Torsten,
 
I think this risks falling into the trap that unless we are absolutely certain about what percentage of warming is due to greenhouse gas concentrations, we should not act. In fact, the case for acting on climate change is based on principles of robust risk management and it is sufficient to know that the evidence indicates the probabilities are reasonably high that if we allow concentrations to continue to rise unabated we will be facing potentially catastrophic consequences by the end of the century.
 
We cannot say with any real certainty precisely what proportion of the warming is due to greenhouse gas concentrations because we cannot measure its total impact directly, or of the impacts of clouds, solar activity, etc. Have a look at figure SPM.2 here for estimates of the uncertainty associated with the various factors that might be contributing to radiative forcing: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-human-and.html.
 
Quite often, 'sceptics' try to score points by drawing attention to uncertainty in our knowledge. In fact, the fatal flaw in their position is they advocate a position that implies that we can be certain that the risks are negligible or zero.
 
Bob

________________________________

From: Discussion list for the Crisis Forum on behalf of Torsten Mark Kowal
Sent: Sat 29/01/2011 11:27
To: [log in to unmask]
Subject: Re: New opinion poll on climate change


Hi Bob, 

You wrote - "one cannot claim that human activities are wholly responsible, and it is not wrong to consider that natural causes have made a contribution. The problem is claiming that most or all of the recent warming is due to natural factors".

So which natural factors may have been sources of the increased radiative forcing, and imbalance in Earth's energy budget? In other words, which factors can be shown to have 'made a contribution', and to what degree (i.e. what percent of the observed 0.8 degrees C surface warming, or of increased ocean heat content), might be attributable to natural factors? 

IPCC hedging statement - "Most" - so what % of what has been observed? - "of the observed increase in global average temperatures since the mid-20th century is "very likely" - that means more than 90% likely in IPCC uncertainty language, but what causes the 10% of doubt? - "due to the observed increase in anthropogenic greenhouse gas concentrations."

You wrote - "one cannot claim that human activities are wholly responsible, and it is not wrong to consider that natural causes have made a contribution. The problem is claiming that most or all of the recent warming is due to natural factors".

See - http://understandinguncertainty.org/node/887

Exactly why is there any "problem is claiming that most or all of the recent warming is due to natural factors"? 

OK, we cannot say "all", but what is wrong with saying "most"? I interpret the literature as amply demonstrating that it is virtually certain that MOST - perhaps more than 90% - of recent warming (over decadal scales) is due to human activities. 

What is incorrect about that interpretation? How much of the warming isn't human-related; and on what evidence base are contrary statements made?

Cheers, 

Torsten Mark

At 11:03 29/01/2011, Bob Ward wrote:


	Brian,
	 
	You have misquoted me - I stated that it is technically correct that natural causes have contributed to climate change. Remember that the IPCC Fourth Assessment Report concluded: "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations."
	 
	As there is still uncertainty about the precise contributions of natural and man-made factors to the warming of the last 50 years, one cannot claim that human activities are wholly responsible, and it is not wrong to consider that natural causes have made a contribution. The problem is claiming that most or all of the recent warming is due to natural factors.
	 
	Bob
	
	________________________________
	
	From: Discussion list for the Crisis Forum on behalf of Brian Orr
	Sent: Fri 28/01/2011 20:13
	To: [log in to unmask]
	Subject: Re: New opinion poll on climate change
	
	
	
	Bob,
	
	A secondary point.
	
	"Climate change is technically down to natural causes"
	
	I presume what you are confirming here is that the climate
	is 'inherently' subject to natural causes. Of course, the very 
	significant
	new factor  - increasing green-houses gases as a result of human
	activity - is swamping the natural effects, but 'technically' they're 
	still
	present.
	
	Brian Orr
	
	On 28 Jan 2011, at 18:59, Bob Ward wrote:
	
	> The Department for Transport has just published the results of an
	> interesting opinion poll from August last year:
	> http://www.dft.gov.uk/pgr/statistics/datatablespublications/trsnstatsatt 
	> /climatejan2011report
	>
	> Predictably, the Daily Mail has focused on the small but detectable
	> change in the proportion of people saying that they are very convinced
	> or fairly convinced that the climate is changing, from 83% in August
	> 2009 (ie before Climategate etc) to 74% in August 2010. But given the
	> amount of misleading nonsense in the mainstream media and blogosphere
	> over that 12-month period, it is perhaps more remarkable that
	> three-quarters of the population still agree that the climate is
	> changing - it shows that the self-proclaimed 'sceptics' are not really
	> having much success with their campaigns of misinformation.
	>
	> Unfortunately, the poll did not include a question on whether climate
	> change is being mainly driven by human activities, although it did
	> include a question about the types of things that contribute to 
	> climate
	> change, to which only 5% answered that they don't believe in climate
	> change and only 15% answered 'natural causes' (which is technically
	> correct anyway). However, it also shows a relatively low level of 
	> public
	> awareness of the specific human contributors to climate change (for
	> instance only 59% think that emissions from road transport 
	> contribute).
	>
	> The proportion of people who report that they are very concerned or
	> fairly concerned about climate change only fell from 76% to 71% 
	> between
	> August 2009 and August 2010. And 72% say that they strongly agree or
	> tend to agree that they would be prepared to change their behaviour to
	> limit climate change, compared with 73% in August 2009.
	>
	> So I would say that these results show that Climategate etc has had a
	> measurable but relatively small effect on people's acceptance of the
	> reality that the climate is changing, it has had an even smaller 
	> effect
	> on whether they are concerned and almost no effect on whether they 
	> would
	> be prepared to act. But there remains relatively low awareness of
	> exactly which human activities are driving climate change.
	>
	> Bob Ward
	>
	> Policy and Communications Director
	> Grantham Research Institute on Climate Change and the Environment
	> London School of Economics and Political Science
	> Houghton Street
	> London WC2A 2AE
	>
	> http://www.lse.ac.uk/grantham
	>
	> Tel. +44 (0) 20 7106 1236
	> Mob. +44 (0) 7811 320346
	>
	>
	> Please access the attached hyperlink for an important electronic 
	> communications disclaimer: http://lse.ac.uk/emailDisclaimer
	
	
	
	Please access the attached hyperlink for an important electronic communications disclaimer: http://lse.ac.uk/emailDisclaimer


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