Preliminary Upper Ocean Heat Data Analysis By Josh Willis – “An Unpublished Update”

Last Fall,  Josh Willis of the Jet Propulsion Laboratory at Cal Tech informed us he would provide an update of the upper ocean heat data; see

E-mail Exchange With Joshua Willis On The Diagnosis Of Global Warming From Ocean Heat Content Changes

This past week Josh contacted me and  has permitted me to post his preliminary analysis along with his e-mail that summarizes the current assessment. He has emphasized that the analysis is preliminary

The new preliminary analysis is plotted below in the same format as used in

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

As he wrote in his e-mail, the analysis should not be used in a scientific publication until he reports on a final version.

An Unpublished Update By Josh Willis

 The text of his e-mails on the ocean heat content data is

I do have to attach a few caveats to this estimate…..  First, please note that this is not ready for publication.  There are a number of other tests I want to run to be sure that I have eliminated any remaining biases in the Argo data before I publish it, so this is just an intermediate update.  So, if you are going to post this on your website, please refer to it as an “unpublished update”.  In other words, if I do find any futher important biases and correct them, the published version could look significantly different.  I don’t think that will happen, but please treat this estimate with an appropriate amount of skepticism.

Second, This estimate only goes back to 2005.  The reason for this is that Argo still has a number of floats for which no PI has responsibility for quality control of the data.  For early incarnations of these floats, this could mean that significant (albeit correctable) biases still exist in the pressure data. Normally, these biases are corrected by the PI, but since these floats are sort of homeless, they have not yet been corrected.  It is also difficult (or in many cases impossible) for the end user to correct these pressure data themselves.  Argo is still trying to figure out how to deal with these data and I sure they will receive bias corrections eventually, but for the moment we need to exclude them. So, for this reason I am still not comfortable with the pre-2005 estimates of heat content.

Anyway, the consequence of this is that we still do not have a good estimate of ocean heat content changes from about 2002 to 2005, when the dominant data source for ocean heat content went from XBTs to Argo floats. For this reason, I remain a bit skeptical of any heat content estimates during that period.  That said, however, I do think that longer-term estimates like those of Levitus et al., Domingues et al., and Lyman et al. are robust with respect to the long-term heat content increases.  The issue with the 2002-2005 period is that the uncertainty during this period is still much larger than any year-to-year fluctuations that may exist.

Finally, as I said above, this estimate is really not ready for scientific publication, so I would ask that you not distribute it to anyone who wants to publish it.  If you want to put it up on the website and talk about it, I am okay with that as long as you make it clear that it is preliminary.

As always, you are welcome to quote any of this email on your blog as well.

Cheers,
Josh

and

“The average warming rate is equivalent to 0.16 W/m^2 over this 5 year period.  I decided not to add the trend line to this plot.  I really feel that adding the trend line on the plot sort of encourages folks to rates like this beyond where they probably should (both in terms of time, and especially in terms of interpretation).

Also, you should be aware of this paper by Purkey and Johnson, a copy of which I have also attached.  This suggests that we are probably missing as much as 0.07 W/m^2 of warming in the deep ocean with analyses like mine.”

Sarah G. Purkey, Gregory C. Johnson, 2010: Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions to Global Heat and Sea Level Rise Budget. Journal of Climate Volume 23, Issue 23 (December 2010) pp. 6336-6351 doi: 10.1175/2010JCLI3682.1.

The Purkey and Johnson  paper has the abstract

 “Abyssal global and deep Southern Ocean temperature trends are quantified between the 1990s and 2000s to assess the role of recent warming of these regions in global heat and sea level budgets. The authors 1) compute warming rates with uncertainties along 28 full-depth, high-quality hydrographic sections that have been occupied two or more times between 1980 and 2010; 2) divide the global ocean into 32 basins, defined by the topography and climatological ocean bottom temperatures; and then 3) estimate temperature trends in the 24 sampled basins. The three southernmost basins show a strong statistically significant abyssal warming trend, with that warming signal weakening to the north in the central Pacific, western Atlantic, and eastern Indian Oceans. Eastern Atlantic and western Indian Ocean basins show statistically insignificant abyssal cooling trends. Excepting the Arctic Ocean and Nordic seas, the rate of abyssal (below 4000 m) global ocean heat content change in the 1990s and 2000s is equivalent to a heat flux of 0.027 (±0.009) W m−2 applied over the entire surface of the earth. Deep (1000–4000 m) warming south of the Subantarctic Front of the Antarctic Circumpolar Current adds 0.068 (±0.062) W m−2. The abyssal warming produces a 0.053 (±0.017) mm yr−1 increase in global average sea level and the deep warming south of the Subantarctic Front adds another 0.093 (±0.081) mm yr−1. Thus, warming in these regions, ventilated primarily by Antarctic Bottom Water, accounts for a statistically significant fraction of the present global energy and sea level budgets.”

My Conclusions

1. First, and most importantly, this data is such an essential climate metric that it should be widely available to everyone in near real time.  It is the most robust metric we have to diagnose annual average global warming.

2. The analysis that Josh has provided extends only a relatively small part of the way through 2010. It will be enlightning to see how the recent change to a La Niña pattern effects the  ocean heat content.

3. IF the diagnosed radiative forcing of +0.16 Watts per meter squared in the upper ocean plus the 0.07 Watts per meter squared below that level are robust in the final analysis, the total of 0.23 Watts per meter squared is significantly below the 0.6 Watts per meter squared predicted by Jim Hansen from the GISS model for the time period 1993 to 2003 (see).

4.  The analysis, however, shows that the climate system (as represented by the oceans) did warm in the annual average since 2005 until mid 2010.

5. The analysis, when ready for the remainer of 2010 and into 2011 will be quite informative. With the onset of the La Niña, the lower atmosphere has cooled rapidly (e.g. see). Whether or not the upper ocean retains its large positive heat anomaly, as clearly evident in Josh’s analysis. will be an important in further testing the GISS and other IPCC model predictions. The deeper ocean heat change on the same time scale will inform us if heat is being transfered downwards and stored at those levels or, if the heat change is small, this will indicate the heat anomaly was radiated into space.

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