Biogeophysical changes to the land surface

I’m generally (though not exclusively) interested in biogeophysical changes to the land surface. What does this mean? Well, there are two ways that the land surface can affect the climate. One is the biogeochemical, the other is biogeophysical. The difference is this:

Biogeochemical generally means changes in greenhouse gases (e.g. carbon dioxide, methane, nitrous oxide etc.) from the land surface. Biogeophysical generally mean albedo, surface roughness and evapotranspiration changes. But whereas biogeochemical changes at the land surface affect the energy balance via the atmospheric composition, the biogeophysical properties affect the energy balance directly.

So biogeophysical changes tend to be things like changes in albedo (the amount of light reflected away from the earth), the way that wind travels across the land surface or the amount of water which evaporates (see cartoon above). All these things change the amount of energy, and therefore heat, at the land surface.

What is so magic about it, to me, is that the effects are often very localised. The atmosphere is very well mixed (generally) and so if you emit carbon dioxide it just mixes all up. Changes to the biogeophysics tend to stick around in one place, so you can have small, local effects caused by changes in the land surface. This is interesting in an abstract way, but moreover, it’s interesting because that’s the scale that we live our lives on – local.