Additional information on the paper “Recent Cooling of the Upper Ocean” by John M. Lyman, Josh K. Willis, and Gregory C. Johnson is given below. It was accepted 31 July 2006 for publication in Geophysical Research Letters.
The abstract reads,
“We observe a net loss of 3.2 (± 1.1) X 10**22 J of heat from the upper ocean between 2003 and 2005. Using a broad array of in situ ocean measurements, we present annual estimates of global upper-ocean heat content anomaly from 1993 through 2005. Including the recent downturn, the average warming rate for the entire 13-year period is 0.33 ± 0.23 W/m2 (per unit area of the Earth’s surface). A new estimate of sampling error in the heat content record suggests that both the recent and previous cooling events are significant and unlikely to be artifacts of inadequate ocean sampling.”
Selected excerpts from the article read,
“From 1993 to 2003, the heat content of the upper ocean increased by 8.1 (± 1.4) X 10**22 J. This increase was followed by a decrease of 3.2 (± 1.1) X 10**22 J between 2003 and 2005. The decrease represents a substantial loss of heat over a 2-year period, amounting to about 21% of the long-term upper-ocean heat gain between 1955 and 2003 reported by Levitus et al., [2005].”
“From 1993 to 2005, the average rate of upper-ocean warming as determined by a linear least squares fit is 0.33 ± 0.23 W/m2 per unit area of the Earth’s surface.”
“The recent decrease in heat content amounts to an average cooling rate of -1.0 ± 0.3 W/m2 from 2003 to 2005, and results in a lower estimate of average warming from 1993 to 2005 than that recently reported for the 1993 to 2003 period [Willis et al., 2004].”
“The cooling signal is distributed over the water column with most depths experiencing some cooling. A small amount of cooling is observed at the surface, although much less than the cooling at depth…..The maximum cooling occurs at about 400 m and substantial cooling is still observed at 750 m…..The cooling signal is still strong at 750 m and appears to extend deeper”
“….the updated time series of ocean heat content presented here (Figure 1) and the newly estimated confidence limits (Figure 3) support the significance of previously reported large interannual variability in globally integrated upper-ocean heat content [Levitus et al., 2005]. However, the physical causes for this type of variability are not yet well understood. Furthermore, this variability is not adequately simulated in the current generation of coupled climate models used to study the impact of anthropogenic influences on climate [Gregory et al., 2004; Barnett et al. 2005; Church et al. 2005; and Hansen et al., 2005]. Although these models do simulate the long-term rates of ocean warming, this lack of interannual variability represents shortcoming that may complicate detection and attribution of human-induced climate influences.”
This is a very important observational study of changes in climate system heat content. While the models predict a general montonic increase in ocean heat content (e.g. see (Figure 1) ), the new observations in Lyman et al 2006 show an important decrease. The explanation of this temporal change in the radiative imbalance of the Earth’s climate system is a challenge to the climate science community. It does indicate that we know less about natural- and human-climate forcings and feedbacks than concluded in the IPCC Reports.
I strongly recommend to look at Figure 1 of Barnett & al.
Ok, then they state:” one global climate model,…, has reproduced the observed changes in ocean heat content with surprising accuracy.”
Surprising?
Roger, I don’t know if I may, but it seems to me that science is a little bit stretched.
Of course they are interested only in “low” frequency…is there a definition of “low”?
Can statistics be used in such a way to get something “significant”?
And more:” The key point is that the substantial differences in the way the observed warming has penetrated to depth in the two oceans is reasonably well captured by the PCM, albeit with the caveats noted above.”
Caveats?
Read and tell me if we can talk about caveats!
And tuning, is it a caveat too?
And why to show output since 1880? Assessing against what?
I stopped to read there.
Unforecasted showers and very cold weather today (cold for August) make me run away from the seaside…
The next week end should turn out to be hot, finaly!
Comment by Paolo M — August 14, 2006 @ 9:35 am
Hello again
Another comment about the large cooling of the upper ocean from 2003 to 2005 indicated by the LWJ06 paper…
It bothers me that the cooling trend coincides with a major change in the measurement network, namely the introduction of the Argo profiling floats. LWJ06 say
“In order to test for potential biases due to this change in the observing system, globally averaged OHCA was also computed without profiling float data (Figure 1, gray line). The cooling event persisted with removal of all Argo data from the OHCA estimate, albeit more weakly and with much larger error bars.”
