THE National Academy of Science's declaration on April 10 that the United States should act immediately to slow global warming followed directly on the heels of NASA's finding that the depletion of Earth's ozone layer was accelerating.
Despite White House claims this week of deepening concern, its response to both events vindicates Hegel's observation that governments never have learned anything from history.
The greenhouse debate is eerily reminiscent of earlier arguments over the ozone layer.
As with the ozone debate, it is the magnitude of impending change, not the underlying theory, that is in dispute.
Emissions of industrial and agricultural gases, primarily carbon dioxide from fossil-fuel combustion, will surely cause global warming if they are not curtailed.
Similarly, there has long been agreement that chlorofluorocarbons, which are used in refrigeration, air-conditioning, foam plastics and solvents, destroy ozone in the stratosphere.
The best estimates is that the globe will warm by five degrees Fahrenheit by late in the 21st century, but current warming is small enough that the future is highly uncertain.
The Earth may heat up by only two degrees, which would be manageable, or by as much as nine degrees, which would be catastrophic.
We won't be sure how much warming is in the cards until it happens. But once altered, the climate, like ozone, will not return to normal for generations.
It is worth remembering that only six years ago global ozone depletion had not yet been detected.
At that time the best estimate of the 1990 depletion was 1 percent. NASA's recent finding is that depletion over the United States has already reached 4 percent to 5 percent.
The administration is still wringing its hands over the potential cost of reducing carbon-dioxide emissions.
But the academy found that efficiency measures, such as increased automobile fuel economy, implemented through federal and state policies, are an inexpensive, perhaps even money-saving way, to slash the risk of catastrophic warming.
The administration's wild exaggerations of costs are reminiscent industry arguments that there were no practical substitutes for chlorofluorocarbons.
But an international treaty signed in London last June will eliminate production of the major ozone-depleting chemicals over the next two decades, permitting the ozone layer to slowly recover.
The supply of air-conditioners, refrigerators and foam cushions will hardly be affected, since companies have been developing profitable substitutes for chlorofluorocarbons since the day that regulation appeared inevitable.
Yet millions of Americans may contract skin cancer and 200,000 are expected to die as consequences of enhanced ultraviolet radiation before ozone levels rebound, according to an Environmental Protection Agency (EPA) estimate.
Worse, we don't know how far ozone depletion will proceed, which ought to chill optimism about our military to adapt to climate change.
The lessons, for those who care to pay attention, is that the ozone debacle could have been avoided.
Shortly after the threat was identified in 1974, the public began boycotting aerosol spray cans in such numbers that the EPA's ban of those containing chlorofluorocarbons in 1978 was anticlimactic.
But with ozone depletion not yet measureable, our government lost interest in the problem.
It stopped short of implementing changes that consumers could not bring about on their own, such as encouraging new technologies for refrigeration.
By the time large ozone depletions could be measured, in 1985, it was too late to avoid calamitous increases in cancer.
Sadly, the White House has responded to both the new ozone findings and the academy report as if it were staffed by amnesia victims.
The White House declared that the accelerating ozone depletion was an occasion for "deliberative and comprehensive" study rather than for speeding the elimination of ozone-depleting chemicals.
The academy's call for federal incentives to encourage energy efficiency by consumers and industry was ignored in favor of modest cuts in the government's own energy use, only two percent of the U.S. total.
Earlier administrations tragically miscalculated the threat to ozone. The Bush administration seems intent on a repeat performance with global warming.
Michael Oppenheimer is senior scientist at the Environmental Defense Fund.