One of the aspects of science communications that can frustrate even its most sophisticated practitioners is the ability of scientists to reach confident conclusions about the big picture even when a field retains significant uncertainties. You can look no further than dark matter for an example: researchers are pretty confident that it's out there, even though we still haven't identified what it might consist of. But climatology remains the field where uncertainties, both real and imagined, are most likely to become front page news. The journal Nature has devoted a series of articles to discussing why that's likely to be the case.

The editorial staff assigned one of their senior reporters to identifying the areas of most significant uncertainty when it comes to climatology and, as that reporter noted, the primary challenge is whittling things down: the most recent IPCC report identified 54 items that it termed "key uncertainties." Contrary to some accusations, this suggests that the areas where climate science needs some work haven't exactly been swept under the rug by the scientific community. But, at the same time, scientists have clearly looked at these uncertainties and decided that they're not so significant that the basics of climate change are questionable.

One of these areas is actually a relatively well known controversy: millennial-scale reconstructions—the famed hockey stick, which shows that temperatures have risen dramatically in the past century. Anybody who has paid careful attention to the "hide the decline" e-mails knows that tree ring indicators of past temperatures have tracked the instrument record until the 1960's, after which subarctic trees diverge.

In this case, there's even uncertainty about the significance of the uncertainty. As the article notes, some argue that we shouldn't put much weight on any tree ring data until we can understand the cause of the divergence. Others suggest that the presence of a hockey stick in non-arboreal data and the continued high temperatures (NASA data places 2009 as the second warmest year on record) mean that the general conclusions are solid.

Two of the other areas identified by Nature are critical to our ability to adapt to the changing climate: fine-grained regional forecasts of just how the climate will be altered, and information on changes in precipitation trends. We've covered the issues with regional forecasts before; suffice it to say that we still can't get great information on what to expect in many key regions of the globe. When it comes to precipitation, all the models show areas of increased and decreased precipitation, but they disagree on which areas gain and lose. More worrisome still, the trends in precipitation we're already seeing are larger than those predicted. Like regional changes, this is the sort of information policy makers need for long-term planning, and we're simply not at the point where scientists are able to provide it.

It may surprise some people that there's only one uncertainty that may actually influence the trajectory of future climates: the impact of particulates. These include things like black soot, which absorbs sunlight to warm the air while there and increases the albedo when it comes back to earth. Sulfate particles also efficiently scatter light and form clouds. The problem here is that we simply don't have a good grip on what's up in the atmosphere now, which means we can't extrapolate any trends. Meanwhile, some scientists have argued that various aerosol particles have slowed down the impact of greenhouse gas emissions through "global dimming"; others suggest that they're a negative feedback that will significantly reduce the climate sensitivity.

Managing uncertainty

But the journal does more than identify the uncertainties; it offers a prescription for identifying and communicating them. The route to management, in the view of one author, is the use of a technique called the Cooke method, named after its developer, Roger Cooke. The basic idea is that, for a risk analysis of an area of significant certainty, you poll a panel of experts, and ask them for their predictions and degree of uncertainty about the topic at hand. But you also ask them questions about related topics with known answers, and use the accuracy of their response to these questions to provide a weight factor that's used to adjust their answer to the unknown.

In the author's opinion, this helps limit the impact of an unfortunate reality: the tendency of those with the least expertise to speak with the greatest confidence. He noted that the Intergovernmental Panel on Climate Change is actually considering using this method for considering low-probability, high-risk events like the collapse of the Greenland ice sheet.

The other problem addressed is the issue of how to deal with the fact that the public as a whole has little sense of the scientific community's confidence in the general outlines of climate change. This, according to someone who studies the topic, is a product of what's called "cultural cognition." The gist of this concept is that the public doesn't always evaluate scientific ideas based on the data or reasoning; instead, they often chose a position based on what they believe would be acceptable to the cultural groups that they belong to.

It's probably safest to let the author's own words describe the phenomenon: "People with individualistic values, who prize personal initiative, and those with hierarchical values, who respect authority, tend to dismiss evidence of environmental risks, because the widespread acceptance of such evidence would lead to restrictions on commerce and industry, activities they admire. By contrast, people who subscribe to more egalitarian and communitarian values are suspicious of commerce and industry, which they see as sources of unjust disparity."

Either of these tendencies can potentially swamp the individual's ability to both evaluate evidence and its implications. So, for example, someone on the liberal end of the spectrum might accept the evidence for climate change, but then turn around and oppose the construction of nuclear plants or powerlines and solar facilities in protected deserts. The flipside is the conservative/libertarian response to the science of climate change itself.

What's to be done? The simplest solution, it's argued, is to have a diversity of science communicators; simply hoping the evidence will eventually overwhelm unjustified skepticism hasn't panned out for science. Instead, what's needed are communicators who can establish a shared cultural understanding with the audiences they're reaching. This won't guarantee that the audience will then reach the same conclusions as the scientists, but the author argues that it can get them to at least evaluate the data.

Nature, 2010. DOIs: 10.1038/463284a, 10.1038/463269a, 10.1038/463294a, 10.1038/463296a