No evidence global warming spawned twister
May 22, 2013 -- Updated 1713 GMT (0113 HKT)
CNN iReporter Brenton Leete took this photo of the tornado on the ground in Moore, Oklahoma, on Monday.
- Expert: Moore tornado likely would have happened regardless of global warming
- Science has stronger support for connection between climate change and drought, heat wave
- More research and discussion is needed about future warming and storms
(CNN) -- Yes, climate change is happening. But it's hard to say that the tornado that ripped through Moore, Oklahoma -- or any given tornado, for that matter -- was influenced by climate change.
Scientific research has not made a clear connection between tornadoes and climate change, said J. Marshall Shepherd, climate change expert and professor at the University of Georgia.
There is currently a much better understanding of how climate change increases the risks of droughts, heat waves and precipitation, he said. There are also indications that changing patterns may influence the intensity of hurricanes. But as far as tornadoes: There's just not a lot of information.
As far as the Moore tornado, "This tornadic storm, in my view, probably would have happened irrespective of whether there's climate change or not," Shepherd said. "The question is: Are we increasing the risk and probability of more extreme events in general as our climate differs?"
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More research and discussion is needed about future warming and the environments that might produce storms, he said.
Trends in tornado occurrence over the last 50 years do not appear to have changed in conjunction with more greenhouse gases in the atmosphere and patterns of rising temperatures, Shepherd said.
Beyond the climate change question, meteorologists don't know a lot about why some thunderstorms produce tornadoes and not others. According to the National Oceanic and Atmospheric Administration, only about 1% of thunderstorms generate tornadoes. However, tornado prediction is advancing and evolving.
Weather, says Shepherd, is like mood -- it changes all the time. The deeper underlying forces we call "climate" are like personality. Greenhouse gases building up in our ocean atmosphere system, from human activity, influence that personality -- which is much harder to undo.
To put it a different way, a driver who is sober has a certain risk of getting into an accident, said Patrick Kinney, the study's senior author and director of the Columbia Climate and Health Program at Columbia University's Mailman School of Public Health. The risk goes up with a couple of drinks. Similarly, as humans pump more greenhouse gas into the atmosphere, that raises the likelihood of extreme weather events.
"Greenhouse gases are kind of like the alcohol in the system of the climate," Kinney said.
Climate change will mean more heat deaths
Earlier this month, scientists measured for the first time an average carbon dioxide concentration of 400 parts per million at Mauna Loa Observatory in Hawaii, representing a new peak for this iconic monitoring station.
More space and science news from CNN Light Years
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Oklahoma City Tornadoes
June 3, 2013 -- Updated 1358 GMT (2158 HKT)
Heavy storms and tornadoes once again ripped through the Midwest. Already devastated areas of Oklahoma were hit again, and this time the damage spread to neighboring states. Here's how you can help.
May 30, 2013 -- Updated 1530 GMT (2330 HKT)
Families share memories and snapshots of those we lost in the Oklahoma tornado devastation.
June 5, 2013 -- Updated 1711 GMT (0111 HKT)
The Oklahoma medical examiner's office says 18 people in that state were killed in the storms. The office has released the names of 11.
June 4, 2013 -- Updated 1358 GMT (2158 HKT)
They chased tornadoes not so much for the thrill, but in the hope that their research might help people avoid the fate to which they succumbed last week.
June 4, 2013 -- Updated 1414 GMT (2214 HKT)
A menacing tornado churned behind Mike Eilts as the storm chaser's truck sped away.
May 27, 2013 -- Updated 1026 GMT (1826 HKT)
Why do people in Tornado Alley keep rebuilding and staying in place after storms rip through? People from Moore share their reasons why.
May 27, 2013 -- Updated 2107 GMT (0507 HKT)
See the best images from the deadly storm.
May 22, 2013 -- Updated 1439 GMT (2239 HKT)
It's one of the most familiar pieces of advice from authorities to people in the path of a tornado: Get into your basement.
May 23, 2013 -- Updated 1155 GMT (1955 HKT)
On Sunday, a mystery photograph fluttered from the sky and landed near Leslie Hagelberg's mailbox in West Tulsa, Oklahoma.
The tornado spanned 1.3 miles -- the length of more than 22 football fields lined up end-to-end -- carved a 17-mile path of destruction.
May 22, 2013 -- Updated 1831 GMT (0231 HKT)
Second-grade teacher Tammy Glasgow walks around what's left of Briarwood Elementary, struggling to pick out of its wreckage the things that once made a school.
May 22, 2013 -- Updated 1319 GMT (2119 HKT)
It was the end of the school day. The kids at Plaza Towers Elementary School were stuffing their backpacks, looking forward to going home, playing with friends, eating snacks.
May 21, 2013 -- Updated 1609 GMT (0009 HKT)
The "Tri-State Tornado" killed 695 people and injured 2,027, traveling more than 300 miles.
See the path of the tornado that ripped through Moore, Oklahoma.
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