Sometimes La Nina never goes away

A thousand years ago the Bosque River Valley was a series of wet meadows through which the river meandered, laying down alluvial sediment that had been accumulating for centuries. But the earth began to dry up during a period of increased solar radiation and orbital forcing caused by a wobble in earth’s orbit that overheated the upper atmosphere which conspired to lock in the dry-with-big-storms La Nina for centuries, a period known as the Medieval Warm Period (CE 950 to 1250). The Southern Great Plains were also dry, activating the sand dune field from Monahans to Nebraska that had been dormant under grass cover for a thousand years. This same warm period brought successful grain crops to Europe and Greenland look like a nice place for a colony. But for the Bosque River, the semi-permanent La Nina drought was punctuated with tropical cyclones and hurricanes that eroded the nearly bare ground and flooded with such intensity that the valley core was washed away all the way down to the bedrock. [The alluvium has since been replaced] The Indigenous People living along the Bosque since the CE 600’s were the Scallorn-point users, whose Archaic wetland, rock-oven and deer centered lifestyle dissipated. As agricultural resource-collectors intruded into the area they were met by violence. Some archeologists say this was the most violent period in ancient Texas history. The Scallorn people were gone by CE 1300. This bleak mega-drought should serve as an analogue for the need for regional plans for water sustainability. Major 20th century droughts pale in comparison to droughts documented in paleoclimatic records over the past two millennia. We may be in the first decades of a centuries long warm period now as the climate is already warmer than the worst of the Medieval Warm Period. Anthropogenic [people-caused] activities are forcing whatever the natural climate drives are, toward long-term heating and dryness. A series of volcanos cooled the earth between CE 1300 and 1860 (The Little Ice Age) and the cooler weather enticed the bison herds back into Texas providing centuries of good hunting for those who came after the Scallorn people.

Dan Young. Unpublished Manuscript, 2022

Connie Woodhouse. “A 1,200-year Perspective of 21st Century Drought in Southwestern North America,” Arizona State University (December 7, 2010)21283-21288.

Earth Institute at Columbia University. “Climate Change could Revive Medieval Megadroughts in US Southwest”, ScienceDaily, (July 24, 2019).

2 thoughts on “Sometimes La Nina never goes away

  1. When the Bosque river flooded in 1996 (I think it was that year), in Waco it looked like the Great Mississippi. Picknick tables doors and cattle were hanging from the tops of old pecan trees. First time I ever saw fire ants form basketball size nests floating on the river. This little river was only 20 feet wide where the Pecan orchard was, but that flood covered half of a 700 acre ranch.

    • That’s cool. I think I remember the high water at the Stephenville park that year.

Comments are closed.