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« Back on Black | Main | Nature: no scrutiny of the academy »
Wednesday
Nov092011

Dangerous climate change?

This is a slightly edited version of a comment Richard Betts left on the discussion forum. I thought it was quite challenging to much of what we hear about climate change in the mainstream media and therefore worthy of posting here as a header post. (Richard, for anyone visiting for the first time, is head of climate change impacts at the Met Office).

Most climate scientists* do not subscribe to the 2 degrees "Dangerous Climate Change" meme (I know I don't). "Dangerous" is a value judgement, and the relationship between any particular level of global mean temperature rise and impacts on society are fraught with uncertainties, including the nature of regional climate responses and the vulnerability/resilience of society. The most solid evidence for something with serious global implications that might happen at 2 degrees is the possible passing of a key threshold for the Greenland ice sheet, but even then that's the lower limit and also would probably take centuries to take full effect. Other impacts like drought and crop failures are massively uncertain, and while severe negative impacts may occur in some regions, positive impacts may occur in others. While the major negative impacts can't be ruled out, their certainty is wildly over-stated.

While really bad things may happen at 2 degrees, they may very well not happen either - especially in the short term (there may be a committment to longer-term consequences such as ongoing sea level rise that future generations have to deal with, but imminent catastrophe affecting the current generation is far less certain than people make out. We just don't know.

The thing that worries me about the talking-up of doom at 2 degrees is that this could lead to some very bad and expensive decisions in terms of adaptation. It probably is correct that we have about 5 years to achieve a peak and decline of global emissions that give a reasonable probability of staying below 2 degrees, but what happens in 10 years' time when emissions are still rising and we are probably on course for 2 degrees? If the doom scenario is right then it would make sense to prepare to adapt to the massive impacts expected within a few decades, and hence we'd have to start spending billions on new flood defences, water infrastructure and storm shelters, and it would probably also make sense for conservationists to give up on areas of biodiversity that are apparently "committed to extinction" - however all these things do not make sense if the probability of the major impacts is actually quite small.

So while I do agree that climate change is a serious issue and it makes sense to try to avoid committing the planet to long-term changes, creating a sense of urgency by over-stating imminent catastrophe at 2 degrees could paint us into a corner when 2 degrees does become inevitable.


*I prefer to distinguish between "climate scientists" (who are mainly atmospheric physicists) and "climate change scientists" who seem to be just about anyone in science or social science that has decided to see what climate change means for their own particular field of expertise. While many of these folks do have a good grasp of climate science (atmospheric physics) and the uncertainties in attribution of past events and future projections, many sadly do not. "Climate change science" is unfortunately a rather disconnected set of disciplines with some not understanding the others - see the inconsistencies between WG1 and WG2 in IPCC AR4 for example. We are working hard to overcome these barriers but there is a long way to go.

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    - Bishop Hill blog - Dangerous climate change?

Reader Comments (285)

@Richard Betts
The IPCC did not endorse the 2K target. It cannot.

However, AR4 WG3 used the 2K target as its preferred, indeed almost exclusive, example when discussing possible and hypothetical policy targets. An unsuspecting reader may easily come away with the impression that the IPCC has indeed endorsed the 2K target.

I highlighted this in my review comments but was ignored.

Nov 11, 2011 at 12:27 PM | Unregistered CommenterRichard Tol

This posting by Richard Betts is all about the impact of global warming.

Richard Betts has admitted that the 2 degree meme is in no way dangerous.

Does he also agree that the 4 degree meme is very unlikely?

So if the a 2 degree change is nothing to fear and a 4 degree change is very unlikely then the negative impact of modest global warming, as we have seen and now expect, is now so minimal that it is not a policy priority.

Perhaps we can all now discuss the positive impacts of modest global warming for a change without fear of criticism.

Nov 11, 2011 at 12:34 PM | Unregistered CommenterMac

Nicely put Richard B, but I must take issue with your statement "Don't assume that because there are extremists on the "other side" that this means the "other side" is completely wrong. The truth is probably somewhere in the middle."

This reminds me of that classic book 'Straight and Crooked Thinking' by R H Thouless. He deals rather well with the error of the mean between two extremes, usually by showing that any position can be presented as such.

I think that you have to stay with the numbers, and not go for the cosy middle ground. (That is not to say that the truth ain't possibly there, only that it's not truth just because it's in the middle!)

Nov 11, 2011 at 12:48 PM | Unregistered CommenterCumbrian Lad

Now I understand...the 2K limit was universally endorsed as a way to show commitment to being green, ie recycling and saving energy.

So they recycled "Y2K" into "2K", saving gazillions of "Y"'s from being printed on paper and on screen in the process.

Perhaps somebody could compute how many gigatons of carbons have not been emitted, by shifting attention from the old scare to the new one.

ps I just received a message from a "K denier" in the year 2021...what could that be about?

Nov 11, 2011 at 12:52 PM | Unregistered CommenterMaurizio Morabito

Richard Betts: Basically, try to discuss issues and argument on their own merits and don't fall into the trap of allowing preconceived ideas about people's background and motivation to cloud the issue.

At the RSIJ presentation yesterday evening, there were many mentions of the Big Conspiracy that is apparently supporting skeptics in the USA and a bit less in the UK. It didn't sound like a debatable point, I really felt it was taken as Truth by many in the room.

