Mark Seeley: Minnesota's weather is a'changing

MINNEAPOLIS — In the hours before the season's first snowfall, Mark Seeley talked climate at the annual meeting of the Agri-Growth Council.

Seeley, the University of Minnesota Extension climatologist and a self-described weather geek, guided audience members through the state's most recent climate trends during his 45-minute presentation.

Minnesota's climate is ever-changing, Seeley said. The items with the most impact on agriculture:

• Warmer winters and higher minimum temperatures.

• Dewpoints. A greater frequency of tropical-like atmospheric vapor.

• Moisture. Amplified thunderstorm contribution.

Seeley credited the state's volunteer weather observers for the data they collect, which gives him a greater idea of climate change, which is occurring across the state.

The change is visible as one glances through the data. The warmest year on record for the 48 contiguous states was 2012; that was the third-warmest year on record in Minnesota. In 2012, flash floods occurred in the Cannon River and Duluth area, which was simultaneous with drought. In March 2012, 800 temperature records were set; the greatest monthly climate anomaly in Minnesota weather history.

Seasonal characteristics suggest winters are changing more than other seasons. At most northern hemisphere locations that are mid-continent based, a similar change in temperature patterns is emerging, Seeley said.

Minimum temperatures are changing by whole degrees in average monthly minimum temperatures, he said. In fact, 12 of the last 16 winters have been skewed to the warm part of the historical distribution.

The last time Minnesotans experienced a real traditional winter was in 1978-1979 when temperatures dropped below 32 degrees on Dec. 6 and didn't warm to 32 again for 66 days.

The change in winter temperature isn't a surprise; it was forecast by those researching climate back in the 1980s, Seeley said.

Recently, climatologists shifted from using 1971 to 2000 as the period to gauge normals to 1980 to 2010. It's always the most recent three decades, Seeley said.

With the change, Minnesota's monthly values went prolifically up. The January minimum temperature increased by 3.4 degrees from the former average, he said. That's a rather dramatic shift from a statistical standpoint.

Consequences of warmer winters and higher minimum temperatures:

• Change in depth and duration of soil and lake freezing.

•More rapid breakdown of crop residue.

• Later fall nitrogen application because soil temperature stays higher than 50 degrees longer.

• Change in survival rates of insect pests, parasites, plant pathogens and soil microbes.

• Reduced energy use for heating.

• Increased number of freeze and thaw cycles.

• Change in plant hardiness zones.

• Longer growing seasons.

• Change in exposure times to mold and allergens.

Dewpoints

The number of 70 degree dewpoints is higher than it's ever been in the state. Minnesota had never recorded an 80 degree dewpoint until the summer of 1983, now most years have at least one 80 degree dewpoint.

Dewpoints of 70 degrees or higher induce stress and are uncomfortable, Seeley said.

Minnesota has the distinction of having the record for the coldest Groundhog Day and the warmest North American heat index. The Groundhog Day record was set Feb. 2, 1996. The heat index record of 134 was set July 19, 2011, in Moorhead.

Minnesota has a long history of heat waves dating to 1883. It's a recent phenomena that the heat waves have been dewpoint driven.

Consequences of increased frequency of tropical-like dewpoints include an increased workload for those who work in heat-related health care, increased stress on livestock, increased demand for environmental controls and changing seasonal dynamics of pathogen, parasite, insect and microorganism populations.

Precipitation

In 2010, Minnesota set a record for the all-time wettest year with more than 34 inches recorded statewide.

The state has been trending wetter, with have the state averaging annual precipitation of 29 inches or greater, Seeley said. This is a 30 percent increase since the 1921 to 1950 period.

More of that precipitation arrives in convective storms. In 2010, 113 documented tornadoes were recorded in Minnesota, including 48 alone on June 27, 2010. There have been three, 1,000 year flash floods in southeast Minnesota since 2004.

In the November 2012 flash flood in northeast Minnesota, the St. Louis River volume was measured at 45,000 cubic feet per second. That obliterated 105 years of flow records, Seeley said.

In June 2012, the river flow was measured at its lowest value ever, 458 cubic feet per second.

The two all-time extremes of 105 years were set within months of each other, he said.

Consequences of changes in precipitation include:

• Altered irrigation, tile drainage, runoff, shoreland and sediment management.

• Change in storm sewer runoff design.

• Mitigation of flood potential.

What's ahead

Minnesota's climate is changing at a startling pace and those changes will have profound consequences, Seeley said.

Minnesotans need to adapt, rather than dismiss the changes that are occurring.