This Earth Day, climate scientists are stepping up their dramatic warnings about the dire consequences of global warming. Earlier this month, in the second installment of its four-part report, the UN-sponsored Intergovernmental Panel on Climate Change said worldwide shifts in weather patterns and rising sea levels could bring drought, hunger, heat waves and disease to all continents. The poorest societies in the most arid regions would be hardest hit, though they have contributed least to greenhouse gas emissions, the UN panel said. It earlier pointed to the increase in human-produced greenhouse gases as the “very likely” cause of a rise in global temperatures over the last 50 years.

On April 16 a group of U.S. scientists who are part of the UN panel identified water shortages and coastal flooding as two key problems for North America, while a group of retired military officers cited rising worldwide security threats stemming from the climate changes.

In the face of the ostrich-like refusal of the Bush administration and its corporate backers to acknowledge the overwhelming scientific evidence that human activities are causing the problem, a growing and diverse environmental movement is taking action.

Environmentalists and the organized labor movement, once at loggerheads, are increasingly joining forces in projects such as the Blue/Green Alliance and the Apollo Alliance, which link efforts to clean up the environment and reverse global warming with the struggle for good jobs.

The environmental justice movement points out that poor working-class people, especially those of color, are most sharply affected by living near environmentally hazardous facilities and polluted sites. The movement is giving rise to joint efforts like the campaigns bringing together environmentalists, unions, elected officials and community and faith-based organizations to cut diesel emissions by ships and trucks at ports including Los Angeles-Long Beach and Oakland, Calif.

The Bush administration’s continuing refusal to recognize the threat global warming poses to human society gives voters one more reason to step up their efforts to deal the far-right Republicans a resounding defeat in 2008.