In the last day or so there have been two new papers on ocean heat, which have had some publicity. Both have just been published in Nature Climate Change. The studies are not in conflict with one another, despite what you might read around the traps. They are complementary. In fact, one scientist, Felix W. Landerer, is an author of both papers.
One paper is about how there has been very little extra heat going into the deep ocean, below 1,995 metres, over the past decade. The other is about how the ocean in the southern hemisphere has been warming more than previously thought.
The study to work out what is happening in the deep ocean worked it out by subtraction. The press release at ScienceDaily.com stated:
To arrive at their conclusion, the JPL scientists did a straightforward subtraction calculation, using data for 2005 to 2013 from the Argo buoys, NASA's Jason-1 and Jason-2 satellites, and the agency's Gravity Recovery and Climate Experiment (GRACE) satellites. From the total amount of sea level rise, they subtracted the amount of rise from the expansion in the upper ocean, and the amount of rise that came from added meltwater. The remainder represented the amount of sea level rise caused by warming in the deep ocean.
The remainder was essentially zero. Deep ocean warming contributed virtually nothing to sea level rise during this period.In other words, all the extra heat is still going into the ocean in the top 2000 metres or so.
Before going any further into that, the other paper is relevant here. This work looked at the ocean heat content and sea surface height, comparing the northern and southern hemispheres. What the scientists found was that it is likely that the estimated increase in ocean heat content for the upper 700 metres of oceans has been underestimated. The reason for this is poor sampling of the southern hemisphere. The scientists say there is strong evidence that in regions where the data is sparse, analytical methods have erred on the low side.
What Paul Durack and his colleagues did was look at the simulated sea surface height changes, after partitioning the northern and southern hemispheres. This matched up with precise altimeter observations. But when they did the same for ocean warming, they found it was not consistent with the observed in-situ-based ocean heat content estimates.
They compared modeled estimates of ocean heat content (OHC) change with observations and noted differences. Acknowledging that it could simply be internal variability that was causing discrepancies, they also figured that some of the discrepancies could be the result of either systematic model errors and/or errors in observations. So they looked further. They compared simulated changes in sea surface height (SSH) with satellite altimetry measurements.
They explained what contributes to rising sea level as follows:
- Steric expansion, water expanding as it gets warmer - which accounts for around 40% of the long term average increase in sea surface height.
- More water - mass contributions from melting land ice. That is, from the cryosphere.
- Halosteric effects - from a change in salinity at the regional level.
- Dynamic effects from changes in circulation. (Sea level is not the same all over.)
In models where there is no representation from glacial melt, the changes in sea surface height at the scale of hemispheres is almost wholly down to water getting warmer (steric changes). The paper goes into a bit of detail about the extent to which ocean heat content corresponds with sea surface height looking at different depths - 0-700m compared with the full ocean depth.) The upshot is that sea surface height is a pretty good indicator of ocean heat content.
So they did some comparisons for different time periods, comparing ratios of sea surface height with ocean heat content for the two hemispheres. The observed sea surface height estimate was within the range of model estimates but the ocean heat content estimates were off until recent years (when there were more observations). That finding lent strong support for errors being in the observations rather than in the models. They looked at it every which way and figured that indeed, the southern hemisphere has been accumulating heat more than was previously estimated.
Here is a neat illustration from the researchers, showing the change in ocean heat content over the last six decades:
|Figure M2. Pacific and Atlantic meridional sections showing upper-ocean warming for the past 6 decades (1955-2011; |
Source: Timo Bremer/LLNL)
So taking these two papers together, it seems that there has been more heat accumulating in the southern hemisphere oceans than previously thought, and almost none in the deep oceans.
How much more heat?
What the researchers found was that this meant that quite a bit more heat is being retained than was previously estimated. The abstract states:
These adjustments yield large increases (2.2–7.1 × 1022 J 35 yr−1) to current global upper-ocean heat content change estimates, and have important implications for sea level, the planetary energy budget and climate sensitivity assessments.
You can read about the paper at ScienceDaily.com.
Impact on climate sensitivity
If you are wondering just how this might affect climate sensitivity estimates, it turns out it could affect them quite a bit. Gavin Schmidt tweeted (revised):
.@sjvatn Revision. Taking account of actual data used (AR5 total heat accumulation), Durack makes 15% diff. ECS -> 1.1-4.7ºC
— Gavin Schmidt (@ClimateOfGavin) October 6, 2014
I wonder how it effects transient climate response - anyone? Whatever, we'd better get a move on with reducing CO2 emissions is all I can say.
What the deniers are saying at wattsupwiththat
Would you be surprised to learn that at WUWT, Anthony Watts has used his "claim" headline with the study showing more ocean heat in the southern hemisphere, but has applauded the study that suggests there has been little if any heat in the deep ocean in the last decade? For the latter study Anthony wrote:
The “heat went to the oceans” excuse and Trenberth’s missing heat is AWOL – deep ocean has not warmed since 2005
The Sceptical Science kidz and Trenberth think that the deep ocean has absorbed all the heat that isn’t showing up in the atmosphere, and that’s [why] we have “the pause”. Well, that’s busted now according to ARGO data and JPL and it has NOT gone into the deep ocean.For once you are right, Anthony. It's not been going into the deep ocean, it's in the southern hemisphere oceans!
