But the proverbial cart is being placed afore the horse here, is it not? Forecasting errors are being posited as such before they have had even 0.1% of a chance to pan out so that their accuracy or otherwise may be evaluated.

As a general follow-up to the dismissal of the literature by some commentators on here, I'll repost the comment that nails it IMO: from Ray Ladbury, who is - OK - known for being outspoken (who can blame him frankly given some of the absurd accusations echoed about regarding climate scientists in general), but when one digests his words slowly they do tend to have a ring of truth about them. Ray is a sound bloke once you get to know him. This was posted elsewhere some 18 months ago, but it is still good advice - indeed it is the best advice that a newcomer to this whole barney could have, and the "IGNORANT" in the first sentence is not an insult - it's implying there's a fascinating world out there once you start reading the literature instead of the Tabloids - so please set forth on that journey. I've appended my comments in square brackets:

"If you don’t know about or understand the evidence that shows incontrovertibly that we are warming the planet, you are IGNORANT. No sin here. You can rectify your ignorance by hard study. [JM - that's the vast majority of us including me, though I'm striving to rectify it]

If you refuse to put in the hard study, then you are WILFULLY IGNORANT and your opinion is worthless. [JM - applies to anything pretty much - sea-angling for example - if you don't work at it, gaining experience and understanding, you'll never up your catch-rate, and blaming e.g. the local East European population might make you feel briefly more comfortable, but will it help? Will it heck!]

If you refuse even to look at the evidence even when it is shoved in front of your face and still insist you understand better than all the experts, then you are a DENIALIST. [JM - true - and I specifically reserve the term these days for people who are paid to spread misinformation for political purposes - the well-known U.S. rightwing thinktanks come immediately to mind. The term "skeptic" is utterly abused with regard to these people: ALL scientists need to maintain skepticism to counter the very human phenomenon of confirmation-bias with which we are every one of us afflicted]

Finally, if you insist that all the scientists are engaged in a global hoax to preserve their lucrative grants (which amount in salary to about what a mid-level IT administrator would make), then you are an IDIOT." [JM - can anybody in their right minds really envision a truly global conspiacy, involving a few thousand scientists from countries as diverse in politics and faiths as China, Iran, the USA, Germany, Russia, Bolivia, etc etc etc managing to achieve same right under the noses of their extemely diverse political systems? Consider for one moment: not ONE religion has ever accomplished such a takeover, despite myriad wars fought in its name, over very many centuries if not longer...]

No: I think Ray nailed it fair and square with those four points. Perhaps the most succint post ever made on the subject, though I expect howls of derision for reposting it!

Cheers - John

But the proverbial cart is being placed afore the horse here, is it not? Forecasting errors are being posited as such before they have had even 0.1% of a chance to pan out so that their accuracy or otherwise may be evaluated.

As a general follow-up to the dismissal of the literature by some commentators on here, I'll repost the comment that nails it IMO: from Ray Ladbury, who is - OK - known for being outspoken (who can blame him frankly given some of the absurd accusations echoed about regarding climate scientists in general), but when one digests his words slowly they do tend to have a ring of truth about them. Ray is a sound bloke once you get to know him. This was posted elsewhere some 18 months ago, but it is still good advice - indeed it is the best advice that a newcomer to this whole barney could have, and the "IGNORANT" in the first sentence is not an insult - it's implying there's a fascinating world out there once you start reading the literature instead of the Tabloids - so please set forth on that journey. I've appended my comments in square brackets:

"If you don’t know about or understand the evidence that shows incontrovertibly that we are warming the planet, you are IGNORANT. No sin here. You can rectify your ignorance by hard study. [JM - that's the vast majority of us including me, though I'm striving to rectify it]

If you refuse to put in the hard study, then you are WILFULLY IGNORANT and your opinion is worthless. [JM - applies to anything pretty much - sea-angling for example - if you don't work at it, gaining experience and understanding, you'll never up your catch-rate, and blaming e.g. the local East European population might make you feel briefly more comfortable, but will it help? Will it heck!]

