13 August 2010

Watching the Wiggles

I wrote the following last winter when there were big snowstorms hitting the US.
Let's see if I can make this simple.

What happens in the weather this week or next tells us absolutely nothing about the role of humans in influencing the climate system. It is unjustifiable to claim that a cold snap or heavy snow disproves or even casts doubts predictions of long-term climate change. It is equally unjustifiable to say that a cold snap or heavy snow in any way offers empirical support for predictions of long-term climate change. This goes for all weather events.

Further, it is professionally irresponsible for scientists to claim that some observed weather is "consistent with" long-term predictions of climate change. Any and all weather fits this criteria. Similarly, any and all weather is also "consistent with" failing predictions of long-term climate change. The "consistent with" canard is purposely misleading.

Knowledge of climate requires long-term records -- on the time scale of a decade and longer. Don't look to the weather to learn about climate, unless you have a long time to watch. Using the weather to score cheap political points in the climate debate appears to be a tactical area of agreement among those who otherwise disagree about climate change.
A climate scientist who I have a lot of respect for wrote me an email and asked the following (and expressed a preference not to be involved in a blog discussion of this, so will remain anonymous):
I am interested in how you would deal with a journalist asking for my reaction to the recent string of historically unprecedented heat waves (eg Europe 2003, Australia 2009, Russia 2010 - and there are many more of course).

As context, can I quote the IPCC SAR (1996): "A general warming is expected to lead to an increase in the occurrence of extremely hot days and a decrease in the occurrence of extremely cold days".

We have indeed seen an increase in the occurrence of extremely hot days and a decrease in the occurrence of extremely cold days, since that projection was published. So...if I point this out to a journalist, and also point out that this was projected by the IPCC 15 years ago, does this mean I have completely and utterly lost my senses? If so, why? How would you respond to the journalist?
Here is how I responded:
I wrote something about this when people on the other side were using the cold weather to make different statements, see this here:


Were I a scientist talking to the media I would deemphasize the efforts to relate weather events to a specific causality.  I would emphasize long term trends since the IPCC defines changes in climate to occur over 30 to 50 years.  And I would point out that the IPCC predictions, such as they are, have always been for the longer-term future rather than the present.

I would also emphasize the rather important point that no practical action hinges on debates over causality of specific events -- the case for aggressive mitigation does not rest on such claims (despite what some scientists claim in public) and the need for adaptation has already been well established.  It is a practically meaningless debate.

I talked to a reporter yesterday and made this analogy:

Suppose that I predict that the price of copper will be $100,000 per tonne in 2050. Suppose further that I watch the daily spot market. Would it make sense to claim that every day (week etc.) of gains in price is "consistent with" and proves my prediction?  Would it make sense to argue that every day of losses in price is "not inconsistent with" my prediction?  Or would it make sense to say that such wiggle watching is not a productive use of my time if the goal is to invest productively?  You know my preference;-)

The scientific community in my view loses credibility when it tells the public in the winter that "weather is not climate" but then in the summer forgets that admonition.
If scientists want to argue the case for mitigation and adaptation to climate change they should!  But in such advocacy the scientific community should avoid making claims about causality of specific events that cannot be judged empirically, have no practical significance and serve only to add political intensity to a field that has seen more than its fair share of waging a political battle through science.