Footnotes on climate change

Climate Change in Minnesota: An MPR News special report

Explore our sources for the story Climate Change in Minnesota: More heat, more big storms to take a deeper look into climate science, the people investigating it, and more.

(1) Those first records, as referenced to in Mark Seeley's book, "Minnesota Weather Almanac," are kept at the Minnesota Historical Society.

(2) Assistant State Climatologist Pete Boulay and another researcher have reported on how early weather observations were made at Fort Snelling. Learn more.

(3) Olaus Opjorden was born in Norway and settled in Milan. He became a pharmacist, as documented in this old biographical sketch, which fails to mention his weather observing -- perhaps a sign that there's a far greater appreciation for that work now than at the time he did it. The Opjorden family received a Family Heritage Award in 2005 from the National Weather Service for keeping the weather observing family tradition alive for over a century.

(4) You can see the trend in average annual temperature for Milan in this graph by Assistant State Climatologist Pete Boulay. Although looking at temperature changes at just one site can be useful, the data become more powerful when combined with other sites in the area, as this map shows.

(5) Weather observers in northern Minnesota have especially tough jobs. Last January during a long cold snap, we visited the weather observer in Embarrass, a town notorious for being one of the coldest spots in the state.

(6) The National Weather Service's latest calculation of normal temperatures is for the period from 1981-2010. January minimum temperatures were up by 2-3 degrees in much of the state, compared to 1971-2000. Learn more.

(7) The United Nations Intergovernmental Panel on Climate Change has summarized observed changes in the climate, including global temperature. There's a lot of variation in warming, with the arctic warming faster than any other place on Earth. Learn more.

(8) Although some individual sites, like Hibbing, show a more than 3-degree uptick, climatologists prefer looking at an average of several different sites within a region of the state. This map shows the variation in temperature changes when tallied by region within Minnesota.

(9) March 2012 shattered temperature records throughout the state. Those who attended St. Paul's St. Patrick's Day parade captured some great photos and video of the summer-like day. Could it have happened without climate change? Research published in 2014 indicates the extreme event was possible under natural variability alone. But taken together with long-term winter temperature data, it's an extreme example of the warmer temperatures Minnesota is experiencing.

(10) The measure of Earth's reflectivity is known as albedo. Dark surfaces have a low albedo, because much of the sun's energy is absorbed instead of being reflected back into space. Ice, snow and other light-colored surfaces have high albedo. This is why you might choose to wear light-colored clothing on a hot, sunny day. Warmer temperatures under global warming melt ice and snow. With less snow and ice cover, the earth can absorb even more energy from the sun. But drawing conclusions about snow and ice cover in a given place can be complex, because clouds also reflect sunlight. Many scientists believe lower albedo is at work in the Arctic, exacerbating the warming that is occurring there. But there's still debate on how much of the so-called polar amplification can be attributed to the albedo effect. Some researchers say temperature feedback is different at low and high latitudes. In Minnesota we don't have good enough data on snow, ice and cloud cover to prove lower albedo is the reason Minnesota is warming faster than other states, but it's a factor. Another factor at work is called arctic oscillation, which leads to natural variability in how warm or cold our winters are. Some scientists have found evidence that climate change is influencing its behavior, bringing warmer-than-average winter temperatures to places like Minnesota. But as with other oscillations, like El Nino, it's a complex problem to figure out how increased CO2 concentrations influence them.

(11) Climate Central, a research group based at Princeton University, analyzed how fast the lower 48 states were warming during the winter. Learn more.

(12) Latimer is a phenologist -- someone who carefully tracks the life cycle stages of plants and animals where they live. (He even has a radio show about it, broadcast weekly on KAXE in Grand Rapids.) Those annual cycles, like when a flower buds or when a bird returns in the spring, are often cued by climate. Detailed notes from observers like Latimer, when combined with climate statistics, can provide long-term historical data on how climate change has affected our natural systems.

University of Minnesota ecologist Rebecca Montgomery, for example, has combined Latimer's data with records from a University of Minnesota entomologist named Alex Hodson, who took notes on different plant species during his walk to work every day from 1941 to 1991. She has put those observations together with records from her own research lab, to show that aspens in Minnesota are now leafing out about two weeks earlier than they did in 1950.