“More weakly” is right. Omitting the Argo float data increases the OHCA estimate in 2005 by 2.1 x 10^22 J (my reading of Fig 1). It changes the 2003 value very little, so it reduces the cooling between 2003 and 2005 by two-thirds.
Of course we have the Argo data now, so surely we should use it? Yes, but changes in the observing system can produce spurious trends. One way they can do this is through biases. The change in temperature associated with the cooling is less than 0.1 degC (Figure 4) so obviously a spurious cooling trend would occur if the Argo CTDs had a cool bias of this order or the older instruments (XBTs mostly) had a warm bias. Could such biases exist? I wouldn’t have thought so, as the people in charge of the measurements programmes are *very* careful.
Then there’s the change in sampling. The standard error is estimated as ~1 x 10^22 J in 2003 and ~0.5 x 10^22 J in 2005 (LWJ06 Fis 1 & 3). I don’t understand the method very well and the description in LWJ06 is brief (same as Willis et al (2004) but without the altimeter data) so I can’t comment on whether the standard error estimates are realistic. But Figure S1 shows that large swaths of the southern ocean were badly under-sampled in 2002 (and presumably not a great deal better in 2003). Estimating the OHCA in 2003 involved relying on the first guess field in these large gaps. I’m not saying this could have biased the 2003 estimate upwards (I would expect the opposite, actually) but it’s a bit worrying, isn’t it?
I’ll be much happier about believing trends in this dataset when we have a few years of Argo under our belts!
Comment by Mark Hadfield — August 14, 2006 @ 4:52 pm
Mark- Thank you again for your input. We both agree that we need more years with Argo data.
However, no one was questioning the data when Hansen, Barnett and others were using the warming upper ocean to suport the claim of model skill at simulating this behavior, as well as attributing reasons for its occurence. We need to apply the same standards to the value that we assign to the data regardless of whether it supports or disagrees with our particular perspective.
Comment by Roger Pielke Sr. — August 14, 2006 @ 8:35 pm
Roger, the authors note a discrepancy between the ocean temp data and altimetry showing a sea level rise. They then infer that this gap would have to be largely from fresh water inflow, but then don’t provide any kind of estimate as to how much fresh water is involved. Is it possible that the gap is so large that it would tend to cast suspicion on their temp data (given that the altimetry is basically unimpeachable)? I don’t know how to run the number, but it doesn’t look as if it would be too difficult for those versed in this kind of thing. If the number substantially exceeds a reasonable outside estimate of fresh water inflow (the recent GRACE icecap measurements plus appropriate terms for other ice melt and Artic river flow increases), it seems to me the paper has a problem.
Comment by Steve Bloom — August 15, 2006 @ 2:44 am
Re #2: Apologies, Mark, for my somehow forgetting that you had already raised the same basic poiont I just made in #4 above. Upon looking at the poster you linked, though, it appears we can run some numbers the easy way. Eyeballing Figure 2, the adjusted rate of sea level rise shown for the two-year period of cooling is about 6 mm/yr. Now let’s see what GRACE has to say: .54 mm/yr from Greenland + .4 mm/yr from Antarctica = +- 1 mm/yr. Hmm. I could go track down the numbers for the other glaciers and the Arctic rivers, but I can’t imagine they would drive the total number past 1.5 mm/yr. So, being generous, the discrepancy is easily a factor of four and represents something like 2,000 km3/yr of water. Hard to miss, one would think.
Comment by Steve Bloom — August 15, 2006 @ 3:33 am
Steve and Mark- There is also the issue as to the accuracy of the estimates of melt from the continental ice sheets. Those numbers certainly are more difficult to quantify than the upper ocean heat content.
Moreover, i) we should expect a lag in the response of glacier melt to a cooling, and ii) glaciers respond to their immediate regional climate, and not a global average (as discussed numerous times on the Climate Science weblog). There clearly has been recent warming in the oceans in the vicinity of Greenland, for example, even as the global average cooled from 2003 to 2005.
