Northland Winters: A Change In Climate

By KBJR Manager

August 4, 2010 Updated Aug 4, 2010 at 11:47 AM CDT

Climate change is one of the hottest topics in politics these days, but are there actually any measured changes in the Northland's climate?

George Kessler joins us with a look at what current research has to say.

For a meteorologist, the first rule of discussing climate change is pointing out the difference between climate and weather.

Weather is the day-to-day, season-to-season condition of the atmosphere.

Within that there can be big storms, record temperatures or calm - and on an individual basis they don't indicate anything about the overall climate.

When you want to examine the climate for changes, you need to expand your time scale - a lot.

The National Weather Service calculates their temperature and precipitation normals by averaging the readings from a period of 30 years.

To see how our climate is changing, I decided to compare the normals from the mid-80's, mid-90's and mid 2000's.

In 1986, our average annual temperature from the previous 30 years was 38 degrees. For the same time period, the average annual snowfall was 76.3".

By 1996, the average annual temperature had increased to 38.4 degrees, with snowfall climbing to an average of 82.6".

The numbers from 2006 confirm the trend, with the annual temperature hitting 39.2 degrees and snowfall up to 83.2".

The movement over the last few decades is clear; statistically we've been getting warmer and snowier.

In the real world, that means the character of our seasons is subtly changing - longer summers, later snows, less ice on the lakes. But when it does snow, we get more of it.

Those numbers tell part of the story, but every Northlander knows that Lake Superior has a direct impact on the conditions for every community along its shores.

A simple switch in wind directions can mean a 30-degree swing in temperature.

The lake isn't an unchanging presence though; a battery of scientists at the UMD Large Lakes Observatory keeps a close eye on conditions, and they've noted some sizable changes.

"We have historical records to roughly 1906 that directly measure temperatures and the lake is 2.5-3 degrees Celsius, 4-5 degrees Fahrenheit warmer than it was a century ago."

Not only the temperatures have increased- the winds on the lake are way up as well.

"What we've observed, looking at seasonal average wind speeds, just averaging all the data collected in July, August and September. Those wind speeds have increased from about 7 knots to about 10 knots over that 25 year period, which is a remarkable increase."

The combination of warmer, more ice-free water has a mixture of impacts- especially when combined with increased winds over the open waters.

Communities used to cooler-by-the-lake see less chilling effect from on-shore breezes in the summer. During the winter months, these same locations would see an increase in lake snows.

Researchers also suspect that these factors lead to increased evaporation, which would contribute to a decline in lake levels. Coupled with the sub-par rainfall of recent years, this has led to near-record lows.

"We sort of skirted close to record lows this summer in August and September. We were very close if we didn't break the record low in September this year."

At bottom, the lake was 20-22" below normal before the rains of October helped with the deficit.

We're still down though- and getting the lake back to its historical norm would require about five inches of liquid precipitation above and beyond our typical amounts.

That's most likely going to have to wait until springtime at the earliest, since winter is traditionally our driest season of the year.

Just as the weather never stays the same from day-to-day, the climate is also naturally prone to variation.

From the data, it's clear that we've seen noticeable changes over the last few decades.

The heart of the current debate is how much of a role humans are playing in those changes and whether we should take steps aimed at preventing further impacts.

For the Northand's Newscenter, I'm meteorologist George Kessler.