change, this region would probably now be entering a cooler, wetter phase.

The Southwest is known to have endured decades-long droughts over the past two millennia, but it has been unclear whether there were longer "megadroughts," lasting for hundreds or thousands of years, and if so, how regular and intense they were.

Peter Fawcett of the University of New Mexico and his co-authors analyzed a lake sediment core from Valles Caldera, N.M., and determined that these megadroughts, which had profound effects on water availability and ecosystems, were caused by the poleward expansion of the subtropical dry zone, in response to natural climate warming.

This climatic mechanism is similar to that predicted for the southwestern USA as a result of man-made global warming, and these extremely dry Pleistocene periods may therefore suggest future climate change in the region.

As the authors note in their article, these future permanent, 'dust-bowl-like' megadrought conditions, lasting decades to a century, are predicted as a consequence of global warming.