Abstract
Climate change is an epic threat. Concentrations of greenhouse gases in the atmosphere are higher than at any time in human history and rising sharply. Predicted consequences include sea-level rise, more severe storms, more intense droughts and floods, forest loss and the spread of tropical disease. Each of these phenomena is already occurring. Every year of delay in reducing greenhouse gas emissions puts the planet at greater risk.
The United States and China play central roles in global warming. During the past century, the United States emitted more greenhouse gases than any other country-a fact often noted, since carbon dioxide, the leading greenhouse gas, remains in the atmosphere for roughly 100 years. However, in 2007, China may have surpassed the United States as the world’s top annual emitter of carbon dioxide.1 Together the two countries are responsible for over 40% of the greenhouse gases released into the atmosphere each year.
