Our planet faces a grave threat from global warming and climate change, which are caused largely by emissions of carbon dioxide and other greenhouse gases generated by human activity. Yet readily available energy technologies could be put in use today to forestall their worst effects. In this issue of Technology Review, we examine some of these technologies and argue that they require not further refinement but a considered, long-term strategy for their deployment.

Atmospheric levels of carbon dioxide – the most common greenhouse gas – have shot up 32 percent in the last 150 years. Geological evidence and climate science suggest that we are approaching a tipping point beyond which sea levels will rise catastrophically. Nevertheless, immediate steps to sharply reduce emissions could still prevent the worst consequences of global warming, according to famed NASA climatologist Jim Hansen (see “The Messenger,” by Mark Bowen). In the meantime, however, humankind is increasing, not decreasing, consumption of fossil fuels – and even getting cleverer about extracting them (see “The Oil Frontier,” by Bryant Urstadt). For the foreseeable future, we will continue to burn fossil fuels: they now provide 80 percent of the world’s energy, and global energy demand will at least double by 2050. “Controlling carbon dioxide while also doubling energy use is a rather remarkable challenge to contemplate,” mused Ernest J. Moniz, an MIT physicist and former undersecretary of the U.S. Department of Energy, earlier this year as he discussed an MIT research and education initiative aimed at confronting the energy crisis.

In meeting this remarkable challenge, we must, in particular, address the problem of coal. It is among the largest sources of carbon dioxide and, regrettably, is also the cheapest and most abundant fossil fuel. But cleaner technology – in which carbon dioxide could be captured and sequestered – is ready to go into new coal plants now (see “The Dirty Secret,” by David Talbot). Similarly, improved versions of today’s nuclear power plants await construction (see “The Best Nuclear Option,” by Matthew L. Wald). Unfortunately, implementation of cleaner technologies has been thwarted by federal aimlessness. The Energy Department keeps changing its nuclear-research strategy, and a “FutureGen” zero-emission coal demonstration project announced three and a half years ago by President Bush hasn’t yet picked a site.

At least one alternative energy technology is also coming into its own. Ethanol production from biomass is already a booming business in Brazil (see “Brazil’s Bounty,” by Stephan Herrera); with help from bioengineered organisms, it could soon be efficient enough to compete directly with traditional energy sources (see “Redesigning Life to Make Ethanol,” by Jamie Shreeve).

There is no escaping the reality that in the end, we will need an energy economy based on solar, wind, and other renewables (see “It’s Not Too Early,” by Marty Hoffert). We’d like to have an all-renewable energy portfolio today. But we cannot wait any longer for new technologies, as Joseph Romm, an Energy Department renewable-energy official during President Clinton’s administration, made clear at a conference in April. “The point is,” he said, “whatever technology we’ve got now – that’s what we are stuck with to avoid catastrophic warming.”