If you refuse even to look at the evidence even when it is shoved in front of your face and still insist you understand better than all the experts, then you are a DENIALIST. [JM - true - and I specifically reserve the term these days for people who are paid to spread misinformation for political purposes - the well-known U.S. rightwing thinktanks come immediately to mind. The term "skeptic" is utterly abused with regard to these people: ALL scientists need to maintain skepticism to counter the very human phenomenon of confirmation-bias with which we are every one of us afflicted]

Finally, if you insist that all the scientists are engaged in a global hoax to preserve their lucrative grants (which amount in salary to about what a mid-level IT administrator would make), then you are an IDIOT." [JM - can anybody in their right minds really envision a truly global conspiacy, involving a few thousand scientists from countries as diverse in politics and faiths as China, Iran, the USA, Germany, Russia, Bolivia, etc etc etc managing to achieve same right under the noses of their extemely diverse political systems? Consider for one moment: not ONE religion has ever accomplished such a takeover, despite myriad wars fought in its name, over very many centuries if not longer...]

No: I think Ray nailed it fair and square with those four points. Perhaps the most succint post ever made on the subject, though I expect howls of derision for reposting it!

Cheers - John

What an excellent post.

I reject the science Tom, all our warming can be attributed to natural variability within our climate sytem. There is no evidence what so ever to suggest the small increase in CO2 levels has lead to any increase in global temperatures. You are trying too make a cake without eggs and flour

 Your evidence consist of manipulated data, hopeless computer simulated modelling, and a complete lack of understanding of albedo effects.

 

Wow

That should be held up as a classic for defining the completely unsustainable position of the denier.

I have detected an increasing desperation in your posts, SC.  This is just so patently rubbish that there is scarcely any merit in either the post or trying to debate it's contents (Polarwind take note)

NS why is my post rubbish, the evidence for warming caused by AGW  is far from settled. I've read countless IPCC papers, and none of them offer any conclusive proof, as my post highlights. 

Just too add also that climate models only ASSUME that their is a large positive feedback as the world warms, note the word ASSUMED, it crops up a few times.

Climate models underestimate the increase of evaporation with temperature.

Climate models overestimate the effect of CO2. This is down to global recorded temps, which contains the UHI component..

The sensitivity of climate models depends on the ASSUMED value of aerosol forcings. This is not measured, but only ASSUMED!

So we have a theory that is settled on ASSUMPTIONS! 

I reject the science Tom, all our warming can be attributed to natural variability within our climate sytem. There is no evidence what so ever to suggest the small increase in CO2 levels has lead to any increase in global temperatures. You are trying too make a cake without eggs and flour

 Your evidence consist of manipulated data, hopeless computer simulated modelling, and a complete lack of understanding of albedo effects.

 

Wow

That should be held up as a classic for defining the completely unsustainable position of the denier.

I have detected an increasing desperation in your posts, SC.  This is just so patently rubbish that there is scarcely any merit in either the post or trying to debate it's contents (Polarwind take note)

That's rich coming from you! So I take you and you alone can undoubtedly estimate the sensitivity of earths temp to anthropogenic CO2 output? 

NS why is my post rubbish, the evidence for warming caused by AGW  is far from settled. I've read countless IPCC papers, and none of them offer any conclusive proof, as my post highlights. 

Just too add also that climate models only ASSUME that their is a large positive feedback as the world warms, note the word ASSUMED, it crops up a few times.

Climate models underestimate the increase of evaporation with temperature.

Climate models overestimate the effect of CO2. This is down to global recorded temps, which contains the UHI component..

The sensitivity of climate models depends on the ASSUMED value of aerosol forcings. This is not measured, but only ASSUMED!

So we have a theory that is settled on ASSUMPTIONS! 

Thanks for putting words into my mouth.  I don't think I have suggested this? 

Which part of your statement:

'I reject the science Tom, all our warming can be attributed to natural variability within our climate sytem. There is no evidence what so ever to suggest the small increase in CO2 levels has lead to any increase in global temperatures. You are trying too make a cake without eggs and flour'

are you suggesting isn't worthy of derision?

1. The global temperature record shows quite clearly that there is a warming trend that is not explained by any known natural cycles.


2. We haven't had a 'small increase in CO2 levels' - we have had a 40% increase in CO2 levels.  That figure is increasing by around another percentage point each year.

You make these daft unsupported statements and you wonder why you get these responses?

