Climate Change in the Piscataqua/Great Bay Region: Past, Present, and Future

Earth ’s climate changes. It always has and always will. However, an extensive body of scientific evidence indicates that human activities are now a significant force driving change in the Earth’s climate system. This report describes how the climate of the Piscataqua/Great Bay region of coastal New Hampshire in the United States has changed over the past century and how the future climate of the region will be affected by human activities that are warming the planet. Overall, the region has been getting warmer and wetter over the last century, and the rate of change has increased over the last four decades. To generate future climate projections for the region, simulated temperature and precipitation from four general circulation models were fitted to local, long-term weather observations. Unknowns regarding future fossil fuel consumption were accounted for by using two future emissions scenarios. As greenhouse gases continue to accumulate in the atmosphere, temperatures will rise, extreme heat days are projected to occur more often and will be hotter, extreme cold temperatures are projected to occur less often, and cold days will be warmer.. Annual average precipitation is projected to increase 12 to 17% by end-of-century and the region can expect to see more extreme precipitation events in the future. Tidal gauge data indicates relative sea level at Portsmouth has risen 0.7 inches per decade over the past eight decades. Projected sea level rise of 1.7 to 6.3 feet will result in higher storm surges and more frequent flooding in coastal New Hampshire