Part Of USA Will Be Warmer, Wetter, More Rain Than Snow, Studies Find
Eastern United States will be hotter and wetter. The region will experience more severe heat waves. New York will be experiencing the highest hike in heat. There will be greater risk of flooding. Winter in the Northeast United States will be significantly warmer and wetter, with more rain likely than snow.
From extreme drought to super storms, many wonder what the future holds for the climate of the eastern United States. A study conducted by researchers at the University of Tennessee, Knoxville, does away with the guessing .
Results show the region will be hotter and wetter.
Joshua Fu, a civil and environmental engineering professor, and Yang Gao, a graduate research assistant, developed precise scales of cities which act as a climate crystal ball seeing high resolution climate changes almost 50 years into the future.
The study found that heat waves will become more severe in most regions of the eastern United States and, that both the Northeast and Southeast will see a drastic increase in precipitation.
The findings are published in the Nov. 6 edition of Environmental Research Letters.
Harnessing the supercomputing power of UT's Kraken and Oak Ridge National Laboratory's (ORNL) Jaguar (now Titan, the fastest in the world), the researchers combined high-resolution topography, land use information and climate modeling. Then they used dynamical downscaling to develop their climate model results. Dynamical downscaling allowed the researchers to develop climate scales as small as four square kilometers.
"Instead of studying regions, which is not useful when examining extreme weather, dynamical downscaling allows us to study small areas such as cities with a fine resolution," said Fu, who is also a professor within the UT-ORNL Bredesen Center for Interdisciplinary Research and Graduate Education (CIRE).
The researchers evaluated extreme events along with daily maximum and minimum temperatures and daily precipitation. For the 23 states east of the Mississippi River, they analyzed the present-day climate from 2001 to 2004 and predicted the future climate from 2057 to 2059. This is the first study to predict heat waves for the top 20 cities in the eastern U.S. For example, Nashville will see a temperature rise of 3.21 degrees Celsius and Memphis will see a rise of 2.18 degrees Celsius.
In comparing present climate to future, the researchers found that heat waves will become more severe throughout the eastern part of the nation. The Northeast and eastern Midwest will experience a greater increase in heat waves than the Southeast, which will almost equalize the temperatures between the future North and current South.
"Currently, the mean heat wave duration is about four days in the Northeast and eastern Midwest and five days in the Southeast," said Fu. "By the end of the 2050s, the Northeast and eastern Midwest will be gaining on the Southeast by increasing two days."
In addition, the Northeast and eastern Midwest are likely to suffer from steeper increases in the severity of heat waves.
"While the Southeast has the highest intensity in heat waves, the northeast is likely to experience the highest increase," said Fu. "We are looking at temperature increases of 3 to 5 degrees Celsius, with New York experiencing the highest hike."
Both the Northeast and Southeast will experience an increase of precipitation of 35 percent or more. Most coastal states will see the greatest increase, of about 150 millimeters a year. Taking into consideration heat waves and extreme precipitation, the Northeast shows the largest increases in precipitation. This suggests a greater risk of flooding.
"It is important that the nation take actions to mitigate the impact of climate change in the next several decades," said Fu. "These changes not only cost money -- about a billion a year in the U.S. -- but they also cost lives."
Another study found more annoying possibilities.
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 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.
The projections assume that GHG emissions will continue to rise, increasing atmospheric CO2 from about 400 parts per million (ppm) today to between 500 and 600 ppm in 2070. Bradley and Rawlins acknowledge that this outlook represents the "most aggressive, most troubling higher emissions trajectory scenario" for CO2 levels, but they point out that so far there is little evidence that society will act to appreciably change the current rate of increase.
Results show statistically significant increases in air temperature region-wide for every grid in each season, but the changes are not uniform. For example, the models collectively project air temperature changes in winter of more than 3 degrees C (5.5 degrees F) across northern Maine, all of New Hampshire, Vermont and the Adirondacks, representing about 50 percent of the Northeast region. In some local areas, the increase could be near 4 degrees C (7.2 degrees F).
By contrast, winter air temperatures increases in southwest Pennsylvania are projected to be lower, only about 2.4 degrees C. In summer, the pattern is reversed and the southwest quadrant of the northeast is projected to be warmer and the changes higher.
 “Extreme Climate Predicted in Eastern U.S.: Storms, Heat Waves With Global Warming”, Dec. 17, 2012, http://www.sciencedaily.com/releases/2012/12/121217121732.htm
The above story is reprinted from materials provided by University of Tennessee at Knoxville, via Newswise.
Y Gao, J S Fu, J B Drake, Y Liu, J-F Lamarque. Projected changes of extreme weather events in the eastern United States based on a high resolution climate modeling system. Environmental Research Letters, 2012; 7 (4): 044025 DOI: 10.1088/1748-9326/7/4/044025
 “Climate Modelers Predict Warmer, Wetter Northeast U.S. Winters by 2070”, Dec. 12, 2012
The above story is reprinted from materials provided by University of Massachusetts at Amherst.
M. A. Rawlins, R. S. Bradley, H. F. Diaz. Assessment of regional climate model simulation estimates over the northeast United States. Journal of Geophysical Research, 2012; 117 (D23) DOI: 10.1029/2012JD018137
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