The discovery of ETI as a high-consequence, low-probability event

The authors use the opportunity of presenting a paper during the 51st International Astronautical Congress in Rio de Janeiro to introduce a numerical method of characterizing the potential significance of any announcement of discovery of extraterrestrial intelligence. This approach uses the Torino Scale (for characterizing asteroid impacts) as a model for constructing a proposed "Rio Scale" to assist the discussion and interpretation of any claimed discovery of ETI.