Climate changes and the local environment:
Genesee County, Michigan has warmed steadily for more than a century. Although average annual temperatures in the state have climbed more slowly than the global trend, they have still risen by around 0.6° C (1.1° F) relative to twentieth-century averages.
Michigan is known for its long and snowy winter seasons. Rising temperatures, however, have sharply shortened the length of winter across the state. The total number of days in the winter season with at least 2.5 cm (1 inch) of snow cover has declined sharply since 1920, with most of the decline happening since 1980. As winter grows shorter, snow falls less frequently.
Yet that does not necessarily mean that winters have become less snowy across the state. Snowfall trends from county to county vary widely, in large part because water in the nearby Great Lakes cools more slowly than air. If the lakes are largely ice-free, warm water can heat up otherwise cool air blowing into Michigan. The air then absorbs moisture and deposits it as "lake-effect" snow in some, but not all of, Michigan.
Now that the Great Lakes are ice-free for much longer than they were, on average, in the twentieth century, blizzards have grown more common in Michigan even as winters have grown shorter. Overall, precipitation in all seasons has increased across Michigan, at a rate of roughly 1.5 mm/year since the 1930s. Much of the increase has come not through extreme events, but a steady rise in wet days that follow wet days. There are signs that cloudiness is now more frequent than it was in the twentieth century.
In this context, Genesee County in Michigan has recently endured particularly extreme and destructive weather. In March 2012, for example, temperatures in a normally cold month soared to a record-shattering 31° C (88° F). In January 2014, a severe snowstorm dropped 18 inches of snow on the county, the second-heaviest fall since 1975.
How we know:
These reconstructions rely on the National Oceanic and Atmospheric Administration (NOAA) State Annual and Seasonal Time Series and a freely available report, "Historical Climate Trends in Michigan and the Great Lakes Region," by Dr. Jeffrey Andresen of the Department of Geography at Michigan State University.
NOAA's State Annual and Seasonal Time Series relies largely on weather station measurements. Adresen's report largely draws on data collected by weather instruments but also includes information from other sources, such as observations from aircraft.
Heat waves and blizzards brought about by rising temperature trends have imposed high costs on Michigan, including Genesee county. Nation-wide statistics suggest that the elderly, especially those with limited mobility and insufficiently insulated or air conditioned houses, are in great danger during both extreme heat and blizzards. Heat waves can also damage roads and train tracks, impose strains on energy and water resources, and lower crop yields if they arrive in key development stages.
Yet in Michigan, a trend towards wetter weather may also have had beneficial impacts for regional agriculture. Computer simulations show that increases in soil moisture available to corn at mid-season, and a rise in plant-available water in the soil profile over the whole season, have both increased corn yields across Michigan. Until now, global warming has therefore had a complex mix of beneficial and destructive impacts on Michigan, and therefore on Genesee county.
Article author: Diana Lowitt, Georgetown University
Article editor: Dr. Dagomar Degroot, Georgetown University