Illustration only: not part of the paper
This paper has been out for a few days, and several people have alerted me to it. This new paper by Compo,G.P., and P.D. Sardeshmukh, 2008: Oceanic influences on recent continental warming. in the journal Climate Dynamics, is now in press. See the PDF here
This paper makes some significant claims regarding what is driving the observed climate changes. The emphasis is on the ocean as the main driving component, and the authors recognize that “a combination of natural and anthropogenic influences” may be at work. While they point to the oceans as a significant driver, they don’t offer much to explain what is driving the oceanic change.
Even so, this is a significant work, and I urge my visitors to read it, because it shows that GHG forcing is not the only occupant of the drivers seat. It also clearly illustrates the need to examine such cyclic ocean influences as the PDO and AMO more closely, and to consider them in projections of temperature.
Abstract:
“Evidence is presented that the recent worldwide land warming has occurred largely in response to a worldwide warming of the oceans rather than as a direct response to increasing greenhouse gases (GHGs) over land. Atmospheric model simulations of the last half-century with prescribed observed ocean temperature changes, but without prescribed GHG changes, account for most of the land warming. The oceanic influence has occurred through hydrodynamic-radiative teleconnections, primarily by moistening and warming the air over land and increasing the downward longwave radiation at the surface. The oceans may themselves have warmed from a combination of natural and anthropogenic influences.”
Conclusion:
“In summary, our results emphasize the significant role of remote oceanic influences, rather than the direct local effect of anthropogenic radiative forcings, in the recent continental warming. They suggest that the recent oceanic warming has caused the continents to warm through a different set of mechanisms than usually identified with the global impacts of SST changes. It has increased the humidity of the atmosphere, altered the atmospheric vertical motion and associated cloud fields, and perturbed the longwave and shortwave radiative fluxes at the continental surface. While continuous global measurements of most of these changes are not available through the 1961-2006 period, some humidity observations are available and do show upward trends over the continents. These include near-surface observations (Dai 2006) as well as satellite radiance measurements sensitive to upper tropospheric moisture (Soden et al. 2005).”
Although not a focus of this study, the degree to which the oceans themselves have recently warmed due to increased GHG, other anthropogenic, natural solar and volcanic forcings, or internal multi-decadal climate variations is a matter of active investigation (Stott et al. 2006; Knutson et al. 2006; Pierce et al. 2006). Reliable assessments of these contributing factors depend critically on reliable estimations of natural climate variability, either from the observational record or from coupled climate model simulations without anthropogenic forcings. Several recent studies suggest that the observed SST variability may be misrepresented in the coupled models used in preparing the IPCC’s Fourth Assessment Report, with substantial errors on interannual and decadal scales (e.g., Shukla et al. 2006, DelSole, 2006; Newman 2007; Newman et al. 2008). There is a hint of an underestimation of simulated decadal SST variability even in the published IPCC Report (Hegerl et al. 2007, FAQ9.2 Figure 1). Given these and other misrepresentations of natural oceanic variability on decadal scales (e.g., Zhang and McPhaden 2006), a role for natural causes of at least some of the recent oceanic warming should not be ruled out.
Regardless of whether or not the rapid recent oceanic warming has occurred largely from anthropogenic or natural influences, our study highlights its importance in accounting for the recent observed continental warming. Perhaps the most important conclusion to be drawn from our analysis is that the recent acceleration of global warming may not be occurring in quite the manner one might have imagined. The indirect and substantial role of the oceans in causing the recent continental warming emphasizes the need to generate reliable projections of ocean temperature changes over the next century, in order to generate more reliable projections of not just the global mean temperature and precipitation changes (Barsugli et al. 2006), but also regional climate changes.”
Roger Pielke writes in his blog:
This is a major scientific conclusion, and the authors should be recognized for this achievement. If these results are robust, it further documents that a regional perspective of climate variabilty and change must be adopted, rather than a focus on a global average surface temperature change, as emphasized in the 2007 IPCC WG1 report. This work also provides support for the perspective on climate sensitivity that Roy Spencer has reported on in his powerpoint presentation last week (see).
Julian Flood — “We spill enough oil on the ocean every two weeks to cover it completely.”
Smokey — “I would be interested in a citation.”
