WASHINGTON — If there were any doubt before, there should be none now. “Solving” the global climate change problem may be humankind’s mission impossible. That’s the gist of the latest report from the Intergovernmental Panel on Climate Change (IPCC), the United Nations group charged with monitoring global warming.

Unless we make dramatic reductions in greenhouse gas emissions (carbon dioxide, methane and others), warns the IPCC, we face a future of rapidly rising temperatures that will destroy virtually all the world’s coral reefs, intensify droughts and raise sea levels. We need to take action immediately, if not sooner.

The IPCC says that emissions need to be cut 45 percent from present levels by 2030 and virtually eliminated by 2050. This would keep the projected increase in global temperatures since the early 1800s to 1.5 degrees centigrade, or 2.7 degrees Fahrenheit. We would escape the worst consequences of global warming.

It’s not clear how this would be done. The reality is that global carbon emissions are rising, not falling. Emissions today are about 60 percent higher than in 1990, according to the World Bank.

There are at least three obstacles frustrating the IPCC’s agenda.

First, we don’t have the technologies to reduce and eventually eliminate emissions from fossil fuels (oil, coal and natural gas). Yes, solar and wind power have made advances, but they still provide only a tiny share of the world’s total energy, about 4 percent. Electric vehicles don’t solve the problem, because natural gas and coal are the underlying energy sources for much of the electricity.

Second, even if we had the technologies to replace fossil fuels, it’s doubtful that we have the political will to do so. Democracies — or, for that matter, dictatorships — have a difficult time inflicting present political pain for future, hypothetical societal gains. Voters abhor higher gasoline and heating-oil prices, which are an integral part of most proposed solutions for global warming. They would dampen demand for fossil fuels and spur investment in substitutes.

The clearest proof of America’s political bias against the future is the treatment of Social Security and Medicare. For decades, we have known that an aging population would significantly boost spending for these programs. What did we do to prepare for this inevitability? Not much.

Finally, assuming (unrealistically) that today’s advanced societies — led by the United States — overcome these obstacles, it’s unclear whether poorer and so-called “emerging market” countries would follow suit. These countries represent the largest increases in fossil-fuel demand, as they attempt to raise living standards. Already, China is the world’s largest source of carbon dioxide emissions, nearly twice as high as the United States.

Economic and population increases boost energy demand. Consider air conditioners. The world now has 1.6 billion air conditioning units, reports the International Energy Agency. By 2050, that could triple to 5.6 billion units. People in advanced societies won’t abandon air conditioning, and people in poorer countries won’t surrender the chance to enjoy it. Much of future demand will come from three countries — China, India and Indonesia.

What is to be done?

Maybe nothing. This seems to be the choice made by many Republicans and the Trump administration, which is withdrawing from the Paris agreement’s commitments to reduce emissions. Trump’s hostility is not as crazy as it sounds. If suppressing global warming is as hard as I’ve argued, one likely response is a series of half measures that don’t much affect global warming but do weaken economic growth. The politicians’ real aim is to brag that they’ve “done something” when all they’ve really done is delude us. Trump would skip this stage.

My own preference is messier and subject to all the above shortcomings. I would gradually impose a stiff fossil-fuel tax (not a 10 or 15 percent tax but a doubling or maybe a tripling of prices) to discourage fossil-fuel use and encourage new energy sources. In addition, some of the tax revenues could reduce budget deficits and simplify income taxes. With luck, a genuine breakthrough might occur: perhaps advances in electric batteries or storage. That would make wind and solar power more practical.

There are risks. It can be argued that this sort of policy, aside from relying on unpopular energy taxes, would represent a triumph of hope over experience. In the name of fighting global warming, we might justify a host of energy boondoggles.

Combatting global warming is a noble crusade, but it’s much harder than the rhetoric implies. If we were serious about cutting greenhouse gases, we could adopt comprehensive wartime controls that empower the government to mandate changes. Or we could accept a worldwide depression as a way to quash job growth and greenhouse gases. Obviously, neither is in the cards.

Robert Samuelson is a columnist with The Washington Post.

Robert Samuelson