Montgomery is collecting records from other phenologists around the state -- some logged in Excel spreadsheets, others scribbled in journals -- and compiling them in one dataset, to not only document changes in the environment, but also to predict future climate change impacts on different plant and animal species.

(13) This chart shows the average percentage of Lake Superior ice coverage between Dec. 1 and May 1 over 40 years. According to professor Jay Austin at the University of Minnesota-Duluth's Large Lakes Observatory, who supplied the graphic, the term "coverage" encompasses a range of conditions. "When it shows '45 percent' that means that either: the lake was 100 percent covered 45 percent of the time, or 45 percent covered for 100 percent of the time, or (much more likely) something in between those two stages."

(14) Ice in and ice out data for many of Minnesota's lakes are available on the DNR's website. If you explore the map showing earliest ice out dates, many of the dates are in the 2000s. Learn more.

(15) Since 2000, the eastern larch beetle has wiped out 15 percent of northern Minnesota's tamarack forests -- over 150,000 acres of trees. It's only the third major outbreak of the beetle ever recorded in North America. The insect historically has been able to reproduce only once per year. But University of Minnesota researchers Brian Aukema and Fraser McKee have found that shorter, milder winters in northern Minnesota have allowed the beetles to sometimes produce two generations per year. That one-two punch of beetles has overwhelmed the trees' defenses and caused the prolonged outbreak. Meanwhile the mountain pine beetle -- the tiny bug that's felled tens of millions of acres of forest in western North America -- appears poised to reach Minnesota in the near future. Climate change has allowed the bug to jump over the Rocky Mountains into the jack pine forest in Alberta, Canada, leaving it with an uninterrupted swath of pines all the way to Minnesota. Forty-below-zero temperatures are enough to kill the beetle. But warmer winters mean we don't see those frigid temperatures as often as in the past. And research the University's Aukema has conducted shows that the beetle would likely find Minnesota's pine trees plenty tasty.

(16) Research shows warming temperatures are expected to accelerate tick invasions and expand ranges. Scientists and public health experts have identified at least two other important factors for the increased incidence of Lyme disease in Minnesota: Greater awareness of the disease and more people venturing into prime tick habitat. Learn more.

(17) Warmer temperatures are helping deciduous trees expand into boreal forests. Buckthorn and other invasive species are able to survive a variety of conditions and therefore could have an easier time surviving in a changing climate. The increased carbon dioxide concentrations are also having an impact on which plant species multiply. For example, research has shown ragweed thrives in the conditions. Meanwhile, climate change is causing more disturbance and stress to native ecosystems. Learn more.

(18) Red maples are among several types of temperate tree species expanding into boreal forests.

(19) These ecosystems are referred to by scientists as biomes, and according to the Minnesota Department of Natural Resources, Minnesota actually has four of them. The three largest ones are the coniferous forest to the northeast, the prairie grassland to the southwest and the deciduous forest, which cuts a diagonal line across the state from southeast to northwest. The fourth is the tallgrass aspen parkland, located in the northwest. The distinct characteristics of each of these four areas helped shape the types of plants and animals that live there. But we should also point out that despite the existence of these biomes, many of their identifying characteristics can already be hard to find not because of climate change but because of land use changes — primarily agriculture. Learn more.

(20) Research has shown that more than a third of Earth's terrestrial ecosystems will undergo biome-scale changes by the end of this century, and the Great Lakes and Great Plains regions have been identified as hotspots for such change. Learn more.

(21) Minnesota's moose population has fallen from roughly 8,000 to 4,000 in less than a decade. Like boreal tree species also threatened by climate change, Minnesota's moose live at the far southern edge of their range. Milder winters and warmer winters can stress them. Warmer weather also allows more ticks and parasites to survive. But researchers believe the rapid rate of the moose decline suggests a cause more complex than warmer temperatures alone. The DNR's study using GPS collars to rapidly respond to dead moose — to try to glean exactly what's killing them -- will wrap up in 2016. The DNR acknowledges that at that point, it may be too late to reverse the decline.

(22) Even Canada is starting to grow corn, as documented by this Bloomberg piece. But climate is not the only factor driving decisions about what to plant where. Commodity prices have a lot to do with it. In recent years, Minnesota has lost hundreds of thousands of acres of conservation lands as farmers decided to plow them up for planting. Crop genetics have also improved.

