CROPS OF THE FUTURE
Julian P. Sachs and Conor L. Myhrvold acknowledge in “A Shifting Band of Rain” that as the global rain band shifts its position northward, “some places are likely to benefit, but many others, we fear, will face dry times.” Then, as with many predictive models of coming climate change, they focus on the detrimental effects of the continuation of such change to human societies and thus seem to advocate a plan A of trying to slow or reverse it. Perhaps it is time to start thinking about plan B: dealing with the results of climate change proactively.

For example, by recognizing that the currently wet areas of the earth will eventually miss a good portion of the Intertropical Convergence Zone (ITCZ) rains they now receive, causing their wet climate crops such as coffee and bananas to no longer thrive, plan B would use this predictive model to encourage countries that will ultimately be within the ITCZ to finance more planting of such crops.
Allen Dart
Tucson, Ariz.

I AM A FORD, I AM A CHEVY
David Pogue is wrong when he writes in “Gadget Politics” [TechnoFiles] that fierce techno loyalty is a recent phenomenon. When I grew up in a small town in Iowa in the 1950s, there were two great lines of social division: Protestant versus Catholic and Chevy versus Ford. (Plymouth people were too weird to seriously consider.)
Bob Swanson
Pocatello, Idaho

COLD ATOMS
In “Demons, Entropy and the Quest for Absolute Zero,” Mark G. Raizen describes experiments in which a one-way laser gate reduces the volume of a gas, and thus lowers its entropy, without increasing its temperature. Raizen points out that the decrease in entropy can be explained by information considerations. Such an explanation is not necessary, however.  The construction of the lasers, the power they consume, and the rest of the experimental apparatus all account for a great increase in entropy. I thought that this increase in entropy must be taken into account, and it clearly offsets the drop in entropy he produced. Information flow is not needed to explain the entropy drop.
Michael Bookbinder
New Canaan, Conn.

RAIZEN REPLIES: I restricted the system of interest to a collection of atoms in a box interacting with a laser beam. We are interested only in the change of entropy caused by that interaction. This is commonly done in thermodynamics, and one does not need to take into account all the entropy that went into the production of the laser beam.

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