Nobody is going to take your odd opinions seriously if you resort to such statements.

I reject the science Tom, all our warming can be attributed to natural variability within our climate sytem. There is no evidence what so ever to suggest the small increase in CO2 levels has lead to any increase in global temperatures. You are trying too make a cake without eggs and flour

 Your evidence consist of manipulated data, hopeless computer simulated modelling, and a complete lack of understanding of albedo effects.

 

Wow

That should be held up as a classic for defining the completely unsustainable position of the denier.

I have detected an increasing desperation in your posts, SC.  This is just so patently rubbish that there is scarcely any merit in either the post or trying to debate it's contents (Polarwind take note)

That's rich coming from you! So I take you and you alone can undoubtedly estimate the sensitivity of earths temp to anthropogenic CO2 output? 

NS why is my post rubbish, the evidence for warming caused by AGW  is far from settled. I've read countless IPCC papers, and none of them offer any conclusive proof, as my post highlights. 

Just too add also that climate models only ASSUME that their is a large positive feedback as the world warms, note the word ASSUMED, it crops up a few times.

Climate models underestimate the increase of evaporation with temperature.

Climate models overestimate the effect of CO2. This is down to global recorded temps, which contains the UHI component..

The sensitivity of climate models depends on the ASSUMED value of aerosol forcings. This is not measured, but only ASSUMED!

So we have a theory that is settled on ASSUMPTIONS! 

Thanks for putting words into my mouth.  I don't think I have suggested this? 

 

Which part of your statement:

'I reject the science Tom, all our warming can be attributed to natural variability within our climate sytem. There is no evidence what so ever to suggest the small increase in CO2 levels has lead to any increase in global temperatures. You are trying too make a cake without eggs and flour'

are you suggesting isn't worthy of derision?

1. The global temperature record shows quite clearly that there is a warming trend that is not explained by any known natural cycles.


2. We haven't had a 'small increase in CO2 levels' - we have had a 40% increase in CO2 levels.  That figure is increasing by around another percentage point each year.

You make these daft unsupported statements and you wonder why you get these responses?

Nobody is going to take your odd opinions seriously if you resort to such statements.

 

I reject the science Tom, all our warming can be attributed to natural variability within our climate sytem. There is no evidence what so ever to suggest the small increase in CO2 levels has lead to any increase in global temperatures. You are trying too make a cake without eggs and flour

 Your evidence consist of manipulated data, hopeless computer simulated modelling, and a complete lack of understanding of albedo effects.

 

Wow

That should be held up as a classic for defining the completely unsustainable position of the denier.

I have detected an increasing desperation in your posts, SC.  This is just so patently rubbish that there is scarcely any merit in either the post or trying to debate it's contents (Polarwind take note)

That's rich coming from you! So I take you and you alone can undoubtedly estimate the sensitivity of earths temp to anthropogenic CO2 output? 

NS why is my post rubbish, the evidence for warming caused by AGW  is far from settled. I've read countless IPCC papers, and none of them offer any conclusive proof, as my post highlights. 

Just too add also that climate models only ASSUME that their is a large positive feedback as the world warms, note the word ASSUMED, it crops up a few times.

Climate models underestimate the increase of evaporation with temperature.

Climate models overestimate the effect of CO2. This is down to global recorded temps, which contains the UHI component..

The sensitivity of climate models depends on the ASSUMED value of aerosol forcings. This is not measured, but only ASSUMED!

So we have a theory that is settled on ASSUMPTIONS! 

Thanks for putting words into my mouth.  I don't think I have suggested this? 

 

Which part of your statement:

'I reject the science Tom, all our warming can be attributed to natural variability within our climate sytem. There is no evidence what so ever to suggest the small increase in CO2 levels has lead to any increase in global temperatures. You are trying too make a cake without eggs and flour'

are you suggesting isn't worthy of derision?

1. The global temperature record shows quite clearly that there is a warming trend that is not explained by any known natural cycles.


2. We haven't had a 'small increase in CO2 levels' - we have had a 40% increase in CO2 levels.  That figure is increasing by around another percentage point each year.

You make these daft unsupported statements and you wonder why you get these responses?

