Over the past half century, the powerful new science of climate and climate change has come into being. Research during that period has settled a fundamental climate question that had challenged scientists since the 19th century: Will human beings, by adding carbon dioxide and other heat-trapping gases to the atmosphere, significantly affect climate? The answer, debated for decades, is now known to be yes. Scientists now understand clearly that humankind is no longer a passive spectator at the great pageant of climate change. They have established that the climate is indeed warming and that human activities are the main cause.1 Every year brings thousands more research papers containing new knowledge of the many aspects of climate change.
Climate researchers know that the case for human-induced climate change has become stronger, more compelling, and increasingly urgent with each passing year. Yet in some countries, notably the US, the proportion of...
