Anyone who's been to a movie theater filled with teenagers knows how hard it is to separate the movie dialogue from the chatter going on all around. This is a classic example of the difficulty in separating signal from background. We also encounter this problem when studying global warming. Climate is inherently variable, so how do we separate out natural variability from human causes? If we have a pretty good idea of normal climatic variability along with how human-produced factors would be expected to affect climate, we can subtract the extreme of normal variability from current conditions, and any difference likely is due to man's actions. When we are ignorant about normal variability, though, questions may become unanswerable.
It's tempting to blame global warming for recent geographic range
changes of animals in the northern Chihuahuan Desert. But, unfortunately, we have a
very poor handle both on natural variability of geographic ranges and how environmental
degradation by humans affect such ranges. The background not only obscures any signal;
it leaves us uncertain as to whether there even is a signal.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.