What we agree on

One of the interesting moments from the Cambridge conference was where Dr Eric Wolff of the British Antarctic Survey tried valiantly to find a measure of agreement between the two sides. I didn't get the details written down, but Dr Wolff has kindly recreated what he said at the time for me, for which many thanks are due.

In the table below, Dr Wolff's summary is in the left hand column and my comments are on the right. Blank implies broad agreement.

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*Everyone in the room agrees that CO2 does absorb infrared radiation, as observed in the lab
*I think everyone in the room agrees that the greenhouse effect (however badly named) does occur in practice: our planet and the others with an atmosphere are warmer than they would be because of the presence of water vapour and CO2
*I'm not sure if everyone agrees that the effect does not saturate with increasing CO2, but we heard a very clear presentation about that from Francis Farley	Professor Farley's explanation was to imagine CO2 as being like ink poured into water. You can add more and more ink and so there is no end to the extra absorbtion you can get. Saturated absorbtion bands are a red herring. This assessment made sense to me. I've set up a separate thread because I imagine some people will want to discuss this.
*It seemed that everyone in the room agreed that the CO2 concentration in the atmosphere has risen significantly over the last 200 years
*Almost everyone in the room agrees that this is because of anthropogenic emissions (fossil fuels, cement production, forest clearance).  We did hear Ian Plimer arguing that volcanic emissions of CO2 are more important than most scientists claim, but he did not explain why they would have changed in a step-like fashion in 1800, after tens of thousands of years with no such changes; and even he agreed that some of the increase in CO2 is anthropogenic.	This is not an area I've ever questioned, but I'm looking forward to finding out more from Ian Plimer about his ideas. I'm not sure I understand Dr Wolff's reference to 1800 either.
***I then suggested that if we agree all these statements above, we must expect at least some warming.
Then moving to whether we already see effects:
*I think everyone in the room agrees that the climate has warmed over the last 50 years, for whatever reason: we saw plots of land atmospheric temperature, marine atmospheric temperature, sea surface temperature, and (from Prof Svensmark) ocean heat content, all with a rising trend. (I briefly touched on the idea, mentioned only by Dr Howard in his introduction, that warming has stopped since 1998.  I used the analogy that it was very warm over Easter, but then cool enough that I had to scrape my car the following week.  But we did not take this as evidence against the idea that we are on a warming trend into summer, in which we know that July will be warmer than June than May than April, etc.).	Yes, but I would like to get some idea of whether the warming we have seen is statistically significant. i.e. a response to Doug Keenan's article in the WSJ.  I think Lucia's work has shown fairly clearly that the trend since the start of the century is very unlikely under 2deg/century, so the analogy is not a good one.
*We probably don't agree on what has caused the warming up to now, but it seemed that Prof Lockwood and Svensmark actually agreed it was not due to solar changes, because although they disagreed on how much of the variability in the climate records is solar, they both showed solar records without a rising trend in the late 20th century.	I didn't take this on board at the time. It would be interesting to see Svensmark's opinion. If the warming really cannot be shown to be statistically significant, how important is this kind of attribution?
*On sea level, I said that I had a problem in the context of the day, because this was the first time I had ever been in a room where someone had claimed (as Prof Morner did) that sea level has not been rising in recent decades at all.  I therefore can't claim we agreed, only that this was a very unusual room.	Not something I know much about, but Morner's concerns seem important. I find the idea that we can't see the adjustments to the data disturbing.
*However, I suggested that we can agree that, IF it warms, sea level will rise, since ice definitely melts on warming, and the density of seawater definitely drops as you warm it.
*Finally we come to where the real uncertainties between scientists lie, about the strength of the feedbacks on warming induced by CO2, with clouds a particularly prominent issue because they have competing effects that are hard to quantify.  I suggested to the audience that we could probably agree that the likely range of warming from a doubling of CO2 was 2-4.5 degrees C (which is actually the IPCC range).  This was the first time I really got any dissent, so I then asked whether we could all agree on at least 1 degree (implying no positive feedbacks at all, even from increased water vapour and sea ice loss).  I got one dissenting voice for that, but there wasn't a chance to find which of the preceding statements he had disagreed with (it would be necessary to disagree somewhere up the line to be consistent with dissenting on this one).	I'm very uncomfortable about the idea of making a prediction about temperature when it is so likely that there is something missing from the models - this seems the most plausible explanation for the temperature trend since 2000/1. Under the scientific method, shouldn't we find out what this is before we start testing again? We may be able to agree that the no-feedback warming is 1 degree C, but there is a great big unknown in the shape of the feedbacks. The idea of overall positive feedbacks seems unlikely to me, given that the Earth's temperature doesn't seem to have got out of control in the past.

