Background: Climate Impacts Overview
Climate Risk: Sea Level Rise and Coastal Flooding
Sea level rise (SLR) projections developed for the Massachusetts coast by the Northeast Climate Adaptation Science Center (NECASC) range from .7 feet (“Intermediate Scenario”) to 1.2. feet (“High Scenario”) in 2030 to 4.0 to 7.6 feet by the end of the century. The projections assume a high emissions scenario for greenhouse gases. As sea level rises, properties will increasingly be impacted by flooding from daily high tides. A study by Linda Shi of Cornell University concluded that along the Massachusetts coast over 15,000 taxable acres currently valued at $8.9 billion could be chronically inundated by three feet of SLR. With warming temperatures coastal storms are projected to increase in frequency and intensity; this combined with sea level rise will greatly increase the destructiveness of coastal storms. The soon-to-be-released Massachusetts Coast Flood Risk Model (MC-FRM) projects the probability, depth and extent of flooding based on the NECASC projections of SLR increases of 1.2 feet in 2030, 2.4 feet, in 2050 and 4.2 feet in 2070.
Climate Risk: Changing Precipitation Patterns and Inland Flooding
Despite projections for increased rainfall and flooding, climate projections for Massachusetts also indicate an increased probability of drought. This reflects analysis that indicates a likelihood of more rain in the winter and spring and decreased rain in summer and fall. The decrease in rain, combined with earlier snow melt, and higher temperatures that will increase evaporation and reduce soil moisture, account for the drought projections.
Drought can have severe impacts on water quantity and quality. Drinking water supply (particularly for communities that are not served by the Massachusetts Water Resources Authority) is a critical vulnerability. Loss of water quantity can also have severe ecosystem effects including low or no flow in streams, and damage to agriculture and forests. If droughts deplete groundwater levels, coastal areas may experience saltwater intrusion in drinking water aquifers. Finally, drought may increase the likelihood of brushfires and forest fires.
Climate Risk: Rising Temperatures and Extreme Heat
As global temperatures rise, there will be both in increase in average temperatures in the Northeast United States, as well as more extreme temperatures (both heat in summer and cold in winter). Scientists predict that Massachusetts will have an increase of days over 90 degrees, from about 11 historic average to upwards to 39 days over 90 by 2030. Extreme heat (multiple days over 90) is a public health threat causing many heat-related illnesses such as heat stroke, heat exhaustion, and putting certain populations at higher risk (older adults, young children, pregnant people, individuals living alone). When heat combines with air pollution such as particulate matter, it can be very dangerous for those with cardio-vascular diseases. Extreme heat can impact infrastructure including pavement, public transit, as well as put strain on the electricity grid causing potential outages and brownouts.