UNITED NATIONS -- The world's leading climate change research organization issued a report yesterday that has renewable energy boosters cheering, as it foresees substantial growth in alternative energy sources over the next 40 years.

But the conclusions reached by that report's authors are colored with multiple caveats and uncertainties not captured by initial media coverage. And what the group chooses to identify as "renewable energy" incorporates one controversial practice while leaving others out.

Namely, the coalition of climate scientists includes traditional wood-burning in poor households' cookstoves as an example of renewable energy, though many experts say this is one of the leading causes of deforestation in the world. The IPCC also chose to ignore nuclear energy in its latest assessment, potentially raising the ire of industry supporters who have in the past celebrated nuclear for emitting no greenhouse gases.

At the close of a gathering of government representatives in Abu Dhabi, United Arab Emirates, the Intergovernmental Panel on Climate Change (IPCC) released its first-ever detailed analysis of alternative energy technologies and their potential role in mitigating greenhouse gas emissions.

The "Special Report on Renewable Energy Sources and Climate Change Mitigation" by the IPCC's Working Group III is 1,000 pages of detailed analysis of how renewable energy usage can expand to 2050, summed up in a heavily distributed 26-page "Summary for Policymakers," a draft of which was leaked to the press early.

Among the IPCC's biggest findings mentioned is its estimate that renewable energy could provide nearly 80 percent of the globe's power by 2050, if fully supported by governments eager to maximize its potential.

That conclusion took many by surprise -- most other comprehensive assessments offered by the energy industry itself conclude that alternative sources will contribute a much lower percentage of the world's power over the coming decades. But the 80 percent contribution estimated by the IPCC represents the most optimistic outcome, one that report authors say is one that's far from certain or 100 percent accurate.

What happens to the forests?

The IPCC is careful to note that this estimate is at the very highest end of a range of scenarios that could play out. Of more than 100 alternative future scenarios, the IPCC narrowed these down to four primary ones, each dependent on how quickly renewable energy technologies and advance and how robustly government policies support their deployment.

Still, the average of all IPCC projections shows renewables supplanting fossil fuels at a faster clip than previously thought.

"More than half of the scenarios show a contribution from RE [renewable energy] in excess of a 17 percent share of primary energy supply in 2030, rising to more than 27 percent in 2050," the IPCC says in the report summary. "The scenarios with the highest RE shares reach approximately 43 percent in 2030 and 77 percent in 2050."

Alternative energy supporters the world over were quick to hail the findings.

In the United States, the American Wind Energy Association, National Hydropower Association, Geothermal Energy Association and Biomass Power Association issued a joint release celebrating the results. They declared that the report shows the heralded IPCC agrees with what they've been saying all along, that "with the right policies to support growth, renewable power sources could dominate the world's energy supply by 2050."

But one complicating factor potentially cancels out much of the optimism espoused yesterday.

The IPCC reaches its estimates by counting among renewable energy sources "traditional biomass" -- the widespread practice in the developing world of scavenging wood for producing charcoal or to burn directly for home heating and cooking.

The U.N.-sponsored body also includes solar photovoltaic, wind power, geothermal and ocean wave technologies as among the renewable sources. But the bulk of the estimated contribution of renewables to global energy supply in its future scenarios is achieved by estimating the energy derived from traditional biomass, according to the "Summary for Policymakers" and charts published by IPCC.

Primitive vs. modern practices
The latest IPCC report estimates that in 2008, the renewable energy sources under their review contributed 12.9 percent of the world's main energy supply, measured in a thermal energy output unit called an exajoule. Half of that is from traditional biomass, the IPCC admits, and the group offers little justification for including this most primitive source of energy in its calculations.

IPCC researchers say their estimates show traditional biomass usage shrinking over time, to be gradually placed by more modern biomass generation, whereby trees felled are actually replanted. But charts showing the possible scenarios of the growth of renewables' share of energy still show biomass as the top source, even out to 2050.

The IPCC's blending of charcoal production with modern practices like biomass cogeneration on farms or wood waste burning near cities makes it difficult to determine how much traditional practices are to be replaced by more modern ones. But the IPCC admits that traditional biomass's share is larger, and the report suggests that its consumption will only fall slightly over the coming decades while modern biomass's share expands gradually.

"The number of people without access to modern energy services is expected to remain unchanged unless relevant domestic policies are implemented," IPCC officials explain.

Still, the group largely defends its future estimates. Although the other renewable technologies each separately represent a much smaller proportion of sources today as compared to traditional biomass, the scenarios laid out by the IPCC's calculations predict a threefold increase in their contribution by 2050 on the low end, and a tenfold expansion in its most optimistic outlook.

Experts say traditional biomass is likely the world's largest source of primary energy, due to widespread poverty in the developing world and the fact that nearly one-fourth of the world's population lacks regular access to electricity, according to the International Energy Agency. But the use of charcoal and felled trees and bushes for cooking food or heat is not celebrated by most environmentalists.

Indoor pollution hazards
The U.N. Environment Programme calls traditional biomass one of the most inefficiently used sources of energy in the world, and several U.N. agencies have been battling the negative health effects of indoor wood burning for years.

"Traditional use of biomass, especially charcoal, is often linked to degradation of forests and woodland resources as well as soil erosion," UNEP experts say in an earlier assessment of biomass's role in climate change mitigation. "Studies have shown that the inefficient use of bioenergy results in significant exposure to indoor air pollution. Women, children and the elderly face higher risks due to long hours spent around solid fuel based fires."

The Belgium based nonprofit Alliance for Rural Electrification estimates that traditional biomass is the main source of fuel for close to 2.4 billion in the developing world, but argues against its use, as "such traditional use of biomass fuels is typically inefficient, relying largely on low-cost sources such as forests and other natural vegetation," it says.

A 2006 study of biomass burning in India and Bangladesh by the Institute for Global Environmental Studies concluded that the practice was a top source of indoor air pollution and a major health problem.

IPCC scientists seem to acknowledge the complicated picture posed by traditional biomass, telling policymakers that its use can either increase or decrease "terrestrial carbon stocks," depending on how sustainable the practice is. To mitigate the negative impacts of traditional biomass, the IPCC recommends that governments careful consider their land-use policies and choices of feedstock that are involved.

The IPCC's latest report issued is its first since its fourth assessment report was issued in 2007. On the group's website, the Working Group III's co-chairman, Ottmar Edenhofer, says its fifth landmark report will be published in 2014 and will borrow heavily from the analysis distributed to governments yesterday.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500