Moderate

Across the central U.S., very heavy (greater than three inches per day) and extreme (greater than six inches per day) precipitation events increased in the period from 1979 to 2009 compared to the 1948 to 1978 period. Model projections for the central U.S. suggest a potential increase in these events, especially during winter months. Other future climate projections indicate that the Midwest may experience two to four more days of extreme precipitation by the end of the century.

Mean annual precipitation is projected to only increase by 0.7 inches under the GFDL A1FI scenario for the final 30 years of the 21st century compared to the 1971 to 2000 baseline. By contrast, annual precipitation is projected to increase under the PCM B1 scenario by an average of 3.8 inches. Changes in precipitation are projected to vary greatly by season. Both models project an increase in precipitation in winter and spring. They differ in projections for summer and fall. PCM projects an increase of 1.8 inches, while GFDL projects a decrease of 5.8 inches in summer.

Some national and global studies suggest that conditions favorable for wildfire will increase, but few studies have specifically looked at wildfire risk in the Mid-Atlantic region. The duration of the fire season in the Mid-Atlantic region is closely linked with increases in average temperature during the summer (Liu et al. 2010). If drought or prolonged dry periods increase in this region as expected, fire risk will increase in both forests and local communities.

Warmer temperatures can lead to decreased soil moisture even without an associated decrease in precipitation, resulting in a temporary inability for a tree to meet water demand.

At a global scale, the scientific consensus is that fire risk will increase by 10 to 30 percent due to higher summer temperatures. For the early part of the 21st century, there is low agreement in this trend across climate models. By the end of the century, however, most models project an increase in wildfire probability, particularly for boreal forests, temperate coniferous forests, and temperate broadleaf forests. Studies from southern Canada also project more active wildfire regimes in the future.

Heavy precipitation events have been increasing in number and severity in the upper Midwest in general and for Minnesota in particular, and many models agree that this trend will continue over the next century. For example, storms in the 99th-percentile category incrased by 42% from 1958 to 2016 across the Midwest. Large storms are also expected to deliver more rainfall as well. In the Midwest, 20-year return storms are projected to deliver 11 to 20% more rainfall by the end of the century. Most heavy precipitation events occur during summer in the Upper Midwest.

In general, fire-adapted systems that have a more open structure and composition are less prone to high-severity wildfire. Frequent low-severity fire has also been shown to promote many species projected to do well under future climate projections, such as shortleaf pine and many oak species. Fire-suppressed systems, on the other hand, tend to have heavy encroachment of woody species in the understory that reduce regeneration potential for these fire-adapted trees. In addition, fire-suppressed systems can be more vulnerable to insect attack.

Due to projected decreases in precipitation during summer or fall and increases in temperature throughout the year, some evidence suggests a slight decrease in surface soil moisture in the Central Hardwoods Region over the next century . In addition, total soil moisture is projected to increase during winter and spring and decrease in the late summer and autumn. Even if there are increases in precipitation in the summer, as a few models suggest, increases in evapotranspiration are projected to lead to lowersoil water availability .

Heavy precipitation events have already been increasing in number and severity in the area, and some models suggest an increase over the next century .

Model projections and other evidence support modest productivity increases for forests across northern Michigan under climate change, although there is uncertainty about the effects of carbon dioxide fertilization. Warmer temperatures are expected to speed nutrient cycling and increase photosynthetic rates for most tree species in the assessment area. Longer growing seasons could also result in greater growth and productivity of trees and other vegetation, but only if sufficient water and nutrients are available.