Dr. James Hansen is good at predicting the weather, which is why two Bush administrations have tried to shut him up.

"It's time to stop waffling so much and say that the greenhouse effect is here and affecting our climate now," Hansen said _ in 1988. President George H.W. Bush's administration complained to his bosses at NASA.

Last month, Hansen, the longtime head of NASA's Goddard Institute of Space Studies, gave a lecture urging immediate action to reduce greenhouse gas emissions. George W. Bush's administration ordered NASA to rein in its scientist. According to The New York Times, NASA ordered a screening of all Hansen's lectures and postings on its website as well as all requests to interview him.

To his credit, Hansen has ignored the restrictions. Speaking out publicly "is probably the only thing capable of overcoming the special interests that have obfuscated the topic," he said.

The campaign to minimize global warming has kept the United States from taking meaningful steps to slow it by increasing mileage standards or backing research to find replacements for fossil fuels. The consequences, after all, will be the problem of some other president.

It's natural to look out at robins on the lawn in January and open water on New Hampshire's lakes and think "global warming." But it's impossible to attribute the weather in any given year or even decade to climate change. Too many questions remain. Yet there is near unanimity in the scientific community that human activities are warming the Earth. Most of the remaining skeptics have ties to the energy industry or other reasons to minimize the problem.

The debate among mainstream scientists now is over how close the Earth is to a "tipping point," after which global warming cannot be slowed or reversed. That point could be pushed back with emissions reductions that are possible with existing technologies, Hansen said, but not if more isn't done in the next decade.

At the current rate of warming, sometime in the next century or so one of the great ice sheets covering Greenland and portions of the Antarctic could disintegrate, with dire consequences. One estimate says the bottom third of Florida would be inundated, and much of Manhattan would be under water.

Lesser calamities attributed to climate change are already occurring. So many polar bears have drowned trying to swim 100 miles or more from ice floe to ice floe or starved on land that some scientists warn of that the species faces extinction.

In 1981 Hansen published a paper that said carbon dioxide and other greenhouse gases would make the world warmer by the 1990s than at any time since the Dust Bowl days of the 1930s. He was right, but nothing was done.

In 1988 Hansen repeated his warning to members of Congress. The next year the federal Office of Management and Budget changed his official testimony to weaken his conclusions. Scientific reports about global warming and have been toned down, censored or suppressed. But the 11 warmest years since the late 1800s, when record-keeping began, have all occurred since 1990.

Last month, Hansen reported on Goddard's website that 2005 could beat out 1998 as the warmest year on record. He was told that he would face "dire consequences" if he kept talking. And Hansen isn't the only scientist being censored.

Nearly two years ago, a group of scientists, including 20 Nobel laureates, accused the White House of routinely suppressing or manipulating scientific results for their own ends. The Bush administration's latest attempt to muzzle Hansen prove that nothing has changed.