jennifer

On Sunday a colleague and I discussed the general issue of correlation versus causation in science. He suggested that 1. There must be a body of work establishing a causal link between anthropogenic carbon dioxide and warming, and also 2. Some work that quantifies the extent of the warming from the anthropogenic carbon dioxide. He assumed as much because our government, the Australian government, is planning major perturbation to our economic system on the basis that carbon dioxide from the burning of fossil fuels is contributing to dangerous global warming. He assumed that the Australian government would not undertake such an action lightly, indeed that such an action would be premised on good evidence establishing a proven causal link between anthropogenic carbon dioxide and global warming. I replied that I was not so sure.

He said he would do a search of the scientific literature on Monday. I said it would be interesting to compare what he turned up from this systematic search of library databases with a few random requests on the internet.

So, Sunday evening I posted a note at my blog, at John Quiggin’s blog and at a yahoo climate science group of mostly so-called climate change skeptics.

Perhaps not surprisingly one of the first to claim that a body of work existed was John Quiggin; a well known climate alarmist. Professor Quiggin went as far as to claim that there are “hundreds of papers on both the causal link and the question of sensitivity” but could only cite a few papers which dabble with the issue of sensitivity later in that blog thread.

By early Monday evening (when I started writing this blog post) the thread at Professor Quiggin’s blog had thrown up only three papers that I thought could potentially provide a causal link and a quantification of the extent of warming. Interestingly one of them was published as long ago as 1938. I had listed the papers earlier in the day at the threads at both Professor Quiggin’s and my blogs to see if other papers were put forward in preference to these, but they weren’t. The papers are:
1. Callendar, G.S., 1938. The artificial production of carbon dioxide and its influence on temperature. Q. J. R. Meteorol. Soc., Vol 64, 223–237.
2. Hofmann, D.J., J. H. Butler, E. J . Dlugokencky, J . W. Elkins, K. Masarie, S. A. Montzka and P. Tans, 2006. The role of carbon dioxide in climate forcing from 1979 to 2004: Introduction of the Annual Greenhouse Gas Index, Tellus B, Vol 58, 614-619.
3. Crowley, T. 2000. Causes of Climate Change Over the Past 1000 Years. Science Vol 289: 270-277.

The Hofmann et al. paper initially looked the most promising to me, is available on the internet (click here) and is the first that I shall consider. (I plan to post comment on the Crowley or Callendar paper tomorrow.)

While the title of the Hofmann et al paper does suggest a “role” is established for carbon dioxide as a forcing/warming agent, in fact it is just assumed in the body of the paper.

The authors simply taken a set of gases (including carbon dioxide) and ascribed an effect: climate forcing. They do not demonstrate a mechanism, or even shown a correlation, between levels of anthropogenic carbon dioxide and global warming.

So, I shall have to conclude that this paper fails the criteria (1. There must be a body of work establishing a causal link between anthropogenic carbon dioxide and warming, and also 2. Some work that quantifies the extent of the warming from the anthropogenic carbon dioxide).

Reading the paper I was struck by the extent to which the authors assume that the increase in atmospheric levels of carbon dioxide since 1750 is primarily a result of “anthropogenic emissions” without explaining why.

There is an extensive scientific literature discussing the notion of causation and how this might be established, for example between environmental stressors and observed effects in natural systems. This literature emphasises that where there are potential alternative explanations for an observed correlation these should be considered.

In the case of carbon dioxide and global warming, Lance Endersbee (former Dean of Engineering and Pro-Vice Chancellor of Monash University) has suggested a direct physical relation between increasingly levels of atmospheric carbon dioxide and increasingly average global sea surface temperatures over the last few decades (click here) suggesting the carbon dioxide is being released from the warming oceans.

Thanks to everyone who has posted and/or emailed papers and comment following my three random requests on the internet last night.

I intend this to be just the second in the series. I shall endeavour to consider the submissions beginning with those that appear the most promising and as a series of blog posts. Of course guest posts, and with alternative opinions, are welcome.

The following chart is largely self-explanatory:

Red: The actual rise of atmospheric CO2 from 1966 to 2006
Pink: The actual rise of human emissions within that 40 year timeframe (starting point at 321 ppm for comparison)
Blue: Human emissions multiplied by 24.41 to parallel atmospheric CO2 growth
Black: The human emissions slope as it would be if CO2 had stagnated in the atmosphere
Gray line: Accumulating atmospheric human emissions with a yearly retention rate of 0.56 — meaning that 44% is absorbed yearly, which contradicts the assertion that CO2 remains in the atmosphere for hundreds or thousands of years.

Alan Siddons
Holden, Massachusetts

————–
Data sources are from the US government’s Carbon Dioxide Information Analysis Center (CDIAC):
http://cdiac.ornl.gov/ftp/trends/co2/maunaloa.co2
http://cdiac.ornl.gov/ftp/ndp030/global.1751_2004.ems

But here’s the trick: How do you convert gigatons of carbon into ppm so you can compare the human and atmospheric trend? Well, CDIAC informs you: Divide gigatons by 2.13.
http://cdiac.ornl.gov/faq.html#Q6

I’ve been having some discussions with a colleague who has never thought too hard about anthropogenic global warming.

Anyway, he says there must be some work/some research results that have been published in reputable scientific journals that:

1. examine the causal link between anthropogenic carbon dioxide and warming, and

2. quantify the extent of the warming from anthropogenic carbon dioxide.

What he really want is links to research papers or citations to research papers.

Cameron Stewart writing in today’s The Australian makes reference to the influence of internet bloggers in succeeding in highlighting that measuring climate change is an evolving science. But, goes on to suggest that “their success has been at the margins only” because we have apparently failed to “prove that these discrepancies negate the broader core arguments about the trends of global warming.”

The article is entitled ‘Key degrees of difference’ and it begins:

“Has global warming stopped? The question alone is enough to provoke scorn from the mainstream scientific community and from the Government, which says the earth has never been hotter. But tell that to a new army of sceptics who have mushroomed on internet blog sites and elsewhere in recent months to challenge some of the most basic assumptions and claims of climate change science…

Read more here: http://www.theaustralian.news.com.au/story/0,25197,24148862-11949,00.html

This is at least the second time in the last two weeks that internet bloggers have been identified by the mainstream Australian media as relevant to the debate on climate change. The earlier story was on ABC Lateline, you can watch the video clip: http://www.abc.net.au/news/video/2008/07/29/2318074.htm . I comment on the Lateline report in an associated blog post here: https://jennifermarohasy.com.dev.internet-thinking.com.au/blog/archives/003290.html.