Science is systematically reducing uncertainties regarding the causes and consequences of climate change. This is critical, for it helps us identify the tradeoffs we must make. It is irresponsible and naive to pretend they don’t exist or won’t be difficult.

Crafting effective solutions begins with considering two questions. First, should we care about a warming climate? If the answer is yes (and I believe it is), logic leads us to the second: What sacrifices are we willing to accept in order to do something about it?

The world is discovering that combating climate change will be an extremely difficult and expensive undertaking. It is especially vexing for the following reasons.

• The atmosphere is a commons with unrestricted access. The benefits of burning fossil fuels accrue to individuals and the costs are borne by all. Our challenge is to design institutions that will effectively “enclose” the commons.

• Carbon dioxide is a persistent atmospheric resident. If overnight we eliminated every source of manmade CO2, the atmosphere would continue warming for 100 years or more.

• If current trends continue, by late century countries in the developing world will be the largest emitters of carbon dioxide. They understand that increasing energy consumption is a prerequisite for their economic development.

About 40 percent of our raw energy consumption is used to generate electricity -- the energy source that drives an ever higher portion of our GDP. Electricity consumption will likely rise another 20 to 30 percent over the next decade. So far, we’ve chosen to meet this demand by burning fossil fuels. (Seventy percent of our electricity is generated from coal, natural gas, and oil.) One consequence: since 1991, gross U.S. greenhouse gas emissions have increased about 20 percent.

Nuclear has a 20 percent share of electricity production. Renewables (i.e., wind, solar, geothermal, and biofuels) contribute 2 percent. As the prices of renewables decline, their share will expand -- slowly. It will not be in time to make the reductions in CO2 emissions many believe are needed to avoid the worst consequences of climate change. Renewables simply aren’t well suited to meet our base-load power demands. And no politician, not even Al Gore, will let the grid go dark.

Here’s the reality environmentalists must face: in all industrialized nations, fossil and nuclear fuels will dominate for decades to come.

Over the next fifty years the world’s poorest will continue to demand more energy, particularly electricity. They understand electrical energy removes drudgery, multiplies human labor, and increases productivity. It builds and lights schools, provides clean water, and powers machinery and computers.

“If people don’t have electricity,” points out Gordon Mwesigye, a senior official in Uganda, “they will cut down trees, and Africa will lose its wildlife habitats....” He understands that poverty is the worst polluter.

“Given the levels of consumption likely in the future,” the UK’s Royal Society and Royal Academy caution, “it will be an immense challenge to meet the global demand for energy without unsustainable long-term damage to the environment.”

Some cling to the myth that the developing world can meet its energy needs with low-tech, renewable approaches. While this may be appropriate in some circumstances (e.g., solar ovens that replace dung-fueled stoves), it is just too expensive to supply these people with renewable sources of energy.

It’s now time to select among imperfect alternatives. Which will we choose? If we’re serious about reducing the amount of carbon dioxide we put into the atmosphere, while still meeting the energy demands of 6 billion people, then it’s time to reconsider nuclear power -- a safe, practical alternative.

France generates more than 78 percent of its electricity from nuclear power. Belgium generates 58 percent, Sweden 45 percent, South Korea 40 percent, Switzerland 37 percent, Japan 31 percent, Spain 27 percent, the UK 23 percent, and the US 20 percent.

Antinuclear activism has not reduced the demand for energy. Instead, ironically, it has contributed to a massive increase in the use of coal; the dirtiest of our fuels. Throughout history, humankind has gradually decarbonized its dominant fuels, moving steadily away from the more polluting, carbon-rich sources. Environmentalists should encourage this transition by carefully examining alternatives.