Climate change (1)

It was always going to happen at some stage. By popular request I am starting a series of 4-5 posts on climate change. Let us kick things off by defining the problem.

Anthropogenic global warming (also referred to as climate change or global climate disruption) is a theory claiming that the Earth’s climate is undergoing a significant shift, primarily as a result of human activity. This change is deemed to be capable of leading to catastrophic consequences like a dramatic sea level rise, crop failures, desertification of large areas of land etc. It is also assumed that, through a united and concerted effort, the humanity can avert the worst outcomes of climate change. So, in essence, we are causing the climate change and we can stop it.

I have followed the issue for the last ten years or so, by studying the material available on the internet. Of the “warmist” blogs I regularly read http://www.realclimate.com . On the skeptical side I follow Steve McIntyre’s blog http://www.climateaudit.com and, largely for entertainment, http://www.wattsupwiththat.com by Anthony Watts. I also read Judith Curry’s neutral blog http://www.judithcurry.com . If a particular issue flares up (as they regularly do) I follow links to other websites which post the relevant material. I do not read research papers but, through following climate blogs, have a general understanding of what is being published in the climate periodics. I have also seen videos of presentations by the likes of Richard Lindzen, Lord Monckton and Ross McKittrick. My professional background in engineering enables me to understand most of the issues involved in the analysis and modelling of the Earth climate and also some of the statistical methods employed. I guess I would fit in the category of a well informed concerned citizen.

Ok – so what is the bone of contention in the AGW debate? Contrary to what you may have heard most players agree that the Earth climate is in a warming phase and that humans are responsible for some of it. The tired old cliches of the oil companies funding the skeptics to “deny” that the Earth is warming are no longer relevant. The critique of the AGW stance is these days a lot more nuanced. To illustrate the point I will quote the views of one of the most prominent skeptics, Steven McIntyre, as stated on his website:

Does your work disprove global warming?

We have not made such a claim. There is considerable evidence that in many locations the late 20th century was generally warmer than the mid-19th century. However, there is also considerable evidence that in parts of the Northern Hemisphere, the mid-19th century was exceptionally cold. We think that a more interesting issue is whether the late 20th century was warmer than periods of similar length in the 11th century. We ourselves do not opine on this matter, other than to say that the MBH results relied upon so heavily by the Intergovernmental Panel on Climate Change in its 2001 report are invalid.

So here we have a AGW skeptic (for want of a better term) claiming that the climate appeared to be warming in the late 20th century. His issue is that this may not be exceptional by historic standards and the Earth may have been equally warm before:

Are you saying the 15th century was warmer than the present?

No, we are saying that the hockey stick graph used by IPCC provides no statistically significant information about how the current climate compares to that of the 15th century (and earlier). And notwithstanding that, to the extent readers consider the results informative, if a correct PC method and the unedited version of the Gasp” series are used, the graph used by the IPCC to measure the average temperature of the Northern Hemisphere shows values in the 15th century exceed those at the end of the 20th century.

To claim that the Earth may have been warmer in 15th century than now is all it takes to be branded a AGW “denier”!

Climate change (2)

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