NORTHPORT — Former Maine U.S. Sen. George Mitchell will address a gathering of international researchers, scientists and students who study the effects of climate change.

Mitchell will present his keynote address on Thursday. The conference, running today through Friday in Northport, will focus on how chemical and physical climate changes influence the Earth’s environment.

The University of Maine, Villanova University and the Czech Geological Survey are hosting the conference. About 400 people are expected to attend. Neither Mitchell’s address nor the conference is open to the public but media coverage is expected.

As a senator, Mitchell led the push for the 1990 reauthorization of the Clean Air Act. He is the author of “World on Fire,” which describes the greenhouse effect and recommends steps to curb it.