Humanity has the hardware in hand to halt the rise in heat-trapping greenhouse gases it pumps into the atmosphere and forestall the worst effects of global warming projected for the end of this century.
The goal could be achieved within the next 50 years by more widespread use of a portfolio of at least 15 approaches - from energy efficiency, solar energy, and wind power to nuclear energy and the preservation or enhancement of "natural" sinks for carbon dioxide such as rain forests, or the conservation tillage techniques on farms worldwide, say two Princeton University researchers in a study published Friday.
The list of technologies has been around for years, the researchers acknowledge. But past studies, such as one conducted by five US national laboratories four years ago, tended to focus on whether these approaches could be used to reach the emissions goals and deadlines in the 1997 Kyoto Protocol without trashing the economy, as some critics of the pact have warned.
Holding out for more research, Bush administration officials have argued that "we need a solution comparable to the discovery of electricity before we can get on with the carbon problem," says Robert Socolow, an engineering professor at Princeton University and codirector of the school's Carbon Mitigation Initiative. "But there isn't a [Michael] Faraday in every generation. If you don't get started, you'll waive an opportunity" to use what's available.
The study, published in Friday's edition of the journal Science, is short on policy recommendations.
"How do you get these [technologies] into the system?" asks Eileen Claussen, president of the Pew Center on Global Climate Change and Strategies for the Global Environment in Arlington, Va. The problem, she says, is more one of politics and cost than whether key technologies currently exist at industrial scales.
Yet by adopting a more scientifically defensible target and a longer time scale to achieve it, Stephen Pacala and Dr. Socolow hope the study helps break a logjam - at least in the United States - over when to begin efforts to stabilize and ultimately reduce the carbon-dioxide emissions that most atmospheric scientists say are contributing to a warming world climate.
The duo argues that applied globally, the approaches they identify could cap atmospheric CO2 concentrations at roughly 500 parts per million. This would be significantly lower than what is projected for 2100 if no actions are taken. And the means they have developed for analyzing the gap between business-as-usual emissions and the stable rate they seek - and the plausibility of using existing approaches to reach them - could help policymakers choose among options.
The study's publication comes at a time when scientific research continues to build what many see as a case for action, even as it also aims to reduce the uncertainties that still surround the direct and indirect effects of humanity's industrial donations of carbon to the atmosphere.
In July, researchers published two studies in the journal Science pointing to the oceans as the largest sink for atmospheric CO2 and measuring CO2's impact on the ocean carbon cycle. The results indicate that the oceans are becoming more acidic, which could endanger a range of marine life.
Meanwhile, climate models are teasing out the potential effects of climate change. Researchers at the National Center for Atmospheric Research in Boulder, Colo., report in Friday's edition of the journal Science that a "business as usual" buildup of CO2 in the atmosphere will intensify large-scale circulation patterns that bring heat waves to the US and Europe. The results suggest that the southern and western US would be among the regions hardest hit by frequent, long-lasting heat waves.
The Princeton team's work also comes when momentum continues to build for more concerted action on climate change, even as the prospects for the 1997 Kyoto Protocol appear dim. In the US, state and local governments, as well as a range of corporations, are adopting approaches to reduce carbon-dioxide emissions. Some of the pressure also is building from insurance and reinsurance companies, who must provide the financial protection for businesses that could be hammered by some of the more extreme weather events a warmer world is projected to deliver.
In Europe, Britain has adopted a goal of cutting its CO2 emissions by substantial amounts over the next 50 years. The European Union, already having a difficult time meeting the shorter-term objectives of Kyoto, are said to be looking at longer timescales for reducing emissions as well.
Socolow and Dr. Pacala argue that such time scales mesh nicely with the typical lifetime for power plants and factories, and can embrace several turnovers in vehicle fleets and new homes. This could allow their portfolio to be phased in with little if any economic disruption. They say their approach, which is global in scope, also buys researchers the time to develop and perfect some of the more esoteric sources of energy - such as nuclear fusion or space-based solar power - that emit no carbon as a byproduct. These and other advanced technologies would then help reduce industrial CO2 emissions, rather than merely lock them in at a fixed level.