June 4, 2008 Record-keeping meteorologists at the National Oceanographic and Atmospheric Administration say this year’s tornado season is one of the deadliest in a decade and may be on pace to set a record for the most tornadoes. And flooding in the Midwest has been at 100-year levels this spring.
“There is considerable concern that climate change due to greenhouse gases species increasing will lead to the enhancement of strong, large storms occurrences, such as hurricanes that also spawn tornadoes when they occur. Increased storm strengths also bring flooding events,” he said.
Gaffney and co-researcher Nancy A. Marley are currently involved in a three-year investigation of aerosols – tiny particles suspended in the air – and their role in climate change.*
Tornadoes are short-lived events and, until recently, scientists had to depend on limited ground observations to study them. Satellites and radar systems are now enhancing researchers’ ability to see their number and strength in detail. But short lived tornadoes are hard to tie directly to climate change due to the limited climatology of tornadoes.
Weather forecasters have examined El Niño and La Niña, important temperature fluctuations in surface waters of the tropical eastern Pacific Ocean, as a potential for past tornado activities in the U.S.
“The data available from NOAA do not support a strong statistical significance to data for direct effects of El Niño or La Niña on frequency or strength of tornadoes,” Gaffney said. “Although, there is considerable concern that climate change due to greenhouse species will lead to significant changes in weather patterns, these currently available data are not conclusive.”
He said the Intergovernmental Panel on Climate Change’s report on severe weather events discusses the topics backed up by NOAA data.
“Basic thought is there’s more energy in the atmosphere, more water vapor evaporating and greater likelihood for stronger heating events that lead to stronger thunderstorms - super cells, that can lead to tornado production,” Gaffney said.
He said tornadoes are complex phenomena that are linked to the number of super cells and their storm strengths. Flooding events are more wide spread than tornadoes, and are more readily tied to climate predictions than tornadoes.
“What we are looking to see, in current and future research and data acquisition, is whether the frequency and strength of tornadoes change as we continue to increase the energy distribution in the atmosphere,” he said. “Currently, this year is looking to be significantly larger in the number of tornadoes seen than in the past few years. That and the record floods that are associated with these strong storm systems, may be a warning of things to come. But more data gathering is needed.”
Gaffney points to the improved Doppler radar systems that have allowed tornado warning times to be advanced as the main tool for gathering this tornado climatology that will be needed to evaluate links between climate change and severe weather events.
*The $625,000 study is funded by the Department of Energy Atmospheric Science Program. He and Marley will discuss severe weather and links to climate during their annual orientation for the DOE Global Change Education Program.
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