Sunday, August 23, 2009

Oh dear

This is getting a bit silly.

Roger now says (quoting me):

"UPDATE: James made this new claim on his weblog titled PM05 resolved (see his comment linked to one of my weblogs in the last paragraph of his post).

Roger,

The change in heating rate in those plots is much less than 0.05K/day near the surface, probably 0.01K/day (green curve = relevant to the real world). How do you reconcile this with the change in heating rate of about 0.1K PER HOUR that you used in your calculations?

The classic book The Climate Near the Ground by Geiger et al (reprinted most recently in 2009) illustrates the error in James’s statement. On page 124, for example, they report changes of at least 0.1C PER HOUR, and often more, as a result of changes in vertical stratification and surface characteristics. The sensitivity of the 2m temperatures to the overlying thermodynamic stability, intensity of turbulent mixing, and surface fluxes is illustrated even in this early study. The authors discuss atmospheric moisture and cloud cover effects elsewhere in their excellent book. I recommend that James read this text to update himself on the surface boundary layer and for an explanation of the physics of minimum temperatures that occur overnight."

However, the confusion here is elementary. The referenced book is talking about the cooling rate during the diurnal cycle - evidently this may vary by O(0.1K) or even O(1K) per hour, for a range of magnitudes of the diurnal cycles. But this has nothing to do with GHG forcing.

The 1Wm-2 or 0.1K per hour that I am complaining about, is not the range of cooling rates due to having gross diferences in the underlying atmospheric state or land surface type, but rather the change in cooling rate that RPSr explicitly claimed would be directly caused at the lower boundary of the atmosphere by a change in GHGs (such as from pre-industrial to present day concentrations). As is plain from the graphs that both of us have shown, the real warming rate due to GHG forcing is a couple of orders of magnitude lower than the value RPSr uses. As importantly, the warming is reasonably uniform with height (near enough for the purposes of this disagreement).

There is (at least potentially) a 1Wm-2 forcing at the ground which may arise from a change in GHGs, but it is abundantly clear that this applies to the land surface and RPSr has made a simple conceptual error in incorrectly applying this flux to the lower boundary of the atmosphere.

6 comments:

Steve Bloom said...

It's not like RP Sr. ever admits error, but that's especially true in this case since Jr.'s credibility is equally at stake. Publication of a critique seems like the only option.

James Annan said...

At least it now seems fairly clear from the recent distraction tactics (eg belatedly trying to convolute the effect of different atmospheric states with that of anthropogenic forcing) that he realises his error.

Hank Roberts said...

So if I understand this correctly, the Pielkes' boundary layer has only one side -- the atmosphere?

James Annan said...

Something like that. Amazingly, he's now trying to pretend he was not talking about CO2 at all!

Steve Bloom said...

Wow, this is really escalating. I'm going to lay in an extra supply of popcorn. :)

Dirk said...

Nice to see RPSr. sink to a new low with his post "Does Gavin Schmidt (and James Annan) understand BL Physics?"

Perhaps the correct question should be:

"Does Roger Pielke Sr. understand micro-meteorology?"

Steve:

You get the popcorn, I'll get the deckchairs & beer.