The Rock Whisperer

By William Davis

The Earth is warming. Determining what this will mean for future generations is one of the greatest challenges in modern science, and Paul Hearty is on a world-class team of scientists seeking answers.

 

 

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UNCW geologist Paul Hearty collected shells dating back to Pliocene from deposits in western Australia. These 3-million-year-old shells represent species that thrived in the warm oceans of the era. UNCW/Jamie Moncrief.

 

An adjunct research associate professor in UNCW's environmental studies department, Hearty is one of five principal investigators on a grant to build a comprehensive model of past climate change by integrating elements of the world's crust, oceans, atmosphere and ice sheets, using fossil and geological data from an ancient warming period. The National Science Foundation has funded the five-year study for $4.25 million, a rare achievement in an age when basic research budgets have been drastically cut.

Approximately 3 million years ago, the Earth was warmer. Global average temperatures were 2-3 Celsius (3.6 F to 5.4 F) greater than today. Known as the Mid-Pliocene Climatic Optimum (PLIOMAX), this interval has received renewed attention by researchers because its temperatures and atmospheric composition are similar to those predicted by global climate change models for the coming century.

"We have to go back 3 million years to find CO2 (carbon dioxide) levels of 400 ppm. Our atmosphere, now at about 393 ppm, will easily reach 400 ppm (parts per million) by the end of this decade," said Hearty.

Over the next five years of the grant, the PLIOMAX team will tackle three major problems in climate science. In the first phase, they intend to use fossil and geological data collected at sites across the world to build a greatly improved database of sea levels and thus ice sheet behavior during the Pliocene.

"Geology has to drive this process. Geology provides first-hand information about the position and movements of sea level," said Hearty.

In a subsequent phase of the project, these data will feed into a series of experiments that will provide estimates of the global sea level under a variety of climate change scenarios. From this work, the team also intends to build a high-resolution comprehensive model of the world's atmosphere-ocean-ice sheet/shelf systems. The ultimate goal of the project is to better forecast the potential behavior of sea level and ice sheets in a warmer world.

For climate researchers, the Mid-Pliocene represents the last great warm period in Earth's history. As the era's climate roughly resembles the late 21st century projected by the U.N.'s Intergovernmental Panel on Climate Change, it has drawn extensive academic interest in recent years. Agencies such as the U.S. Geological Survey and the British Geological Survey have begun major efforts to construct data models from this period.

While there is general agreement about the temperatures of the Mid-Pliocene, controversy exists about the extent to which these warmer temperatures and higher carbon dioxide levels affected global sea levels. Researchers agree that sea levels were higher during the Mid-Pliocene, but the magnitude of the rise has been hotly debated. Researchers' estimates have ranged from 10 meters (32 feet) to around 40 meters (131 feet) higher than today. Higher sea levels are directly tied to the melting of the world's polar ice sheets such as Greenland and Antarctica.

Hearty is hesitant to make predictions based on the past. He acknowledges the complexities of predicting the future through studying geological and modeling data. Climate science deals with a massively complex system, and the variables that led to sea level rise 3 million years ago included more than simple temperature and CO2 relationships.

Even so, the most conservative estimates of sea level rise during the period would, if repeated in a warming future, dramatically change the shape of the world's coastlines. On a geological scale, measured in millions of years, the ocean has risen and fallen many times due to climate change. Hearty said important geological evidence of this can be found throughout Southeastern North Carolina, which once was submerged beneath the ocean.

Hearty will serve as one of the principal investigators on the grant, a prestigious spot on a project featuring an all-star team of researchers from the top universities in the United States. The project's leader, professor Maureen Raymo of Columbia University, is recognized as a global leader in the field of paleoclimatology and paleoceanography.

Hearty has worked and published with the team for years, including leading a field expedition in Australia whose findings provided the rationale for the larger study. Raymo praised Hearty's fieldwork skills, calling him one of the best in the world at interpreting sea level changes from rocks and analyzing fossil data.

"Paul is an amazing field geologist with decades of experience looking
at the coastal record of sea level change. I call him 'The Rock Whisperer,'" said Raymo.

The grant's other principal investigators-geoscientist Rob DeConto of
University of Massachusetts-Amherst, physicist Jerry Mitrovica of University of Toronto and earth scientist David Pollard of Pennsylvania State University - all have world-class
reputations in their fields. In recommending the grant for full funding, the NSF reviewers cited the vast expertise of the team as a major factor in the decision.

Hearty's role will be to lead field expeditions collecting the fossil and geological evidence that will make up the raw data to be used by the ice and crustal modelers. One of the chief hurdles in accurately modeling the past and future behavior of global climate has been a lack of sea-level data.

By understanding the response of nature to past global changes, he hopes that future generations will be better prepared to deal with the anticipated effects of climate and sea-level changes.

"None of us think that in our human lifetime or even over several generations, sea level is going to rise 25 meters," said Hearty.

But it will rise. It has in the past, and it will again in the future. Hearty said that addressing these changes will be one of the major challenges of the world's future leaders.

"We're tinkering with a natural machine we don't understand," said Hearty.