Climate change is already contributing to sea-level rise and flooding. Droughts and storms are growing more intense. Ice caps are melting; snow cover is diminishing. And the ocean is becoming more acidic.
These changes threaten human food supplies, even as the global demand for food increases, and the problems can only be expected to worsen in the decades ahead, as will their ripple effects. A warmer planet with longer and more intense heat waves, for instance, doesn't just undermine farming. It also breeds disease.
That is the message the International Panel on Climate Change delivered in a report based on 12,000 scientific studies. The potential economic costs of these changes are staggering: The World Bank estimates it will cost $75 billion to $100 billion a year for adaptation measures in poor countries. And it is not difficult to imagine that the effects of climate change will contribute to greater levels of political instability around the world, as traditional forms of subsistence are undermined and battles over resources intensify.