DALLAS -- Vice-President Al Gore believes that the greatest threat facing civilization is human caused global warming, so reducing its threat will be an important plank in his presidential campaign.

Gore even advocates that the U.S. sign a treaty that would reduce energy use and economic growth in order to avoid global warming. Before other candidates follow Gore's lead, they should examine the current state of global warming science.

In 1988, James Hansen, director of NASA's Goddard Institute, brought "global warming" to the public's attention for the first time when he testified before the Senate that he was "99 percent" certain " . . . the [human caused] greenhouse effect has been detected and it is changing our climate now."

During the last 150 years, the Earth has warmed between 0.3 and 0.6 degrees Celsius and carbon dioxide (CO2), a primary greenhouse gas, has increased approximately 30 percent.

Using these facts and climate models, Hansen and others argued that the earth's current warming is due to increased CO2 caused by the use of fossil fuels.

Shortly after Hansen testified, in 1990, the best climate models were predicting that, absent reduced greenhouse gas emissions, the earth would warm between 4.5 degrees and 6.0 degrees Celsius by 2050.

Scientists worried that absent a sharp and immediate reduction in CO2 disaster would occur. Now, however, these same models indicate that Earth will warm between 0.8 degrees to 3.5 degrees Celsius over the next 100 years.

And a 1995 U.S. government survey of the global climate literature predicts even less warming ¾ between 0.5 degrees and 2.0 degrees Celsius by 2100.

Clearly, Climate models are crude predictors of global climate change. Furthermore, a study in Science October 2, 1998, refutes the claim that the current warming could only be caused by human activities.

It showed that 12,500 years ago global temperature rose by more than 20 degrees in approximately 50 years. This natural change was more than 10 times the "catastrophic" warming environmentalists claim only humans could be causing and it occurred in half the time.

Even if global warming is occurring the United States may be blameless since rather than being a carbon "polluter," it turns out that the U.S. is an "air filter."

According to an October 16, 1998, article in Science, North America removes more carbon (about 2 billion tons) from the atmosphere than it emits (1.5 billion tons) each year.

One reason is the tremendous regrowth of eastern U.S. forests ¾ trees remove CO2 from the atmosphere.

And a March 12, 1999, paper in Science may have finally explained why, contrary to what global warming theory predicts, most of the present warming occurred before 1940 ¾ preceding the majority of human-caused CO2 emissions.

In the paper, researchers concluded that when the earth shifts from glacial to warm periods every 100,000 years or so, temperatures rise before CO2 levels.

In the middle of the last century, the earth came out of a "Little Ice Age" during which global temperature was about 1 degree cooler than at present.

Thus, one would expect an increase in CO2 to follow the temperature increase arising from the end of the little ice age.

By 1998, James Hansen, the father of global warming, had changed his tune, writing "The forcings that drive long-term climate change are not known with accuracy sufficient to define future climate change."

Hansen's about-face should give presidential candidates pause when developing their position on global warming. Al Gore rushed to judgment about global warming, others shouldn't make the same mistake.