And while the US appeared to soften its stand as the week progressed, officials involved in talks on the issue suggest that plenty of tough bargaining still lies ahead. Kyoto is about additional efforts. Yet the protocols clearly permit the use of sinks, a senior US official here says, and they permit countries to claim credit for forest, crop, and range land that already exists. The official adds that the US made it clear when the ribbon was being tied on the protocols at Kyoto that if the US wasn't allowed to take credit for sinks that already existed, the US couldn't sign the agreement. In the end, he says, when it comes to reducing carbon, the atmosphere doesn't care where or what actions are taken.
Researchers acknowledge the point.
Writing in Climate Policy, a new journal devoted to climate-change issues, they add that the challenges come in trying to set up a system to govern the use of sinks to meet targets. The uncertainty is huge. One of those uncertainties involves trying to distinguish between natural variations in the carbon uptake of plants in a plot and those that occur because of human intervention. In an attempt to help define natural changes, French climatologist Philippe Bousquet led a team that used atmospheric measurements and computer simulations to track changes in carbon exchanges among the forests, oceans, and the atmosphere during the 1980s and 1990s. In a study published in today's issue of the journal Science, they found that, globally, CO2 exchanges over land can change dramatically several times over a decade.