More on Globally Averaged Surface Temperature

This whole blog-to-blog comment conversation thing can get a bit maddening. What we really need is to all sit down in a room together. I think a lot of the misunderstandings that turn into arguments would instead play out as useful conversations. Plus we could drink beer*.

Today’s disjointed conversation has Mark Hadfield raising good questions in the comments here on Inkstain:

There’s no doubt that this metric (globally averaged surface temperature) doesn’t tell the whole story, but it’s quite another thing to suggest that it tells us nothing, or very little. Now I’m not suggesting that Roger (Senior) is suggesting such a thing, but the trouble is that on this issue, as on many others, I find it hard to work out what Roger *is* suggesting.

Over on his blog, Roger responds:

Here is what I am “suggesting”. For the assessment of global heat content changes (”global warming”) over the last 50 years, we focus on the assessment of ocean heat content changes, as the primary metric to assess the radiative imbalance of the climate system ( We avoid using the trends in the globally-averaged surface temperatures, since this diagnostic is fraught with a wide range of problems, including the most recent one that we identified in our GRL paper ( For earlier time periods, we have no choice but to use an estimate of global averaged temperature trends, but we need to recognize the very large uncertainty that exists with such a climate metric.

I don’t think globally averaged surface temperature tells us nothing. In fact, I think it answers a question the general public has, which is “how much warmer is it getting.” People live in air at the surface, so by “warmer,” it’s surface temperature they want to understand. That’s why I defended Juliet Eilperin last month against Roger’s criticism, and why I’ll probably do an end-of-the-year story for the paper that includes a discussion of the fact that 2005 is the warmest year ever. But I also am increasingly persuaded that an overemphasis on that one s

* I don’t really like beer. It’s metaphor.


  1. Rogers position makes no sense at all. The sfc T record is *far* better characterised than the ocean heat content. His comment about his GRL paper is misleading/wrong. I have no objection at all to suggesting that looking at the ocean heat content is a good idea. I agree with that. Use it to assess the radiative imbalance (but don’t let RP appropriate that as his idea: its not). But if you want to know if its getting warmer, look at the sfc T, as you say. Its not just where we live, its where much of the ecosystem lives.

    I think Rogers problem is that he feels the needs to say something new! exciting! controversial! Totally contrary to the “consensus-science” viewpoint, its far easier to get noticed by saying something new! etc! But… he’s scratching around for new! things to say, and not really finding very much, so ends up pushing what he has too far.

  2. John

    Yes, running a conversation on different blogs can be confusing, but you keep on encouraging it by mentioning interesting stuff you’ve seen elsewhere!

    I have taken my part of this conversation over to Roger’s site.

    IIRC William advocates the newsgroup sci.env as a forum for such conversations, but I’ve never been brave enough. I have seen some seriously pathological discussions on Usenet!


    RE “His comment about his GRL paper is misleading/wrong.”

    How so?

  3. Mark – Wasn’t a criticism of you. The thing is, even when it’s all in one place the comment back and forth isn’t nearly as effective as an actual conversation, with the possiblity of quicker and easier iteration.

    William – Please not with the ad hominem stuff. I don’t care about Roger’s motivations, or who deserves credit for the idea. Let’s sort out the substance here. It sounds like on the substance you have no great disagreement – or if you do have a disagreement, you haven’t articulated it beyond the point (with which I agree) that surface temperature is relevant because it’s where people live. As for your ecosystem point, I’d argue there’s a lot of ocean ecosystem too. Seems like keeping tabs on both is of some relevance.

  4. John – I disagree: if you want to understand what RP Sr is saying, just looking at the science isn’t enough. But that can go elsewhere.

    As to the substance… there really is none. RP Sr’s entire argument is near substanceless, and where there is substance its dubious (his “For the assessment of global heat content changes (”global warming”) over the last 50 years” is just silly – its an attempt to redefine the words GW to suit his meaning). If you’re really interested in the radiative imbalanc of the system… then look at the radiation balance! Which the ocean temperature won’t give you. Etc etc.

    Mark – RE “His comment about his GRL paper is misleading/wrong.” – I haven’t fully read his GRL paper. My suspicion is thats its a fairly minor point, BUT even if that is wrong his paper does *not* identify anything to do with “globally-averaged surface temperatures, since this diagnostic is fraught with a wide range of problems”… well, I re-iterate my point that John didn’t like.

  5. John, I suspect you know this but just to make sure, of course global surface temp is calculated both with and without ocean temps included; the one commonly bandied about is the combined figure. These are ocean *surface* temps, which are a quite different kettle of fish from the ocean heat content (i.e., the heat content of the total ocean volume) that RP Sr. prefers. Also, of course the ocean surface is where most marine life lives.

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