Topic : abrupt climate change

1. Interpreting Climatic Catastrophe: Media vs. Sciencescience as interpreted through the mediaor, why scientists are afraid of reportersDon BarberGeology DepartmentScience in Society Brownbag DiscussionFall 2004: “Science’s Audiences”

2. Topic: abrupt climate change • Science representatives: paleoclimatologists, computer modelers, oceanographers and meteorologists • Audience: the non-specialist, but “informed” lay public, from students to politicians. • Medium: print and broadcast media– newspapers, web and television.

3. The story (message from science) Feedbacks and thresholds in Earth’s climate system imply that our ride into the greenhouse-warmed world may be bumpy. “Bumps” (rapid warming/cooling, rapid aridification/excess moisture) are of more concern to society than gradual change.

4. Climate Science’s message and motivation (1) Many facets of global warming are uncertain: temperatures, sea level rise, storminess. Some changes will be easy to take in stride. Adaptability is a human hallmark. However, we’re nearing global carrying capacity (e.g., food production). And populations continue to grow. Fossil fuels will run out. We’ll have to change energy use patterns, regardless of climate change. Society’s adaptability is compromised.

5. Climate Science’s message and motivation (2) Adaptation to abrupt change is more difficult than adjusting to gradual change. (Although as Catherine points out, abrupt changes do tend to catalyze action, whereas gradual change allows for complacency and inaction). Available science: much uncertainty, but probability of abrupt climate change is not zero* [see next 2 slides]. Precautionary principle says, in this case, hedge bets: at least make plans, or even make preparations now so as not to suffer so much IF abrupt change occurs.

6. What is the probability of abrupt climate change? *Tough to say. The National Research Council report, Abrupt climate change: Inevitable surprises, 2002, Nat’l Academy Press, Washington, DC., 230 pp., said: “Current practices in the development and use of statistics related to climate and climate-related variables generally assume a simple, unchanging distribution of outcomes. This assumption leads to serious underestimation of the likelihood of extreme events. Many decisions [currently] are based on statistical calculations that are appropriate for stationary climates, such as the use of 30-year normals. … However, in light of recent findings related to nonstationary and often highly skewed climate-related variables, current practices can be misleading.”

7. ** Another oft-repeated statement is that climate scientists see nothing in the system that forbids, for example, the shut-down of North Atlantic Deep Water formation. This type of abrupt change in ocean circulation would cause downwind cooling of the UK, Europe and Scandinavia (of uncertain magnitude). This sort of change in ocean circulation is presently one of the explanations for past episodes of abrupt northern hemisphere cooling due to altered freshwater balance of the Atlantic. We anticipate changes to the hydrologic cycle due to global warming, and thus a similar change in ocean circulation might occur. The fact that we don’t see anything forbidding that sort of change, leads us to say that it COULD happen. That is, the probability of such a change is not zero. Yes, this is not very satisfying. But that’s about where it stands.

8. Audience traits: generalizations concerning perceptions and acceptance; these apply for many natural hazards • Individual are prisoners of their own experience: “the climate seems fine to me.” • Small probabilities & small anticipated personal impacts are not concerns. If low probability, might be “random.” If random, might be “act of God.” Leads to inaction. • Hierarchy and prioritization of worries. Climate change low on list of “things to worry about.” • Dissonant risk perception: denial of any threat.

9. Audience reactions: Information overload --> lecturing doesn’t work; dialogue seems to work better. Given short attention, spans, it is difficult to convey the issues adequately. Issues easier to understand if key points (why it matters, or why you might care) and points of disagreement are emphasized. To garner interest, media emphasizes extremes, and tries to find alternate views, even if they are on fringe.

10. Example of the range of media coverage on this topic, based on press briefing held at the Amsterdam global change conference (2001) Briefing title: "Beyond global warming: critical thresholds and abrupt changes." The press met with climate scientists including Stefan Rahmstorf, from whose website this example is taken. (http://www.pik-potsdam.de/%7Estefan/Media/amsterdam.html) What panelists said: “Past climate change has often taken the form of abrupt, non-linear change rather than slow and gradual development. There is a risk that such non-linear changes might occur in the future if anthropogenic warming goes beyond certain limits, which cannot be quantified at this stage.”

11. A relatively balanced account was given e.g. in a release by Reuters written by Matt Daily.  As reported correctly, Rahmstorf listed several "low probability, high impact'' scenarios that could cause sharp changes in the earth's climate, including the melting of the West Antarctic ice sheet, the death of tropical forests, shifts in monsoon circulation and changes in ocean currents. "Nobody believes these things are highly probable,'' he said. ''But we do need to be conscious of them when making climate policy. We need to take into account the risks of accidents or surprises.''

12. A journalist at the briefing asked whether there was any indication that ocean currents in the Atlantic were already changing. Rahmstorf replied that until recently in his estimation there was none, but that a paper by oceanographers from the Faroe Islands, Britain and Norway had just been published (Hansen et al., Nature Vol. 411, pp. 927-930) which argued that there had been a weakening of the flow through the Faroe Bank Channel by 20% over the past 50 years. Rahmstorf made it clear that this was only the flow through one channel and the evidence for the weakening was indirect, based on theoretical (though plausible) calculations from temperature and salinity data, since no direct current measurements were available going far enough back in time to observe long-term trends.

13. What some media made of it The moderate Reuters account, sank with little trace - hardly anybody thought it was worth reporting. But a week later, Fred Pearce in New Scientist presented a pepped-up version under the headline: "Most predictions on global warming are probably wrong" starting out with: "WITHIN a century, Europe could be in the grip of a big freeze." The article says: Rahmstorf predicts that as the world warms in coming decades, this"deep-water formation" will rapidly decline as less ice forms and more fresh water flows into the Arctic from rivers. "Until three weeks ago I would have had to admit that this was a purely theoretical calculation,” he says. “But now we have received data showing that the current has decreased by 20% since 1950.”

14. What's wrong with that? Rahmstorf was not predicting anything, he was talking about risks that have a low probability of occurring. In the media briefing he made the comparison with an airplane trip with a probability of 1% that it will crash. Clearly, somebody who points out such a probability is not predicting that the plane will crash. On the other hand, passengers might find this information relevant to their decision whether to board the plane, and in the same way, the risk of non-linear responses of the climate system is relevant to discussions of a precautionary approach to climate policy.

15. The journalist invented the supposed direct quote. It was neither said, nor authorized by Rahmstorf. Besides the fact that this is not good journalistic practice, the quote is incorrect in several ways. Rahmstorf did not say "we have received data", he simply pointed out that a paper was published by other scientists. The quote makes something sound very definite ("showing that it has decreased") when there is only the first indirect evidence that it might have decreased. All the articles made it appear as if the current concerned is the North Atlantic Current; in fact we were discussing the deep flow through Faroe Bank Channel. This is only one of three main return flows connected to the North Atlantic Current, so any conclusions about the latter are rather speculative.

16. No climate model has ever- simulated a cooling of Europe within this century. Even the worst case scenario, which Rahmstorf published in a model sensitivity study (Climatic Change, 43, 353-367) , shows a cooling only after the year 2100. The media thus prove to be even more non-linear than the climate system, amplifying and distorting a reasoned and sensible discussion at a scientific conference into dramatic headline news.

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