Transcripts

MIKE MULCAHY: State Climatologist Jim Zandlo can't say why we're having a drought. He can tell you that the jet stream has been taking an unusual northerly course, keeping weather fronts and moisture away from the Midwest. But he says there's no answer for why that happens. Zandlo can, by assigning numbers to temperatures and rainfall, determine how widespread the drought is and how it compares with previous years.

JIM ZANDLO: Those calculations of the drought severity are as extreme in some parts of the state as we've ever seen it. For instance, in the northwest part of the state, we've reached numbers that were as bad as 1934. An important point to bear in mind is that the geographical extent this year of those extreme and severe values of drought are not as far reaching as in 1934. Granted, it's not a small drought. It covers a lot of area. But 1934 still stands out as much worse in some ways.

MIKE MULCAHY: Zandlo says 60% of the nation was dry in 1934, as compared to about 40% this year. Other good news he sees as he examines his records is that the drought may not last much longer.

JIM ZANDLO: When we look at extreme drought, in the state at least, that is, in Minnesota, we tend to see that periods of extreme drought do not tend to be long-lived. In fact, the longest period of time that the whole state has averaged a state of extreme drought has been 12 months. So we see that most periods of extreme drought will end within a year's time.

MIKE MULCAHY: This data has led Zandlo to conclude that we should have a relatively normal winter coming up, both in terms of snowfall and temperature. But he says it could take a while to recover from the effects of the drought and that rain this fall is needed to restore moisture to the soil. Ironically, the drought comes at the end of what Zandlo says was the wettest 10 years in Minnesota's history.

JIM ZANDLO: It is actually fairly common in our record to see a rapid changeover from a very wet condition to a very dry condition. Sometimes we've seen occasions for extended periods, such as that 10-year period, switching over to a wet to a very dry condition, but also individual years that have in essence flip flopped their state. For instance, the year 1910 for the Minneapolis-Saint Paul record is the driest year of record. 1911 is the wettest year on record.

MIKE MULCAHY: As the heat and dry weather have spread across the Midwest this summer, there's been some speculation that the greenhouse effect may be to blame. The predicted global warming from increased levels of carbon dioxide in the atmosphere may come to pass, says Zandlo. But he says there's little evidence to show anything humans have done has contributed to the drought.

JIM ZANDLO: The event that we're seeing right now does have counterparts in the past in years such as 1910, 1934, 1976, some of them quite far back in time. We saw droughts as intense as now and did not have the explanation, for instance, of a greenhouse effect. I think the point to be made there then is that these kinds of things are-- that is, droughts are a natural part of our climate. We might in some future date exacerbate them, exacerbate the frequency at which they occur. But I don't think that we should say that this is the greenhouse effect in this particular event.

MIKE MULCAHY: State Climatologist Jim Zandlo appeared on MPR's midday program. I'm Mike Mulcahy.