These are challenging times for climate scientists. There is widespread disagreement about the cause and meaning — and extent — of global warming: They thought the polar icecaps were melting, but now it seems that this may be within the bounds of normal variation. There is unexplained methane in the atmosphere, and no one is sure where it comes from — except that they are nearly certain that human industrial and agricultural activities are not the source. The changes may not be global at all but merely regional.
The above questions are all the more difficult to answer satisfactorily because of our limited ability to engage in direct observation and the relative scarcity of the relevant instrumentation . . . on Mars.
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