“CLIMATE CHANGE is occurring, is very likely caused by human activities, and poses significant risks for a broad range of human and natural systems.”

So says — in response to a request from Congress — the National Research Council of the National Academy of Sciences, the country’s preeminent institution chartered to provide scientific advice to lawmakers.

In a report titled “America’s Climate Choices,” a panel of scientific and policy experts also concludes that the risks of inaction far outweigh the risks or disadvantages of action. And the most sensible and urgently needed action, the panel says, is to put a rising price on carbon emissions, by means of a tax or cap-and-trade system. That would encourage innovation, research and a gradual shift away from the use of energy sources (oil, gas and coal) that are endangering the world.

None of this should come as a surprise. None of this is news. But it is newsworthy, sadly, because the Republican Party, and therefore the U.S. government, have moved so far from reality and responsibility in their approach to climate change.

Seizing on inevitable points of uncertainty in something as complex as climate science, and on misreported pseudo-scandals among a few scientists, Republican members of Congress, presidential candidates and other leaders pretend that the dangers of climate change are hypothetical and unproven and the causes uncertain.

Not so, says the National Research Council. “Although the scientific process is always open to new ideas and results, the fundamental causes and consequences of climate change have been established by many years of scientific research, are supported by many different lines of evidence, and have stood firm in the face of careful examination, repeated testing, and the rigorous evaluation of alternative theories and explanation.”

Climate-change deniers, in other words, are willfully ignorant, lost in wishful thinking, cynical or some combination of the three. And their recalcitrance is dangerous, the report makes clear, because the longer the nation waits to respond to climate change, the more catastrophic the planetary damage is likely to be — and the more drastic the needed response.

That response, the panel concluded, ought to include not only a strong policy to begin reducing greenhouse gas emissions but also a plan to begin adapting to climate change, some amount of which is already inevitable; more research into climate science and alternative energies; and active engagement in international efforts to control climate change. Given the global nature of the problem, the report says, U.S. action can’t be sufficient, but “strong U.S. emission efforts will enhance our ability to influence other countries to do the same.”

What happens when Congress asks a question and gets an answer it doesn’t like? The response from Texas Rep. Joe Barton, senior Republican on the House Energy and Commerce Committee, provides a clue. “I see nothing substantive in this report that adds to the knowledge base necessary to make an informed decision about what steps — if any — should be taken to address climate change,” Mr. Barton told the New York Times.

He’s right, of course — there is essentially nothing new, and that’s the point. Every candidate for political office in the next cycle, including for president, should be asked whether they disagree with the scientific consensus of America’s premier scientific advisory group, as reflected in this report; and if so, on what basis they disagree; and if not, what they propose to do about the rising seas, spreading deserts and intensifying storms that, absent a change in policy, loom on America’s horizon.