WASHINGTON -- GLOBAL WARMING is “unequivocal,” according to the just-released report by the Intergovernmental Panel on Climate Change. The most likely culprits are people — all of us. Yet, apart from insightful comments by former Vice President Al Gore, there has never been much public discussion about the role of human population growth in global warming.

Prof. Tim Dyson, of the London School of Economics indicates that a 40 percent cut by 2050 in per-capita carbon emissions in the developed world could be completely cancelled by population growth.

It’s time to open a “second front” in the battle against global warming by stressing the need for population stabilization, sooner rather than later. Scientists warn that temperatures will continue to rise unless we stabilize greenhouse-gas levels. Global warming will be accompanied by increased sea levels, resulting in massive flooding of homes and destruction of fragile wetland habitats.

To slow down this process, experts estimate that global CO2 emissions must be slashed. Yet the United Nations projects that world population will rise 40 percent — reaching 9.1 billion — by 2050. And even if we change our ways, the environmental footprint of each human being will never reach zero.

As population increases, the challenge of slowing climate change becomes ever more difficult. After all, it is people, not birds or bears, who drive Hummers and hybrids and who heat and cool homes and offices. Although the vast majority of population growth occurs in the least-developed nations, the people there, too, are using more fossil fuels every day as they seek better lives.

What can we do? We know that family planning works everywhere. When women and couples are free to make their own informed choices and have access to family planning resources, they choose to have smaller families. Thirty years ago, for example, Mexican women had almost seven children each. Today, thanks to education and the availability of family planning, they have an average of 2.4 children.

Globally, at least 350 million couples lack family planning services. Here in the United States, one-third of all births are unplanned. And the Bush administration’s family-planning failures, from its global gag rule against abortion to ideologically driven abstinence-only programs, contribute directly to millions of unwanted and unplanned births. If we could cut in half the number of unwanted births in the U.S. alone, we’d have about 5 million fewer births over 20 years.

Family planning makes sense for people – and for our fragile planet. It’s vital to focus on thorny technical issues such as tax credits, energy alternatives and emissions trading programs. These efforts are especially important here in the United States, where less than 5 percent of the world’s population produces about 25 percent of the world’s carbon-dioxide emissions. But cutting energy consumption must be coupled with stabilizing population.

More people use more energy. If we had zero population growth, part of the global warming problem would, well, melt away. Global warming is too big a problem to be solved by energy experts alone. It’s about people. It’s about how many of us there are and how we choose to live our modern lives. It’s about the very personal decisions we make about whether, when, and how many children we choose to have. We can start by supporting the notion that every woman and every couple should have the resources and power to control their own reproductive lives.

If every child is planned, we’ll go a long way toward solving global warming and making a less-crowded and healthier world.

John Seager is the national president of Population Connection, formerly Zero Population Growth.