Personally I consider it a bit of a "nutter thinking". Unfortunately, it is fully endorsed by the Grantham.

What worries me is that I simply do not know where people convinced of the reality of such a nutty idea, can put people like me, having no connection to any meaningful source of anti-AGW funding (I must have earned around £300 out of four years of articles on the subject, and I have never been paid in order to write, on commission that is).

And since they have no place for me, I will never belong to "their" debate. Sometimes I think it'd be easier to join EIKE ;-)

Nov 11, 2011 at 1:01 PM | Unregistered CommenterMaurizio Morabito

MM - "Now I understand...the 2K limit was universally endorsed as a way to show commitment to being green, ie recycling and saving energy."

That is another way of stating it. I would add, "............. or else" at the end.

Now we are being told that it is nonsense, not something that climate scientists actually believe in themselves. There is nothing to fear about the 2K limit. So why did they allow such nonsense dominate the debate?

It can only be because they determined that fear of the 2K limit would bring changes in human society not based on any science but based on advocacy, politics and adherence to ideology.

Nov 11, 2011 at 1:04 PM | Unregistered CommenterMac

And here's more about the "K scare of 2021"...including, as if it were anything new, anal retention.

Come to think, somebody should check if greenie vegan diets do lead to potassium deficiency. That'd explain far more than Mooney's "mutated Republicans".

Nov 11, 2011 at 1:25 PM | Unregistered CommenterMaurizio Morabito

Richard Betts

I didn't 'question your motives' in a pejorative sense. I asked you what you thought you were doing. I'm still bemused, especially after reading the comments on this thread. You do not correct the 99% nonsense, so most people here have decided that you are endorsing it.

That's deeply unfortunate.

We're back to

Sceptics: there's no wolf. It's all lies.

Nov 11, 2011 at 2:24 PM | Unregistered CommenterBBD

Nov 11, 2011 at 12:34 PM | Mac


Richard Betts has admitted that the 2 degree meme is in no way dangerous.

You are wrong, I didn't say that. What I actually said was:


While really bad things may happen at 2 degrees, they may very well not happen either - especially in the short term (there may be a committment to longer-term consequences such as ongoing sea level rise that future generations have to deal with, but imminent catastrophe affecting the current generation is far less certain than people make out. We just don't know.

As I think I've said before, it's all down to attitude to risk. Uncertainty works both ways - large uncertainties mean there are risks at the bad end, including the possibility of low-probability, high-impact outcomes. Given that we don't know what the risk is, but think it is non-zero, do we take action to reduce that risk? That's a political decision not a scientific one, and will rely on judgement calls (like most complex decisions, political or otherwise). I'm just saying that having made that judgement call, the science should not then be skewed to support it, as this could then influence other important decisions in undesireable ways. The uncertainties are large and we have to recognise that, formulate policy accordingly and be sure that scientific evidence appropriate informs several different policy areas that may rely on it.

Nov 11, 2011 at 2:57 PM | Unregistered CommenterRichard Betts

Richard, Betts, Nov 11, 2011 at 12:04 PM

I do agree with you about the obvious coarseness of the 'debate' around climate threats. It is hard to trace the origins of such an unpleasant, and of course poorly defined atmosphere, but I think it may really have got boosted by the declaration many years ago that there was no debate, or that the 'debate was over'. This position was adopted, perhaps with some enthusiasm, by the BBC in particular, and by associated media such as The Guardian and The Independent. There we have seen established a culture in which to challenge their degree of alarm about climate is to step beyond a pale, and be treated with blatant contumely.

That can change at short notice, as fashions come and go within the political class. The players will merely move on to somewhere they see with more liveliness or with more leverage for their political aspirations or predispositions.

But what may not be so easy to 'forgive and forget' is the impact on wave after wave of children who have been subjected to the political schemes of some of those who have found alarmism over climate such a wonderful, attention-getting, and indeed lucrative vehicle for their point of view. A point of view that has little compassion for humanity, little regard for the great achievements of technology, and is willing to see children deliberately disturbed by nightmarish visions in order to recruit new 'activists'.

Let me add my tuppence worth to the admiration expressed by many for your participation on this site. I think there is no uncertainty at all in noting your civil, insightful contributions which make it clear that the 'other side' is not entirely lacking in thoughtfulness and a willingness to discuss things with we outsiders.

Nov 11, 2011 at 3:02 PM | Unregistered CommenterJohn Shade

I'd like to echo John Shade's comment (just above this one). Thank you, Richard Betts, for your participation and illuminating comments and responses.

Nov 11, 2011 at 3:13 PM | Unregistered CommenterColdish

Nov 11, 2011 at 12:34 PM | Mac

Forgot to say - my opinion on 4 degree is still reflected in my
paper.

See Figure 2, which shows that 4 degrees above pre-industrial is within the "likely range" for 5 out of the 6 main emissions scenarios considered by IPCC in AR4.

Nov 11, 2011 at 3:14 PM | Unregistered CommenterRichard Betts

Richard Betts, "likely range" .............. but are these not upper end projections?

Nov 11, 2011 at 3:39 PM | Unregistered CommenterMac

Even 2 degrees doesn't look likely from any extrapolations except those from computer models that are unvalidated, hugely unfit for purpose and reliant on a mythical net positive feedback: I say mythical because it doesn't appear in the zero stratospheric cooling since 1995, the zero warming overall in the last 13 years (and yes i do exclude BEST here) nor in the zero increase in ocean heat content since accurate records began in 2003. Quite simply the expectation of 2 degrees is based merely on a show of hands from people whose livelihood depends on the scare of thermageddon.

