They supply brushstrokes for climate change portrait

• Climate Change in Minnesota: An MPR News special report

Much of what we know about Minnesota's changed climate rides on the shoulders of hundreds of weather volunteers over more than 100 years.

Since a fur trader in the Red River Valley measured the temperature and precipitation in 1807, these observers have written down millions of measurements that, given enough time and taken in the aggregate, morph from weather into climate.

None have been more diligent than the Opjorden family in Milan in western Minnesota, who started writing down rain, snow and temperature measurements in 1893.

"Dad did it, and I got started doing it and just kind of stuck with it," said Luther Opjorden one rainy day last fall. He's been checking the totals every day for the past 32 years. His father Torfinn did it for 57 years before that, and his grandfather Olaus, a Norwegian immigrant, started the tradition.

"The value of the meteorological record, like other scientific works, is not fully realized at the time it is made."

The Milan weather station is one of more than 200 sites in Minnesota where volunteers send in daily data to the National Weather Service. Fifty of the stations have records going back more than 100 years.

"Thirty-seven hundredths," Opjorden announces after looking at the rain guage. "Or as my dad would say, and I tell everybody, 37 cents worth."

Overall, Milan is about a degree warmer than it used to be, he said, although that's not obvious from paging through the family's handwritten records on onion skin paper. The documents are tucked away in an old briefcase, and Opjorden has plastered a stern note on the front with packaging tape: "KEEP OLD OLD WEATHER RECORDS."

"The coldest I've recorded I think has been 33 below. If I flip through these I think the hottest I had was 100 degrees. The records kind of speak for themselves."

Minnesota's mid-continent location brings that incredible range. And then even on a given day, year to year there is a lot of variation. The National Weather Service relies on 30-year averages to describe the climate, said Michelle Margraf of the National Weather Service, who coordinates the network of volunteer observers.

"You have to know how much rainfall is normal for an area to know how big the culvert needs to be under the road or how far you have to bury your pipes," she said. "We're just grateful for all the people who had the foresight back then to start marking down the daily information. There's days when there's blizzards or it's 30 below and you have to have a real passion to want to go out there and take the measurements."

Vern Ferch had that kind of passion. He manned a weather station in Waseca for a third of its 100-year history until he retired in 2001.

Ferch remembers really cold days when his fingers felt like they would freeze off, or times he dialed up the National Weather Service to report a major storm.

"I still remember that number."

Ferch and the others at the University of Minnesota's Southern Research and Outreach Center were honored last summer for their century of weather observations.

What Ferch, Opjorden and others have done is supply the individual brush strokes for a painting, said state climatologist Greg Spoden. In congratulating the Waseca crew, he quoted a 1898 federal Weather Bureau document:

"The value of the meteorological record, like other scientific works, is not fully realized at the time it is made."