Climate change, global warming, the words are tossed out frequently these days-but do we even know what it means? Why is the climate changing? What are greenhouse gasses? Isn't climate always changing?

Display demonstrates the increase of greenhouse gasses, especially CO2 (the red and white molecules), over time. Oxygen is pure white. Chlorofluorocarbons are white and green.

Toby Stephenson, curator of The Bar Harbor Whale Museum, which an affiliate of College of the Atlantic, has worked with museum staff to create an exhibit exploring climate change at the museum-perhaps the only such exhibit in Maine. Stephenson, an associate of the college's marine mammal research arm, Allied Whale, launched the exhibit due to the topic's urgency-and its complications.

"Climate change exists," says Stephenson. "The greenhouse effect is not in itself bad. But humans are only comfortable within a very narrow temperature range-and that range is being tipped. We're talking about only a couple of degrees, a minute adjustment if you look at global change in temperature from one ice age to another." But this minimal change might have a major impact.

The exhibit begins on the astral level, with a graphic look at the greenhouse gasses in our atmosphere and how their composition has changed over the years. Eventually, more regional issues are featured, especially the marine life of the North Atlantic. For instance, says Stephenson, algae live on the underside of winter ice flows. This algae is the food of krill, which is the basis of the oceanic food chain. With increased warmth, there are fewer ice flows and less algae, potentially altering the amount of food available for all oceanic life.

And yet, says Stephenson, "we didn't want to scream that the sky was falling." What he does want to do is help people understand what climate is, how it affects the atmosphere, the essential connection between climate and oceanic currents, and how complicated change can be, with warming of the seas potentially causing cooling of the atmosphere in certain locations. Through this knowledge, Stephenson hopes, visitors can become responsible environmental stewards.

Located at 52 West St. across from the whale watch pier in Bar Harbor, the Bar Harbor Whale Museum is supported by COA and the Bar Harbor Whale Watch. It is Maine's only museum dedicated to the study and understanding of whales and seals familiar to the Gulf of Maine. All exhibits are created by students, faculty and associates of College of the Atlantic. Additional exhibits feature a life-size model of a 50-million-year-old whale, and extensive whale skeletons.

The Bar Harbor Whale Museum is open daily through Oct. 31. Hours through June 30 and from Sept. 1 to Oct. 31 are 10 a.m. to 8 p.m. In July and August, the museum is open 9 a.m. to 9 p.m. Admission is free, donations and gift shop purchases support the research work of Allied Whale. For more information, call 207-288-0288.