It’s complicated


This is a photograph of my chicken-scratch handwriting on the whiteboard today in the climate course I’m teaching.  The students learned about present-day climate and how different components of the climate system interact with each other (ocean, atmosphere, cryosphere, biosphere, land cover), then we talked about deep-time climate changes, like when dinosaurs lived in New England.  And now, 5 weeks into the material, we are talking about the last ice age, 20,000 years ago, and how an initial cooling caused by a decrease in solar radiation reaching the high northern hemisphere latitudes in summer lead to a whole lot of feedbacks.  Ice sheets grew, increasing albedo (the reflectivity of earth), thus causing an additional cooling.  A cooler atmosphere is a drier atmosphere, which influences vegetation and biomes and thus more dust is in the air.  More dust then reaches the oceans to supply nutrients to phytoplankton that use CO2 and release O2, thus causing an additional cooling.  And so on and so on.  Photograph by BSW Jr.


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