SINGAPORE — Extreme weather, from heat waves and drought to snowstorms and floods, is nothing new. The big question is what are the causes. Are they natural or man-made, or a combination of both?
If the causes are natural, there is not much we can do except prepare and recover as quickly as possible after disaster strikes. If human activity is the main cause, it should be possible to take remedial action, provided countries can agree how to apportion responsibility and share costs.
Recent advances in the study of tree rings in Asia confirm connections between climate change and the collapse of past civilizations. Teams of scientists from Japan and other countries spent more than 15 years traveling across the region to locate living trees old enough to provide long-term records. Prize finds included a Vietnamese cypress tree over 1,000 years old and a hemlock of similar age in the mountains of Nepal.