(This article was written by Dr. S. Elwynn Taylor, Iowa State University, several years ago for the Farm Business Management Education Programs in Minnesota.)
I don't know how many times I told my children to "Stop complaining, you should have seen the winters when I was a kid." The 20-ft deep drifts, the cows walking away because the snow pack was over the fences and the snow was solid enough to support the animals, the drifts up to the eves of the house. And we walked to school (or went on skis or snow shoes). Awhile back folks researching the impacts of the North Atlantic Oscillation (NAO) produced an analysis of winter harshness for the Midwest and the East Coast. Sure enough, by their standards the winters were harsher from 1950 to 1980 than they have been since. True the mild winters of those long gone years were not bad even by current standards and the "rough" winters of the past twenty rears were almost as harsh as those memorable years in my recollection.
They call it an "oscillation" because it does spend twenty or so years on the negative side and a similar span of years in the positive mode. It has been positive since 1980 and may be about to enter the generation of harsh winters once more. Snowmobile enthusiasts, take heart.
Of course the northern Pacific Ocean does about the same thing, it is called the Pacific Decadal Oscillation (PDO) and seems to change about twice as often. It is the air pressure pattern that impacts the Midwest storm systems but a lot of factors influence the pressure. For the past 30 plus years we have had satellites that do a fine job of making a thermal image of the Earth, accordingly sea surface temperature patterns are clear to anyone's view and the impact of sea temperature on the weather everywhere has become apparent.
Everyone knows the climate has changed over the past ten thousand years or so. After all Minnesota is not capped by an ice sheet at this time. But it is the recent changes that seem to concern people the most. Make no mistake, people can and have impacted the climate of the entire planet. This became a demonstrable fact with the "Ozone hole." Global Warming is not as clear cut, likely because the Earth has intervals of warming and cooling that mask impacts by man to date. Human impacts aside we are in a warming trend and there is a natural warm/cool cycle of about 89 years in this world. It seems that the worst year (drought of Dust Bowl proportions) of each century occurs at about the climax of the warming phase of the cycle. That would likely happen about 2025 but the intervening years are likely to bring increasingly harsh droughts when they do appear.
We still have a great deal to learn about the climate, but we do know that it changes, it has always changed, and it will always change. Our concern is how fast, how much, and how come? With the renewed interest in Hurricanes since 2004 we have noted that the number of storms in the Atlantic follows a 20-year cycle and the number of storms striking the US seems to be on a cycle of 50 years or so. It is just recently that anyone noticed that plant growth in the Midwest is in phase with the Atlantic storm cycle, not that the storms impact the Midwest but that there is likely a common driving factor thus far not identified.
The message is more than "what goes around, comes around." It is that we cannot expect to hold in the climate of this decade. Second, this has not been so bad, only twice has Minnesota led the Corn Belt in corn yield and they were both during the past 10 years. With all this good news comes the caution I wrote about in an earlier issue, that the Midwest is now due for a major drought (the most recent being in 1988) and this would not be the time to neglect the risk management tools open to the manager of an agricultural enterprise. The nation-wide hype on "Global Warming" may in some cases be exaggerated, however, the excitement does come at a good time; climate is in a variable mode, and variations are not conducive to consistent yields and price stability. Some are saying that the strong impact of El Nino and La Nina during the past 30 years is because of "Global Warming," others that the stronger El Nino effects give rise to the observed global warming.