Nobody is going to take your odd opinions seriously if you resort to such statements.

 

Maybe you should read all the post, a common theme amongst the doomslayers. Now which part of ASSUMED don't you understand?

But your original post didn't use the word 'assumptions' (not 'assumed' by the way, as you are in nit-picking mode).

You cannot wriggle out of it that easily - or indeed at all.

It's a common theme amongst the rabid deniers that they change the subject or refuse to answer a valid question when they realise they've been found out yet again.

Now, would you care to deal with the facts as I enumerated above or are you going to indulge in some more ducking and diving?

 

 

That's rich coming from you! So I take you and you alone can undoubtedly estimate the sensitivity of earths temp to anthropogenic CO2 output? 

NS why is my post rubbish, the evidence for warming caused by AGW  is far from settled. I've read countless IPCC papers, and none of them offer any conclusive proof, as my post highlights. 

Just too add also that climate models only ASSUME that their is a large positive feedback as the world warms, note the word ASSUMED, it crops up a few times.

Climate models underestimate the increase of evaporation with temperature.

Climate models overestimate the effect of CO2. This is down to global recorded temps, which contains the UHI component..

The sensitivity of climate models depends on the ASSUMED value of aerosol forcings. This is not measured, but only ASSUMED!

So we have a theory that is settled on ASSUMPTIONS! 

SC, I think you are right to question the science, as should everyone. I also think you have a point regarding the climate models given the erratic performance of the weather models after only 4-5 days. Perhaps there is a difference and I'm happy for someone to explain why?

I also think you are right to highlight the many ambiguities in climate science including feedbacks, range of warming etc.  So on reflection, I was perhaps too harsh to dismiss your post as total nonsense.

Having said that I must say that to reject the science seems bizzare. If 99.9% of the experts in a particular field are telling you something then I think it is probably a good idea to listen to them. It is clear the world has warmed and that CO2 has increased. As Gandalf says, there is no known natural cycle that accounts for this - at the moment

I'm prepared to accept the science, while keeping an open mind and an awareness of the ambiguities. My interest lies in the politics of climate, not so much on the 'is it happening', more the 'what we do about it'. 

Aye, Northern Sky, and I agree on that. We have big problems coming up with shortages in liquid (=transport) fuels too. Surely to goodness it makes sense to look at any possible workarounds, rather than to keep pretending that none of this will happen!!??

The people I call deniers are extremely, extremely dangerous, for the simple reason that they can not see a single problem with ever-continued human expansion and consumption. As Douglas Adams would have said: "This is, of course, impossible"!

If you think it's possible folks, then shove some yeast in a jar with a handful of sugar & a bit of water - see what the ultimate result is!

Cheers - John

That's rich coming from you! So I take you and you alone can undoubtedly estimate the sensitivity of earths temp to anthropogenic CO2 output? 

NS why is my post rubbish, the evidence for warming caused by AGW  is far from settled. I've read countless IPCC papers, and none of them offer any conclusive proof, as my post highlights. 

Just too add also that climate models only ASSUME that their is a large positive feedback as the world warms, note the word ASSUMED, it crops up a few times.

Climate models underestimate the increase of evaporation with temperature.

Climate models overestimate the effect of CO2. This is down to global recorded temps, which contains the UHI component..

The sensitivity of climate models depends on the ASSUMED value of aerosol forcings. This is not measured, but only ASSUMED!

So we have a theory that is settled on ASSUMPTIONS! 

SC, I think you are right to question the science, as should everyone. I also think you have a point regarding the climate models given the erratic performance of the weather models after only 4-5 days. Perhaps there is a difference and I'm happy for someone to explain why?

I'll have a stab NS. The weather model may be wrong after 4-5 days, but only (as an example) because a weather system went a couple of hundred miles north or south of its predicted path. What the weather model showed would still be within the range of expected weather - it just happened to be incorrect. Now, if you ran the weather model for 50 years, you'd have no hope of it ever predicting the weather correctly beyond a week or ten days. However, if it's good model*, the range of weather it provides at a point should average out to give the actual climate at that place - the right amount of sunshine, rain, snow, right range of temperatures etc. This is essentially what climate models do, except they run at lower temporal and spatial resolution than weather models despite including more variables (to save on computing time).

