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.