Even in the absence of earthquakes, the venerable seismograph still records tiny deflections of the needle as that familiar roll of paper glides through. Once considered random fluctuations, geophysicists now say that atmospheric disturbances at sea are the cause of this noise, enabling seismic records to be used to expand our historical knowledge of past storms, potentially settling the global warming debate.

"Microseismic noise is generated from atmospheric storms located over oceans," said geophysicist Carl Ebeling from Northwestern University (Evanston) at the recent Geological Society of America annual meeting (Portland, Ore., Oct. 18-21, 2009). "The energy from these storms couples to the water column and ultimately to the earth under the water where it travels as seismic waves."

Ebeling and Northwestern professor Seth Stein are examining past records trying to discern the "seismic signature" of storms. If they are successful in correlating storms with microseismic noise, then they will be able to extend our knowledge about how frequent and how intense past storms have been, giving climatologists hope in answering questions like whether today's storms are intensifying in response to global warming.

"The reason this is important is that rising sea surface temperatures are driving a debate as to whether global warming is causing storms to become more frequent and more powerful," said Ebeling. "There's one group out there that says 'yes,' there is another group that says 'no' and there is a group that says we don't have enough data because our observations only started in the mid-1960s when satellite observations began to be recorded."

What Ebeling wants to do is extend the database of storm observations back to the end of the 19th century by correlating the microseismic signature of storms to the historical seismic records which began with the invention of the seismograph circa 1880. Since then, paper rolls all over the world have been recording microseismic noise.

"These seismic records offer an independent way of looking back in time to answer these questions about whether storms are getting more powerful today or not," said Ebeling.

The National Science Foundation (NSF) agrees, giving Ebeling a three-year grant to program his microseismic signatures into a pattern-recognition algorithm that can be used to deduce the frequency and intensity of storms from seismic recordings.

"So far we've proven the concept with historical data from hurricane Andrew in 1992," said Ebeling. "We were able to find statistically significant correlations between microseismic noise and the atmospheric pressure and wind speed associated with the storm."

Over the next three years, Ebeling plans to create a computer model that can recognize the signature of storms in seismic data, allowing all those paper rolls to be converted into a history of storm frequency and intensity. By extending our knowledge base of past storms all the way back to the 19th century, climatologists should be able to settle the global warming debate.