So if your climate model produces the right kind of weather consistently (i.e. the climate, with its inherent variability), it hardly matters that it can't predict next Tuesday's weather.

*This is oversimplified - climate models are not just weather models run for longer. For example, weather models ALL have a radiative drift because they're not in equilibrium. They don't need to be, because they only run for a couple of weeks and the imbalance doesn't wind up having an effect. Some climate models need an artificial correction to counteract this, but more modern ones, starting with HadCM3, are good enough not to 'drift'.

I also think you are right to highlight the many ambiguities in climate science including feedbacks, range of warming etc.  So on reflection, I was perhaps too harsh to dismiss your post as total nonsense.

Having said that I must say that to reject the science seems bizzare. If 99.9% of the experts in a particular field are telling you something then I think it is probably a good idea to listen to them.

Yes the uncertainties do need highlighting. However SC is not correct in his assertion that climate models assume positive feedback; that's an emergent property of the models. In fact I can tell you four of the main factors that cause it to emerge:

i) The absorption characteristics of all GHGs are programmed in. Most importantly, that includes water vapour.

ii) The clausius-clapeyron equation is programmed in. This governs evaporation and the humidity of the model's atmosphere. That equation dictates that humidity increases with temperature (and of course we know water vapour is a GHG, ergo positive feedback).

iii) The albedo of various surfaces is programmed in. Most importantly, that includes ice and snow.

iv) Because ice and snow cover increases with a cooling climate and decreases with a warming climate, it must be a positive feedback.

What's more, climate models do not overestimate the effect of CO2. The radiative effect of CO2 is well known, it's pretty much impossible to mis-estimate. It's what the model then does with that particular radiative forcing that is important, but it certainly can't be claimed to be an oversensitivity to CO2. If a model is oversensitive, it's because it's oversensitive to all forcing, not just CO2 forcing.

 

 

That's rich coming from you! So I take you and you alone can undoubtedly estimate the sensitivity of earths temp to anthropogenic CO2 output? 

NS why is my post rubbish, the evidence for warming caused by AGW  is far from settled. I've read countless IPCC papers, and none of them offer any conclusive proof, as my post highlights. 

Just too add also that climate models only ASSUME that their is a large positive feedback as the world warms, note the word ASSUMED, it crops up a few times.

Climate models underestimate the increase of evaporation with temperature.

Climate models overestimate the effect of CO2. This is down to global recorded temps, which contains the UHI component..

The sensitivity of climate models depends on the ASSUMED value of aerosol forcings. This is not measured, but only ASSUMED!

So we have a theory that is settled on ASSUMPTIONS! 

SC, I think you are right to question the science, as should everyone. I also think you have a point regarding the climate models given the erratic performance of the weather models after only 4-5 days. Perhaps there is a difference and I'm happy for someone to explain why?

I also think you are right to highlight the many ambiguities in climate science including feedbacks, range of warming etc.  So on reflection, I was perhaps too harsh to dismiss your post as total nonsense.

Having said that I must say that to reject the science seems bizzare. If 99.9% of the experts in a particular field are telling you something then I think it is probably a good idea to listen to them. It is clear the world has warmed and that CO2 has increased. As Gandalf says, there is no known natural cycle that accounts for this - at the moment

I'm prepared to accept the science, while keeping an open mind and an awareness of the ambiguities. My interest lies in the politics of climate, not so much on the 'is it happening', more the 'what we do about it'. 

If 99.9%  Did you get that figure from reliable source?

not thatb wilki is overly reliable but here is a list of sceptic scientists...

http://en.wikipedia.org/wiki/List_of_scientists_opposing_the_mainstream_scientific_assessment_of_global_warming

But either way, since when did science become ruled by consensus? If 99.9% of scientists believed the world to be flat or the Earh is the centr of the universe, that would not make it right. So it is with the AGW THEORY.  There is some evidence that Man made Co2 is helping warm the earth above its norm (whatever that is), but equally there is evidence showing that Man made Co2 has little or no effect. The truth is, there is a great element of doubt and the whole thing has become an economic and political nightmare. Could you imagine if someone proved to the world that man made AGW did not exist?

