Outline Observations: · Scales assume a dominant role in communicating natural hazards to the media and society at large. · Confusion, misunderstanding, and sensationalism are often associated with Asteroid and Comet Impact Hazard Predictions. · The scales pertinent to Asteroid and Comet Impact Hazard Predictions are partially ineffective. Explanations: · The Torino Scale is flawed. · It provides no indication as to how the public should respond to an impact hazard prediction. · Competing Scales are reducing the effectiveness of the message. · References to the Torino Scale and the Palermo Scale are problematic, in that they are ignoring the two scales incompatibilities: they were devised for wholly different purposes and they yield results that are essentially incommensurable. Recommendations: · Couple the Torino Scale’s assessments with clear descriptions or recommended actions designed specifically for the general public. · Devise an IAU policy to encourage accuracy, consistency, and clarity in reports of impact predictions. Reviewing the Torino Scale; Critiquing the Critiques Communicating the risk that near-Earth objects (NEOs) pose to the general public presents a serious challenge to the astronomical community. The challenge stems, in part, from the unique character of the NEO hazard. The concept of asteroids and comets colliding with the Earth represents the most extreme example of a low probability, high consequence event - outside the domain of our common lived experience. The NEO hazard is highly prone to sensationalism, especially in the wake of two Hollywood blockbusters (Armageddon and Deep Impact) depicting havoc wreaked by earth- approaching celestial bodies. Finally, cosmic impact events differ from other hazards in that, in theory, impact dates that lie far in the future can be forecasted with great accuracy. This risk communication challenge was addressed by the Torino Scale, a simple hazard scale system devised to encourage “careful and responsible communication between astronomers and the public” (Binzel, 2000). Since its creation, the Torino Scale has since been criticized by numerous parties, many of whom have suggested modifications to the existing scale or new scales altogether. However, the Torino Scale’s detractors have all but ignored the scale’s raison d'être: “to place into context the level of public concern that is warranted for any close encounter event within the next century” (Binzel, 2000). To examine the success or merit of the Scale, we must do so in the context of its justification for existence. To deride the Torino Scale on the basis of supposed goals - projected by the critic(s) - is a non sequitur. This is not to say that the Torino Scale effectively realizes its purpose; it does not. Before we evaluate the Scale according to its stated goals and recommend improvements, let us review past criticisms and suggested alternatives to see where they have gone awry. William J. Cooke, suggests that the Torino Scale is “too coarse” to establish the risk threshold required to trigger an asteroid defense. This assertion is supported by the claim that the Torino Scale neglects the “attention span” of the average person (100 years). He proposes a risk number (RN) scheme and challenges others to establish RNdefense: a value that dictates when society should defend against an asteroid/comet, without which “an adequate mitigation means cannot be designed and developed” (Cooke). Cooke’s evaluation ignores the fact that the Torino Scale does include a time element: it is defined as being relevant only for the next century (100 years - precisely his quantification of a human “attention span”). His implicit acknowledgement that a hazard scale must motivate some form of human response is laudable, but his critique of the Torino Scale is unfounded. Joaquin Perez proposes that the Torino Scale “fails to satisfy minimal validity and simplicity criteria” (Perez, e-mail correspondence). He suggests that the Scale has technically flaws; most notably that a “very likely” (0.80 < P < 0.95) collision with an energy of one hundred million megatons is considered less threatening than a certain (P > 0.99) one megaton collision. Perez then submits modifications to reduce the Scale’s technical/mathematical weaknesses. His effort are valiant, but his suggestions fail to increase the simplicity and hence the public intelligibility of the Scale. The Torino Scale has “natural limitations” (Binzel, 2000) that, arguably, could be slightly improved with continual tweaking. However, this would only serve to cause confusion and undermine public confidence - counter to the scale’s intended purpose. Jonathan Tate recommends a refinement of the Torino Scale on the bases that the current scale has been little used and that “a single number carries no advantage if lengthy explanation is required”. These claims are false; the scale has been used in several appropriate instances since its development and as it continues to be used, public confidence