Global Warming Causes Severe Storms
Research Meteorologists See More Severe Storms Ahead: The Culprit -- Global Warming
January 1, 2009 — Research Meteorologists found that the temperature changes brought on by global warming are significant enough to cause an increase in the occurrence of severe storms. Severe storms are those that cause flooding, have damaging winds, hail and could cause tornados. Their study revealed that by the end of this century, the number of days that favor severe storms could more than double certain locations, such as Atlanta and New York. Researchers also found that this increase would occur during typical stormy seasons and not during dry seasons when it may be beneficial.
As new storm forecasts hit home, areas already prone to severe weather need to be on the lookout for more storms. The latest forecast says global warming spells bad news for those areas.
Nancy Werner has seen many storms blow through trees in her yard, but there's one storm she'll never forget.
"We started hearing things land on our house," Werner said.
A stump is all that's left of what she heard falling. "We went upstairs and found limbs through our ceiling," Werner said.
The storm cost Werner $40,000 in repairs, but more severe storms could add up to a lot more. Research meteorologists at Purdue University are using climate models to study future weather conditions that would most likely produce a severe storm. Severe storms are ones that cause flooding and have damaging winds and hail. Some spawn tornadoes.
"What we found is that increases in human-induced greenhouse gases will lead to more frequent severe storms in the United States," Jeff Trapp, Ph.D., a meteorologist at Purdue University in West Lafayette, Ind., said.
Based on the models, the researchers believe the number of days that favor the formation of severe storms could more than double in places like Atlanta and New York. These added storms will likely hit areas during already heavy storm seasons and extend wet weather seasons.
"This obviously impacts people in terms of potential hazards to their life and property," Dr. Trapp said.
Researchers hope warning homeowners of increased storm days will help more people prepare earlier. Werner already has a plan in place.
"We've decided we're going to a hotel," she said. Researchers plan to use higher resolution models to find out how often future storms will spawn tornadoes.
HOW STORMS DEVELOP: Storm clouds form as moisture evaporates from the earth into the atmosphere, where the droplets jostle against each other. The air cools off rapidly as it reaches higher altitudes. Sometimes a cold front -- the boundary between where the cold air from one air mass meets the surrounding air -- will force warm, moist air upward into the colder air. This moist air cools off and the water vapor condenses onto tiny particles in the air, called condensation nuclei, collectively forming clouds. The process continues: more and more water vapor turns into liquid and the moist air warms up even more and rises higher and higher. A thunderstorm results.
WHAT CAUSES LIGHTNING? As more and more water droplets collide inside a cloud, their atoms bounce off each other more forcefully. This knocks off electrons. The ousted electrons gather at the lower portion of the cloud, giving it a negative charge, while the upper part of the cloud becomes positively charged. Eventually the growing negative charge becomes so intense that electrons on the Earth's surface are repelled and burrow deeper into the Earth. The Earth's surface becomes positively charged, and hence very attractive to the negative charge accumulating in the bottom of the cloud. All that is needed is a conductive path between cloud and Earth, in the form of ionized air.
ABOUT GLOBAL WARMING: Global warming refers to an average increase in the earth's temperature, which has risen about 1 degree Fahrenheit over the past 100 years, and to changes in climate. A warmer earth may lead to changes in rainfall patterns, and a rise in sea level, for example, as the polar glaciers melt. Some of this rise is due to the greenhouse effect: certain gases in the atmosphere trap energy from the sun so that heat can't escape back into space. Without the greenhouse effect, the earth would be too cold for humans to survive, but if it becomes too strong, the earth could become much warmer, causing problems for humans, plants and animals.
The American Meteorological Society and the American Geophysical Union contributed to the information contained in the TV portion of this report.
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