Richard Betts and the 2 Degree Threshold

The climate skeptic and denier blogs have been awash with the blog comments left by Richard Betts on the skeptic site Bishop Hill. Betts is Head of Climate Impacts at the Met Office and one of the key contributors to the ground-breaking ‘4 Degrees and Beyond‘  conference held in Oxford in 2009 and the subsequent set of formal academic papers published by the Royal Society (see here).

I only occasionally frequent the skeptic blogs for the reason that they rarely manage to convey both sides of the argument. An intellectual prerequisite of any successful hedge fund manager is the ability to assimilate and assess an investment thesis from all angles: if your initial judgement is that a particular stock or bond is a ‘buy’, the first thing you do is go and read every piece of research that suggests it is a ‘sell’. To put it bluntly, if you invest your money with a portfolio manager who does not have this discipline as some part of their investment  process, you are a fool and deserve to lose your money.

Keeping this in mind, the blogosphere is rife with analysis by persons who not only don’t try to understand the merits of the opposing argument, but frequently don’t even bother reading them.

So what had me trawling through the comments on Bishop Hill (the original post can be found here, and Betts is active in the comments sections as well)? Well this attack on the concept of ‘dangerous’ climate change:

Most climate scientists do not subscribe to the 2 degrees “Dangerous Climate Change” meme (I know I don’t). “Dangerous” is a value judgement, and the relationship between any particular level of global mean temperature rise and impacts on society are fraught with uncertainties, including the nature of regional climate responses and the vulnerability/resilience of society. The most solid evidence for something with serious global implications that might happen at 2 degrees is the possible passing of a key threshold for the Greenland ice sheet, but even then that’s the lower limit and also would probably take centuries to take full effect.

Andrew Revkin, the New York Times opinion writer on all things environment and climate change in his Dot Earth column asked Betts to amplify his thoughts. Betts reply is worth reading in its entirety and can be found here. However, here are a couple of the most important passages:

The science suggests that, by and large, the risk of major negative impacts of climate change increases with higher levels of global warming. However, this in itself is not enough to define what level of warming is “dangerous,” especially since the projections of actual impacts for any level of warming are highly uncertain, and depend on further factors such as how quickly these levels are reached….., and what other changes are associated with them.

And then critically,

With such uncertainties, it’s all down to attitude to risk — “dangerous climate change” should be defined in the context of the level of risk that is considered acceptable. It’s a judgment call.

A deep dive into the comments in the original Bishop Hill post throws further light on what Betts actually means—and what he doesn’t mean. To a another commentator’s claim that Betts has admitted that the 2 degree meme is ‘in no way dangerous’, Betts has this to say:

 You are wrong, I didn’t say that. What I actually said was:

“While really bad things may happen at 2 degrees, they may very well not happen either – especially in the short term (there may be a committment to longer-term consequences such as ongoing sea level rise that future generations have to deal with, but imminent catastrophe affecting the current generation is far less certain than people make out. We just don’t know.”

He follows this with the following comments that comes close to encapsulating my own view of how climate change should be viewed: that is, through a prism of probabilities and outcomes. In Betts words:

As I think I’ve said before, it’s all down to attitude to risk. Uncertainty works both ways – large uncertainties mean there are risks at the bad end, including the possibility of low-probability, high-impact outcomes. Given that we don’t know what the risk is, but think it is non-zero, do we take action to reduce that risk? That’s a political decision not a scientific one, and will rely on judgement calls (like most complex decisions, political or otherwise). I’m just saying that having made that judgement call, the science should not then be skewed to support it, as this could then influence other important decisions in undesireable ways. The uncertainties are large and we have to recognise that, formulate policy accordingly and be sure that scientific evidence appropriate informs several different policy areas that may rely on it.

Where I think I disagree with him is in the idea that climate scientists can remain honest, neutral and detached brokers of impartial information, with politicians making all the judgment calls. The politicians are floundering with the complexities of climate change as things stand anyway. But that is a topic for another post.

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