Time for Action on Global Climate Change.

Remember all that talk about how global warming was going to change our lives? It already has.

A new federal report on the impact of climate change condenses the latest science from a variety of disciplines. Among the findings:

— Heavy downpours are now twice as frequent in the Midwest as they were a century ago. Summer and winter precipitation have increased.

— Large heat waves have become more frequent in the Midwest over the past 30 years than at any time since the Dust Bowl years of the 1930s.

— Average temperatures have increased noticeably, despite year-to-year variation. The growing season has increased by more than a week, allowing more non-native plants and animals gain a footholds.

The report from the federal U.S. Global Change Research Program unequivocally describes the cause of climate change. It's "due primarily to human-induced emissions of heat-trapping gases."

That's a far cry from public position taken by the administration of former President George W. Bush, who didn't release a climate status report during his eight years in office.

A federal court forced the administration to release a draft climate report last year. The new report is based on that document, along with subsequent studies that have become available since then.

It spells out regional impacts of climate change — both those that have occurred and those that can be expected in the future.

Those regional impacts make a personal and compelling case for addressing the problem. "This is not some theoretical thing that will happen 50 years from now," said the report's co-author, Anthony Janetos.

"Things are happening now."

They say that if you put a frog in a pot and then turn up the heat, he won't notice until the water boils.

Global warming has the same effect on many people. Its impacts have occurred slowly over time. Coupled with normal seasonal variations, they've seemed almost undetectable.

But they're very real. They can be — and have been — detected and measured. That's given us the ability to make changes before the worst effects become unavoidable.

But so far, Americans have been unwilling to act on that information. Now that a bill to curb greenhouse gas emissions has been introduced in Congress, many people are objecting because of the estimated cost.

But doing nothing could be even more expensive.

The report predicts that by the end of the century, the Illinois climate could be similar to the current climate of Louisiana or Texas.

By then, national average temperatures could have increased by as much as 11 degrees.

The greatest risk of all is summarized in four words: "Thresholds will be crossed."

Climate systems and ecosystems contain what you might consider points of no return.

Cross them and things will never be the same. Pack ice disappears, permafrost melts and animals that are superbly adapted for those environments disappear forever.

That can trigger so-called feedback loops — other changes that exacerbate the impact of climate change. The melting permafrost, for example, could release large quantities of carbon dioxide.

The time to address global climate change is now, when the worst environmental and economic impacts still can be avoided.

Congress should enact legislation that caps and reduces the emissions of greenhouse gases. The Obama administration should redouble efforts to negotiate an effective international treaty that cuts emissions around the globe.

REPRINTED FROM THE ST. LOUIS POST-DISPATCH.

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