Comment by Roger Pielke Sr. — August 15, 2006 @ 6:12 am
Roger, you write “Hansen, Barnett and others were using the warming upper ocean to suport the claim of model skill at simulating this behavior”
For worse, Feb 22, 2005 in discussing Barnett’s presentation at AAAS panel Fred Singer pointed that
“But when we consult Barnett et al, Science 2001, that used the same basic data, we can see a cooling trend in the deep ocean between 1976 and 1985. Barnett gives no explanation for this and his models don’t show it. [Note: There was a strong warming of the atmosphere and sea surface between 1976 and 1980.]”
Well, we have scientists, we have models, we have assertions, but you all see what’s missing.
Timo
Comment by Timo Hämeranta — August 15, 2006 @ 11:06 am
I’m no climatologist but perhaps that’s valuable here. The question was raised about switching to ARGO skewing the results of the OHCA. From my reading of figure S1, the image from 2002 has clearly distinct shipping lanes visible that are at significant variance from the waters around them. Assuming (I think correctly) that the data quantity (and quality?) for those shipping lanes is far higher than outside them, can we not assume that the image from 2005 post-ARGO is more accurate assessment of real conditions than the data from 2002?
Most interested in your replies.
Alex
Comment by Alex Avery — August 15, 2006 @ 12:38 pm
Re #6: Roger, it remains that the discrepancy is huge and there’s no good explanation for it in the paper. Do you have some reason to suspect errors in the GRACE results? It’s interesting that Lyman et al seem to think GRACE will be the means of getting the ultimate answer on this.
Comment by Steve Bloom — August 15, 2006 @ 12:55 pm
Steve (and Mark) have raised important scientific questions that need to be addressed. Regardless, however, the multi-decadal global climate models did not have upper ocean cooling of the magnitude that has been recently observed in any of their projections. This should give pause to their use to make confident global-average and regional predictions of the climate in the coming decades.
Comment by Roger Pielke Sr. — August 15, 2006 @ 4:14 pm
Dear All,
Thanks for all of the comments and questions raised about our paper on this thread as well as the earlier one. I wanted to comment on a couple of issues raised in these posts. I’ll start with the sea level question first, and then try to address some of the concerns regarding the introduction of Argo data and sampling error.
In fact, we have calculated thermosteric sea level as part of our analysis, however, it was not included here as we wanted to keep the paper somewhat short. Anwyay, as you can tell from the heat content curve that is in LWJ06, the average temperature of the upper ocean was roughly the same between 2000 and 2005. Hence, upper-ocean thermosteric sea level change over that period is roughly zero as well. This suggests that most of the nearly 3 mm/yr of total sea level rise over this period was due to either deep warming, or input of fresh water. The most recent numbers for mass loss in Greenland is 0.7 mm/yr, and in Antarctica it is about 0.4 mm/yr over this period. Estimates of the contribution of mountain glaciers have been as high as 1 mm/yr for recent years. This gives a contribution of freshwater input of around 2.0 mm/yr over these years. This is still somewhat short of the 3 mm/yr total sea level rise from altimeter data, but there is still a good deal of uncertainty in all of the estimates of freshwater input. Given the error budget in the freshwater input and the reports of accelerated melting (see all three links above), the records of total sea level rise and land-bound ice melt do not render our observed cooling unlikely.
With regards to the introduction of the Argo data, let me start with the possibility of an instrument bias. The Argo floats contain very high quality temperature sensors that claim to have an accuracy of 0.005 deg.C. I don’t know if this has been rigorously verified yet, but the Argo temperature data is generally thought by the Argo science team to be of very high quality. This does not preclude, of course, biases in instruments such as XBT’s that formed the core of the earlier observing system. For this reason, we also calculated the heat content change from 2003 to 2005 using ONLY Argo data, and still found a loss of about 3 x 10^22 J over these years. This was mentioned briefly in the paper, but did not make it into figure 1.
