Global Warming Didn’t Hurt Italian Agriculture
June 12, 2002
CHURCHVILLE, VA—Climate alarmists are fond of telling us that global warming will threaten our farms and food supplies by causing more droughts, floods and storms. But 122 years of detailed climate records from the University of Pisa, in Italy, say the rapid half-degree Centigrade warming of the past century has actually helped that region’s farmers.
A team of Italian scientists recently analyzed a detailed set of climate records going back to 1878: maximum and minimum temperatures, last frost days and first frost days, lengths of dry spells, rainfall and evaporation rates, etc.
The Pisa researchers say that “extremely cold temperature events have decreased and extremely warm temperature events have remained unchanged.” Nighttime temperatures don’t go as low as often as they previously did. That means fewer killing-frost nights, without much additional daytime heat stress on plants.
In fact, the biggest news from the Pisa weather records is that the growing season has increased 47 days since 1878. That means bigger crops and far less frost risk for the farmers.
Pisa’s high-rainfall events in the spring decreased over the 122 years, but additional cloud cover also cut water evaporation so there was little change in field moisture. For farmers, the only significant moisture impact of the warming was a decrease in moisture-surplus days in the fall. Since fall is the wettest season in North Italy, and the big summer crops are already harvested, this mainly meant reduced risks from flooding and soil erosion.
The longer growing seasons that Pisa has recently enjoyed echo the European experience during the Medieval Climate Optimum, between 950 and 1300 AD. Temperatures then were 2 to 3 degrees Centigrade warmer, on average, than today. The crops were so abundant that Europe’s population rose by 50 percent! (That won’t happen in the 21st century, since Europe already has abundant food and its birth rates are far below replacement.)
Most of Europe’s famous castles and cathedrals were build during the Climate Optimum since there were more workers than ever before, and ample harvests to feed non-farm specialists such as stonemasons and sledge drivers.
The Italian experience since 1878 is very good news if the world is headed back to higher temperatures. That seems likely, according to recently analyzed seabed cores from the floor of the North Atlantic Ocean. Iceberg debris on the sea bottom indicates nine mild global coolings (with more bits of rock ground off Canada by glaciers and floated out to sea in icebergs) and nine mild global warmings in the past 12,000 years. The 1300-year cycle coincides exactly with a known cycle in the magnetic activity of the sun.
That apparently means we’re about 200–300 years or so into a 650-year mild global warming. The growing seasons are likely to get even longer. Remember we called it
the Medieval Climate Optimum—the best weather humanity ever recorded.
Earth’s plants and animals have evidently been through this climate cycling many times before, and farmers have been adapting to dynamic weather trends for 10,000 years. We just haven’t had the climate records to look back at the process.
Oh, by the way, our plants also evolved in a period when carbon dioxide levels in the air were much higher than they are today. More CO2 for plants is like more oxygen for people. The plants and trees grow better. Perhaps as much as 15 percent of the crop yield increases during recent decades may be due to higher levels of CO2.
DENNIS T. AVERY is a senior fellow for Hudson Institute of Indianapolis and the Director of the Center for Global Food Issues. He was formerly a senior policy analyst for the U.S. Department of State. Readers may write him at Post Office Box 202, Churchville, VA 24421
This article was published by Knight Ridder Tribune
Dennis T. Avery is based in Churchville, Va., and is director of global food issues for the Hudson Institute of Indianapolis.
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