The policy is in tatters anyway; people being more affected by the day to day market price of oil and gas than by green policies so far and green energy funding is diving worldwide. As for climate impacts; almost anything we do to help current, normal impacts would also be good for any postulated 5% increase (or decrease) that may or may not occur from climate change.

So it's probably a good thing for people to stress their job is based on any climate impact rather than increased climate impacts.

Nov 11, 2011 at 3:48 PM | Unregistered CommenterJamesG

Dr Betts,

On the " Impacts on the Developing world" page of the Met Office website one reads that "Developing countries around the world could face tough new challenges as climate change unleashes more extreme storms, raises sea levels and causes floods and droughts".

The use of "could" makes the challenges conditional, while the use of "as" - rather than "if" - makes it plain that the Met Office expects more "extreme storms ... etc.", without any qualification or reserve, or any timeline.

Are you comfortable with this sweeping statement, which simply ignores the uncertainty of climate change ?

Nov 11, 2011 at 5:04 PM | Unregistered CommenterCassio

Richard,
"my opinion on 4 degree is still reflected in my paper. See fig 2..."
This is a slightly misleading statement. The paper is a review paper and Fig 2 is straight out of the IPCC report. I am still not quite clear of the extent to which you support the IPCC position.

There is a lot of good sense in your 12.04 comment which I urge people to read and think about carefully. In particular this, which is a mistake I used to make:

Don't assume that because there are extremists on the "other side" that this means the "other side" is completely wrong.

Also this:
Extremists at your own end can reflect badly on you.

It's a mystery to me why only a tiny handful of climate scientists (Pielke Curry Zorita) seem to have realised this.

Nov 11, 2011 at 6:04 PM | Unregistered CommenterPaul Matthews

I have always considered the '2k' declarations to be political statements NOT scientific. Temperature cannot be averaged. Ask any real scientist.

Nov 11, 2011 at 10:32 PM | Unregistered CommenterDolphinhead

Nov 11, 2011 at 5:04 PM | Cassio

Thanks. I believe we are updating those pages, I'll check on the wording there (I agree the language should be more careful).

Nov 11, 2011 at 10:42 PM | Unregistered CommenterRichard Betts

Nov 11, 2011 at 6:04 PM | Paul Matthews

Thanks for your comments.

The paper is part review and part new analysis. Section 4 onwards presents model runs that hadn't been published before, and the earlier sections provided context including pointing out that the AR4 results for the A1FI scenario had not been particularly highlighted before. I still think those projections are plausible, noting the large uncertainty ranges. It's the impacts stuff I am less happy with - the range of climate possibilities are often not reflected in the range of possible impacts, and additional impacts uncertainties are often underplayed too.

So broadly speaking I am happy with the AR4 WG1 conclusions but less so with some of those of WG2. (No firm opinion of WG3, it's largely outside my field except for some of the forestry stuff).

Nov 11, 2011 at 10:54 PM | Unregistered CommenterRichard Betts

Richard, A number of us have commented in the past that these impact assessments appear to be always negative. Do your imact assessments not take account of benefits? I know that that could easily double the work involved (might bolster the case for your new computer :) ) but surely the work is just misleading without it? Would you accept a set of accounts that only showed the costs and not the income (would the taxman?)

Nov 11, 2011 at 11:17 PM | Unregistered CommenterCumbrian Lad

Richard has previously admitted that there are benefits to increased CO2 and warmth, but that his community are disposed to ignore them (airbrush them out or deeply bury them somewhere obscure, in the interests of 'message'). He has a very long hard road to convince them of this folly, despite it has spawned countless recruits to scepticism.

Nov 11, 2011 at 11:55 PM | Unregistered CommenterPharos

I had asked [Nov 11, 2011 at 4:28 AM ] Richard Betts:

Apart from signing up as "expert reviewers" to AR5 (which may or may not be feasible or appropriate for many of us), what would you suggest that those of us who (like you) do not subscribe to the alarmist 2 degrees C meme can do to support your efforts to bring some realism and clarity to the (for all intents and alarmist purposes currently non-existent) debate?

To which he had replied inter alia [Nov 11, 2011 at 12:04 PM]:

I don't think IPCC has actually formally endorsed the 2 degrees thing, has it?

Difficult to know ... particularly considering Pachauri's latest pronouncement:

Pachauri painted a grim picture of the adverse impact of climate change and claimed that the temperature may increase by 1.5. to 2.5 degree Celsius due to global warming. Referring to Bihar, Pachauri said the state was likely to face flood situation due to melting of glaciers in Nepal and adjoining reasons.[emphasis added -hro]

Modi, Pachauri stress on measures to stem global warming

Nov 12, 2011 at 5:55 AM | Unregistered Commenterhro001

Richard
In the first place if you are programming a computer model any projection can be made "plausible" if you try hard enough. Secondly, "the large uncertainty ranges" translate loosely as "we really don't have a clue" and the bigger the range the more that's true.
As for "range of possibilities" vis-a-vis "range of possible impacts" that really does take you into the realms of futurology. You don't actually know what the effects are going to be for any given scenario and you don't actually know how accurate the scenarios are going to be for any given range of conditions.
All you have is the output of your computer which you have programmed with what you believe to be the relevant raw material. Or at least what you hope is the relevant raw material.
And, as Cumbrian Lad says, where is mention of the benefits of additional warmth? We do know that warm is better than cold; civilisations have thrived in warm periods and declined in cool ones; fewer people die of excess heat than die of excess cold; plants thrive better in warm climates than cool ones.
And then, of course, there is the question of what is actually meant by a two degree rise in temperature. Two degrees above what? Starting from when?
And where? If the greater part of the warming is going to be at higher latitudes then Pachauri's scaremongering about Bihar, for example, is meaningless. (On his previous record it's probably meaningless anyway but that's a different discussion).
We're still at the stage where we don't even know what it is we don't know.

