Answering Climate Questions

RESEARCHERS USE PALEOCLIMATE RECORDS FOR COMPUTER-BASED MODELING TO UNDERSTAND UNPRECEDENTED CONDITIONS

APRIL 2024
by nick wilson

"You cannot fully understand today’s climate by just looking at the last 10,000 years ... we must have a much longer-term perspective.’

Charles David Camp

Mathematics professor (on left, also pictured is Rapha Coutin, a math major and Frost Research Fellow.)

Millions of years before humans came along, the Earth experienced wide-ranging changes in climate conditions, from ice age cycles to warming and cooling trends. Comparing this paleoclimate history to the current conditions yields startling results, and a Cal Poly research team is using that history to better understand climate shifts of the past eras and project what the future holds.

“The climate has been changing substantially over the last 65 million years and longer, and in all of the changes over those millions of years, we’ve seen nothing like the changes occurring during the last 200 years,” said Cal Poly mathematics Professor Charles David Camp, who specializes in climate-related data analysis and mathematical modeling.

To understand what these unprecedented climate conditions might mean for future generations, Camp and his student research team use paleoclimate information to create mathematical models of the underlying processes and transitions moving at geologic time. These processes interact with current human effects on the climate, and so understanding how Earth’s climate is changing in the background may help project future conditions.

“It’s helpful to understand what the underlying systems are,” said Rapha Coutin, a fourth-year math major and Frost Research Fellow. “It’s one thing to understand ‘How does carbon affect our current climate?’ But that only helps us so much as to what we understand our current climate to be. And that is a product of much longer time-scale processes going on.”

Coutin has participated in the study over the past two years and made it the focus of his senior project. He and fellow student researchers are investigating questions that include: How do the 100,000-year ice-age cycles over the past million years compare to the faster 41,000-year ice-age cycles that occurred in the early Pleistocene, which began roughly 2.5 million years ago? Why did that transition in ice-age cycles occur? And can we predict future changes?

Using paleoclimate records such as tree rings, ice cores and ocean sediment cores, Camp and the student researchers contribute to a larger scientific community effort. Ice core and ocean sediment samples provide proxy data, preserved physical characteristics that offer the best possible insights into the environment of bygone eras. These physical characteristics reveal past warming and cooling trends, the prevalence of volcanic eruptions and dust storms, changes in wind patterns and other climate behavior.

Scientists at other institutions analyze the composition of air bubbles, particles and dissolved chemicals trapped inside ice or the carbonate shells from the seafloor in these samples and share that data publicly.

Camp and his student team use this data and mathematical models to investigate the underlying causes for the observed changes in Earth’s climate over the past 5 million years.

“As we can’t investigate long-term climate variability phenomena in the lab, computational models have become a central tool in climate research, particularly for understanding the processes that cause the observed variability,” Camp said.

The team’s conceptual, computer-based modeling uses sets of differential equations “which describe how variables such as carbon dioxide levels, ocean temperature and ice volume change over time, with the ultimate goal of realistically simulating the processes Earth’s physical system is undergoing,” Coutin said.

In the last million years or so, ice ages, also known as glacial periods, typically lasted about 90,000 years and were separated by warmer interglacial periods stretching roughly 10,000 years. Earth is currently overdue for an ice age.

“The last ice age was 12,000 years ago,” Camp noted. “The previous interglacial cycle was 90,000 years before that, which was a little bit warmer than this one. So, all of recorded human history has occurred during this latest interglacial warm period.”

Excerpt from the group's research poster titled "Aspects of Modeling Pleistocene Gacial Cycles: Asymmetric Memory and Stochastic Forcing."

The research team’s models reach back beyond this recorded history as scientists and mathematicians work together in hopes of discovering the underlying processes that cause such significant shifts in Earth’s climate. As Camp said when presenting at Cal Poly’s Initiative for Climate Leadership and Resilience’s Climate Solutions Now conference in October 2023, the importance of analyzing long-term climate behavior cannot be ignored.

“I firmly believe that you cannot fully understand today’s climate by just looking at the last 10,000 years, which encompasses all recorded human history,” Camp said. “To really understand our present climate, we must have a much longer-term perspective.”