As for a potential errors introduced by changes in sampling, I should first say that this type of error is contained in our estimate of the error bar. We feel that our technique for estimating the sampling error is fairly robust because it relies on altimeter data which provides excellent date coverage everywhere between 66 degrees of latitude. With regards to figure S1, the year 2002 was in fact the worst year for sampling in the Southern Ocean and by 2003 some of region in the far south was being sampled by Argo floats. The poor coverage in 2002 is reflected in the large error bar for that year shown in Figure 1. Finally, although it is not shown in the attached paper, it is possible to actually use the altimeter data to reduce the effects of sampling error on the global average heat content curve. This was the technique used in the Willis et al. (JGR, 2004) paper. Effectively, this technique allows the estimate to “relax” back to the variability observed by the altimeter (times a regression coefficient), rather than relaxing back to the mean in regions where profile data is sparse. If this technique is used and altimeter data is included, the cooling remains and is in fact, slightly more distinct (some of the earlier wiggles in the time series are reduced when this technique is applied).
For all of these reasons, we feel that the cooling signal is fairly robust, and not due to changes in the observing system.
Comment by Josh Willis — August 15, 2006 @ 10:05 pm
I am trying to understand the statement “the average temperature of the upper ocean was roughly the same between 2000 and 2005″ along with a loss of about 3 x 10^22 Joules in the same time period. Maybe the information I am missing is the relationship between heat content and temperature. In other words, how many joules does it take to raise the ocean temperature by 1 degree C?
Comment by Blair Dowden — August 16, 2006 @ 5:56 am
Blair - Re: #12
Prior to 2003, the trend in ocean heat content was still positive as shown in figure 1 of the paper. Between 2000 and 2003, ocean heat content increased by roughly 3 x 10^22 Joules, then decreased by about the same amount between 2003 and 2005.
Comment by Josh Willis — August 16, 2006 @ 9:29 am
Josh, John Fasullo has an interesting early critique of your paper over on the Real Climate site. Would you comment on some of the points he is raising.
Comment by Bryan Sralla — August 16, 2006 @ 2:51 pm
Re #11: Thanks for responding, Josh. The Chen et al Greenland paper you linked says .54 mm/yr in the final paragraph, so I’m not sure where your .7 Greenland number comes from, but that’s a minor point since the mountain glacier number could well be higher (the source you linked is four years old and it looks like you didn’t include a term for the Arctic rivers).
So, taking 2 mm/yr as a fair conservative estimate, why are you comparing that with the 3mm/yr measured sea level rise instead of the 6 mm/yr net sea level rise for the last two years shown in Figure 2 of your poster? I agree that the difference between 2mm and 3mm isn’t huge given the cumulative errors involved, but 2mm versus 6 mm seems like a discrepancy that requires an explanation.
Comment by Steve Bloom — August 16, 2006 @ 5:38 pm
Re #16: If you want to get a response on something like this, please link the thread and list the comment number.
Comment by Steve Bloom — August 16, 2006 @ 5:40 pm
Re #13: Thanks, Josh, of course that makes sense. But to help me put the values being discussed into perspective (ie. what does 3 x 10^22 Joules really mean?), I would like to know how much increase in ocean heat content is required to raise the average temperature of the layer being measured by one degree. Is this a reasonable question, or is there some other factor I am not taking into account?
Comment by Blair Dowden — August 16, 2006 @ 7:22 pm
RE #17
LWJ06 (the GRL paper) Figure 4 shows the globally average temperature change from 2003 to 2005 vs depth. The maximum drop is at 400 m and is ~0.08 degC, the average over the 0-750 m layer is (by my eye) between 0.03 and 0.04 degC. If you multiply that by the area of the World Ocean, the thickness of the layer and the heat capacity & density of water, you should recover the figure of 3×10^22 J. (I haven’t checked.)
Comment by Mark Hadfield — August 17, 2006 @ 12:02 am
Re: #16, Let me try this again.
Josh, John Fasullo comments on your paper http://www.realclimate.org/index.php/archives/2006/08/ocean-heat-content-latest-numbers, comment #14. He is citing the TOA-CERES data as being inconsistent with your findings. Could you comment on this please.
