Guest essay by David Archibald

There were two papers published in 2013 that, when considered together, paint a bleak picture of North American climate and agriculture for the rest of the century and beyond. Firstly from the abstract of “Multidecadal to multi-century scale collapses of Northern Hemisphere monsoons over the past millennium”1 by Asmerom et al.:

“Late Holocene climate in western North America was punctuated by periods of extended aridity called megadroughts.” And “Several megadroughts are evident, including a multicentury one, AD 1350–1650, herein referred to as Super Drought, which corresponds to the coldest period of the Little Ice Age. Synchronicity between southwestern North American, Chinese, and West African monsoon precipitation suggests the megadroughts were hemispheric in scale. Northern Hemisphere monsoon strength over the last millennium is positively correlated with Northern Hemisphere temperature and North Atlantic SST.” And “the megadroughts, including the Super Drought, coincide with solar insolation minima, suggesting that solar forcing of sea surface and atmospheric temperatures may generate variations in the strength of Northern Hemisphere monsoons.”

So droughts in North America are coincident with solar insolation minima. We already know of the cause and effect relationship between solar cycle minima and East African rainfall. West African drought has been found to be linked to Atlantic sea surface temperatures2.

With that knowledge, all we need to predict the timing of the next megadrought in North America is a long term solar activity forecast. That was also provided in 2013 by Steinhilber and Beer3. They predict a deep low in solar activity starting straight away and continuing for 150 years. This is Figure 4 from that paper:

Figure 4 from Steinhilber and Beer – Prediction of solar activity on the left axis and total solar irradiance on the right axis. M, D and G refer to the Maunder, Dalton and Gleissberg minima respectively. The lighter grey band is based on FFT (fast Fourier transformation) and the darker grey band is based on WTAR (wavelet decomposition using autoregression). As the paper demonstrates, amplitudes of solar activity are better predicted by the FFT method than by the WTAR method.

In effect, Figure 4 predicts a megadrought for North America from at least 2050 to 2200. Generations of people will experience what a Dalton Minimum is like, all their lives. In the meantime it will get colder and drier. In terms of the effect on agricultural productivity, productivity of corn production in the Corn Belt falls by 10% for each 1°C fall in annual average temperature. The Corn Belt also moves south by 144 km for each 1°C fall in annual average temperature. Soil quality declines to the south of the Corn Belt though so farms won’t be as productive. For example, one hundred years ago Alabama had four million acres planted to cotton. Today only 1.3 million acres are devoted to all agricultural crops. Unable to compete with the Corn Belt as it is now, a lot of acreage in Alabama has reverted to pasture and woodland.

A fall in annual average temperature of 2.0°C might decrease production by 20% and the southward move to poorer soils might decrease production by 10% (purely a guess, but I do have a botany major). What drought might do on top of all that is a 30% fall for a total decrease in production in the range of 50% to 60%. Two big corne states, Illinois and Indiana, had corn production falls of 30% in the 2012 drought year:

The US could then feed 600 million vegetarians instead of the current 1.2 billion vegetarians. Food that we would want to eat will become expensive with wide price swings. That is what these two papers are saying about what the future holds for us.

David Archibald, a Visiting Fellow at the Institute of World Politics in Washington, D.C., is the author of Twilight of Abundance (Regnery, 2014).

References

Asmerom, Y. et al., 2013, “Multidecadal to multi-century scale collapses of Northern Hemisphere monsoons over the past millennium” PNAS vol.110 no. 24 9651-9656 Shanahan, T.M et al., 2009 “Atlantic Forcing of Persistent Drought in West Africa” Science, Vol. 324 no 5925 pp. 377-380 Steinhilber, F. and Beer, J., 2013, “Prediction of solar activity for the next 500 years” Journal of Geophysical Research: Space Physics, vol. 118, 1-7

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