Worse than that, though. Anthony headed up his article about the deep oceans. You know, below 1,995 metres, with one of "Bob Tisdale's" charts of ocean heat. Guess what it was. Yep, the top 700 metres.
It gets even worse than that. Look see. I've put the data from NOAA on top, and Bob Tisdale's chart underneath. They look quite different. Bob and Anthony are hiding the incline, by leaving off the last two years.
|Data Source: NOAA|
|Source Unreliable: WUWT|
From the WUWT comments
This first lot are from the WUWT article about the southern hemisphere ocean heat content.
DHR has it wrong. Sea level estimates are pretty right, it's the ocean heat content that was underestimated. It was sea surface height that pointed to the errors.
October 6, 2014 at 11:03 am
Does this mean that sea level has increased more than we thought?
Gerry, England is waiting for the ice age that doesn't seem to be comething.
October 6, 2014 at 11:40 am
What we need is some serious cold to turn the ‘pause’ into a decline and then see them try and argue that out with a straight face. Mind you, given all the data fiddling going on, perhaps they are already ‘hiding the decline’.
Steven Mosher better watch out or he'll become a full-blown "warmist" instead of a luker. Maybe he's already made the transition.
October 6, 2014 at 1:03 pm
people complained that the ocean was poorly sampled. The worry was that the sampling was biasing the result.people complained that the land was undersampled and worried the sampling would bias the result.
Yup. undersampled. If you increase sampling you will find out that the present is warmer than we think
I see the same thing in air temperature records.
E.M.Smith acted the class clown and wrote:
October 6, 2014 at 1:19 pm
So the net net of this is that due to the excessively warm southern ocean where all that lost heat has been hiding (waiting for The Lost Boys of climate science to find it?) has been so amazingly heated that it is making more sea ice than Ever before and a lowest ever Antarctic measured temperature Ever?
It must be a cold heat….
Ian H got hold of the wrong end of the stick. There were no such assumptions made at all. Honestly, the press release was not that hard to understand.
October 6, 2014 at 3:28 pm
They simply assume that both hemispheres should be showing the same temperature trend and ‘correct’ the southern hemisphere measurements to match the Northern hemisphere ones. And this in the face of very low Arctic ice with record Antarctic ice levels (face palm). I await their next paper with interest. No doubt they will attempt to address this problem by correcting the record Antarctic sea ice measurements to make them match the Arctic ice loss. Actually no – they wouldn’t get away with that. We have photographs. Yet they do think they can get away with doing the exact same thing with deep sea temperature measurements because there are no photos of those.
ntesdorf wrote a rather silly comment
October 6, 2014 at 3:46 pm
With most of the population and most of the large cities and industrial areas being in the Northern Hemisphere, UHI is always likely to increase temperatures more than in the Southern Hemisphere, which is mainly water. No surprises here….no need to adjust the data.
AnonyMoose - well, what can I say about this? What a nong! (Will that do?)
October 6, 2014 at 7:04 pm
“our results suggest that global ocean warming has been underestimated by 24 to 58 percent”
So the models should be made more sensitive to carbon dioxide… with makes their failure during the last 18 years even worse. It’s better than we thought.
This next lot are from the deep ocean paper, which was posted second. It just goes to show the short attention span of WUWT readers (among other things).
Mark Bofill missed the memo.
October 6, 2014 at 11:24 am
It’s not in the atmosphere.
It’s not in the deep oceans.
what does that leave?
Cowtan and Way find some at the poles. All? Not by a long shot.
Can we go home now?
Alan Poirier prefers to live in fairyland than here on Planet Earth.
October 6, 2014 at 2:26 pm
There never was any missing heat. Trenberth’s energy budget is simply wrong. Fantasy physics.
Dave in Canmore speculates in the silly way deniers do. If Dave can't be bothered looking elsewhere for science, surely he could at least read what WUWT posts.
October 6, 2014 at 11:43 am
I havn’t done the calcs myself but isn’t the heat capacity of the oceans so massive that even if extra greenhouse heat was somehow being absorbed by the oceans, wouldn’t it be so small as to be unmeasurable anyway?
Anyone have any references for this calculation?
Ocean heat content numbers are too big for Bob Tisdale to manage. Like all science deniers, he likes to minimise things so he doesn't get too scared. He wrote:
October 6, 2014 at 3:22 pm
I don’t bother with OHC data anymore. I’ve been presenting depth-averaged temperature data at different depths recently. OHC data are presented in terms of Joules*10^22 and that makes the warming look astronomical. Presenting it in deg C puts it into terms people understand and also shows how small (miniscule) the actual change in temperature has been.
W. Llovel, J. K. Willis, F. W. Landerer, I. Fukumori. "Deep-ocean contribution to sea level and energy budget not detectable over the past decade." Nature Climate Change, 2014; DOI: 10.1038/nclimate2387
Paul J. Durack, Peter J. Gleckler, Felix W. Landerer and Karl E. Taylor "Quantifying Underestimates of Long-term Upper-Ocean Warming." Nature Climate Change 5th October 2014. DOI: 10.1038/nclimate2389