Nov 12, 2011 at 11:25 AM | Unregistered CommenterMike Jackson

Mike Jackson, I have just come back onto the thread to ask Richard a question which is somewhat relevant to your post. I was wondering how they put the models together, what parts were empirical data and what parts were assumptions, and the question came to my mind as to whether there was any empirical data for the increase of water vapour with an increase in temperature, and if there was not then what assumptions had gone into the model and what were the uncertainties of the assumptions. Clearly you don't have to dig very deep to become very suspicious of the models.

The first question I asked Richard on this blog was why there was not a single upside to rising temperatures. He said there was in the IPCC report, and there was, it said, I'm paraphrasing, there would be up to 20% increases in crops, but these are likely to be devastated by the increased precipitation. Some benefit.

I do hope you don't mind me interrupting your conversation with Richard BBD got into a mighty huff about it yesterday.

Nov 12, 2011 at 11:43 AM | Unregistered Commentergeronimo

geronimo
I am certainly not going to get into a huff if you join in. I've never seen blog posts as private conversations and I don't really see how they can be.
You've taken my thinking a step further then I had the courage, or the time, to go this morning.
My knowledge of computer programming is limited to some pretty basic stuff in BASIC 20+ years ago so if anyone cares to tell me I'm talking rubbish I'm not in a position to argue. But it seems to me that you have to make certain assumptions when you start with a program and the danger, as I see it, with models is that since computers are stupid and can only say 'yes' or 'no' when you ask them a question you more or less have to tell them what the answer is to a given set of circumstances. (Yes, I know they're more sophisticated but the GIGO principle still operates!)
If you tell them in the initial programming to ignore everything except CO2 (I exaggerate of course) then that is what they will do. If you give them a series of parameters and ask what will happen given a certain level of CO2 now and in 50 years time you must have already told them what is happening now in which case you have already made an assumption as to the extent to which CO2 is responsible for what is happening now. If you ignore clouds or ENSO or sunspots or cosmic rays or any one of a hundred other things and the assumptions you feed your Beast with are wrong then you will get wronger all the way down the line.
Which is more or less what I meant when I said we don't know what we don't know.
As for the benefits of a warmer world, we know that there are such benefits from the historical record and we can also draw certain inferences from the desperate attempts by a clique within the climate science community, and more so among the environmentalists, to play them down or "disappear" them. The very fact that these benefits are still being played down or ignored or denied is in itself a pretty strong indication that there is a little more, or perhaps a lot less, than science involved.

Nov 12, 2011 at 1:47 PM | Unregistered CommenterMike Jackson

So much suffering, so much despair, so much wasted diversion of our precious few experts in atmospheric physics, so much hot-headed waffling in the media, so much bile, so many foolish pieces of legislation, so many facile 'studies', so many misguided campaigns to scare the young into compliance. And all because of what? Ultimately, the outputs of computer models programmed to be alarming. The absurd political impact of the 'Limits to Growth' models no doubt inspired the same or similar schemers to leap upon climate models with whoops of glee. CO2 rising, industry produces CO2, mostly back then in the 'West', models can be run to give CO2 a dramatic role, or any other role, by twitching the adjustable parameters. Go for it!

But Mike Jackson (Nov 12, 2011 at 11:25 AM) has nicely summed up the reality:

In the first place if you are programming a computer model any projection can be made "plausible" if you try hard enough. Secondly, "the large uncertainty ranges" translate loosely as "we really don't have a clue" and the bigger the range the more that's true.
As for "range of possibilities" vis-a-vis "range of possible impacts" that really does take you into the realms of futurology. You don't actually know what the effects are going to be for any given scenario and you don't actually know how accurate the scenarios are going to be for any given range of conditions.
All you have is the output of your computer which you have programmed with what you believe to be the relevant raw material. Or at least what you hope is the relevant raw material.

I suspect the models have been put on a pedestal and given a prominence, and a credibility, which they are very far indeed from deserving. I cannot but help wonder if atmospheric physics would have gone further and faster in the past 30 years or so if GCMs had remained a novelty item, pursued by some just in case they could squeeze something useful out of them other than refining short-term extrapolations of the development and paths of already existing features such as cyclones.

Nov 12, 2011 at 1:49 PM | Unregistered CommenterJohn Shade

Mike you're right about the computers, that's why I asked if they had empirical data that they could feed into the computer for water vapour. If they don't then someone has to devise a table with CO2 and water vapour which will tell the computer how much water vapour is released relative to the amount of CO2 induced warming. Then they would have to calculate how much positive feedback they would get from the increased water vapour and come up with an increase in temperature. If they haven't done lab tests to calculate the increased heat from the positive feedback then they will have to calculate them in some way using the forcing equations. And that is holding the other 4 million parameters that make up the climate constant while all this goes on. At least that's what I think they would have to do, the computer won't make up the answer for them it will do calculations but they have to provide the equations and the data.

