Robust

Cold-season soil temperatures are projected to increase between 1.8 and 5.4 °F by the end of the century, and total frost depth is projected to deline by 40 to 80 percent across northern Wisconsin and western Upper Michigan by the end of the century. These conditions could increase water infiltration into the soil and reduce runoff, but they may also lead to greater soil water losses through increased evapotranspiration.

A variety of models project that across the Upper Midwest, more winter precipitation will be delivered as rain, more snow will melt between snowfall events, and the snowpack will not be as deep or consistent. Lake-effect snowfall may increase in the short-term, but these events may convert to rain as temperatures increase.

A variety of models project that winters will become more mild across New England and northern New York as temperatures increase. Warmer temperatures will cause more winter precipitation to be delivered as rain. Snowfall, snow depth, and snow pack duration are all expected to be reduced.

Shorter-term fluctuations in the variability of ocean dynamics, atmospheric shifts, and ice mass loss from Greenland and Antarctica have been connected to recent accelerations in the sea level rise rate in this region. Sea levels have risen over the past century, and all global climate models agree that sea level will rise over the next century. Worst-case and lowest-probability scenarios project that sea levels in the region could rise upwards of 11 feet (3 m) on average by the end of the century.

Heavy precipitation events have increased substantially in number and severity in the across the Northeast over the last century, and many models agree that this trend will continue over the next century. Extreme precipitation events could lead to more frequent or severe flooding and an increase in soil erosion. Monthly precipitation in the Northeast is projected to be about 1 inch greater for December through April by end of century (2070–2100) under a high emissions scenario.

All global climate models agree that there will be changes in precipitation patterns across the assessment area, but there is large variability among projections of future precipitation. Most climate models project increases in annual precipitation. Seasonally, winter and spring are also generally projected to have increases in precipitation during the next century. Projections of summer and fall precipitation for this region vary, with many models projecting decreased precipitation or only very slight increases.

Evidence at both global and local scales indicates that growing seasons have been getting longer, and this trend is projected to become even more pronounced over the next century. Warmer temperatures will result in fewer days with minimum temperatures below 32°F and a shorter freeze-free season.

All global climate models project that temperatures in New England and northern New York will increase over the next century as a result of continued increases in atmospheric greenhouse gas concentrations.

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.

Evidence at both global and local scales indicates that growing seasons have been getting longer, and this trend is projected to become even more pronounced over the next century. As seasons shift so that spring arrives earlier and fall extends later into the year, phenology may shift for plant species that rely on temperature as a cue for the timing of leaf-out, reproductive maturation, and other developmental processes. Longer growing seasons could also result in greater growth and productivity of trees and other vegetation, but only if balanced by available water and nutrients.