***
As would I. This sounds like one of those “we lose 32 species every week” claims that is merely a WAG. Since he said “we” it wouldn’t appear as if he’s claiming natural seepage.
Smokey,
I’m going to side with streamtracker (note the “r”) on associating “paradigm” with the AGW hypothesis (presuming that he was also). If there was ever an apt application of the Kuhnian concept of “normal science” and a “reigning paradigm” it is AGW. Just look at the flap that took place with the APS recently. Most “scientific societies” have issued statements supporting the AGW hypothesis. I have recently read numerous papers on “natural climate variability” (since I’m researching the issue myself) and these days any paper that alleges natural climate variability is likely to have a qualifier along the lines of “but this doesn’t disprove AGW,” or “but this is merely masking AGW.”
Now, you might ask when did the revolution — from “natural climate variability” to “AGW” take place? It was gradual. And I suspect it was originally benign, in the sense that proponents had no idea that it would become the storm of contention it is today. The early proponents probably just looked at it as a way to make their research “relevant to public policy.” Nobody does science for its own sake any more. Okay, that’s an exaggeration, but you don’t get grant money to doing science for its own sake. You have to justify the research you are doing somehow. How are you going to justify research in natural climate variability? Actually, I can think of a few ways. But somewhere, some time ago, somebody opened the flood gates for grant money on the impact of rising CO2, and here we are today with AGW as a dominant paradigm of normal science for climate studies.
I have on my desk — because of the research into natural climate variability I’m doing — a book, well a compendium of studies published by the Natural Research Council, entitled Natural Climate Variability on Decade-to-Century Time Scales published in 1995. In it is an interesting paper by Keeling and Worf entitle “Decadal Oscillations in Global Temperature and Atmospheric Carbon Dioxide.” The final words of the article? “Financial support came from the National Science Foundation via Grant …. and from the U.S. Department of Energy via Grant ….”
To do science these days, you have to sell it. And for a long time, selling it as investigating AGW has paid off, making it a paradigm of normal science in climate studies.
Basil
“Overall, the results suggest that the dominant mechanism for the land warming in these simulations is enhanced downwelling longwave radiation. ”
Mindless nonsense. Back-radiation warming cannot occur. The emissivities of the surface are 1000 times greater than those of the GHGs.
The atmosphere warms the surface by conduction. The heat capacity of the atmosphere is 1/2000th that of the oceans.
counters:
Generally I agree with your synopsis of the paper. I’m agnostic on the possible influence of GHG on ocean heat content, there’s science to support conduction of heat from warmer air into the seas. The gotcha is this:
TSI & total solar phenomenological influence (that’d be TSI + cosmic rays) seem to coincide strongly with total global warming, with avg TSI levels decreasing circa 1992 – date. Since latent heating is characteristic of the oceanic “heat bucket” the post-1998 situation has seen a temperature plateau consistent with both the gradual reduction in solar effects and the massive heat release from the ’98 el Nino.
Research shows the recorded TSI levels of the 1950’s – 1980’s was markedly higher than previous imputed TSI, suggesting that a great deal of the ocean & air heating was from the unusually active sun. Lief Svalgaard however thinks that historical TSI proxies are underestimating TSI prior to the 1950’s, and if we are to recalibrate them then the sun might be exculpated from most of the extra warming of last 50 years. Svalgaard is cautious however, and in light of the recent temperature plateau (sea & air), I’d lean toward the former analysis, implicating the sun in at least 30 percent of the warming until 1998, if not 50.
If sea temperatures were going consistently up while air temperatures were plateaued, then I’d be quite ready to implicate GHGs with the seas sponging up heat conducted from the air, esp. in light of a still-dimming sun. But instead we see neither accelerated warming of either the air or seas with the sun still dimming.
Intuitively this leaves me with a quandary (as I shift my spot along the fence…): Which force is most dominant?
Basil, Thank you for a well considered response. But the assumption that the ‘current paradigm’ is AGW is based on false information, namely, that the majority of earth scientists and meteorologists by and large agree with it, isn’t true.
The public certainly seems to agree with AGW. Advertising works. If you contend that the current paradigm is AGW in the public’s mind, I would agree. But that’s not what I was referring to, and I don’t think steamtracker was either.
The current paradigm – among scientists – is a healthy and overwhelming skepticism of the AGW conjecture: click
Are you practicing up?
Arrrrr.