Understanding the Causes and Implications of Climate Change

Katie Huston for TEI

To understand the causes and implications of climate change, we need to understand its history, explains Ray Bradley, a University Distinguished Professor in the Department of Geosciences, who heads the Climate System Research Center at UMass Amherst.

Bradley specializes in paleoclimatology, the study of climate change on the scale of Earth’s entire history. “What we’re trying to do is understand the variability of climate, and how that relates to where we are today – putting present climate in long-term perspective in order to better assess the human effects on the climate system,” he says. “If we can understand how the whole system works, that might help us understand better how to anticipate what the future will be like.”

Bradley’s research uses a variety of natural data sources, including tree ring records, lake sediment, stalagmites and ice core records, to understand how natural factors such as volcanic eruptions and solar variability have affected the Earth’s temperature since our planet was formed.

“Before humans started putting greenhouse gases into the air, the natural factors were still operating, and they’re going to continue to happen in the future. So we have to understand what those factors might be,” Bradley says.

His research has confirmed that the Earth’s temperature today is setting record highs. He contributed to the Intergovernmental Panel on Climate Change reports that won the 2007 Nobel Peace Prize, which the panel shared with Al Gore. “The present temperatures around the world are as high as they’ve been for at least a thousand years, probably several thousand years,” he says. Although the human impact on climate is now undeniable, he says, historical perspective is still vital.

“The big concern right now is global warming. We’re trying to figure out: were there periods in the past where the climate was unusually warm? If so, why, and what can we learn from these periods of time?” he says. Such an understanding can ensure that researchers don’t underestimate the human impact today.
As director of the Climate System Research Center, Bradley oversees or is involved in a variety of projects with about three dozen colleagues, who are faculty members, post-doctoral students, graduate students and research scientists.

“That’s the fun part,” he says. “You see a lot of the world.”

In 2006, Bradley received a grant from the National Science Foundation to study the climate impact of volcanoes in the Arctic system by looking for and dating ash layers in sediment.

In January 2002, Bradley and Research Professor Doug Hardy climbed the 19,341-foot Mt. Kilimanjaro in Tanzania, which Bradley calls a “fantastic place.” The Climate System Research Center had set up an automated weather station on the mountain’s northern ice field in 2001 to characterize the climate at the summit, understand causes of environmental change and help interpret the ice core record from the northern icefield on the mountain.

“We had about 20 porters to carry all the gear to set the station up,” Bradley said. “It’s very hard physically because of the altitude.”

Researchers from the Center have also conducted research on top of the Quelccaya ice cap in Peru; analyzed the chemical record of rainfall in stalagmites in Bermuda, Brazil, Yemen, Oman and Mexico; and worked in the Canadian Arctic, at 82 degrees north latitude, where Bradley and colleague Doug Hardy once narrowly avoided an encounter with a polar bear.

Bradley and his colleagues don’t only work in exotic locations, though. Closer to home, post-doc Mark Besonen has studied the sediment record in Mystic Lake, in Medford, Massachusetts. Each time a hurricane occurs, it washes large amounts of sediment into the lake. The lake record corresponds to known hurricanes, but extends back up to a thousand years, allowing Besonen to compare the frequency of hurricanes before and after Europeans arrived in the U.S.

Future climate change research, Bradley says, needs to focus on more detailed understanding on a smaller scale. “What people are most interested in now are impacts on society and impacts on ecosystems,” he says.

For example, mountain regions of the world are changing “even more dramatically” than the Arctic, Bradley says, and high altitude areas impact everything below them. “If the snowpack on the mountain disappears and turns to rain instead of snow, then seasonal runoff changes,” he says. “Much of the runoff in the big rivers comes off of the high mountains, so we need to understand what goes on in the mountains,” he says.

Ultimately, natural variability is essential to comprehend and address the effects of greenhouse gases. “It’s really a complicated system, and we need to understand it better,” Bradley says.