SEAS Scientists Explore the World's Ever-Changing Climate

Jul 20 2017 | By Jessica Driscoll

Mark Cane; Michael Tippett; Lorenzo Polvani
Mark Cane (Photo by Eileen Barroso); Michael Tippett; Lorenzo Polvani (Photo by Eileen Barroso)

Earth’s climate is constantly changing. With this change comes an increased frequency of extreme and potentially devastating events like floods, droughts, and storms, which impact populations around the globe. Columbia engineers are working to shed light on what leads to climate variability, how humans play a role, and how we are all affected. Their research is an important part of worldwide efforts to better predict and prepare for the consequences of climate change. Here is a look at three researchers who are at the forefront.

Delving into Large-Scale Changes
Climate variability impacts food security, health, and economies. Mark Cane, G. Unger Vetlesen Professor of Earth and Climate Sciences and professor of applied physics and applied mathematics, investigates the disparities of climate past and present for better insight into how to understand, anticipate, and manage the impact.

“I would like to understand the physics of climate variations that impact people on our planet, including the ones we are now inflicting on ourselves,” he says.

Cane has been studying the cyclical phenomenon known as El Niño—a complex weather pattern resulting from variations in ocean temperatures in the equatorial Pacific—for more than 30 years. When El Niño forms, it causes well-known patterns of extreme weather events around the globe. His research has informed better understanding of the impact of El Niño on human activity, including agriculture, health, and conflict.

Cane is also concerned that there’s still no clear explanation for historically abrupt changes in the paleoclimate, such as a period known as the Younger Dryas—between 11,000 and 13,000 years ago—when the world slipped two-thirds of the way back into a full ice age in just one decade.

“It is disconcerting that we can’t explain such a dramatic climate change,” Cane explains. “We have done better with explaining smaller-scale changes, like droughts, in the last millennium, which are related to La Niña–like Pacific Ocean states (the opposite of El Niño). It seems that greater solar radiation makes these states more likely to experience droughts, though this idea is still somewhat controversial.”

Studying What Sets the Stage for Storms
Better information about storm risks in the current climate (and in the future) could help societies take actions to be more resilient through better infrastructure and risk management.

Michael Tippett, lecturer in the Department of Applied Physics and Applied Mathematics, explains that climate prediction—unlike weather prediction—deals with statistics of weather events, and some of its variations can be predicted well in advance.

“El Niño can be predicted months in advance. And the impact of anthropogenic climate change on global mean temperature can be projected decades in advance,” he says. “The important question is how these predictable climate signals modulate the frequency and intensity of extreme weather like hurricanes and tornadoes.”

Over the last few years, Tippett and his team have identified environments favorable for severe thunderstorms and tornadoes.

“Last year, and again this year, we’ve been able to use that understanding to forecast seasonal tornado and hail activity, something never done before,” he says.

Quantifying the risk of rarer events—such as a major hurricane hitting New York—is more difficult because historical records are inadequate.

“We’re taking our understanding of tropical cyclone formation, movement, and intensification to build a model that combines statistical and physical knowledge and can inexpensively simulate thousands of years of hurricane activity,” explains Tippett. “Such a model can then be used to answer questions about the 100-year storm probability for a particular location.”

Examining Ozone Depletion
Over the last 30 years, the depletion of the ozone layer due to chlorofluorocarbons (CFCs) has had reverse negative impacts on the climate system. The entire Southern Hemisphere has been affected, as the formation of the ozone has altered winds, rain, and even the currents in the Southern Ocean.

“The ozone hole affected precipitation in southeastern South America as well as Australia and South Africa. In some regions of Argentina, for instance, it’s been raining a lot more there over the last 40 years, allowing agriculture to expand,” says Lorenzo Polvani, professor of applied physics, applied mathematics, and earth and environmental sciences.

But with stricter regulation of the use of CFCs, the ozone hole is expected to close between 2060 and 2100. “This ozone hole has a cooling effect on the lower stratosphere, and as it closes in the next few decades the resulting warming there will affect the winds in a very significant way,” says Polvani. “Regions that benefited from increased precipitation because of the ozone hole will actually face direct consequences with the hole’s closure.”

Polvani’s research has been instrumental in bringing attention to the importance of the ozone hole in climate systems. “International agreements about mitigating climate change cannot be confined to dealing with carbon alone—CFCs and other ozone-depleting substances need to be considered too,” he says.

Just as climate change is impacting the environment, it also impacts the practice of engineering. That’s why Columbia Engineering researchers are thinking differently about this challenge. Their work underpins mitigation solutions designed to slow the effects of climate change, detailed models to more accurately gauge how solutions will affect society, and adaptation strategies to help the world adjust to expected and actual climate change.