Scientists waited a long time to declare that global warming was real. And they waited even longer to declare that it resulted from human activities.
And they are still waiting to announce what is becoming increasingly obvious: It isn't going to take nearly as long as had been expected for profound changes to take place.
Good scientists are always cautious scientists, and that chiefly explains their reticence. But now, nearly every research institution involved in the study of global climate change -- from the American Academy of Sciences to the atmospheric department at your local university -- has issued reports citing overwhelming evidence that the planet is changing.
But how much will it change? How will that affect us? And how soon?
Those are the tough questions, and some of the answers will remain elusive for years to come. After all, predicting climate, even day to day, is foggy at best. Given the variables, it may be the most difficult science of all.
But many experts confide privately what they aren't yet ready to announce publicly: Change is accelerating at a dramatic rate.
A cascading effect is now in place. Rising temperatures cause greater releases of greenhouse gases, which in turn cause temperatures to rise, resulting in even more gases being released, and so on.
The most disturbing report on that phenomenon was published recently in Science. But like so many reports, it seems to deal with events so far away and so arcane that it's easy to look the other way. Yet the consequences will land on everybody's doorstep.
Here's the bottom line of that report: The permafrost that blankets northern Siberia is thawing.
Wow, you say, Siberia. So far away.
But here's the statement that needs to be printed on every politician's forehead.
That permafrost contains 75 times more carbon than is released by burning fossil fuel around the entire planet for an entire year. That number is worth repeating. More carbon than all our cars and factories will release in 75 years.
The scientists who wrote the report, all of whom are at the University of Florida, called that a "potent, likely unstoppable contributor to global climate change if it continues to thaw." And, by the way, that's not much of an if. It will take decades, and probably centuries, for that process to be reversed.
Siberia's permafrost, which is supposed to remain frozen for most of the year, covers nearly 400,000 square miles and contains about 500 billion metric tons of carbon.
"You start thawing the permafrost, microbes release carbon dioxide, that makes things warmer. More permafrost thaws and the process continues," says Ted Schuur, an assistant professor of ecology at the university and one of three authors of the report.
A report issued by the university noted that "If all the Siberian permafrost thawed, decomposed and released its carbon in the form of heat-trapping carbon dioxide, it could nearly double the 730 billion metric tons of carbon in the atmosphere presently, an outcome that would have huge warming impact."
Permafrost is not limited to Siberia. Any thawing, whether it be in Alaska or northern Europe, will result in the release of some greenhouse gases, but Siberia is more extreme. The layers of permafrost there are very deep, so the carbon that is trapped has been in place for a very long time.
Samples that Schuur brought back from Siberia to his laboratory in Gainesville contained carbon that dated back tens of thousands of years as organic material became trapped in the soil.
Further examination revealed that the carbon from the Siberia samples was released very rapidly as the soil thawed.
"If these rates are sustained in the long term, as field observations suggest, then most carbon in recently thawed (permafrost) will be released within a century -- a striking contrast to the preservation of carbon for tens of thousands of years when frozen in permafrost," the scientists conclude in their Science paper.
It's easy to find examples of changes that are already taking place.
The Mendenhall Glacier, just a short drive from my home in Juneau, Alaska, is one of the premier tourist attractions in the state. It is a spectacular river of ice that extends up a vast valley carved by the glacier as it gorged its way down through the rocky cliffs that tower above.
When I first saw it as a young Coast Guard officer on duty in Alaska, I was awed. I'm still awed today. But the Mendenhall is rapidly becoming a shadow of its former self. It is melting and receding at a rate of several hundred feet a year.
Just a few years ago, scientists thought the 500-square-mile ice field that feeds the glacier would soon start to get colder, part of an anticipated natural cycle.
But the Mendenhall, like nearly every other glacier in Alaska, is disappearing. Just 200 years ago, the toe of the glacier was where the Juneau airport is today. Now it's several miles -- that's miles -- back into the spruce-covered hills.
Living in Alaska, I find it's sometimes kind of nice to think that the planet is growing warmer. But there's a price to be paid. And the loss of the Mendenhall Glacier pales in the face of horrendous storms, starvation and inundation of coastlines that are sure to come.
Don't think of it in terms of centuries, or even decades. It's happening now.