There would be world wide chaos as people wonder why they are paying co2 taxes on this, that and everything! It is in no ones interest to have the AGW theory debunked, there simply is too much money at stake for goverments and companies!!

If 99.9%  Did you get that figure from reliable source?

not thatb wilki is overly reliable but here is a list of sceptic scientists...

http://en.wikipedia.org/wiki/List_of_scientists_opposing_the_mainstream_scientific_assessment_of_global_warming

But either way, since when did science become ruled by consensus? If 99.9% of scientists believed the world to be flat or the Earh is the centr of the universe, that would not make it right. So it is with the AGW THEORY.  There is some evidence that Man made Co2 is helping warm the earth above its norm (whatever that is), but equally there is evidence showing that Man made Co2 has little or no effect. The truth is, there is a great element of doubt and the whole thing has become an economic and political nightmare. Could you imagine if someone proved to the world that man made AGW did not exist?

There would be world wide chaos as people wonder why they are paying co2 taxes on this, that and everything! It is in no ones interest to have the AGW theory debunked, there simply is too much money at stake for goverments and companies!!

Well you cannot have it both ways, as you intimate.  Your two statements are incompatible - 'lots of scientists are sceptics' to suggest a lot of support for the sceptical position then you really cannot turn to the argument that consensus doesn't matter.

As you know a lot of those sceptics are not climate scientists.  Also as you know the impartiality of a number of them is tainted by association with the fossil fuel industry or their lobbyists.

Your flat earth analogy is correct but not in the way you have used it.  When first it was proposed that the earth was round that view was dismissed. It started as a tiny minority and grew as the evidence mounted and became conclusive.  At what point did the evidence become conclusive?  That is the issue with the AGW debate.  AGW started out as a proposal from a very few scientists - evidence has grown.  The only issue is whether that evidence is yet conclusive.

There is plenty of evidence that the Earth is warming in response to GHGs (not only CO2).  There is precious little evidence that it is not.

Your final comment is nonsense I'm afraid.  If CO2 was found not to be an issue we would still need taxes because fossil fuels are finite and we have to wean ourselves off them.

I find your use of the word 'debunked' offensive.  Go and look it up.

Who said this?

Do you agree that from 1995 to the present there has been no statistically-significant global warming

Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.

Do you agree that according to the global temperature record used by the IPCC, the rates of global warming from 1860-1880, 1910-1940 and 1975-1998 were identical?

An initial point to make is that in the responses to these questions I've assumed that when you talk about the global temperature record, you mean the record that combines the estimates from land regions with those from the marine regions of the world. CRU produces the land component, with the Met Office Hadley Centre producing the marine component.

Temperature data for the period 1860-1880 are more uncertain, because of sparser coverage, than for later periods in the 20th Century. The 1860-1880 period is also only 21 years in length. As for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different (see numbers below).

I have also included the trend over the period 1975 to 2009, which has a very similar trend to the period 1975-1998.

So, in answer to the question, the warming rates for all 4 periods are similar and not statistically significantly different from each other.

Here are the trends and significances for each period:

Period	Length	Trend (Degrees C per decade)	Significance
1860-1880	21	0.163	Yes
1910-1940	31	0.15	Yes
1975-1998	24	0.166	Yes
1975-2009	35	0.161	Yes

Who said this?

Do you agree that from 1995 to the present there has been no statistically-significant global warming

Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.

Do you agree that according to the global temperature record used by the IPCC, the rates of global warming from 1860-1880, 1910-1940 and 1975-1998 were identical?

An initial point to make is that in the responses to these questions I've assumed that when you talk about the global temperature record, you mean the record that combines the estimates from land regions with those from the marine regions of the world. CRU produces the land component, with the Met Office Hadley Centre producing the marine component.

Temperature data for the period 1860-1880 are more uncertain, because of sparser coverage, than for later periods in the 20th Century. The 1860-1880 period is also only 21 years in length. As for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different (see numbers below).

I have also included the trend over the period 1975 to 2009, which has a very similar trend to the period 1975-1998.

So, in answer to the question, the warming rates for all 4 periods are similar and not statistically significantly different from each other.

