Wednesday, February 21, 2007

Legal theories of causation, hurricanes, and climate change (Part 1: But-for causation)

I'm going to apply the Dilbert Rule to the hurricane-global warming issue - that the only approach to a problem happens to be the only one you know. So let's take the legal approach to the question of the causal relationship of global warming and hurricanes, through a hypothetical:

A new-born baby in Mississippi was orphaned and injured in Hurricane Katrina. The court-appointed guardian decides to sue every corporation, entity, and individual she can reach for causing global warming and injuring her ward. What result?

Some preliminaries: first, I chose an orphaned newborn to dismiss the counter-argument that the victim actually benefits from the modern economy - no unclean hands here. Second, this isn't a full-scale legal analysis - in the real world, this lawsuit would face all kinds of procedural hurdles, some legit and some seized upon by judges looking for an excuse to push this judicial-career-consuming morass out of the courtroom. What I'm really focusing on is the causation.

The law requires two types of causation be satisfied before it will conclude that the defendant "caused" the injury to the plaintiff. First is the "cause-in-fact" requirement that global warming resulted in injury to the baby. This legal requirement can be simplified (in this case, anyway) to the "but-for" question. But for global warming, would the baby have not been orphaned and injured?

I'm now ready to finally say something halfway interesting, I hope: a judge could easily go beyond the current arguments about whether warming has intensified and find that anthropogenic global warming actually caused Hurricane Katrina. The way to determine this is with a thought experiment, imagining what the world would have been like without AGW.

Imagine some invention in 1850 had the incidental effect of absorbing all the excess carbon dioxide and methane we've produced since then. Would the baby have been injured in this thought experiment by Hurricane Katrina? Considering that Altantic hurricanes generally result from tropical waves, which themselves are the results of minor disturbances in African weather systems, and considering how different the no-warming world's weather would have been on a day-to-day level, it's nearly impossible to imagine that a hurricane like Katrina would have hit Mississippi at the same time in 2005 in the no-warming world. That world would have had hurricanes, but they would have been different hurricanes at different times taking different paths. But for global warming, Hurrican Katrina would not have happened.

This still leaves the second type of causation required in an injury claim like this one, called proximate cause or, confusingly, "legal causation". I'll save that for my next post.

More information on cause-in-fact is here.

Part 2 of this series is here.

Part 3 of this series is here.

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