So there you go. Quite a lot of agreement on the basics, but some pretty interesting differences kicking in one we get on to the detail of what it means. We can discuss the agreement or otherwise in the comments. If I get some time I might put together a survey to get a better idea of how strong our agreement or disagreement on Dr Wolff's points is.

I also thought it would be interesting to see if we can get a measure of agreement on some sceptic talking points too. A couple of mainstream scientists I met at Cambridge have agreed to take a look at the specific points I raise above - namely the question of whether the warming in the temperature records is statistically significant and to what extent Lucia's work shows that the IPCC models have overstated the warming. I have discussed Lucia's work with a couple of other scientists since, and neither seemed to have strong objections to her work, although they were disinclined to place much weight on the results.

Underlying both of these areas is a simple question of whether the variability in the surface temperature records can be described with an AR1 model. Doug Keenan seems to me to have shown quite conclusively that it cannot (Doug's technical background document is required reading on this subject).

So my question for climate scientists would be this:

"Do we agree that the AR1 assumption for surface temperatures is inappropriate?"

Comments

[Simon Hopkinson]

Emily Shuckburgh write:

Shub, you say above that "In blog comments, everyone's going to come across as more belligerent than they are. One has to internally calibrate for that - it is an occupational hazard." But does that have to be the case?

Well... yeah, really. The content is what the content is.

The presumption is that abusive content (trolling) will be ignored (and occasionally removed), and that, otherwise - regardless of whether it is accordant or not - where content is presented rationally and reasonably, it is given due consideration.

That is the (netiquette-compliant) blog format, and it is this way because it is functional. The choice to participate or not is the individual's own, but the debate within the blogosphere will move along with or without.

[Shub]

Dr Shuckburgh,
Thanks for your comments. Firstly, this sort of a topic is always a problem (always). "what do we agree on". As you might have seen by now, whenever a discussion of this sort starts, you will have many people disagreeing to what you, as a scientist, might percieve to completely basic and axiomatic.

For example, Dr Judith Curry has a thread, taking off the just the same topic as here where she lists one of the points: "We can all agree that there has been a significant rise in CO2 in the past century". I don't agree with this statement at all. What is meant by "significant" here? Under what framework? Has CO2 not been higher than the present level in the earth system before then?

The end result is that there is a wide range of disagreeing comments, all worded to varying degrees of rhetorical strength. No wonder you would conclude that "this thread is different". Indeed, as a scientist, your attitude might be: "if I assume X, Y and Z to be true, what can I discover about the climate?" whereas many people 'here' are more like "Is X true?", "Is Y fully substantiated?". This is what probably comes across as 'corrosive skepticism', as being 'different' and true, there a quite a few of them (us).

Indeed the unhesitating assertion that everything in climate science is now 'settled' is precisely the reason why there are so many men and women from the Notes from the Underground (as far as an apparent defiance for the sake of it goes) in the skeptics camp. The scientists are perhaps not directly to be blamed for it, but I rarely see any scientists pulling up activists and journalists who spread this nonsense day in and day out either.

The second thing of course, is that one guy, gets so many varieties of responses to what he initially thought was a reconciliation exercise, from a side he harbored some sympathy for to begin with...yes, he would definitely feel attacked. But let me assure you, that was not the intention. It is just an artifact of the blog mode of conversation. You can again recall Dr Curry's treatment at the hands of the consensusists when she submitted her opinions to a hostile review of the Bishop's book at the 'scientist' blog Realclimate. It was literally, thousands of comments, almost all in the most unparliamentary of language, and not a shred of sympathy for someone viewed as having gone over to the dark side.

We don't do that here. It may seem a bit heated here, (if I may take the liberty to talk for my fellow commenters), but not very much. But that said, I will strive to be more welcoming and less harsh as well.

[Emily Shuckburgh]

Thank you Shub.