So, when the current batch of models show that the world was warmer than the thermometer measruements in the early twentieth century, the simply say, "aerosols", and put more aerosols into the climate model until they match the temperature. And hey ho they've proved that it would have been warmer except there were clearly more aerosols around then. As far as I can see they could equally have said TSI and reduced the TSI until the models reached the right temperature, but there's empirical data on the TSIs which means that they have to find something they can't measure because all the empirical data they have doesn't explain why the models show the early 20 century warmer than the thermometers. So it must be aerosols, because clearly there are no unknown unknowns in climate science, everything is known and the science is settled.

I could, of course, be talking complete bollocks and there is nothing in the models that can't be measured against empirical data.

Nov 12, 2011 at 7:41 PM | Unregistered Commentergeronimo

I posted this earlier I don't believe they could have made enough improvements in the models in the last 4 years to overcome the problems laid out by Dr. Trenberth. Although I bet Richard does:


Here's Trenberth on the models, I think he bitterly regrets this momentary lapse into truthfulness:

"...None of the models used by IPCC are initialized to the observed state and none of the climate states in the models correspond even remotely to the current observed climate. In particular, the state of the oceans, sea ice, and soil moisture has no relationship to the observed state at any recent time in any of the IPCC models. There is neither an El Niño sequence nor any Pacific Decadal Oscillation that replicates the recent past; yet these are critical modes of variability that affect Pacific rim countries and beyond. The Atlantic Multidecadal Oscillation, that may depend on the thermohaline circulation and thus ocean currents in the Atlantic, is not set up to match today’s state, but it is a critical component of the Atlantic hurricanes and it undoubtedly affects forecasts for the next decade from Brazil to Europe. Moreover, the starting climate state in several of the models may depart significantly from the real climate owing to model errors. I postulate that regional climate change is impossible to deal with properly unless the models are initialized."

Read the whole thing here:

http://blogs.nature.com/climatefeedback/2007/06/predictions_of_climate.html

Nov 12, 2011 at 7:54 PM | Unregistered Commentergeronimo

Mike, John, Geronimo,

An atmospheric general circulation model (GCM) simulates the large-scale circulation of the atmosphere as a fluid, the exchange of energy between the atmosphere, the surface and space, the transport of energy through the atmosphere, and the circulation of water and its changes of phase (solid, liquid, vapour) - all with equations grounded in physical understanding, solved every few minutes (in model time) at points on a grid with spacings of between a few km and several hundred km depending on the exact set-up of the model. Other more empirical equations represent the larger-scale consequences of processes which take place at temporal and spatial scales too small to be explicitly represented by the models. The same principles apply to ocean GCMs - and climate models tend to be coupled Ocean-Atmosphere GCMs so also allow for the interactions between oceans and atmosphere, which is very important for some key climatic phenomena such as ENSO which appear to be emergent properties of the interactions between atmosphere and ocean.

Indeed the phrase "emergent properties" is very important here, because the whole behaviour of the simulated atmosphere and ocean does simply emerge as a consequence of having all the equations set up to interact with each other, initialised with observed data, and then left to their own devices. The general circulation of the atmosphere, such as the jet streams, Hadley circulation (rising motion near the equator, sinking over the deserts), monsoons and ENSO remarkably do just happen as a natural outcome.

These models are used for both numerical weather prediction (ie: weather forecasts) and climate simulations, and the Met Office uses essentially the same model for both applications. So the ability of our model to simulate the character of the atmosphere realistically is tested several times a day. Of course, the models can't forecast the weather on a specific day-by-day basis more than a few days ahead, but the long-term statistical behaviour can be compared with the long-term statistics of observed weather to see whether the general character is realistic - things such as mean, max and min temperatures, precipitation etc, and frequency of blocking anticyclones, position of north Atlantic storm track, frequency and magnitude of El Nino events, timing of the Asian monsoon, and other phenomena. In some cases the models do reasonably well at these kind of things, if other cases they don't. Nevertheless it is quite remarkable (IMHO) that the general behaviour of the atmosphere can be simulated to a reasonable degree of realism in this way.

In the quote given by Geronimo above, Kevin Trenberth is talking about the specific problem of getting the regional details right for specific times, as opposed to getting the general statistics right over long periods as I described above. Progress is steady but slow in that area - so our ability to project regional climate variability over the next few years currently remains limited, but we're getting there.....

The problem for evaluating the models for longer-term climate change (several decades and longer) is that when we look at what the models do when we apply a change in the conditions, such as an increased concentration of greenhouse gases or aerosols, or we change the land surface properties to represent deforestation, different models give different results, especially at regional scales. And while we can compare the models with observations to see if the general long-term statistics of weather and climate are simulated realistically, we haven't got enough change in the observational record to evaluate the models' abilities to simulate long-term change of the scale projected for the future (but they do simulate the changes seen over the last few decades reasonably well at global scales - less so at more local scales, especially for precipitation. Nevertheless, we don't just use them as black boxes, we do examine the actual physical processes that are being simulated within the models and see whether these are consistent with observations of the real world. In a way, the models provide a means to test the internal consistency of numerous more specific pieces of understanding about how aspects of the climate system work, and also a means to examine the implications of a change in an input quantity (eg: GHG concentrations) for the behaviour of the system as represented by the equations which express our current understanding.

