Monitoring the temperature of the ground provides a compelling argument for the existence of global climate change caused by humanity's impact on the planet, a physics professor told Marietta College students and faculty Friday.
"This is as close as I've seen in everything I've studied to a 'smoking gun,'" Marshall Bartlett, assistant professor of physics at Virginia's Hollins University, said during a presentation as part of Marietta College's Physics Colloquium.
While Bartlett cautioned it is not a direct link, he said research he's been involved with for nearly 20 years shows the Earth is taking in more heat energy than it is giving off at a rate that matches what models suggest would happen based on the amount of carbon dioxide pumped into the atmosphere over the last century.
"The numbers just work out too close ... to just be a coincidence," he said.
Bartlett spoke to about 60 people in the college's Anderson Hancock Planetarium, taking them through the process he became a part of as a graduate student at the University of Utah to study what ground temperature can reveal about climate change. While there is a difference between air temperature and ground temperature, Bartlett said that over time the former impacts the latter in measurable ways.
"In effect, the ground is acting like a thermal tape recorder for what is going on at the surface," he said.
Using data from boreholes drilled around the world, the researchers examined ground surface temperatures over a long period of time. In this way, Bartlett said, they dealt more directly with "nice and clean" physics than another accepted way of monitoring historical temperature data - examining tree rings. Temperature affects tree rings but so do other factors.
Their data agreed with past studies that warming started around 1840, consistent with growing industrialization that would have put more carbon dioxide into the atmosphere.
Bartlett explained in detail how the researchers set up a geothermal climate change observatory in Utah to measure air and ground temperature in the same place at the same time and how the effects of snow were factored in to account for its possible impact on ground temperature.
While there is more study needed, Bartlett said the research suggests the planet might be warming at a higher rate than other studies have indicated.
Senior Marietta College physics major Ashley Parker, of Zanesville, said Bartlett presented a lot of evidence for climate change caused by an influx of carbon dioxide. She noted the issue is very controversial and many people are still skeptical of conclusions that have been drawn.
"I just feel like all of the skeptics just aren't aware of the data," she said.
Bartlett said some people simply have a hard time believing humanity could make such a dramatic impact on the planet. And some struggle with the implications of climate change and how to combat it.
"That means major changes in economic systems, other things, which are unpalatable," he said.
Bartlett also said some of the controversy may come from the uncertainty of what exactly climate change means.
"Is that the end of life as we know it or does that just mean a little less beach-front real estate in Florida? We don't know," he said.
But he did point to examples of climate change's impact on the world, such as a species of bird known as the Mexican jay laying eggs about two weeks earlier than it did four decades ago. Another example was polar bears wandering into a Canadian town and being found to be malnourished because their food source, seals, are moving farther away due to ice formations breaking up.
"Global climate change is really about more than just the Earth's temperature changing over time," he said.