Isaac Held's Blog

Animation of horizontally homogeneous non-rotating radiative-convective equilibrium courtesy of Caroline Muller.  The model is SAM (System for Atmospheric Modeling) the principal architect of which is Marat Khairoutdinov.  Transparent shading is condensate concentration; colors on the surface indicate near-surface air temperature.  See text for further description.

The starting point for most of my thinking regarding climate sensitivity is the simple 1-dimensional radiative-convective model introduced by Suki Manabe and Dick Wetherald in 1967.  See also Manabe and Strickler, 1964.  For an early review of this kind of modeling, see Ramanathan and Coakley, 1978. Sadly, Dick Wetherald passed away very recently; although it is a very small gesture, I would like to dedicate this post to his memory.

18. Noise, TOA fluxes and climate sensitivity

A model configuration used to study how temperature variations in the equatorial Pacific force temperature variations in other ocean basins and the land. Figure courtesy of Gabriel Lau.

Consider a simple energy balance model for the oceanic mixed layer (+ land + atmosphere) with temperature $T$ and effective heat capacity $c$.  The net downward energy flux at the top-of-atmosphere $R$ is assumed to consist of a radiative relaxation, $- \beta T$, plus some noise, $N$.  With imposed flux from the deep ocean to the mixed layer, $S$:

$c \frac{dT}{dt} = R + S = -\beta T + N + S$

The assumption is that there is no external radiative forcing due to volcanoes or increasing CO2, etc. Can we use a simple one-box model like this to connect observations of interannual variability in $R$ and $T$ to climate sensitivity?