未来30年美国东北部将出现暖冬气候

A new high-resolution climate study by University of Massachusetts Amherst climate scientists, the first to apply regional climate models to examine likely near-term changes in temperature and precipitation across the Northeast United States, suggests temperatures are going to be significantly warmer in all seasons in the next 30 years, especially in winter. Also, they project that winters will be wetter, with more rain likely than snow. Writing in the current issue of the Journal of Geophysical Research, Michael Rawlins and Raymond Bradley of the Climate System Research Center at UMass Amherst, with Henry Diaz of NOAA's Climate Diagnostics Center, Boulder, Colo., provide the highest resolution climate projections to date for the Northeast from Pennsylvania to Maine for the period 2041 to 2070. The study used data from multiple climate model simulations run at greatly improved resolution.

Rawlins says, "One of the most important aspects of our study is that we can now examine in more detail what's likely to occur across the region with a grid size of approximately 31 x 31 miles (50 x 50 km). Previous studies used much more coarse-scale general circulation model data. This represents a significant step forward."

Bradley adds, "Regional climate models have been around for a while, but they have not been applied specifically to the Northeast region. At this point what we can provide are 'broad brush' estimates of how things will change over the next 30 to 50 years. People should not over-interpret these results. Further research is needed to scale these down to individual locations. But for natural resource conservation managers, water resource managers and others responsible for planning ahead, we expect our region-specific results will be helpful."

Overall, the researchers say the region is projected to warm by some 2 to 3 degrees C by mid century, with local changes approaching 3.5 degrees C in winter. Precipitation will go up as well, particularly in winter, but again not uniformly across the Northeast. The UMass Amherst climate scientists say confidence in the precipitation（沉淀） change projections for spring, summer and autumn is lower, given smaller changes relative to natural weather variability.

"The only clear signal of change for precipitation is noted in winter, which appears to be heading toward wetter conditions, consistent with current trends," Rawlins says. Winter precipitation is projected to rise significantly above natural weather variability, around 12 to 15 percent greater from southwest Pennsylvania to northern Maine, with the exception of coastal areas, where projected increases are lower.

"But we shouldn't expect more total seasonal snowfall," he adds. "Combined with the model-projected temperature trends, much of the increase will occur as rain. We're losing the snow season. It is contracting, with more rain in early and late winter."

For this study funded by NOAA, Rawlins and Bradley used available outputs from an ensemble of regional climate models (RCM) from the North American Regional Climate Change Assessment Program to look at potential changes in seasonal air temperature and precipitation between the present, (1971 to 2000), and a future period, (2041 to 2070) across the Northeast. They performed a rigorous evaluation of each model's ability to represent current climate by comparing its outputs to actual weather station data.