Unfortunately, we don't have
good ocean heat content data for this period, while the data we do have — global mean atmospheric surface temperature — is dominated by ocean oscillations.
And since we don't have
good ocean heat content data, nor any satellite observations, or any measurements of stratospheric temperatures to help distinguish potential errors in the forcing from internal variability, it is inevitable that there will be more uncertainty in the attribution for that period than for more recently.
To accurately evaluate the efficacy of volcanic forcing you would need to have
better ocean heat content data for the period following a major eruption.
Not exact matches
However, the large - scale nature of
heat content variability, the similarity of the Levitus et al. (2005a) and the Ishii et al. (2006) analyses and new results showing a decrease in the global
heat content in a period with much
better data coverage (Lyman et al., 2006), gives confidence that there is substantial inter-decadal variability in global
ocean heat content.
Alternatively, more direct observations of that radiative imbalance would be nice, or
better theoretical and observational understanding of the water vapor and cloud feedbacks, or more paleoclimate
data which can give us constraints on historical feedbacks, but my guess is that
ocean heat content measurements would be the
best near term bet for improving our understanding of this issue.
Remember too that
ocean heat content increases were a predicted consequence of GHG - driven warming
well before the
ocean data was clear enough to demonstrate it.
We now have excellent proxy volcanic
data and pretty
good ocean heat content proxy
data over the past 2000 years, during which their were both warmer and cooler periods.
I don't know about all of you, but I do find that the uncertainty around e.g. the various issues related to
ocean heat content or issues regarding connecting the Argo float network to other
data networks is SO much
better covered in Judith's bizarre and uniquely repetitive mischaracterizations of other scientists» comments, than by the published science and its critical review.
Without
good heat content data it is very hard to gauge but logically there is no upper bound on how powerful an effect
ocean oscillations can have.
Ideally the zero point would be modulated by
ocean heat content and / or ssts, since it is the comparison between energy into the
oceans vs. energy radiated back out that determines warming or cooling, but we don't have much historical ohc or sst
data so a fixed zero point would seem to be the
best that can be done.
Figure 8: Argo
ocean heat content — source — climate4you —
well worth multiple visits for a range of up to date
data.
Then about three years ago, those same scientists, using those same
data sets, admitted there was a pause, and spent their energy explaining why it didn't matter (
ocean heat content being a
better proxy was the most popular).
But worse is your paper with Nic Lewis, which seems to go out of its way to get a low ECS by purposely not using the
best data available for surface temperatures,
ocean heat content, and with no consideration of aerosols at all.
If the model Curry and colleagues discussed had incorporated the latest
ocean heat content data, their relatively low
best estimate for climate sensitivity would have been more in line with previously reported, higher estimates.
We are still going to have to wait for the «definitive»
ocean heat content numbers, however, it is important to note that all analyses give long term increases in
ocean heat content — particularly in the 1990s — whether they include the
good ARGO
data or exclude the XBTs or not).
Exactly how
good is the
ocean heat content data on which this argument is based?
You might get
better results using
data starting in 1850 (or 1851 — there is a slight jump) rather than 1900, and TOA radiative imbalance rather than
ocean heat content data, for your analysis.
I'm not as
well read on this subject as I would like but I know that Dr Craig Loehle has recently completed a study of the
ocean heat content anomaly
data compiled by Willis et al (2008b), his findings show that since the Argo array of profiling floats programme began taking accurate measurements in 2003, that the
ocean has been cooling during the period 2003 — 2008.