Josh Willis graciously replied to the Climate Science weblog of August 14 2008 entitled “An Odd Weblog By Josh Willis” on the JPL weblog site
Reply by Josh Willis
Roger, thank you for the comment and the cross-link to my blog. I’m glad you enjoyed the gambling analogy, but I’m not gambling on the models or ignoring the Joules in the Great Ocean Heat Bank. I’m just looking at the bigger picture. Like the casino owners.
True, ocean heat content is the better metric for global warming, and the past few years of no warming are interesting. But tacked on to the 50-year-record of ocean warming before that, the last four years pretty much ARE just a wiggle. And yes, the estimates of global surface temperature do have errors and uncertainties. But the record of sea surface temperature also shows about 1 degree C of warming over the last 100 years. Remember, the oceans are 2/3 of the Earth’s surface and that record has fewer problems than the temperature data over land. Between the long-term records of ocean heat content, land and ocean surface warming, global sea level rise (about 20 cm over the last 100 years) and the increase in atmospheric CO2, you get a pretty simple, consistent picture of man-made warming. No models required.
Of course, the data are not perfect. Our understanding and our climate models are missing important pieces of the puzzle. But let’s not miss the forest for the trees. You don’t have to count every tree around before you realize you’re in the woods, just like a casino doesn’t have to win every bet to turn a profit.
Despite all the uncertainties, I think it is pretty clear that humans have already warmed the planet. And if we continue to add more CO2 to the atmosphere, we will warm it even further.”
Reply by Roger A. Pielke Sr.
Josh- Thank you for your reply. My response is given below:
1. In terms of global warming, there is not a “bigger picture” than the diagnosis and monitoring of ocean heat content changes. This has been shown effectively, for example, by
Barnett, T.P., D.W. Pierce, and R. Schnur, 2001: Detection of anthropogenic climate change in the world’s oceans. Science, 292, 270-274
and
Levitus, S., J.I. Antonov, J. Wang, T.L. Delworth, K.W. Dixon, and A.J. Broccoli, 2001: Anthropogenic warming of Earth’s climate system. Science, 292, 267-269.
They both found global warming using the upper ocean heat content change, and also concluded that the ocean is by far the largest location within the Earth’s climate system where this occurs.
To emphasize this point, Barnett et al wrote in their conclusions that
“Perhaps the most important aspect of this work is that it establishes a strong constraint on the performance and veracity of anthropogenically forced climate models. For example, a climate model that reproduces the observed change in global air temperature over the last 50 years, but fails to quantitatively reproduce the observed changed in ocean heat content, cannot be correct. The PCM has a relatively low sensitivity (less anthropogenic impact on climate) and captures both the ocean- and air-temperature changes. It seems likely that models with higher sensitivity, those predicting the most drastic anthropogenic climate changes in the future, may have difficulty satisfying the ocean constraint. To our knowledge, the PCM is the only model currently able to do this and still accurately reflect the changes in surface air temperature over the last 50 years.”
Thus, there clearly are serious issues with using the global average surface temperature to diagnose global warming. Since the land portion of the data, particularly minimum temperatures, has made up much of the reported warming, the major issues that we have identified do significantly affect the global average trend. The warm biases we have found do not eliminate the increase in surface temperature, but it does significantly reduce the magnitude of the increase (e.g., see for just one example).
A question for you is when will you be posting upper ocean heat content anomaly maps and long term trends in near real time? This would substantially elevate the scientific discussion of global warming.
2. You conclude that the warming over the last 100 years is man-made and attribute this to “the increase in atmospheric CO2″. It is actually quite straightforward to show that no more than 30% of the human positive radiative forcing can be attributed to CO2 (see), and this assumes we understand the role of natural variability in the radiative forcing, which we clearly do not (e.g. see).
Models cannot, of course, by themselves be used to prove anything. They can only be used as hypotheses which is tested against the data.
As Jim Hansen stated
“The Willis et al. measured heat storage of 0.62 W/m2 refers to the decadal mean for the upper 750 m of the ocean. Our simulated 1993-2003 heat storage rate was 0.6 W/m2 in the upper 750 m of the ocean. The decadal mean planetary energy imbalance, 0.75 W/m2, includes heat storage in the deeper ocean and energy used to melt ice and warm the air and land. 0.85 W/m2 is the imbalance at the end of the decade.”
However, the imbalance since 2004, at least for the upper ocean, has been essentially zero.
My question to you is what would have to occur in terms of the accumulation of upper ocean heat content for you to reject the IPCC climate model predictions of global warming? For instance, what accumulation in Joules must the upper ocean have for the 10 year period starting in 2004 for you to not reject the model predictions of this quantity?