Archived Story

Recent weather may point to climate change

Published 12:16pm Friday, June 1, 2012

May’s rather sparse rainfall total may have been a reminder that climate change is being felt across Minnesota.

Climate scientists have noted that a growing percentage of the rain we receive is arriving in major downpours from thunderstorms. These storms tend to be a bit fickle in how they distribute moisture, dropping huge quantities of rain on one community and leaving the next dry as an old bone.

The Austin area has been the dry bone for months now. Several times during May radar showed heavy rain events in the general area, but little of that moisture reached the ground here.

Last week I watched for a couple of days as a band of storms and rain oriented on a line from southwest to northeast, stretching from Iowa to Duluth, hovered just a couple of counties to the west of Austin. It never moved into our area and we stayed relatively dry, even as heavy rains provoked mud slides in the metro area.

Over the Memorial Day weekend, central Minnesota had line after line of thunderstorms roll through and some communities, such as Brainerd, received inches of rain in just a day or two and, by anyone’s estimates, is pretty well flooded.

When climatologist Mark Seeley was in town a few weeks ago to talk about climate he noted that historically 60-62 percent of rain in the state came during thunderstorms. Now it’s 72-75 percent.

It’s dangerous to generalize from just a few months’ data, so the past weekend and past month may not really be artifacts of major climate change. Indeed, most of us who enjoy watching the weather have noticed there’s just about never a “normal” year. Or a normal month or week or day, for that matter. Climate scientists study decades worth of data to reach conclusions about how weather and climate are changing.

Still, whether recent observations truly fit the trend in climate change, it’s hard not to generalize.

It will be interesting, along the same lines, to think about another trend that Seeley noted during his talk at the Nature Center: Generally increasing dew points.

Although it doesn’t grab headlines the way temperature, rain and wind do, dew point is a major indicator of weather events. High dew points equate, approximately, to high humidity. When the air is humid, temperatures feel warmer than they really are. Just as wind makes winter’s cold feel harsher and is measured by the wind chill index, humidity combines with warm summer temperatures to increase the heat index.

Nine of Minnesota’s last 10 heat waves have been driven by the heat index rather than purely by high temperatures, Seeley said.

Even when it’s not a heat wave, high dew points contribute to warm temperatures. During the day, water vapor in the air warms up, then slowly releases that warmth during the night — averaging out the temperature differences between day and night and making it harder to cool off in the evening.

With summer just around the corner, that will be something to think about on those warm, muggy, buggy evenings.

Always a primary

A letter to the editor earlier this week gave some people the impression that the city of Austin will be forced to hold a costly primary election because there are more than two mayoral candidates. Not so, election officials say. Federal and state laws require that the primary be held to accommodate national and statewide primaries — so there was going to be a primary election in the city regardless of how many people are running for mayor.

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