CORRELATION OR CAUSE?

Senator Field, Family First, doubts that the Earth is getting warmer, and that greenhouse gases, in particular carbon dioxide, are the principle agencies for the increase in temperature.

He points out the mean temperatures have not risen for the past fifteen years, and that carbon dioxide (CO2) has been rising exponentially during that time. Therefore, he concludes that CO2 may not a principle driver of mean temperature increase, and that it is more likely that the observed increase in mean temperature is due to natural causes. So, he would then contend, any attempt to mitigate global warming would be an unnecessary economic cost.

Steve Fielding is going to ask Al Gore to answer his question, since he was not satisfied with the answers provided by the Government scientific advisors. I doubt whether Al will be able to give Steve an answer he will find satisfactory.

Why does not Steve do what all other normal, non-scientific individuals do and go to Google, and from there to Wikipedia’s “Global Warming” and from that article to an appropriate reference, for example, “Understanding and Attributing Climate Change”?

The more fundamental question is how does the Earth’s climate system work. For example, everybody knows about lightning, but who understands how and why plasma is formed within the bolts of lightning. Usually in the atmospheric system there are delays between cause and effect, sometimes because of counteractions. The suggestion has been made that it takes thirty years for the greenhouse gases pumped into the environment to have an effect. The magnitude of the effect may be difficult, for all I know, to estimate, since it is genuinely an “unknown known” since 390.7 ppm of CO2 (as of May 2009) in the atmosphere has never occurred before in human experience.

The article mentioned above addresses the question: Can the warming of the 20th Century be explained by natural variability? The answer is summarized as follows:

It is very unlikely that the 20th-century warming can be explained by natural causes. The late 20th century has been unusually warm. Palaeoclimatic reconstructions show that the second half of the 20th century was likely the warmest 50-year period in the Northern Hemisphere in the last 1300 years.

This rapid warming is consistent with the scientific understanding of how the climate should respond to a rapid increase in greenhouse gases like that which has occurred over the past century, and the warming is inconsistent with the scientific understanding of how the climate should respond to natural external factors such as variability in solar output and volcanic activity.

Climate models provide a suitable tool to study the various influences on the Earth’s climate. When the effects of increasing levels of greenhouse gases are included in the models, as well as natural external factors, the models produce good simulations of the warming that has occurred over the past century. The models fail to reproduce the observed warming when run using only natural factors.

When human factors are included, the models also simulate a geographic pattern of temperature change around the globe similar to that which has occurred in recent decades. This spatial pattern, which has features such as a greater warming at high northern latitudes, differs from the most important patterns of natural climate variability that are associated with internal climate processes, such as El Niño.

Of course, it is possible the language is too difficult to understand, so we should go to popularizer of science. Here David Attenborough, and his guest, fits the requirement:

If the models were junk science, as suggested by Freeman Dyson for example, they would not be able to distinguish in terms of predictions between natural and non-natural cases.

The answer to Steve Fielding seems to be that the observed increase in global mean temperatures cannot be explained by natural causes and it can be explained by anthropogenic causes, especially by means of greenhouse gases, such as carbon dioxide.

The World Climate Research Programme (WCRP) observes:

• The Earth System behaves as a single, self-regulating system comprised of physical, chemical, biological and human components;
• Human activities are significantly influencing Earth’s environment in many ways in addition to greenhouse gas emissions and climate change;
• Global change cannot be understood in terms of a simple cause-effect paradigm;
• Earth System dynamics are characterised by critical thresholds and abrupt changes;
• Human activities could inadvertently trigger such changes with severe consequences for Earth’s environment and inhabitants;
• In terms of some key environmental parameters, the Earth System has moved well outside the range of the natural variability exhibited over the last half million years at least; and
• An ethical framework for global stewardship and strategies for Earth System management are urgently needed.

These propositions are not exclusive. Each of these propositions are testable, they can be observed, so they are scientific and have provisional strength – we can act on them. Further, they are logically consistent, or to the extent that they are, they represent the way in which the Earth’s climate system works. We can add to them, but we cannot subtract from them, if each is verifiable. Therefore they represent a basis for the climate debate, rather than cherry picking the data?

My question to Senator Fielding is which of these propositions does he not understand or wish to deny? At the very least by establishing a provisional common framework, we might be able to have a dialogue that arrives eventually at the truth based on observation, which after all is the goal of scientific inquiry. As in a democratic process, the purpose, as I understand it in science, is never just to have a debate, but to find something out.

UPDATE:

Now at last we get to see the graph that changed Steve Fielding’s mind. CO2 is rising, but temperature is not. Imagine that. (via Liz at Public Opinion). Do the propositions above, which admittedly can be improved, give any insight into this apparent contradiction? Do we conclude on the basis of this graph that the science is wrong? What accounted for the fit between the model predictions up until about 2002? If there is a delay between the level of atmospheric CO2 and other greenhouse gases, why was there a fit between average temperature and CO2. We are not dealing with a linear system, but the forcings and feedbacks processes will have some effect eventually, and perhaps effects that cannot be envisaged. Hoping for the best is one option, but it is not the intelligent option. Homo sapien sapien might do better than that.

As I recall, we are talking about a 0.3 or 04 change in average temperature, with we ignore the event that seems to have affected the climate in 2006, and if my memory is accurate the error for this graph was point at 0.33 degree Celsius. Thus is it conceivable that the observed correlation holds – but in these matters I defer to the people who know about such things. I would be asking the statisticians and climate scientists for their judgments.

It is fair enough to be sceptical, but the obvious candidates for such doubt are those with special interests and apparently no sense whatsoever of public and social responsibility. That is the attitude that capitalism the great servant of the public good that it is, and always has been.

ELSEWHERE:

Kevin Drum explains the graph. Now Steve does not need to speak to Al or anybody else. The Earth’s climate is warming – imagine that! More importantly, what is to be done about it? Over to you, Steve. Think about putting families and all other people first?

Advertisements