Nevertheless, such pessimistic scenario calculations are not only allowed, but are strongly condoned, for instance by the IPCC (2001), which employs these types of pessimistic scenarios as a central part of its regular assessments. This is well justified, given the most important outcome of these scenario calculations: scientists learn, and they learn a lot about the behavior of the earth system. The key is ensuring that the results are reported to the public and policy-making sectors as clearly and responsibly as possible, which is part of the purpose of the intense IPCC review procedure. On the other side of the dichotomy, serious scientific research into geoengineering possibilities, such as discussed in the publications by Crutzen (2006) and Cicerone (2006), is not at all condoned by the overall climate and atmospheric chemistry research communities. Quite the contrary, according to Cicerone, “refereed publications that deal with such ideas are not numerous nor are they cited widely”. In the discussions that surrounded the drafting of Crutzen’s article, there was a passionate outcry by several prominent scientists claiming that it is irresponsible to publish such an article focused on a particular geoengineering proposal. Such critical responses to discussions on geoengineering have a long history, as discussed by Schneider (2001).
The Geoengineering Dilemma: To Speak or not to Speak
An intriguing dichotomy has developed within the field of atmospheric and climate research. On the one side, it has become common practice to examine pessimistic future scenarios of anthropogenic pollutant emissions and their environmental impacts. Not surprisingly, compared to the alternative “best guess” or “maximum feasible reduction” emissions scenarios, the pessimistic scenario simulations tend to predict large changes in the climate system and air quality. These scenarios can certainly attract attention to the possibly disastrous consequences of a careless environmental stewardship. However, they can also backfire politically, being seen as “unrealistic scare tactics” or “Hollywood horrors” put forth by scientists with environmentalist agendas. Furthermore, each simulation can only show one potential outcome among many possible states for a strongly perturbed climate. The predicted extreme outcomes of pessimistic scenarios will tend to vary widely from model to model. Unless this is communicated effectively, it can lead to confusion among policy makers, and can reduce confidence in such predictive studies.