Let’s distinguish the following main issues:
- To what extent is climate change occurring, and to what extent is it man-made?
- To what extent is that (going to be) a problem?
- What can or should we do about it?
The first questions are strictly scientific; the middle has a judgment value to it, and the latter is primarily a political/moral judgement (and has more to do with technology than with climate science).
We have made much more progress in addressing the first question than in addressing the last one. The limiting factor in addressing the issues relating to climate change is not a lack of knowledge about the exact nature of the changes; rather, it is the unwillingness of society to deal with (the consequences of) this knowledge. Even if climate change is less bad than currently expected, we need to dramatically step up our policy response.
I don’t say this to downplay the uncertainties in climate science; there are many, and many of them are large (scientifically speaking). However, within realistic boundaries of the uncertainty, we still don’t do enough to deal with the issue: Any realistic change in our scientific understanding is not going to change the needed policy response, at least not in the short to medium term (~decades). As Herman Daly noted: “If you jump out of an airplane you need a crude parachute more than an accurate altimeter.” And Tom Yulsman: “With a bit of luck, maybe we can agree that regardless of [the details regarding] climate change, we need an Apollo-scale effort to develop transformational energy technologies.” How to shape that effort is the next generation question.
So the ‘next generation questions’ in my view relate to the last one: How are we going to deal with this? There are a lot of tough questions to be answered in that arena, e.g. relating to different technologies (nuclear, biomass, CCS, electric vs hydrogen transport, geoengineering, to name just a few highly contested topics), and relating to more institutional-political matters (e.g. carbon tax vs cap and trade, landuse, changes in consumption patterns, equity issues). Michael Tobis has some excellent writing on the latter topics.
Regarding the ‘next generation of questions’ strictly relating to climate science, some examples of important areas with high uncertainty are the following:
- Regional climate effects
- Climate sensitivity
- The role of aerosol and clouds
- Sea level rise (update: added after Heiko’s suggestion)
However, we need to keep in mind that uncertainty goes both ways, and that science usually progresses with small increments: Three steps forward, two steps back. It is wise to be very skeptical of any claim that the science is radically wrong. Any new piece of evidence just adds to the puzzle; it doesn’t replace existing evidence. Context and perspective are key, and they are often missing in loud proclamations against the consensus.
Let me give an example from an area of research that I’ve been working in for a number of years: Aerosol formation. For at least a decade, sulfuric acid has been regarded a key compound in the formation aerosol particles. The potential contribution of other compounds (ammonia, iodine, ions, organics) has been (and still is) hotly debated, but if someone tries to tell me that sulfuric acid has no noticeable effect on aerosol nucleation, I would not tend to take them very seriously, unless they have extraordinary evidence to back up that (scientifically radical) position. Nothing is impossible, but it’s not very likely.
I think we know a great deal more about the role of CO2 in the climate system than we do about the role of sulfuric acid in aerosol nucleation. I don’t expect a landslide change in scientific thinking on the subject. If someone does, they better bring very strong evidence to the table; a photograph or two won’t do.
(update: the next post elaborates on the major climate science uncertainties)