If humans heated the earth, perhaps our technology can cool it, too. A look at the science of geoengineering and how it might be used to address global warming.
Shrinking glaciers mean longer hikes to water flocks
Why some say travelers should think twice before boarding.
Is this trip necessary? A jet lands in Montreal. Proponents of air travel tout its importance to the global economy. Detractors say per-passenger emissions carry too high a cost.