(Sorry, this is probably slightly rambling!)

The point is, while we cannot predict for certain how the long-term statistics of weather (ie: climate) will shift as a result of increased GHG concentrations or other drivers of change, it is not the case that we have absolutely no idea! The models give us a range of possibilities that are consistent with our current understanding.

Whether any of these possibilities are "benefits" or "threats" is not part of the model as such, but down to an examination of the implications in the light of past experience. (so yes we do look at positive impacts as well as negatives - the model is not set up to look at either "good" or "bad" things, it just indicates changes in weather/climate of all kinds.)

Nov 12, 2011 at 11:33 PM | Unregistered CommenterRichard Betts

Nov 12, 2011 at 11:25 AM | Mike Jackson

Sorry, I missed your specific question

And then, of course, there is the question of what is actually meant by a two degree rise in temperature. Two degrees above what? Starting from when?
And where?

It usually means a 2 degrees Celcius increase in long-term (multi-decadal) global mean temperature relative to pre-industrial, with "pre-industrial" assumed to be represented by the global mean estimated for the last few decades of the 19th Century which is when the global coverage of instrumental temperature records (not proxies) became sufficient for such an estimate to be credible.

Nov 13, 2011 at 12:13 AM | Unregistered CommenterRichard Betts

Perhaps we should take more heed of Los Alamos National Laboratory, whose 2005 paper “Our Calibrated Model has No Predictive Value” conceds that even perfect fit models, on perfect data, may have no predictive ability whatever

... we show that cases can exist where calibrated models have no predictive capability. This occurs even when there is no modelling error present. It is also shown that the introduction of a small modelling error can make it impossible to obtain any models with useful predictive capability.

We have been unable to find ways of identifying which calibrated models will have some predictive capacity and those which will not.

Nov 13, 2011 at 5:05 AM | Unregistered CommenterRick Bradford

Nov 12, 2011 at 11:33 PM | Richard Betts

From what you say you must have an indication of the models accuracy of predictive capacity against short term, medium and long term periods. So for example, how accurate are the models output for a two to three day forecast, 70%,80%,90%?

Nov 13, 2011 at 7:44 AM | Unregistered CommenterLord Beaverbrook

Dr. Betts,

You say: "....the last few decades of the 19th Century which is when the global coverage of instrumental temperature records (not proxies) became sufficient for such an estimate to be credible."

At the same time respected scientists were measuring atmospheric CO2 concentrations that were at least equal to modern day measurements, as reported by Beck, and others. If this is indeed the case (and the ice core methodology is found to be flawed) does this not completely invalidate the CAGW hypothesis?

Nov 13, 2011 at 10:26 AM | Unregistered CommenterRoger Longstaff

Richard Betts
Too much for my feeble brain on a Sunday morning! Thankyou for the detail, most of which I actually do understand!
I realise that the relationship between your Cray and my Commodore 64 is, shall we say, tenuous. Nevertheless, my point was that at some stage a programmer has had to make assumptions. If I can give an obvious example: it is fairly clear that the general consensus is a 1.2-1.5C increase for a doubling of CO2, absent any feedbacks. There is still a debate (quite heated in places) as to whether the feedbacks are positive or negative or even both under different circumstances. Unless the program can decide for itself which, somebody must have instructed it to assume one or the other.
At which point the question arises: where did the programmer get the information to make that decision?

With regard to the 2 degree question, I wasn't actually directing it specifically at you; it was more a general sort of musing on the question!
You say it "usually" means an increase in long-term global mean temperature relative to pre-industrial, which implies that there are other interpretations as well which immediately increases the uncertainty.
You also define pre-industrial as the global mean estimated for the last few decades of the 19th century. So you don't actually know what that temperature was and I'm afraid I'm of the school that in this context equates "estimates" with "guesses". On top of which I've been told never to trust anything before 1900.
I quite understand the reasoning that by, say, 1880 instrumental temperature records had made great strides but in most of Africa? Russia east of the Urals? Massive areas of the American mid-west? Large swathes of South America? Antarctica?
And, apart from the fact that you now had reliable (-ish) temperature records, why then? Why not the depths of the LIA? Or any other arbitrary date between the Roman Warm Period and now? Where is any serious evidence that two degrees warmer than 1880 (assuming the figure for 1880 is accurate) is something to worry us?
The thing is that this "two degree" figure is floating free. It has no anchor. It has no specific justification for its existence because there is no logical point in time or on the temperature scale to pin it to.
And I come back to my conclusion from yesterday: at this stage we don't even know what it is we don't know.

