More than three decades after his groundbreaking work on climate change rocked the world, East Lyme scientist John Jasper is again in the spotlight with the publication of a study this month in the scholarly journal Science that paints the most complete picture yet of where the Earth’s climate may be heading.

It’s not a pretty picture.

The massive study titled “Toward a Cenozoic history of atmospheric CO2,” with dozens of coauthors including Jasper, looks at 66 million years of geologic history related to the Earth’s carbon-dioxide levels, coalescing dozens of the most prominent scientific studies from around the world. Among the conclusions: Earth has not had its current high level of carbon dioxide in the atmosphere for the past 14 million years, and the effect of greenhouse gas buildup can have effects that likely will last for centuries.

Jasper, a one-time Pfizer Inc. chemist who later founded his own company, Molecular Isotope Technologies LLC (with the trademark, Nature’s Fingerprint), said he already is seeing the effects locally as salmon and lobster disappear from Connecticut waters where he likes to fish. Global warming is not just an issue for people, but for the marine environment as well, he said, pointing to water-temperature increases recorded by Millstone power station of more than 2 degrees in the past 35 years.

“Imagine that ... your body temperature rose up two or three or four degrees,” Jasper said in an interview Dec. 13 at Flanders Fish restaurant. “It probably tells you that you're not doing well.”

A press release from the Columbia Climate School quotes Bärbel Hönisch, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory, who coordinated the consortium. “This study gives us a much more robust idea of how sensitive the climate is over long time scales,” Hönisch said.

No direct reports about the Earth’s atmosphere are available going back millions of years, so scientists must rely on what are known as “paleo proxies” or “proxy data” that in Jasper’s work are reconstructed from chemical analysis, either of organic compounds or inorganic compounds.

“This is a very conservative production of what the CO2 level looked like,” he said. “It's not a matter of speculation. It's a matter of diligent work of dozens of scientists.”

Jasper’s paper 33 years ago, coauthored with leading biogeochemist John M. Hayes, was one of the foundations of the new climate report. In that earlier study, Jasper and Hayes had the insight to calibrate organic stable-isotopic records from a sediment core from the Gulf of Mexico to a CO2 gas record of an ice core from Antarctica which later allowed colleagues to reconstruct carbon-dioxide results going back to a time millions of years ago when Earth was much warmer than it is today.

The work of Jasper and Hayes is so fundamental to our understanding of climate change today that an eco-novel titled “Carbon Dreams” by Susan M. Gaines, published in 2001, used their study as inspiration for her book about science and society.

Jasper, then a graduate student of marine organic geochemistry, said he met Hayes, then perhaps the leading isotope chemist in the world, at the Gordon Research Conference in 1986. They soon realized their work and interests complemented each other’s and that their collaboration could lead to the development of a fundamental iway to track climate-change over time.

A follow-up analysis by Commonwealth Scientific and Industrial Research Organisation, Australian Government, showed the air contained about 280 parts per million of carbon dioxide in the late 1700s; the measurement today is about 420. According to scientific calculations, this already has resulted in about 2.2 degrees of warming since the late 1800s.

“If you want us to tell you what the temperature will be in the year 2100, this does not tell you that. But it does have a bearing on present climate policy,” coauthor Dana Royer, a paleoclimatologist at Wesleyan University, said in a press release about the new study. “It strengthens what we already thought we knew. It also tells us that there are sluggish, cascading effects that will last for thousands of years.”

Climate modelers are expected to use the study to develop more robust predictions of climate change over the next few decades, according to the release, and the project’s data are open to public scrutiny and continually updated.

One of the main things that people should take out of the study, said Jasper, is the knowledge that “there are many well-credentialed, well-experienced, and dedicated scientists who have addressed the CO2 matters over many decades.”

He said he hopes the study will bring the issue of climate change back into the open as politicians debate the best policies going forward.

“I would hope that by having an informed public about basic science that rational climate policies will evolve.” Jasper said.

Lee Howard is The Day’s business editor. To reach him, email l.howard@theday.com.