Questions like "Is X true?", "is Y fully substantiated?" should be part of the basic lexicon of a scientist. I am all for encouraging that kind of discussion. It is important.

Best wishes,

Emily

[D. Robinson]

Bish, Is there a mistaken double negative in this line

"I think Lucia's work has shown fairly clearly that the trend since the start of the century is very unlikely under 2deg/century, so the analogy is not a good one."

I thought that Lucia's work had shown fairly clearly that the trend since the start of the century is very likely under deg/century. Or am I missing your point??

[sHx]

"Firstly, when models are run out for a century into the future..."

One of these days I'll chance upon an explanation as to why climate models run out for a century into the future. This one came close, but no cigar.

To be blunt, I don't trust anyone, whether he is a prophet or crystal ball gazer or a climate scientist, who says he can predict what is going to happen a hundred years hence, especially if the prediction is an impending catastrophe and the prescription is to abandon the 'sinful' ways.

It is not like we have detected a comet coming our way in 2100 and we refuse to take the threat seriously. If only the climate system worked like a clock...

What is the justification for climate predictions so far into the future, anyway? Do they make predictions for 5, 10, 20, 30, 50 years from now, as well? How have they been holding up so far?

[Bart Verheggen]

Neil,

That's not at all how I would interpret Wolff's comment, but if you want to feel offended, I guess I can't stop you.

[diogenes]

I wonder if it would not be better to turn the debate on its head. If you look for points of agreement between the believers and the sceptics, you find yourself easing towards a position where the science is settled. Although uttering such a phrase brings all sorts of insults from the scientific community, that is the impression that the believers are trying to create - that there is nothing to argue about. Instead, sceptics should focus on the points that are not agreed or where there is considerable debate.

[Norseraider]

We should applaud courageous types like Dr. Wolff and Dr. Curry, who, despite their individual beliefs, are willing to reach out and engage with sceptics in sensible discussion.

Despite having a (non-climate) science degree, and definitely not being in the pay of Big Oil (honest!), I am still treated like a crook and an idiot by some of my best friends when we talk about global warming! Well, I say "talk", but too often it has degenerated into quite appalling screeching, name-calling and belittlement of my 'socially unacceptable' views.

This gives me grey hairs, and helps no-one get to the bottom of things. I cannot recall another scientific topic so divisive. So, regardless of whether we disagree on the points of the debate, we should be very happy to have people like Dr. Wolff who allow us to engage in debate at all!

Once we can hold our views without being ostracised, then we can begin to prove our point through proper discussion, and I still believe we will succeed (otherwise I wouldn't be a sceptic!).

[Neil Craig]

Diogenes I think that is a very good point. See what the areas of disagreement are and whot sort of measurements would be accepted by either side as falsifiying their position. It is now generally accepted that, as defined by Popper a theory must be falsifiable to be scientific.

According to Dr Wolff's assessment the areas on which there were disagreement were:#

on whether CO2 absorbtion goes up linearly with thge amoint of CO2 or tails off. Personally I would have thought the latter obvious but it is certainly something amenable to experiment.

on whether the obserbed heating, including the alleged "step change" in warmth in 1800 was certainly of anthropohenic cause. This is clearly the important one. It should be possible to determine from ice if there was a step change in CO2 then and from history if there was a similar one on human release of CO2.

that there has been a rising trend over the last century. This would seem to depend on how consistent the "trend" has to be to be a trend. Perhaps some supporters of alarmism could state what degree of deviation from a constant rise would, in their opinion, invalidate the hypothesis. It is possible that some may have alrerady done so up to 1999 when the trend appreaerd constant, at least for 20 years.

on whether the warming trends of the 1980/90s (and 1930s) can or cannot be accounted for by solar variation. No ideas here.

on whether there has or has not been a provable statistically significant sea level rise over recent decades. This should be a matter of fact either way.

on what the actual level of feedback is. I said earlier I thought it likely to be less than one or we would not have recovered from the Medieval Warming, the Climate Optimum or others but the alarmists seem convinced it is 2 - 4. I think it should be possible to at least narrow the range here.

[Punksta]

BH: The idea of overall positive feedbacks seems unlikely to me, given that the Earth's temperature doesn't seem to have got out of control in the past.

There wasn't industrialisation in the past. So the question is, how large are present human CO2 emissions compared to natural variations of it in the past ?