Here are the trends and significances for each period:

Period	Length	Trend (Degrees C per decade)	Significance
1860-1880	21	0.163	Yes
1910-1940	31	0.15	Yes
1975-1998	24	0.166	Yes
1975-2009	35	0.161	Yes

It was said nearly two years ago by Phil Jones, since then the waming sicne 1995 has become statistically significant you will see that the periods with statistically significant warming are all 20 years plus. I am not sure why 1975 to 1998 and 1995 to 2009 were separated out though. It is normal to use periods of 30 years or more for changes in climate as this way you minimise the impact of decadel  variability.

Marcus, go and look at the global temperature trends for the last century or more. That deals adequately with your concern about multi decadal variability.

In addition as regards the UK it is very striking seeing the trend of the CET: there is most clearly and unargubly a distinct warming trend.

Marcus, go and look at the global temperature trends for the last century or more. That deals adequately with your concern about multi decadal variability.

In addition as regards the UK it is very striking seeing the trend of the CET: there is most clearly and unargubly a distinct warming trend.

Marcus, go and look at the global temperature trends for the last century or more. That deals adequately with your concern about multi decadal variability.

In addition as regards the UK it is very striking seeing the trend of the CET: there is most clearly and unargubly a distinct warming trend.

Of course there's a warming trend in global surface temperature! I have never said there isn't. The role of multi-decadal changes is generally excluded from being a factor because it cannot be easily be differentiated from any forcing terms. Multi-decadal changes are of a comparable time-scale to the total period of warming, and likely to be of greater magnitude than the slow-and-steady warming due to anthro-GHG. Warming feedbacks then have to be attributed between warming from forcing and warming from multi-decadal changes: hence the uncertainty in all this, which few express appropriately.

OK Marcus.  Maybe this is an issue of definition.

You said 'multi-decadal changes' and I assumed from that expression that your meaning was natural changes occurring over several decades.  On that basis I thought that the global trends over the last 100+ years addressed that point.

I think you need to demonstrate possible natural mechanisms for these 'mulit-decadal changes' - otherwise the door is open to pick any potentially random period of time and propose that there is some as yet unknown natural forcing at work.

As far as I am aware there is nothing known that might account for the warming trend over this extended period other than GHGs?

Of course the issue concerns the confidence level that may be attributed to GHGs as the agent. We know the IPCC says it is 90% confident, which given the complexities is a remarkably high number - and higher than their previous assessment.  I suspect the next one won't put it any lower.

 We know the IPCC says it is 90% confident,

For your information Gandalf.

A large number of scientists contributing to the IPCC have decided to have a middle eastern style rejection of the way the organization falsely represents their views.

This appears to be based upon their belief that the IPCC has gone too far with the idea of mans impact on global climate and intend to set up an alternative scientific organization debunking most if not all of the IPCC'S projections and I Quote"False science and manipulation of politics"

Interesting times ahead, my friend.

Edited by user  01 April 2011 13:42:09  | Reason: Not specified

 We know the IPCC says it is 90% confident,

For your information Gandalf.

A large number of scientists contributing to the IPCC have decided to have a middle eastern style rejection of the way the organization falsely represents their views.

This appears to be based upon their belief that the IPCC has gone too far with the idea of mans impact on global climate and intend to set up an alternative scientific organization debunking most if not all of the IPCC'S projections and I Quote"False science and manipulation of politics"

Interesting times ahead, my friend.

Well I know many perhaps most of the contributors to the physical science (working group 1) of the IPCC and this is just nonsense, none of them have.

 We know the IPCC says it is 90% confident,

For your information Gandalf.

A large number of scientists contributing to the IPCC have decided to have a middle eastern style rejection of the way the organization falsely represents their views.

This appears to be based upon their belief that the IPCC has gone too far with the idea of mans impact on global climate and intend to set up an alternative scientific organization debunking most if not all of the IPCC'S projections and I Quote"False science and manipulation of politics"

Interesting times ahead, my friend.

Watch the use of the word Debunk as GTW finds it offensive....

I thought this rather amusing...

http://blogs.telegraph.co.uk/news/geraldwarner/100030204/climategate-two-more-bricks-fall-out-of-the-ipcc-wall-of-deceit-rainforests-and-polar-bears/

Edited by user  01 April 2011 14:26:31  | Reason: Not specified