Detroit ? Just in time for today’s 37th anniversary of Earth Day, the Earth is back. Green is cool; global warming is hot.

“It’s a great time to be an environmentalist,” said Lana Pollack, executive director of the Michigan Environmental Council in Lansing. “I really believe the public has reached a tipping point in terms of concern and understanding about global warming. There’s been a big change, even in just the last year.”

Consider:

Wayne County runs its road-maintenance and salt trucks on biodiesel, and Novi is urging all developers to build green buildings, which conserve energy and water.

Fuel-efficient cars and trucks powered by gas engines and electric motors are proliferating, as General Motors joins Toyota, Honda and Ford in the hybrid race. GM unveiled a plug-in hybrid concept at the Detroit auto show in January that may never need gasoline.

The Earth is big on magazine covers. May’s Vanity Fair magazine is its Green Issue; California Gov. Arnold Schwarzenegger’s fight against global warming graced a recent Newsweek cover.

Retailers are joining the green movement. The goal of the world’s biggest retailer, Wal-Mart, is to get 100 percent of its energy from sustainable sources and produce zero waste. Home Depot, the nation’s second-biggest retailer, announced plans last week for a line of 3,000 eco-friendly products like natural insect killers and energy-saving light bulbs.

A Detroit Free Press-Local 4 Michigan Poll of students at the state’s three biggest universities this month found that 3 of 4 students think global warming will worsen in the next 15-20 years. On no other issue, including global terrorism and nuclear proliferation, were students so pessimistic about the future.

A USA Today/Gallup Poll last month found that more Americans than ever before – 60 percent, up from 48 percent a decade ago – believe global warming is already changing the world’s climate. A slightly larger percentage of Americans think it will cause major or extreme changes in climate and weather over the next 50 years.

There are still skeptics – led by conservative talk show hosts like Rush Limbaugh – but their numbers and power are dwindling.

Even ExxonMobil, an oil company that was funding global warming skeptics who create the impression that the science on climate change is iffy, has stopped funneling money to skeptics and says it’s time to take action, said Andy Hoffman, a University of Michigan business school professor who studies business reaction to environmental issues.

He calls this the “third wave” of the environmental movement, following waves around 1970 and 1990.

“I think the growing scientific, social and political consensus is that global warming is real and has to be dealt with, and that’s the driver of this third wave,” Hoffman said.