Wisconsin has experienced significant climate shifts over the last 25 years, consistent with broader global warming trends. The changes are characterized by warming temperatures, particularly during winter nights, and an increase in precipitation, especially heavy rainfall events.
Key shifts in Wisconsin's climate:
* Warming Temperatures The state has warmed by approximately 2-3°F since 1950, with projections indicating an additional 3-9°F warming by mid-century. The most significant warming has occurred during winter, with some areas experiencing an average increase of 4.5°F in winter temperatures. Winter nighttime low temperatures have warmed more rapidly than daytime highs and summer temperatures, with some nighttime lows increasing by 4 to 7 degrees Fahrenheit between 1950 and 2020. This leads to fewer extremely cold days and nights.
* Increased Precipitation and Extreme Rainfall Wisconsin has become wetter, with average annual precipitation increasing by 5 to 10 percent in most of the Midwest over the last half-century. More specifically, southern Wisconsin has seen about a 20% increase in annual total precipitation since 1950. The state has experienced some unusually wet years recently, with 2018 and 2019 being among the wettest on record. Heavy rainstorms are more frequent, and rainfall during the four wettest days of the year has increased by about 35%. This trend is projected to continue, leading to an increased risk of flooding.
* Reduced Ice Cover Ice cover on the Great Lakes is forming later and melting sooner, a trend observed since the 1970s. Small lakes are also freezing later and thawing earlier, shortening seasons for ice fishing and skating.
* Longer Growing Seasons Warmer temperatures have led to longer frost-free growing seasons.
These shifts have a range of impacts across the state:
* Agriculture While a longer growing season could benefit some crops, extreme heat and increased extreme precipitation events pose challenges. They can stress crops and livestock, make planting and harvesting more difficult, increase soil erosion, and promote pests and diseases.
* Ecosystems and Wildlife Rising water temperatures in streams and lakes favor warm-water fish species over cool-water and cold-water species like trout, threatening the state's fishing industry. Changes in forest composition are also anticipated.
* Public Health and Safety More intense and frequent heavy rains can result in flooding, harming infrastructure and increasing algae blooms, bodily harm, and illness. Increased frequencies of extreme heat can cause heatstroke and exacerbate chronic illnesses.
* Tourism and Outdoor Recreation Warmer winters limit the season for activities like ice fishing, snowmobiling, skiing, and snowboarding, impacting local businesses that rely on winter tourism. Increased rain during warmer months can also damage and reduce access to parks and other natural resources, affecting camping, hiking, and other outdoor activities.