Many people fear that human activity is changing the climate in ways that will prove catastrophic. Others hold that fear to be overblown or entirely mistaken. Some even claim that because of the rising concentration of atmospheric carbon dioxide, the world is becoming a better, more productive place. For example, because of fertilization by carbon dioxide, crop yields are rising, while because of the gentle carbon dioxide-induced warming of the planet, crop lands are extending Northward, while rainfall is increasing in the dry lands to the South of the Sahara. As a result, starvation in the poorest parts of the world is being held at bay.
The disagreement about climate change has long been intense, and positions have become deeply entrenched. The scientific debate has become rancorous. Scientists have been accused of data manipulation and fraud. Scientists have sued one another for libel. And a leading scientist recently quit the climate science field because of its "craziness."
In the public domain, the debate has become highly politicized. Former US President, Barack Obama, has claimed that climate change "is a threat that may define the contours of this century more than any other" (Whatever exactly the contours of a century may be.). Former US Vice President Al Gore has likened denial of climate change to racism. NASA's former top climate scientist and Director of the Goddard Institute for Space Studies, James Hansen, has been arrested repeatedly as a participant in protests against pipeline development, tar sands development, and coal mining.