Comment by Bryan Sralla — August 17, 2006 @ 7:57 am
Hello, everyone. Interesting discrepency. I wonder if the original paper describes how interpolation was done over the missing data - I apologize in advance, as I haven’t access to the paper. Slide 7 of the PowerPoint deck over at http://www.clivar.org/organization/pacific/south_pac_workshop/presentations/SPac_Intro_ignaszewski.ppt shows the global data coverage of Argo as of 30 September 2005. As you can plainly see, North of 60 there is only data basically for the Greenland and Norwegian Seas. The data from the large Barents, West Siberian, East Siberian, Chukchi and Beaufort Seas, the Baffin Bay and the Denmark strait as well as the polar Arctic Ocean appear not to exist. Normally this couldn’t influence the results overmuch, as the Arctic Ocean is only ~10% of the polar ocean. But if we consider the mean polar temperature anomalies (see http://en.wikipedia.org/wiki/Image:Global_Warming_Map.jpg for a map), the missing data seem to be experiencing much greater warming then the sampled North Polar data, at the ocean surface at least. The Beaufort Sea and areas north appear particularly striking, with some of the highest mean temperature anomalies observed on the planet, around 1.5 oC for the region. Compare this with the modest surface temperature changes of ~0.5 oC for the sampled region, and you the sense of my post. (It’s not my idea, tho’ - credit goes to Fergus Brown, post #10 over at RealClimate: http://www.realclimate.org/index.php/archives/2006/08/ocean-heat-content-latest-numbers/). In terms of power integrated over area, only northern Eurasia has a higher regional warming in absolute terms - which suggests to me that sea surface warming in the Arctic west of the Canadian archipelago might change the total sea energy balance by quite a bit. Any thoughts? (crossposted to RealClimate.org)
Comment by Steffen Christensen — August 17, 2006 @ 4:13 pm
ice is melting -> ocean gets cooler, what’s not to understand ? We get ice to the drink for the same reason at McDonalds.
Comment by dz — August 20, 2006 @ 5:29 am
Sorry dz, the ice was already there. Melting the ice does not make the water colder. As the ice in your soft drink melts, the temperature of the soft drink will remain unchanged.
Only placing ice in liquid water will make the water colder. That is not what is happening in the Arctic.
Comment by Jim Clarke — August 21, 2006 @ 11:39 am
re: #22
Yes, Jim, I totaly agry with what you wrote, but then it raises me a question: how come it is stated that see level is raising because of the melting ice? I will try to explain what i mean. If ice is already there, melting the ice does not make the water colder, that is correct. But if ice is already there, melting the ice does not increase water(or sea) level too. Floating ice in the water alocates same amount of space as after it will melt and become liquid (Archimedes). For example with a drink: if i fill a drink with the ice, the water level will stay constant all the time, even after all the ice is melted. Because of it, it could be only two ways to say:
1)ice was already there(in the sea), that is why melting ice does not change the see level or sea temperature;
2) because of melting additional ice which was not in the sea, water level is raising and that is definetly will lower ocean water temperature, because melting ice is colder that averange ocean temperature;
anyways, my point is, if a sea level is raising because of the melting ice, the ocean should be getting cooler too.
Comment by dz — August 22, 2006 @ 2:11 am
RE: #23
Hey DZ;
I think I grok your point; however, I don’t know that I would agree with example number 2). Just because you have increased the energy of the ice whether it is on land or in the ocean to the point it is now liquid does not mean that where the melt water enters the ocean is any warmer then the melt water. By the same token, if the land melt water increases the ocean depth by 3mm in a fixed column does this reduce the total column temperature, if so it is so small as to be lost in the noise. A sudden simple chill breeze or 15 seconds of evaporation could add enough of a chill to the temperature of the total column as the melt water when comparing 3mm added to over 400 meters present.
Now the addition of the fresher water can have an effect on the rising ocean as it is less dense then the sea water that was displaced by the ice and is more dense than the ice. I think the better allusion would be a glass filled with ice and just a little fluid in the bottom. Where the ice level far exceeds the fluid level in the glass, as it melts, the fluid level increases to some percentage of the height of the ice and air pocket height. However, the temperature of the fluid in the glass has not increased, only the energy in the air surrounding the glass and the surface the glass is resting on has been reduced. After the ice has melted out, the fluid will begin to increase in temperature to achieve an equilibrium with its surroundings.
Dave Cooke
Comment by L. David Cooke — August 22, 2006 @ 10:16 am
Dave, thank you for your replay, and yes, you are right, there is too little amount of water melting to influence ocean temperature. That means Al Gore have bad season for his scary news
- no major hurricanes so far, and ocean is getting cooler probably not because of the global warming.
