Response To Chick Keller’s Guest Post #2

Chick Keller posted his perspective on the climate issue with respect to our 2009 EOS article in his guest post

Guest Post #2 By Chick Keller

I find there is quite a bit that we agree on. For example, we both accept that the human addition of CO2 is a first order climate forcing. However, we differ on aerosols and land use/land cover change. In our EOS article, we concluded that these are also first order climate forcings and that

“As with CO2, the lengths of time that they affect the climate are estimated to be on multidecadal time scales and longer.”

Our disagreement may be due to what we use to define a first order climate forcing. I offer a definition here:

A first-order climate forcing is one that has a significant effect is altering major global circulation features such as ENSO, the PDO,  and the NAO.  It is these circulation features that determine our weather patterns on all time periods, rather than the magnitude of the global average surface temperature trend.

Chick agrees with me on the importance of ENSO, for example, as he wrote in his guest post.

I discuss the importance of heterogenous climate forcings due to aerosols and land use/land cover in one of my first posts in 2005 on on my weblog;  see

What is the Importance to Climate of Heterogeneous Spatial Trends in Tropospheric Temperatures?

This is why the diabatic heating patterns from the human input of  aerosols and from land use/land cover change represent a first order climate forcing.

On another issue, Chick has,  misstated the role I see of the oceans within the climate system. He wrote in yesterday’s post

“However, Roger has not dealt sufficiently with what I consider a really large problem, that of understanding and simulating the many pathways of energy within the climate system.  Especially Roger ignores the oceans with their great heat capacity and their ability to strongly modify atmospheric behavior.”

This is inaccurate as I have published on this topic; e.g. see

Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335

Pielke Sr., R.A., 2008: A broader view of the role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55.


Rial, J., R.A. Pielke Sr., M. Beniston, M. Claussen, J. Canadell, P. Cox, H. Held, N. de Noblet-Ducoudre, R. Prinn, J. Reynolds, and J.D. Salas, 2004: Nonlinearities, feedbacks and critical thresholds within the Earth’s climate system. Climatic Change, 65, 11-38

we wrote

“Even an elementary description of Earth’s climate system must deal with the fact that it is composed of the above subsystems all interconnected and open, allowing fluxes of mass, energy and momentum from and to each other…”

I look forward to continuing this constructive dialog with Chick where we can each clarify our perspectives on the climate issue.

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