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Figure 1: Minnesota has experienced a significant increase (45%) in the amount of precipitation that falls during the heaviest storms since the 1950s. Source: Fifth National Climate Assessment, Fig 2.8. [https://repository.library.noaa.gov/view/noaa/61592].
Over the past several years, you may have noticed a change in rainfall. You may have to water your garden more, while at other times, your yard may be underwater. Precipitation patterns in Minnesota have shifted because of climate change. In recent decades, Minnesota and the Midwest have experienced a 45% increase in the amount of precipitation that falls during the heaviest storms each year (Figure 1). In general, the changing patterns experienced in Minnesota mirror changes seen in the United States and around the globe.
In this Hot Topic, we will explore how climate change is affecting precipitation and anticipate how such shifts will influence landscapes.
Learning Objectives
Learning Objectives
Examine historic, current and projected precipitation trends in Minnesota
Understand the relationship between climate change and precipitation
Explore how precipitation changes interact with current and future plants in our landscapes
Climate Change and Precipitation in Minnesota
Climate Change and Precipitation in Minnesota
Minnesota is experiencing warmer temperatures as a part of climate change. From 1895 to 2024, the average annual temperature in Minnesota warmed by 3.2 degrees Fahrenheit. In the next 30 years, Minnesota is projected to warm another 3.8 degrees Fahrenheit compared to the 1995-2014 annual temperature average. Temperature change is one variable, but its effect is amplified by its impact on precipitation.
In Minnesota, precipitation patterns are expected to continue changing as the climate warms. You may have already noticed more drastic, fluctuating extremes of wet and dry weather conditions. This “water whiplash” is made worse by the atmospheric sponge effect. Warm air holds more water than cool air, acting like a sponge, as it absorbs moisture from the soil and surface water. Warmer temperatures driven by climate change are supercharging this effect. When weather systems from warm, humid areas move into Minnesota, they bring larger amounts of moisture than in the past. This also helps explain increasing droughts: warmer, dry air moving into the region can collect and remove moisture from surface water, soil and plants, similar to a dry sponge absorbing extra moisture. The potential results will vary depending on the location in the state, the concentration of greenhouse gases in the atmosphere and the season.
Winters and springs are projected to generally become wetter. Winter temperatures are warming much more quickly than summer temperatures. By 2050, wintertime average low temperatures are projected to increase by between 4.5 and 6.5 degrees Fahrenheit. With warmer temperatures, more winter precipitation is expected to fall as rain instead of snow. In fact, the days with more than one inch of snow on the ground are projected to decrease by up to 15 days per year! As plant-lovers know, snow cover can be critical to insulate and protect plants from cold and pest damage.
The summer and early autumn seasons are projected to be drier in the future. Most places in Minnesota may see longer stretches without rainfall during the growing season (Figure 2). However, year-to-year variability will be high, with some very wet summers and others very dry. In addition to fewer days with rainfall, warmer temperatures during the growing season will remove more moisture from soil, plants and surface water. As a result of the drying effect of the atmospheric sponge, the water needs of plants may increase significantly during future growing seasons and drought may become more common.
Figure 2: Minnesota is projected to experience longer periods with no precipitation by mid-century (2040-2059). Statewide, the average number of days without precipitation could increase by 1.1 days.*
Figure 3: Minnesota is projected to experience an increase in the number of days with more than 2 inches of precipitation by mid-century (2040-2059).*
In contrast to more frequent and severe droughts, projections suggest that when precipitation does fall, it will come from larger, more intense storms. In Minnesota, we have already observed an increase in days with a high volume of rain. Most of the state is expected to see an increase in days with at least two inches of rain over the next 30 years (Figure 3). Intense rainfall may mean that more water will run off the landscape, rather than soaking into the soil. Increased runoff and less water absorption may result in more flooding along bodies of water and in cities.
Given the relationship between increased temperature and precipitation, we know that our future weather will change. We will likely experience greater fluctuations between extremes over time; but a critical question for gardeners is, how will these changes affect the plants and our gardens?
Consequences for the Garden
Consequences for the Garden
Overall, the fluctuations in precipitation caused by climate change will make it difficult to predict the water needs of our plants. Our yards and gardens will need to be resilient to a variety of conditions, including flooding, drought, intense rainfall and winter weather. We will also need to be attentive and carefully manage the soils in our gardens, as changing precipitation patterns and amounts can amplify erosion and loss of nutrients.
Wetter winters and springs increase the likelihood of flooded landscapes. Flood events can destroy a yard, washing away plants, soil and nutrients in fast-moving water. Floods and waterlogged soils can be damaging in other ways. Plants use oxygen to complete cellular processes; roots in soaked soil cannot take in oxygen. Additionally, plants that are submerged in floodwaters cannot absorb carbon dioxide or light for photosynthesis.
As our summers and autumns get warmer and drier, flooding after droughts may become more common. Flooding can be especially damaging after an intense rainfall on dry, drought-stricken soils, as compacted, dry soils may repel water instead of allowing it to soak in. Water may run off, causing flooding and soil erosion. Runoff can strip nutrients from the soil and carry them to waterways, encouraging harmful algal blooms.
Warmer, drier conditions during the growing season could negatively impact plants. In hot weather, plants lose more water through transpiration. Increased transpiration and water loss may cause drought stress and lead to plants closing their stomata, the pores on their leaves that let carbon dioxide in and oxygen and water out. When plants close these pores, it can interfere with photosynthesis, leading to fewer leaves, shoots and flowers. Some drought-stressed plants may increase their root growth and density to help them obtain water in dry soils. However, this root growth can be at the expense of above-ground growth. To prevent drought stress and keep our garden plants healthy, supplemental water will be required, increasing the demand for ground and surface water.
The effects of drought stress can linger into future seasons. If a plant is already drought stressed, it is less likely to withstand additional cold stress. Due to the lower water content, dry, drought-stricken soils are colder than wet soils. The water in wet soils holds more heat, preventing frost from penetrating as deeply. Wet soils are usually warmer than the surface air, protecting plant roots. If soils are dry, cold temperatures reach more deeply into the soil, potentially killing plant roots. Historically in Minnesota, thick snow cover has helped insulate plants from cold winter soils. The projected reduction in snow cover for future winters increases the chance that plants will be harmed by cold temperatures.
Finally, warmer, wetter conditions during the growing season can increase weed, disease and insect pressure. Weeds often thrive in harsh conditions that stress landscape plants, so hot, dry weather may make weeds more competitive. Plants stressed by too much or too little water will be less able to survive threats from insects and diseases. Gardeners will need to be vigilant in scouting emerging pests and proactively managing them.
Looking Ahead
Looking Ahead
What’s a gardener to do in the face of such environmental extremes and dramatic changes? While it may seem daunting, there are several steps you can take to make your yard and garden more water-resilient as the climate changes. Stay tuned for the upcoming Clean Water toolkit to learn more about what you can do to buffer against precipitation changes and help protect Minnesota’s water resources!
*Figures 2 and 3 are based on an intermediate emissions scenario (SSP 245) and are sourced from climate.umn.edu v1.1 beta.
Test Your Knowledge
Test Your Knowledge
Additional Resources
Additional Resources
University of Minnesota Climate Adaptation Partnership
Use the Minnesota Climate Mapping and Analysis Tool (MN CliMAT) to view climate change projections for your neighborhood
View regional climate summaries for Minnesota
View climate data using NOAA's Climate at a Glance tool
Learn more about water whiplash and the atmospheric sponge with UCLA
Gardening resources from University of Minnesota Extension
References
References
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