Follow-Up #3 – On Real Climate Comment #98 Alex Harvey asked a question. Below is my answer:
Thank you for your question
“Could you elaborate on why you believe that Argo should be able to detect the movement of heat into the deep ocean and why you believe that it hasn’t detected it?”
If you look at current data such as from the ECMWF; e.g. see http://www.ecmwf.int/products/forecasts/d/charts/ocean/real_time/xzmaps/
you can see areas of positive and negative temperature anomalies. Using the entire Argo network, such “lumps” of greater or less than average Joules should be seen in the analyses as one examines all of the profiles.
Follow-Up #2 – Gavin writes
[Response: I am well aware that temperature is a different quantity than heat, and have no objection to people tracking the accumulation of heat, but ‘global warming’ is simply not defined in this way. This is not a ‘fundamental disagreement’, this is simply you redefining the term ‘global warming’. For me (and almost anyone else you care to ask) global warming refers to the increase in global surface temperature anomaly. Indeed, ‘warmth’ is not a pure function of Joules – ice and water at 0 deg C have the same ‘warmth’, but very different heat contents. The very natural definition of warming is in terms of temperature; when people say that something has warmed, it means that the temperature has risen. You would be much more effective at communicating your scientific points if you used words in ways other people were already used to. – gavin]
Gavin – This is one reason why we have a different view of this issue. You write
“Indeed, ‘warmth’ is not a pure function of Joules – ice and water at 0 deg C have the same ‘warmth’, but very different heat contents”.
They do not have the same “warmth”, just the same temperature. There is more “warmth” with the liquid water. This is not semantics, but basic physics. If we want to properly monitor global warming, it must be in units of heat.
You are correct that when ” people say that something has warmed, it means that the temperature has risen”. However, when a scientist say that something has warmed, it means that the Joules have increased.
Follow-Up To One of Gavin’s responses relative to his claim of an independence of the GISS, CRU and NASA surface temperature analyses.
7 Oct 2011 at 10:21 AM
[Response: Yes, it actually is. And the Berkeley effort will show it again. – gavin]
The Berkeley analysis is a more independent assessment. We agree on that, and that it supports the GISS/NCDC/CRU trend findings with respect to the mean. This still does not make the GISS/NCDC/CRU independent.
The issue of why you persist in retaining the surface temperature trend as the primary metric of global warming is a puzzle to me. We, of course, need surface temperatures for a wide variety of other reasons. However, if significant heat is being transported to deeper depths, I assume you would agree that the surface temperature trend would underestimate global warming and influence the calculation of “climate sensitivity”. But let us know if you disagree and why.
Gavin further responds
[Response: “Climate sensitivity” is classically defined as the change in surface temperature as a response to radiative forcing. It is an equilibrium concept that is almost completely divorced from the flux of heat into the deep ocean. One could define a new concept – “total heat content sensitivity” (in J per W/m2 – odd unit) which would be related to the standard sensitivity, but also to the ocean mixing processes. Given that concept one could attempt to estimate it from observations and diagnose it in models and one could try and make a case that this was somehow more relevant in terms of impacts or vulnerability. All of these things could be done. But, as far as I am aware, none of them have. Thus, the standard climate sensitivity remains the focus of attention. I would suggest that if you want to change that, you should embark on the steps I gave above rather than simply co-opting language and changing standard definitions. So, to directly answer your question, since surface temperature changes define global warming, they cannot underestimate it. If you really mean to say that surface temperature increases don’t tell you much about deep ocean heat content changes, then this is of course true. But in that case I’m not sure what point you are trying to make. – gavin]
My response is
Gavin – You write
“surface temperature changes define global warming”.
Here is where we have a fundamental disagrement. Global warming is defined by the accumulation of heat in the units of Joules. Surface temperature changes by itself is not heat.
Gavin Schmidt presented a post (h/t to Erik)
I have submitted the following comment on the Real Climate weblog
Gavin – I am glad you noticed my post
Torpedoing Of The Use Of The Global Average Surface Temperature Trend As The Diagnostic For Global Warming
We seem to disagree on several points. First, you write
“The second point is related to a posting by Roger Pielke Sr last week, who claimed that the Meehl et al paper ‘torpedoed’ the use of the surface temperature anomaly as a useful metric of global warming. This is odd in a number of respects. First, the surface temperature records are the longest climate records we have from direct measurements and have been independently replicated by multiple independent groups. I’m not aware of anyone who has ever thought that surface temperatures tell us everything there is to know about climate change, but nonetheless in practical terms global warming has for years been defined as the rise in this metric. It is certainly useful to look at the total heat content anomaly (as best as it can be estimated), but the difficulties in assembling such a metric and extending it back in time more than a few decades preclude it from supplanting the surface temperatures in this respect.”
However, we now have a robust way to diagnose upper ocean heat content. We should move to that metric, starting in ~2003, as the primary metric to monitor global warming.
Also, NASA, GISS and CRU analyze their data differently, but they have a large overlap in their raw data; see my post
Erroneous Information In The Report “Procedural Review of EPA’s Greenhouse Gases Endangerment Finding Data Quality Processes”
“the surface temperature records …. have been independently replicated by multiple independent groups.
This is not correct.
Finally, you write
“Obviously heat going below 700m must have passed through the upper ocean. However, the notion that Argo could see this is odd. Argo measures temperature, not flux. The net flux into a layer is calculated by looking at the change in temperature. It cannot tell you how much came in at the top and left at the bottom, only how much remained. – gavin]”.
You are, of course, correct that Argo measures temperatures, but unless you can show the temporal sampling period is too long, or the spatial sampling is too sparse, the downward movement of heat would be seen in positive temperature anomalies as they move towards lower depth. Similarly, if this heat were to re-emerge, we would also see it as the anomalies move upwards.
Also, if there is large amounts of heat being stored at depth in the ocean, this means that the global annual average surface temperature trend is not sampling this heat. This surface temperature trend would be underestimating global warming.