kilometres and killed 435 million cubic metres of trees in British Columbia, Canada, since 2004.

Regionally, these events have had large socio-economic and ecological impacts. The windstorms that hit Europe in 1999, for example, destroyed one-third of the region's annual carbon sequestration4 by forests, and halved the price of timber in France and other affected countries. But such events are insignificant over decades and at the global scale. The Pacific El Niño and La Niña climate oscillations — primarily the tropical forest and peatland fires associated with them — are the only regional disturbances evident in globally averaged atmospheric CO 2 records5.

At the same time, atmospheric records and forest inventories show that forests have been taking up ever more CO 2 in the past 50 years1. Experimental and modellingSecretary of State John Kerry and Obama administration officials are meeting with major companies on Monday to launch the American Business Act on Climate Pledge, the White House announced. The pledge asks the companies to set goals to make substantial progress toward reducing their impact on climate change.

Thirteen corporations are taking part in the pledge so far: Alcoa, Apple, Bank of America, Berkshire Hathaway Energy, Cargill, Coca-Cola, General Motors, Goldman Sachs, Google, Microsoft, PepsiCo, UPS, and Wal-Mart. The companies pledge to invest a combined $140 billion to reduce their environmental impact and generate more than 1,600 megawatts of new renewable energy.

“No corner of the planet and no sector of the global economy will remain unaffected by climate change in the years ahead,” the White House said in a