The American Electric Power Co. Inc. coal-fired John E. Amos Power Plant in Winfield, W.Va., in July 2014. (Luke Sharrett/Bloomberg)

On climate change, we need to go beyond the tired story line of “deniers” vs. the “scientific consensus.” Until it’s discredited by falling temperatures, global warming is a reality. We can still debate how much has occurred and the share attributable to human activity, but the more relevant question is what — if anything — can be done about it. President Obama’s plan to cut greenhouse-gas emissions from electric power plants, accounting for roughly one-third of U.S. greenhouse emissions, shows the practical limits in a democratic society.

Let’s assume, for simplicity’s sake, that the plan works perfectly. It achieves its goal of reducing carbon emissions from power plants in 2030 by 32 percent from a base year of 2005. Other problems fade. Court challenges to the regulations are rejected. The expansion of solar and wind generation does not lead to less reliable electricity supplies. Greater efficiencies and cheap natural gas avoid sizable consumer rate increases.

Even under these favorable assumptions, Obama’s plan won’t immediately depress global temperatures, which — if the logic of climate change holds — will be higher in 2030 than today.

A refresher course in global warming explains why. What counts are the amounts of carbon dioxide and other greenhouse gases in the atmosphere. It’s these concentrations that are said to trap heat and raise temperatures. The concentrations have gone from roughly 280 parts per million (ppm) of carbon dioxide in preindustrial times, around 1800, to about 315 ppm in 1960 to 400 ppm now. As long as concentrations increase, so does the potential for more warming.

Obama’s plan doesn’t reduce these concentrations. It just cuts — but does not eliminate — the annual emissions into the atmosphere. These emissions raise concentration levels, which are now growing by about 2 ppm per year, says Princeton climate scientist Michael Oppenheimer. True, Obama’s plan might slow this a tad. However, the larger point is that ongoing power plant emissions, though diminished, would continue to boost concentration levels.

Here’s the dilemma. Eliminating fossil fuel emissions from coal, oil and natural gas would presumably stabilize most human impact on global warming. But if done now, it would also destroy modern economies because fossil fuels provide four-fifths of the world’s primary energy. There’s no quick way of finding substitutes for all the fossil fuels. A single-minded focus on global warming would plunge the world into depression.

Politicians straddle the dilemma by talking tough on global warming while giving priority to the economy. Obama’s approach seems in this spirit. His rhetoric last week was stark. “No challenge poses a greater threat to our future and future generations than a changing climate,” he said. Compared with this threat, his plan is modest. Indeed, it builds on existing trends. Electric utilities have already cut carbon emissions by about 15 percent since 2005 by switching from coal to cheap natural gas, which has about half of coal’s emissions.

We need more candor on global warming. Obama’s plan is a big deal for electric utilities and, if it goes awry, potentially for millions of households. The plan is complicated. States receive emissions goals and can meet the goals through various policies (energy efficiencies, a cap-and-trade program, a carbon tax, more natural gas generation, preferences for wind and solar). Love it or hate it, the plan still contributes to higher carbon dioxide concentrations. It may be worth doing; we may learn valuable lessons. But it’s no panacea.

Similar considerations apply globally. In 2010, major countries adopted a goal of limiting the worldwide temperature increase to below 2 degrees Celsius (or slightly below 4  degrees Fahrenheit) from the preindustrial period. The International Energy Agency in Paris recently estimated that meeting this goal would, in effect, require all fossil fuel emissions to be eliminated by 2040. Needless to say, this isn’t going to happen. As the agency has noted, countries’ policies “fall short of the action necessary to meet the 2 [degrees] C climate goal.”

There is a “mission impossible” quality to curbing global warming, though few say so openly. The dependence of economic growth on fossil fuels seems too strong to overcome. There are two hopes for doing so. One is that the warming predicted by some computer models is overstated; there is much uncertainty.

The second hope is that technological breakthroughs liberate economic growth from fossil fuels. It’s easy to list desirable advances: better batteries and electricity storage (this would favor more wind and solar power); safer and cheaper nuclear power; and cost-effective “carbon capture” (this would store power plants’ emissions underground).

The Internet shows that rapid technological revolutions are possible. On the other hand, these energy technologies have been explored for decades — and they still aren’t available.

Read more from Robert Samuelson’s archive.