Comment on “Climate control requires a dam at the Strait of Gibraltar”

While we appreciate the editor's desire to publish contributions of general scientific interest, societal relevance, and controversial nature, Eos should not sacrifice scientific rigor to achieve this. Publication of "Climate Control Requires a Dam at the Strait of Gibraltar" by R. G. Johnson ( Eos , July 8,1997) was irresponsible. The connection between Mediterranean salinity and ice age initiation is only postulated but not substantiated through quantitative reasoning supported by data. Climate is complex because many competing feedbacks act simultaneously. Even if every single one of the hypothesized mechanisms were correct, there would always be competing effects, so quantitative analysis is needed to determine the net response. For example, it is hypothesized that a warming of the Labrador Sea would lead to additional land ice formation, but one could argue equally well that the extra ice would simply melt because the surroundings were warmer. Some of the postulated mechanisms are blatantly inconsistent with what is known about fluid mechanics (e.g., the existence of the “fluidic switch,” through which, apparently, a tiny current can deflect a large one) or about climate dynamics (if global warming could indeed lead to an ice age, i.e., global cooling, current climate would be unstable).