in it will increase and the scale’s integer values will begin to be associated with their explanations. This is a well-established characteristic of risk communication; “the number of times that a risk communication is repeated has a positive effect on public belief in the information” (Mileti et al., 1991). Californians have learned to readily associate Richter Scale values of earthquake magnitudes with the “lengthy explanations” that support them. Tate further criticizes the Torino Scale because its hazard ratings are liable to change - asserting that this feature makes the Scale “of little value to the media or general public”. This feature is a part of other hazard indices such as the Saffir- Simpson Hurricane Scale that have been embraced by journalists and civilians alike. Tate also opposes any mention of “background hazard”, an element of the problem he deems irrelevant. How else is society to relate to an impact prediction and decide whether it warrants action or not? Society’s inaction as pertains to the background hazard represents an implicit judgement that we can all live with the background threat without taking exceptional measures. Informing the public that a potential impact rises significantly above the background is thus of great utility. Tate’s remedy to the aforementioned ills is a two-parameter matrix that labels each “event” with a “threat level” composed of an appropriate letter and number describing its probability and its consequence respectively. Noting that it is “advisable to have pre-agreed and templated (sic) actions ready for use”, Tate then offers a second 2-D matrix (the “action matrix”) that dictates an appropriate response based on an event’s “threat level” and the time to impact. Tate’s suggestions may have some merit, but in no way do they address the problems of underuse and inadequacy that he emphasizes. A pair of two-dimensional matrices are far too complex to serve as a tool of public communication and would certainly be of less utility than the Torino Scale. Another attempt to quantify the cosmic impact hazard, the Palermo Scale, was developed by an international team of researchers to “facilitate communication among astronomers”(Chesley et al., 2001). The authors carry out their task because the simplicity of the Torino Scale renders it “unsuited for use by specialists in characterizing large numbers of events and in prioritizing objects for observation and analysis” but admit that it is “a clear and very simple measure of the hazard posed by a potential collision” (Chesley et al., 2001). The authors note that the Palermo Scale is “not intended for public communication of impact risks” yet it has been cited by the media. A recent article posted on CNN.com referred to asteroid 2002 NT7 (detected on July 9 by the Lincoln Near Earth Asteroid Research Project) as “the first object to be given a positive value, of 0.06, on the Palermo scale of potential threat posed by asteroids” and makes no mention of the Torino Scale. A follow-up article stated that “NASA's Near Earth Object program gives the asteroid a rating of "0" on the Torino impact hazard scale — within a range of "events meriting careful monitoring," but not concern”, this time refraining from referencing the Palermo Scale. Reuters.com reported Tim Spahr (an astronomer at the Minor Planets Center of the Harvard-Smithsonian Center for Astrophysics) as saying, “We have a scale called the Palermo scale that takes into account size and possible impact velocity and comes up with a rating for an object." The article noted that “2002 NT7 is the first "positive" object on the scale system, meant to predict how much damage an asteroid would do if it just happened to hit”. The purpose of the Palermo Scale has been utterly misinterpreted by this report. Though the intentions of the creators of the Palermo Scale were clearly not to confuse or misinform the public, the presence of a second impact hazard scale has done just that. What is a lay audience to make of an asteroid that registers a zero on one scale and a positive, non-zero value on another? The Torino Scale’s Real Weakness The Partnership for Public Warning (PPW) recently published a report outlining several unanimous recommendations devised to improve the Homeland Security Advisory System (HSAS). One such recommendation stressed that the HSAS “be clear about the risks and the actions required to reduce the risks” (Partnership for Public Warning, 2002). Indeed, the natural hazards community has long acknowledged the relationship between warning systems and human response: “warnings are effective only if they are accurate and result in appropriate action” (Working Group on Natural Disaster Information Systems, Subcommittee on Natural Disaster Reduction, 2000). Joanne Nigg’s article, Risk Communication and Warning Systems cites three key components of a public warning message, one of which is that “people must be told what they can personally do to reduce their exposure to danger” (Nigg, 1995).