Nov 13, 2011 at 10:43 AM | Unregistered CommenterMike Jackson

Richard Betts on models
There is no doubt that GCMs have some utility in meteorology, and indeed in helping with weather forecasts. There is no doubt that they could be good fun to work with as far as climate is concerned, given the huge range of outcomes you can get from them from ice-covered earth (very stable, as I recall) through ice-free poles (as in most of the planet's history), and presumably to hothouse conditions. Out of this melee, this smorgasbrod from the still generally insoluble Navier-Stokes equations of fluid flow, some good may be possible. Modellers are guessing at the best fixes for the lack of horizontal resoultion, for poorly understood aspects (e.g. aspects of cloud formation), for the messiness induced by a very irregular surface poking well up into the troposphere in places, almost all water in others, and on top of that spinning and orbiting with various degrees of wobble and long timescale variations. Plenty scope for fun and for speculation. Used well, such models could and no doubt have contributed to productive discussions in academia. But once outside those groves, what have they done. what dreadful uses have they been put to, what grossly misleading assurances have they given to the politically driven or the emotionally unstable??? This is the crisis which exercises so many of us here - the misuse of patently inadequate climate modelling by those who had a prior agenda of wanting to dismantle industrial civilisation such as Maurice Strong, and the Club of Rome. It is easy to invite ridicule by hinting at conspiracy, but such conspiracy usually implies secrecy and covert actions. We need not appeal to either in this case, since the public record is revealing enough. It even gets worse, when the succour given to the so-called 'deep-greens' is recognised. To view mankind as contemptible, to call for not merely the destruction of industry but for the destruction of humanity, is indeed remarkable and extreme. If one regards the CAGW Faith as having a mainstream, a kind of Church of England if you will, then one can extend the analogy to include matches to extreme religious fanatics of the kind that have been noted from time to time for hundreds of years. The problem now is that the extent and powers of governments is way beyond what we have mostly seen before, and hence the scale and scope of their blunders can be so much the greater. I regard legislation such as the UK's Climate Change Act as one such blunder. I regard the concomitant indictrination of children strongly supported by the previous governent (e.g. remember those scary 'bedtime story' adverts financed by HMG?) as particularly harmful, and indeed completely unforgiveable. So, by all means continue with your modelling, and keep trying to find useful insights that might give good practical guidance. But be aware of the bigger, sinister picture. That is what exercises many of us here.

Nov 13, 2011 at 11:24 AM | Unregistered CommenterJohn Shade

My last post should have begun ('Re Richard Betts on models'). As it is, it could be misconstrued!

Nov 13, 2011 at 2:52 PM | Unregistered CommenterJohn Shade

A very nice summary, John Shade .

As for Dr. Betts and his great faith in models for predicting the climate 100 years from now, when will your models predict the weather more than a week from now?

And I think Mike Jackson also hit the nail squarely on the head with:

And I come back to my conclusion from yesterday: at this stage we don't even know what it is we don't know.

I suspect most of us on this blog would be very supportive of serious research being done on the issues and factors surrounding the weather, what causes and changes it, and how we can eventually predict it, but so far all we have seen are a bunch of charlatans making preposterous claims that would make even a snake oil salesman blush.

I have been reporting the pine-cone-eating behavior of the squirrels in my yard for several weeks now, and folklore indicates that they are preparing for a more severe than average winter. So far, they have been right. It is pretty damning when a bunch of squirrels are doing a better job. That is really, really sad. I would certainly prefer a somewhat more "scientific" prediction.

Richard, it is time to clean up your field's act and get serious about being scientists and not activists out to save the world from imagined dangers. Hopefully, your willingness to interact with us on this blog is an indication of your willingness to do so.

Nov 13, 2011 at 3:09 PM | Unregistered CommenterDon Pablo de la Sierra

I would like to respectfully ask Richard Betts whether the GCM's produce the marked asymmetry in tropospheric temperature trends between the northern and southern hemispheres described in the paper I referred to upthread at 9:12 PM Nov 10, 2011, and if so whether the model identifies a specific primary terrestrial or celestial mechanism for that asymmetry, and how is that asymmetry predicted to progress?

The paper was this one

http://www.atmos-chem-phys.org/11/10727/2011/acp-11-10727-2011.pdf

Nov 13, 2011 at 4:00 PM | Unregistered CommenterPharos

Don Pablo
Man has become far too sophisticated to believe that "lesser beings" have anything to teach him.
He forgets that while he has a superstore down the road and an electric socket to hand, that squirrel relies on getting it right or he doesn't see another Spring!
And at the risk of becoming boring on ths subject, our politicians don't understand (or don't care) that while that squirrel will live or die this winter by his own instincts and his own efforts, they are killing increasing numbers of our old and poor who are faced with a choice as to whether they "heat or eat".

Nov 13, 2011 at 4:04 PM | Unregistered CommenterMike Jackson

and let me link to this, where Naomi Klein manages to claim both that we know nothing about nature and must therefore live by its rules and, simultaneously that we must exert our authority over nature by doing more planning. The people who write this drivel are the chattering classes from whom more and more of our politicians derive - incapable of clear, incisive thought, determined that they know best for everyone.

http://timworstall.com/2011/11/13/yes-naomi-klein-is-an-idiot/

Nov 13, 2011 at 5:26 PM | Unregistered Commenterdiogenes

On models: if the CO2 thingy is removed, would the models not show over say, the last decade, a neutral temperature trend, and if they did would they not better reflect reality?

And if they don't?

Nov 13, 2011 at 5:34 PM | Unregistered Commentersimpleseekeraftertruth

Mike Jackson

And at the risk of becoming boring on ths subject, our politicians don't understand (or don't care) that while that squirrel will live or die this winter by his own instincts and his own efforts, they are killing increasing numbers of our old and poor who are faced with a choice as to whether they "heat or eat".

