A team of Duke University researchers led by Jim Clark looking at core drillings found repeated dust bowl periods during "the mid-Holocene period of 5,000 to 8,000 years ago in parts of the Dakotas, Montana and western Minnesota".
PORTLAND, ORE. – Events like the great Dust Bowl of the 1930s, immortalized in "The Grapes of Wrath" and remembered as a transforming event for millions of Americans, were regular parts of much-earlier cycles of droughts followed by recoveries in the region, according to new studies by a multi-institutional research team led by Duke University.
Some of those prehistoric droughts in the northern Great Plains of what is now the United States also lasted longer than modern-day dry spells such as the 1930's Dust Bowl decade, according to sediment core studies by the team.
The group's evidence implies these ancient droughts persisted for up to several decades each. At their heights, prairie fires became uncommon because there was too little vegetation left to burn. The ages of charcoal deposits suggest instead that prairie fires occurred during intervening wet periods, with each wet-dry cycle lasting more than a century each.
Too many people believe that whatever weather one has seen in one's own lifetime is "normal". When weather suddenly veers from the pattern one has become accustomed to there is a human tendency to look for some exceptional cause such as human intervention. While human intervention may well be changing the climate the climate is not stable to begin with. We should expect large climate changes as natural.
Even the 1930s drought was not unique in modern times with the 1890s having gone through a drought period as well. But there was no John Steinbeck around to write a great novel about the 1890s drought let alone a silver screen adaptation of the story.
The regularity of these ancient droughts make much more recent Great Plains droughts in the 1890s and 1930s appear "unremarkable" by comparison, Clark said, even though the contemporary ones "walloped people."
The study did not speculate how the findings might relate to anticipated future climate change, when a surge of carbon dioxide from human activities is predicted to cause Earth's climate to warm appreciably.
"What we can say that is relevant is that these sort of drought cycles are common and most of the climate models predict increased aridity in continental interiors in the future," Clark said.
"One could speculate that the droughts could be all that much worse when you realize that it's not only climate change from changing CO2 content in the atmosphere, but also this natural variability out there that we don't fully understand."
Another drought on the Great Plains would wipe out agriculture over a large area and drive lots of people to migrate away from the region. It would also reduce river flow down the Missouri and Mississippi rivers and that would reduce the navigability of those rivers for shipping as well as reduce the amount of water that could be taken from the rivers for irrigation.
Whether or not humans reduce their emissions of green house gasses sooner or later the Earth is going to go through some large regional and eventually even global climate shifts. Those of us who live long enough to be around when rejuvenation therapies are developed will likely then live long enough to witness many large changes in Earth's climate.
However, not all the natural changes lying in our future will come to pass. At some point humans are going to start intervening to prevent some changes while perhaps in other cases humans will engineer other desired changes. Expect to see less desert in the future as some nations decide they would rather cause local climate changes to make their deserts more hospitable to human habitation. This will lead to international disagreements when other nations calculate how conversion of deserts to forests in some regions will cause changes they do not like in their own regions.
|Share |||Randall Parker, 2004 August 04 12:31 PM Climate Trends|