BioEd Online

Bringing greenhouse gas emissions under control looks to be both achievable and affordable, on the basis of the most recent report of the Intergovernmental Panel on Climate Change (IPCC).

Today marks the end of an often fraught week of talks by the IPCC's Working Group III, which evaluates strategies to counter the rising levels of greenhouse emissions.

Their summary report¹, released in Bangkok, Thailand, says that stabilizing atmospheric greenhouse gases at a level likely to avoid the worst effects of global warming would cost no more than 3% of global economic productivity by 2030 — an average of 0.12% per year.

This is cheaper than many observers had expected it to be, and most see it as affordable; environmental groups represented on the panel, such as Greenpeace, have called it a small price to pay.

But US officials say that this would lead to a global recession, and argue that greenhouse levels should be stabilized at a higher level. "This report underscores the importance of a strong curve of emissions reductions," says James Connaughton, chair of the White House Council on Environmental Quality. "But no world leader will pursue a strategy that would lead to economic recession."

Counting the cost

The IPCC report, produced and approved by hundreds of scientists, engineers and government representatives, sets out a range of scenarios for bringing greenhouse gases into line. They focus on the stabilization of atmospheric gases at various concentrations.

It is widely agreed that to avoid the most dangerous effects of climate change, warming should be kept below 2 °C over today's temperatures. This probably means stabilizing greenhouse gases at between 450 and 550 parts per million (p.p.m.) of CO₂ equivalent. Currently they are at around 430 p.p.m. CO₂ equivalent and rising by 2 p.p.m. each year.

The report says that achieving stabilization at 535 p.p.m. CO₂ equivalent will require emissions cuts of between 50% and 85% by the middle of this century. Strategies to cut greenhouse emissions include targeted capping schemes such as the Kyoto Protocol, improved energy efficiency, and switches to alternative fuel sources such as nuclear and renewables.

Other, more modest scenarios laid out by the report will cost less. Stabilizing levels between 535 and 590 p.p.m. CO₂ equivalent will cost between 0.2% and 2.5% of global economic productivity by 2030, whereas allowing levels to stabilize at even higher concentrations could even bring economic benefits of as much as 0.6% of gross domestic product, through improved efficiency measures.