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Another climate model paper in Nature misses a whole class of feedbacks

Posted By Jo Nova On May 27, 2016 @ 1:28 am In Global Warming | Comments Disabled

It’s always the same.  A new paper adds one more magical fine-tuning-cog to the models and promises “more accurate predictions”. There are a million small cogs we can add and it takes years to show they don’t deliver. These wheels can spin forever. The real climate machine has a whole extra exhaust pipe to which the models are blind.

 Why some climate processes are more effective at warming Earth

Climate models, feedback, water vapor, carbon dioxide, 2016, David Evans.

Conventional models assume increasing atmospheric CO2 warms the surface, then apply the feedbacks to the surface warming. But if feedbacks start up in the atmosphere instead, everything changes.

The assumption (bolded below) is the problem –

There are many processes which affect the surface climate: changes to the sun’s activity, to the cloud cover, precipitation patterns, or soil water content to name just a few. Currently climate scientists relate these processes by looking at how much they change the energy budget, described by perturbations in the radiative forcing. The existing assumption is that if a given process introduces a certain radiative forcing, then there will always be the same response in the surface air temperature. However, this assumption doesn’t hold for the temperature response on climatological scales because it neglects variations in the effective heat capacity of the atmosphere.

They are still focused on the effect of any and every “radiative forcing” on the surface of Earth. All “forcings” are not the same. It seems so banal — 2 extra watts in the upper trop is not the same as 2 watts on the surface.  If the forcing occurs ten kilometers up, then feedbacks up there are what matter first. But this whole class of feedbacks don’t even exist in the GCM’s. If the extra energy just reroutes to space direct from the upper troposphere, who cares how thick the boundary-layer is?

The river of energy wants to flow to cold space. That’s “downhill”. Water vapor is the most important greenhouse gas. It provides a path (call it a pipe) to space. Why wouldn’t energy take the shortcut?

Dr David Evans added in this class of feedbacks and fixed the basic model (that’s the conventional mental construct that generates the Global-Worrier-fear.)

A description of the minor cog below — Yada yada, deckchairs etc:

The effective heat capacity of the atmosphere is defined by the volume of air that is heated, which is described by the depth of the boundary layer. This is the layer of air just above the ground and it is essentially separated from the rest of the atmosphere. The depth of the boundary-layer can vary from just a hundred meters in very cold conditions to several kilometres in warm conditions. Because of these big differences in the effective heat capacity, the surface air temperature has a very different sensitivity depending upon where and when a forcing occurs. So the addition of an equal amount of energy across the globe means that the places with deep boundary layers will warm less than those with shallow layers, as there is a much greater volume of air through which that heat is spread.

This is the reason that some climate forcing processes are more effective than others at warming or cooling Earth. Those processes which act in the places and times that have shallow boundary layers will trigger a stronger temperature response.

REFERENCE

Richard Davy, Igor Esau. Differences in the efficacy of climate forcings explained by variations in atmospheric boundary layer depth. Nature Communications, 2016; 7: 11690 DOI: 10.1038/ncomms11690

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