(23) Minnesota was a pioneer in setting up a network of volunteers who measure rain totals, as detailed in this history piece. The network now has more than 1,500 observers.

(24) The network Kunkel is referring to is the National Weather Service's Cooperative Observer Network, which covers every state. The National Climate Assessment has a detailed description of the increase in heavy downpours.

(25) The University of Minnesota's Peter Snyder says climate scientists often refer to the atmosphere being more juiced under global warming. It's similar to a baseball player being able to hit more homeruns when using steroids. A research institute in Boulder, Colo., created a video explaining this idea, and you can learn more about what happened to baseball statistics during the juicing era here. However, Snyder cautions that a lot of the spring and summer precipitation in Minnesota is convective — usually thunderstorms covering a small geographic area. Warm-season precipitation is heavily influenced by the low-level jet stream, so the increased capacity for heavy rains due to climate change is only part of the story.

(26) The 30-year average annual precipitation for Waseca is 34.7 inches. You can see in this summary from the University of Minnesota's Southern Research Outreach Center how remarkable June 2014 was. The weather station celebrated 100 years of records last August.

(27) The city of Mound released sewage into Lake Minnetonka to prevent it from backing up into basements. We documented other damages from the storms here. See photos of high water levels on Lake Minnetonka.

(28) This page from the State Climatology Office offers a summary of those events, including links to historic documents.

(29) MPR News documented the damage during that storm, and here's a summary from state climatologists.

(30) Unofficial rain totals in some Duluth neighborhoods were close to 10 inches with some rain gauges filled to capacity, though official records came in lower. A U.S. Geological Survey report noted record stream flows, some of which had a 1 in 500 probability of happening, but no formal analyses have been done to determine what the event would have looked like without climate change. Experts agree wet conditions leading up to the storm June 19-20 made the area even more vulnerable. See before and after photos of the event.

(31) Gov. Mark Dayton called a special session of the Legislature to address the damages. Learn more.

(32) The Office of the Legislative Auditor recommended in March 2012 that the Legislature set up a special account for dealing with natural disasters. Three months later, Duluth and other northeastern Minnesota communities suffered major damages and by August the Legislature had approved $167.5 million in flood relief. In 2014 the state Legislature set aside $3 million for a disaster relief account, but that money wasn't enough to respond to the heavy rains and flooding that hit southern Minnesota that spring.

(33) Francis offers a good summary of current research on arctic amplification and the jet stream on page 135 of the Bulletin of the American Meteorological Society's Society's State of the Climate in 2013 report. Some scientists have countered that there isn't enough evidence of jet stream shape changes. Still others have concluded the "polar vortex" winter of 2014 is much less likely to occur under climate change. But many scientists agree something is happening with the jet stream that's worth further exploration, especially as it relates to climate change.

(34) The National Climatic Data Center's storm event database allows users to look up specific events or locations. But it warns that there have been changes to the data collection and processing procedures over time.

(35) Brooks spoke at the University of Minnesota in 2012. A video of his presentation is available here.

(36) In recent years, a big area of climate research has looked at attributing specific events to human-induced climate change. Scientists do this by analyzing the underlying conditions present during a given extreme event. It would be like arriving at the scene of a train wreck and piecing together all the layers of evidence to come up with an explanation of what happened. In climate science, computer models are used. "Scientists run a computer model with human effects on climate, and they look at the odds of getting something like the summertime heat in Europe in 2003, then they run the same model without any human influence but with changes in the sun and volcanoes -- then they compare and contrast," said Benjamin Santer, a climate scientist at the Lawrence Livermore National Laboratory in California. By looking at the different combinations of factors, the scientists can conclude if climate change increased the likelihood of a heat wave or flood happening. For example, a group of NOAA scientists concluded recently that climate change increased the probability of Australia having a heat wave in 2013. Santer said analyzing specific events drills down to a level people care about. "It's a little more difficult, I would contend, to be concerned about a change in the average temperature of the planet than to be concerned about, say, the drought in California."

(37) Taken from Seeley's presentation before the Minnesota Environmental Quality Board in June 2014.