It is NOT a confidence level. It is projected as one,but it is not. If you read the IPCC summary statement for policy makers 2007, it becomes perfectly clear. It is the SUBJECTIVE opinion of the authors of the report. The process through which this subjective opinion was arrived at is not mentioned. But if you get any further information on the process you can let me know
Hey let me be clear as it seems it is you who does not get the point even when articulated several times. Confidence level comes out of scientific tests. It is an objectie observation not a subjective belief- so the 90-95% confidence is NOT a confidence level. How does the subjective belief comes into existence is a different question
Wrong - Confidence levels come from statistics not science out of scientific tests. They are used to ascertain if a certain group of data showing a specific outcome is statistically significant.
If you do not know how the IPCC have reached their 90/95% assumptions then i dont see how you can say whether it is or isnt a confidence level.
Robmb, statistics is a tool for scientific tests. You conduct scientific tests and use statistics to determine the confidence level. IPCC has done no such tests. It is not witin the ambit of IPCC to do its own research. The report specifically statest that the confidence levels are the EXPERT judgement of the authors so they are subjective opinions of the authors
call it what you will but confidence tests are a statistics tool. it may surprise you to know that they are used by marketeers, PR companies, political analysts et al. None of whom are scientists doing scientific experiments.
Enough - the point here is that i and i assume you would like to know how the confidence level of 90/95% has been reached. You assume that it is purely judgmental on the part of the IPCC authors. i am going to try and find out if they have used any real stasts analysis to reach their conclusions. in the meantime lets leave it at that.
I think WIYM is right. When science meets politicians, politicians ask the "Is it really happening?" question. Scientist rambles on for an hour about cloud feedbacks, solar variation, albedo changes at the poles...and then the politician says "Yes, but is it really happening".
Just a guess: it is possible that the given uncertainty is related to the main area of doubt: uncertainty in the cooling effects of aerosols. Checking the scientific assessments of these forcings, there is an outlying chance that anthropogenic aerosol cooling is exactly balancing out anthropogenic CO2 warming.
Obviously, this leaves the big question as to what has caused the recent warming open, and doesn't solve the CO2 problem since CO2 will continue to increase while aerosols stabilise (because they don't last very long in the atmosphere). But since it is possible, an uncertainty has to be assumed.
Personally, I think this is your classic 11-1 jury decision, where 1 member of the jury is just a member of the awkward squad
Just as we don't know the future anthropogenic CO2 emissions (except the projections from GIGO model), we also don't about future anthropogenic aerosol emission, so how can we know anything?
India and China are Industrializing in a very rapid rate. The industrial pollution we saw from 1750 onwards was based on development of around roughly a billion people (this guess is based on current population of USA and other developed nations). The combined population of India and China currently is 2.4 Billion people with an average per capita income of around US$ 750. Per capita income of USA is US$ 25,000 which is roughly indicative of the income level of developed nations. How do you account for CO2 emission and aerosol emission from these underdeveloped nations industrializing their economies?
Even if we accept human made CO2 as the causal mechanism why can't we go into another global cooling period from the anthropogenic aerosol emissions from India and China? Any ideas
Even if we accept human made CO2 as the causal mechanism why can't we go into another global cooling period from the anthropogenic aerosol emissions from India and China? Any ideas
Yes, aerosols stay in the atmosphere for a year or so. CO2 levels build up (essentially stays around for centuries. Even if we have 5-6 huge volcanoes next year producing massive amounts of cooling in 2009-2011 they will be washed out and we'll be back to warming in 2012-2013.
Am I missing something here? The global cooling from 1940-1980 (four decades) has been largely attributed to anthropogenic pollution. These anthropogenic pollution was created due to Industrialization of a relatively small number of people. On the other hand we are currently seeing a relatively much larger number of people going through the same industrialization process.
Now why do you discount the fact we can go into a global cooling period for a much longer time scale due to a much larger scale pollution that's happening now?
I observe a silence from Steve_M on the issue. Anyone else wants to have a go? I would really like to know
Sorry, like a good scientist I went to bed
The temperature graph they showed on the Swindle programme was a little out of date, and was selected by Durkin because it was "less wiggly" than the real NASA data such as:
data.giss.nasa.gov/gistemp/graphs/
it looks quite different, and the 40-years of cooling is not so apparent.
The main point though is that surface temperatures are more quickly affected by aerosol cooling because they shield the earth from the sun. Greenhouse gas warming is a more gradual heating of the whole atmosphere which takes decades to have its full effect. If we stopped emitting any CO2 tomorrow warming is expected to continue for some decades.