But i found another strange think about this melting ice.
I was reading your answer about how the water dense can have an effect on the rising ocean and decided to check some numbers. Here is what i get from the link above:
Antarctica it is about 0.4 mm/yr
It is stated on this Web site about Artic Ice sheet and sea-level:
“We found that the mass of the ice sheet decreased significantly, at a rate of 152 ± 80 cubic kilometers of ice per year, which is equivalent to 0.4 ± 0.2 millimeters of global sea-level rise per year”
I just tried to find out how much 1 cubic kilometers of the ice will add fresh water which being less dense than sea water will contribute to sea-level rise. Here is what i got:
152 cubic kilometers (of Artic ice)/
361 million square kilometers (The area of the World Ocean)= 0.4 millimeters.
Is that means all the melted Artic ice mass goes into sea-level rise? I am confused, what is going on here ?
Comment by dz — August 23, 2006 @ 1:04 pm
O.K., Antarctica ice sheet is not inside the water, so it’s just adding fresh water into the ocean, still, how 152 cubic kilometers of the ice will raise sea-level same as 152 cubic kilometers of sea-water? I think from the cubic kilometer of ice it will be much smaller amount of water.
Comment by dz — August 23, 2006 @ 1:25 pm
dz,
a very recently updated review of the ice sheet melting stuff can be found here:
http://www.co2science.org/scripts/CO2ScienceB2C/subject/i/summaries/icesheetgreen.jsp
Comment by Paolo M — August 23, 2006 @ 4:15 pm
Suzuki, Mother Nature
It does indicate that we know less about natural- and human-climate forcings and feedbacks than concluded in the IPCC Reports.Remember when Sheila Copps was fired from her Environmental Ministry Cabinet position for admitting Global Warming was more th…
Trackback by ThisCanadian — August 23, 2006 @ 8:44 pm
Re #26/7: dz, the difference in volume is actually rather slight. Also, the meltwater raises sea level because of the density change.
The Idsos (co2science.org) are a good source for information only if you’re interested in having your skeptical/denialist views reinforced. Note in particular their practice of not linking to the texts or even the abstracts of the papers they interpret.
Comment by Steve Bloom — August 23, 2006 @ 9:42 pm
re: 29
Steve, i understand what you say, but i am not sure i understand what is your point by saying that. Here are some numbers:
density at 0 degree Celsius:
ice 0.917 g/cm(cubic)
water 0.9998 g/cm(cubic)
seawater 1.02 g/cm(cubic)
difference between ice and water 8%
difference between water and seawater 2%
If you are saying a difference in density between ice and water is slight(%8), why to mention a difference between density of water and sea water(2%) in the next sentence ? Another thing, if we are talking about ice melted in Arctic on the land and we measure it in cubes, the density change in the sea does not play any role here -a cubic of liquid is a cubic, it does not matter if it is more dense or less dense as a seawater, it will allocate same amount of space to rise the ocean.
The density change in the sea could be mentioned talking about melting ice which is already in the sea, as 2% of melted water mass will be contributing to sea level rise. But i think it is a very small effect. To rise an ocean 0.4 mm just because of the difference in density, it is needed 50 times more amount of the ice to melt as it was melted in Arctic.
Anyways, this density thing not going to save anyone, as it is probably way less than possible error in measurements.
re: 27
Thank you Paolo for the link, it is really good article to read about, as it is mentioning a lot of different scientific research and opinions, and trying to compare each other and tell which one may be wrong or right and why. Off cause, their conclusion may be just another opinion, but i think it is a better way to discuss, instead of someone just dropping you data and “forgetting” to mention others people opinion or research which contradicts their views, but focusing instead on the stories what is going to be if they are right. Well, personally i am more interesting to hear stories why they think they are right and others are wrong, instead off talking me about hungry bears and who knows else what.
Comment by dz — August 24, 2006 @ 6:11 pm
Global Cooling
Blog brother AlexC sends me a link to a Q and O blog post on global warming. Written by Dale Franks (neither a Q nor and O), the post captures my position very well. Silence and I have talked past…
Trackback by Three Sources — August 26, 2006 @ 9:13 am