Our new Minnesota normal: Warmer and wetter
2011 brings a shift in assessing weather.
The year 2011 will bring a change in the weather -- or at least what we think of as normal weather.
New "normal" settings for temperatures, rainfall and snow for Minnesota -- indeed, for 10,000 U.S. locations -- will be published later this year by the National Climate Data Center, which calculates them once a decade, much like the census. For the Twin Cities and much of Minnesota, normal will probably mean warmer and wetter.
The normal overall temperature for January for the Twin Cities could be 2.7 degrees warmer than the normal that's been in use for the past 10 years, based on previous calculations. That's a sizable jump in climate terms, but once people adjust to the new average, it's possible they might not be alarmed.
"It's going to be tricky from an education standpoint," said University of Minnesota Extension climatologist Mark Seeley. "We have to keep the public aware that across our lifetime we're seeing trends that are even more significant than we can see from a 30-year context."
What's a climate normal?
A climate normal is, by international agreement, an average of weather conditions over 30 years. It's intended to indicate what weather conditions might be typical in any given place.
For the past decade, the normals were based on weather from 1971-2000. The new set will cover 1981-2010, so Friday was the final day of the next 30-year climate normal period.
Assistant state climatologist Pete Boulay noted that the new tables will exclude the cool decade of the 1970s, replacing it with the warm '00s, so normal temperatures will almost certainly rise. Boulay also said that the Twin Cities' snowiest-ever December, in 2010, will probably make December the snowiest month of the year in the climate normals, jumping ahead of January and March.
Climate normals have long been used by farmers and horticulturists, architects, public works managers, snow-removal planners, climate forecasters and, of course, the media. In some states, they're used to set utility rates.
They can also be used to measure climate change, because they stay put while the local conditions change. But climate change itself may be undermining their usefulness.
"If normals are getting warmer, then comparing temperatures to a warmer average is not going to be seen as a big deal anymore," said Anthony Arguez, the NCDC's climate normals project manager.
Many industries that have long used normals in their planning are turning to other calculations, Arguez noted, because the climate has been changing faster than the normals have. An NCDC analysis showed that across much of Minnesota and Wisconsin, January nighttime temperatures were 5 degrees warmer from 2001-07 than the standard 30-year normal. Xcel Energy now uses 20-year normals to help predict energy needs, said spokesman Tom Hoen.
"Climate change makes it more difficult for normals to represent what's going on," Arguez said.
'Moving averages'As a result, the Climate Data Center is looking at new types of "normals" to use in addition to the 30-year averages.
The data center is considering compiling "moving averages," calculating 30-year averages every year instead of once every 10 years.
Another strategy would be to build an upward tilt (they call it a "hinge") into the normals at the year 1975, when the current significant warming trend began. That would allow normals to be cast forward on a trend rather than reflect the past, and could shift to accommodate cooling trends as well.
A third approach would be to build normals based on strong trends over periods of time much shorter than 30 years, to give them more immediacy.
Those alternatives are under review and may not be in use until 2013, Arguez said.
Bill Patzert, a climatologist with NOAA's Jet Propulsion Laboratory, took a different view. Patzert was contacted through a climate-change "ready-response" network of researchers.
He said climate normals are "misleading" because they don't cover enough time. He'd like to see normals based on 50-year periods at least, and longer where more records are available.
In Minnesota, in the midst of a blizzard engulfing his home in Fergus Falls Thursday, retired DNR hydrologist Terry Lejcher noted that his region has received 70 more inches of rain and snow since 1991 than indicated in the 1971-2000 normal. Otter Tail Lake is higher than it's been at any time since the 1930s, and even at the onset of winter, residents are sandbagging their homes to keep floodwaters out. Much of the water in that region flows west to the Red River of the North, which has seen epic flooding and flood fighting in recent years.
"It reinforces for me that a normal is nothing but a snapshot," Lejcher said. "In fact, what we're seeing is normal. There's a lot of variation in the climate. Most people's perception is that something is seriously wrong here. But everybody's life span is so short."
Bill McAuliffe • 612-673-7646
