And then there's just plain habit. It's "a huge but boring force," Gifford said. "We just tend to do today what we did yesterday."
So what can advocates do to promote concern and action about global warming?
Gifford cites steps such as convincing people they really can make a difference by taking a bus rather than driving, or by insulating their homes. And messages that focus on taking action to become an "ecological hero" will probably work better than those that portray such actions as a sacrifice, he said.
Swim, who chaired a recent American Psychological Association task force that summarized psychological research relevant to climate change, said appeals stressing the impact of climate change on people and animals may be more effective than those that just talk about seas and temperatures rising. (She is now investigating whether such messages are more likely to make people act).
Elke Weber of the Center for Research on Environmental Decisions at Columbia University said people might respond to projections of what global warming could do to places they care about, like their favorite ski areas or their beach homes.
It's also important for the news media to talk about climate change and what people can do, Swim said. While the Copenhagen talks have gotten plenty of attention recently, in general "there's more in the paper about health care reform than about climate change," she said.
And individuals can talk to their friends about their own concern and actions, Swim said. She sets aside one day a week when she makes a special effort to minimize her own carbon emissions from driving by doing such things as biking or just staying home.
"Most people don't know I have a carbon-free day," Swim said. "I should probably tell more people about that."