Thinking about this, there are at least two other good reasons to be careful about attributing events to manmade climate change:
- At some point, people are going to demand compensation for weather catastrophes due to climate change. Many, like U.S. farmers, will already be getting some compensation for the U.S. drought, regardless of its cause, and of course many on the east coast will (rightly) be getting government help to repair Sandy's damage. But, probably sooner than later, everyone is going to get into the act -- owners of ski resorts, oyster harvesters who see their beds affected by ocean acidification, coastal homeowners threatened by rising seas, India should their monsoon fail, and on and on and on. Such compensation will be especially important to the poor of the world, and since many activists wish to minimize climate change for their sake, being careful about attribution now will prevent smearing cause-and-effect into a meaningless smudge. If every storm is due to climate change, then all you have is a new climate state with everyone, in some sense, affected equally (or so some might argue.)
- Geoenginnering, when and if it occurs, will double this problem -- there will be those who say that a geoengineering scheme reduced their rainfall, altered their monsoon, dimmed their land. At the same time there will be demands from those seeking protection from manmade climate change. These future arguments will no doubt make today's arguments look like childhood squabbles, played out in courts, international bodies, and between countries with nasty weapons and large armies. So, again, being careful about cause-and-effect is crucial (and responsible).
If everything is due to climate change, then in a sense nothing is, because economics as currently understood has no way to price the cost of every weather event in existence.