So, the cooling effect of all those postwar emissions kicked in straight away whereas the warming took a while.
No problem Steve. Now the IPCC report clearly acknowledges the global cooling between 1940-1980 so does the favourite AGW webiste realclimate.org So it is a bit misleading on your part to suggest that Durkin was out to mislead us.
Having said that, you don't really answer my question why can't the global cooling happen again due to industrial pollutants as the industrialization pace in India and China over the last 10 years have gathered pace and is going to gather even more pace in the coming years?
The sulphate aerosol explanation was always an ex-post explanation by the AGW lobby brought in to prevent falsifying of the CO2 theory. Now it has done its job, it seems they have conveniently forgotten to account its effect in the future climate projections. Somehow this is not important anymore
I was at the IPCC AR4 (fourth assessment report) launch in the Royal Society in early March. The uncertainty was banded into two categories depending on data.
If statistical data was available then uncertainty is provided as confidence limits calculated in the normal way. This was objective.
In other areas where data was not clear/available then confidence was based on expert opinion (i.e discussions with numerous key experts) in these cases it was subjective.
For example when the reports says something is very likey, it is subjective but means that 90% of those asked thought that it to be the case. Almost certain means 99%, etc.
As I've mentioned in previous posts scientists are very conservative when giving subjective opinions (well, no always) - so subjective opinions of AR4 were almost certainly conservative by their nature.
jjej102, thanks for the clarification. Can you give me an example of the prediction, when the objective criteria was used? Also the overarching claim of the IPCC report that it very confident that human made CO2 is responsible for recent global warming- is this a objective or subjective statement?
No problem Steve. Now the IPCC report clearly acknowledges the global cooling between 1940-1980 so does the favourite AGW webiste realclimate.org So it is a bit misleading on your part to suggest that Durkin was out to mislead us.
The 3rd assessment report technical summary has a plot on page 26 does show 0.1 degree of cooling spread more gradually across the 1940-80 period, which is still half of the cooling in Durkin's plot. The 4th assessment report summary for policy makers plot (on page 17) looks more NASA-like - again this was available for 6 weeks before the programme aired.
He was able to correct his plot to remove the NASA logo between Thursday showing and Monday showings, but not able to correct the curve?
I do not know what the emissions of sulphate from China and India are. I'm assuming that they will be fairly assessed in models given that sulphate, dust and chemistry models are the big research area. It's a little premature to say that because we aren't seeing a new global dimming, the theory must be wrong.
"It's a little premature to say that because we aren't seeing a new global dimming, the theory must be wrong."
Hey Steve, are you saying that the AGW theory says we are heading for a global dimming? That's a distinctly unAGW like statement. But if you have seen the light, so be it
WIYM - the 90% confidence of AGW is ultimately a subjective assessment.
By all accounts during this decision some scientists wanted to push for almost certain 99% sure and others for likely <90% - to me this feels like they caught the scientific mood well.
It's a little premature to say that because we aren't seeing a new global dimming, the theory must be wrong.
OK I've sensed you coming to this conclusion and I mean that it is a little premature to come to this conclusion in the light of my unsatisfactory responses. Go away, read up on climate forcings, compare the assessments of the impacts of Indian and Chinese pollution then see what you think. I suspect you'll find the amounts of pollution aren't as large as one might think, or perhaps that it is just swamped by the high level of GHGs.
Good - glad to see that soemone has managed to give a real explanation of the confidence levels. Thanks for that jjeh. Would also be interested in examples of the objective conclusions. Presumably the calculation of man made co2 over the past 30 years as a % of the total co2 increase is one of these?? If so and the science is caste iron on the fact that more co2 in the atmosphere creates more warmth (not linear and with no exclusio of other factors) is it not possible that the 90% conclusion of AGW since 1980 is objective?
Yes that is right - proving that CO2 is from human emissions is relatively straightforward. Carbon derived from fossil fuels, which has been around for many millions of years has virtually none of the isotope carbon 14, as this isotope is unstable and has decayed over the time (half life 5700 years). The decay of this isotope is what enables carbon dating to work.
You may ask, why is all the carbon in the atmosphere not depleted of carbon-14? Well atmospheric carbon has its carbon 14 stock replenished through a nuclear reaction involving cosmic rays and nitrogen in the upper atmosphere (where it takes a while for fossil carbon to reach). I know this sounds a bit sci-fi but this is well understood atmospehric physics.
So fossil fuel derived carbon = no carbon 14, atmospheric carbon = known carbon 14 therefore the ratio of fossil and atmospheric carbon can be derived and hence the anthropogenic carbon emissions calculated (therefore an objective result).
