Public skepticism about global warming may be growing, but the scientific consensus is as solid as ever: Man-made climate change is real, and we ignore it at our peril. But if that issue is settled (and it should be), there is an equally big and important question that remains wide open: What should we do about it?

One prescription that is bandied about with increasing frequency certainly sounds sensible: The world should drastically cut the amount of greenhouse gases that it pumps into the atmosphere each day. Specifically, we are told, the goal should be a 50 percent reduction in global carbon dioxide emissions by the middle of the century.

Even its backers concede that achieving this target won't be easy - and they are right. In fact, they are so right that they are wrong. Allow me to explain.

Our dependency on carbon-emitting fuels is more than enormous. It is overwhelming. For all the talk about solar, wind, and other hyped green-energy sources, they make up only 0.6 percent of global energy consumption. Renewable energy overwhelmingly comes from often-unsustainable burning of wood and biomass by people in the developing countries. Fossil fuels account for more than four-fifths of the world's energy diet. So, in order to cut global carbon dioxide emissions by half by the middle of the century, we would obviously have to start getting a lot more of our energy from sources that don't emit carbon.

Can we do this? According to the International Energy Agency, here's what it would take to achieve the goal of cutting emissions by 50 percent between now and mid-century: 30 new nuclear plants; 17,000 windmills; 400 biomass power plants; 2 hydroelectric facilities the size of China's massive Three Gorges Dam; and 42 coal- and gas-power plants with yet-to-be-developed carbon-capture technology.

Now consider this: The list does not describe what we would have to build between now and 2050, but what we would have to build each and every year until then!

One more thing: Even if we managed to do all this (which we obviously cannot), the impact on global temperatures would be hardly noticeable by 2050. According to the best-known climate-economic model, this vast undertaking is likely to wind up reducing global temperatures by just one-tenth of 1 degree Celsius (one-fifth of 1 degree Fahrenheit), while holding back sea-level rises by only 1 cm (less than half an inch).