Mike, it's part of nature's way. It is called Winter Kill. Each winter winter, the cold kills off the old and weak so as to reduce the population of the herd, feed the predictors and keep the balance in the homeostatic model. I never thought that the Greens were in favor of this for us, but I guess they are. At least some of our politicians appear to be. I think they prefer the euphemism of "collateral damage" or "unintended consequences" but the effect is the same.

However, perhaps we should start a new movement against Green Winter Kill. That is what it is. I think it is not the humans killing the watermelons as Josh shows in his cartoon, but the other way around.

Nov 14, 2011 at 12:04 AM | Unregistered CommenterDon Pablo de la Sierra

I think you're right, Don Pablo.
It brings us back to Wirth's admission that global warming is irrelevant. It's all about preventing development which the Greens apparently fail to understand is what gives them the comfortable lifestyle they have now.
What do they really think life was like in 18th century England?

Nov 14, 2011 at 12:26 PM | Unregistered CommenterMike Jackson

It is a shame that Richard Betts has run away from this debate when the going gets tough. Just like ZedsDeadBed.

CAGW is the greatest scientific fraud in history.

Nov 14, 2011 at 3:15 PM | Unregistered CommenterRoger Longstaff

@Roger

I'd just like to stick up for Richard here.

We scientists - as in many other areas, I know - very often do long hours. There is no overtime paid for this, of course. Science communication and engagement activities such as discussing on this blog is extremely time-consuming. In a given fortnight, I might spend one day or 2-3 evenings on longer replies plus many short tweets while walking to work, waiting for buses, etc. I would guess Richard does about 3-4 times this judging by the content he adds here.

This is time we could be spending on our work (publications, writing grant proposals), our family, and our own interests. Our colleagues that do not do "public engagement" are at an advantage, because very little of it can be put on a CV or added to other metrics of academic success such as the REF. I would say we have to consider this an interest/hobby rather than our jobs: our workplaces encourage it in theory, but in practice it gains us very little (rather than a bit of respect, perhaps).

So...please...if it takes us a while to respond, it's because of the reasons above, not because we are trying to avoid the questions. I do try to skim most of your comments and Bishop's posts, but we can only reply if we have time. Personally, I try to prioritise areas I have most experience in rather than answer everything.

Best wishes,

Tamsin

Nov 14, 2011 at 3:28 PM | Unregistered CommenterTamsin Edwards

I think Richard would agree that we also try to prioritise answering direct scientific or technical questions, rather than questions of policy or broad CAGW-is-fraud type comments.

Nov 14, 2011 at 3:31 PM | Unregistered CommenterTamsin Edwards

@Tamsin,

Thank you for a response. However the CAGW fraud is based upon your "science" - and it is causing death and hunger for no purpose except the enrichment of academics, government tax collectors and carbon scam merchants. We are turning crops into petrol and littering our countryside with useless, expensive windmills while pensioners freeze and parents can not feed children.

I do not know how "climategate scientists" sleep at night.

(Definition of "climategate scientist" - see Harry_Read_Me)

Nov 14, 2011 at 3:42 PM | Unregistered CommenterRoger Longstaff

Roger

Please could you cut Richard and Tamsin a bit of slack.

Nov 14, 2011 at 4:11 PM | Registered CommenterBishop Hill

Apologies Your Grace - and to Richard and Tasmin.

I must try not to get so angry about this............

Nov 14, 2011 at 4:22 PM | Unregistered CommenterRoger Longstaff

Hello,

Thanks Bish. I did think putting science in quotation marks is a bit cheeky! But apology very much accepted, and I know many people here are angry.

We are all frantically trying to get results finished in time to submit papers by July 31st next year so they can be included in AR5. Believe me, your (plural) concerns are on my mind as I work. For example:

a) I recently moved from proprietary software to free so that my analyses can easily be repeated. Once papers are published I will give the code, and where possible the input data, to the journal and/or on my university page.

b) Once I publish some of my draft papers, I intend to start a blog with plain English summaries of them all.

c) I also stick up for you all (or most of you ;) ) when talking to colleagues who are rude or use the "d-word"...

d) Just the other day I was talking to friends about the thought-provoking threads here about personal responsibility of scientists. The glaciologists' vociferous response to the Atlasgate error is an easy choice to make, as would be responding to misrepresentation of my own work. But as quite a junior scientist, I'm still trying to judge where it's my place to speak publicly on behalf of others in my field - particularly on topics such as attribution, which are not my own research area, or on topics where the media interpretation is mildly, rather than wildly, wrong.

That's not to say that other scientists disagree with me or Richard. On the contrary, there is wide spectrum that I would hastily and inappropriately characterise as the Lovelock/Rahmstorf (and others) worst-case-scenario end ranging to the Annan/Hargreaves (and others) low-sensitivity end. But the vast majority of scientists just want to keep their head down and do science, and not get involved in (a) communication (b) political conversations (c) political decision-making (d) polarised debate.

We scientists do have a responsibility to ensure that our results are communicated effectively and interpreted correctly, and this blog has made this even more clear to me. But not everyone feels equipped to join the fray. Richard's strong presence here is more a reflection of his commitment to communication of the science than of any kind of maverick status.

Sorry Richard, maybe you like the maverick status ;)

Cheers,

Tamsin

Nov 14, 2011 at 4:49 PM | Unregistered CommenterTamsin Edwards

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