Finally, good news about global warming: It's possible to virtually choke off emissions of greenhouse gases that scientists say are heating up the planet without also breaking the bank.
That's the key message in a report released May 4 by the UN-backed Intergovernmental Panel on Climate Change (IPCC). The 38-page document, summarizing a larger tome of more than 1,000 pages, focuses on ways to curb greenhouse-gas emissions, mainly carbon dioxide, and on the economic effects that different approaches to cutting emissions could have.
Increased energy efficiency, wider use of renewable energy sources, shifts in land use and farming practices, and wider use of nuclear energy – among other measures – could substantially reduce the risk of feeling the worst effects of global warming outlined in two previous IPCC volumes released earlier this year.
To be sure, these mitigation efforts will come at a cost to economic growth. The biggest gains happen when the price of carbon hits $100 a ton, according to the authors, raising the cost of fossil fuels such as oil or coal. By some estimates, that would translate into US gasoline prices from $0.25 to $1 a gallon higher than today's.
But in the context of global economic activity, that cost is modest, according to the report. Under its most aggressive emissions-reduction scenario, still-robust economic growth rates would slow by an average of only 0.12 percent a year between now and 2030 – or by roughly 3 percent over the entire period.
This scenario would aim to hold the atmosphere's greenhouse-gas concentrations by year 2100 inside a range that would limit the long-term rise in global average temperatures to between 2 and 2.4 degrees Celsius (3.6 to 4.3 degrees Fahrenheit). Higher temperature ranges would generally come at a lower economic cost, but also could raise the risk of incurring some of the more dramatic effects of climate change, such as floods, droughts, heat waves, and sea-level rise. If greenhouse-gas concentrations are allowed to double their pre-industrial-era levels by the end of this century, that most likely would lead to an average temperature increase of 3 degrees C. (5.4 degrees F.).
To keep temperature increases at a minimum countries must begin to crack down on emissions quickly, the report says. Delays would lead to countries building "more emission-intensive" factories, power plants, and other infrastructure around the world, it says.
The report comes against a backdrop of greenhouse-gas emissions – mostly carbon dioxide – that have risen some 70 percent over the past 35 years, and could rise by up to 90 percent by 2030, according to Bert Metz, a senior researcher at the Netherlands Environmental Assessment Agency and one of the co-chairs for the group producing the new IPCC report.
The report lays out the potential to cut emissions in a wide variety of ways, including cleaner energy sources, tighter building standards, higher vehicle mileage standards, biofuels, and new farming techniques. These measures could substantially offset growth in carbon emissions "and even bring emissions below current levels," Dr. Metz says. "That is a significant potential."
The final wording in the IPCC summary resulted from a week of sometimes torturous talk in Bangkok among delegations from 105 countries.
From the White House's perspective, the results validate President Bush's reliance on new technologies to achieving his goal of reducing the country's carbon "intensity" by 18 percent by 2012. The Bush administration aims to limit the rate of carbon dioxide emissions per unit of growth in the nation's gross domestic product (GDP).
The report "really highlights the importance of deploying a portfolio of clean-energy technologies globally," said Harlan Watson, who headed the US delegation to this week's negotiations in Bangkok. "It's totally consistent with President Bush's approach to addressing climate change."
But others say the administration should find little solace in other aspects of the report. It places little value on carbon intensity as a benchmark for progress, since even a more efficient economy still pumps CO2 into the atmosphere – where it will stay for centuries.
"You can use an intensity number as long as your intensity decrease is bigger than your economic growth, because that would mean net reductions in emissions," says Jonathan Pershing, an economist with the World Resources Institute in Washington and a lead author of a chapter in the new report. But that is not the case with the current US approach. The economy is still pumping CO2 into the atmosphere. Indeed, carbon intensity in the industrialized world has been falling for some time, Dr. Metz adds, because of "business as usual" investments in energy efficiency. But CO2 emissions have still grown. In addition, many see a worrisome rise in emissions in developing countries – particularly China and India.
Moreover, Dr. Pershing continues, if a country is trying to set up an emissions-trading scheme for CO2 between businesses or industries – a widely discussed approach to capping emissions – using intensity targets instead of absolute cuts in emissions leads to a hopelessly complex system.
While voluntary approaches can lead to measurable cuts in emissions, they hold little hope for reductions beyond "business as usual," the IPCC report says.
The report is expected to add impetus to efforts in the US Congress to take more aggressive action against global warming. "The warnings could not be more alarming," said Rep. Edward Markey (D) of Massachusetts, who chairs the House Select Committee on Energy Independence and Global Warming. "But this report also gives much reason for hope. We know what we need to do to protect the planet.... With scientists, business, and the American people all supporting action, Congress needs to get on board with real solutions today."
The IPCC's smorgasbord of solutions also includes some that have the potential to set environmental groups at odds with each other. Already, several have criticized the report's inclusion of nuclear energy as a helpful technology in cutting carbon emissions, citing issues of safety and waste disposal.
Others see a significant role for it. "Countries that have the capacity to use nuclear power have an obligation to do so," says James Connaughton, who heads the White House Council on Environmental Quality.
Biofuels present another flash point, even among environmental groups. Several see strong climate and energy-security reasons for shifting from oil-based gasoline and diesel fuels to plant-based ethanol or biodiesel. But a statement from one coalition of largely environmental groups largely based in Europe, including the Global Forest Coalition, Biofuel Watch, and the Gaia Foundation, roundly condemns the IPCC's biofuels option as "a climate disaster in the making." Expanding the use of biofuels, they argue, could threaten rain forests as countries replace large tracts with plantations of biofuel crops, such as palms and soybeans.