Using a climate model that incorporates anthropogenic greenhouse gas emissions, scientists have recently concluded that the Earth is absorbing more energy than it emits. The energy imbalance, when compared to temperature measurements, indicates a lag in atmospheric warming.

• Hansen, James et al. "Earth's Energy Imbalance: Confirmation and Implications." Science 308(5727): 1431-1435 (3 June 2005). Science Express on 28 April 2005 at www.sciencemag.org.

The study's results are substantiated by ocean heat content measurements and surface air temperature records over the past decade. The authors suggest that even if we were to halt changes to atmospheric composition today, we should expect to see an increase in warming of 0.6 degrees Celsius in the future. This leads the authors to underscore the need for early action, given that ice melting and sea level rise will advance in years to come due to the climate system's inertia.

Implications: The energy imbalance and the lag in climate response cited in Hansen's study suggests there are signifi cant climate effects that will only reveal themselves with time. We are thus committed to considerable additional future warming from historic emissions -- but also, unless we cut emissions sharply, we will see considerable additional future effects. As a result of thermal inertia, delaying action is likely to amplify change in the future.