I thought I’d document a thread of discussion on climate change in the Letters to the Editor pages of The Canberra Times over the last few weeks.

We begin with a letter published on May 11:

I believe in climate change – it is with us every day and despite their best efforts and supercomputers, our meteorologists struggle to provide worthwhile forecasts of these changes for more than a few days ahead.

Can those who predict global warming because of rising carbon dioxide levels really have better data and models than our meteorologists, or do they have another agenda in making forecasts for decades ahead, and with no probability qualifications regarding the likelihood of these possible extreme outcomes?

As an engineer with some grasp of physics, complex systems, and so on, my understanding is that modelling the climate and making credible forecasts is very complex indeed, and depends on continual refinement of the modes, taking into account the observed climate parameters.  Thus, the recent obsession with a trace gas, such as carbon dioxide, as the driver of global warming is difficult to accept as a sound scientific judgement; it is not even the major greenhouse gas.

The other major flaw in the claim that carbon dioxide is the cause of global warming is the inconvenient trust that for nearly three decades of the 20th century, the Earth cooled, while carbon dioxide levels continued to rise.  It would therefore seem that the hypothesis is wrong, and that factors other than atmospheric carbon dioxide levels are more important in driving climate/temperature changes.

A second inconvenient truth is that the forecasts by the International Panel on Climate Change in 2000 of continuing rising temperatures have proved to be incorrect; carbon dioxide levels continue to rise, but temperatures are falling. Thus, I continue to be amazed at the claims of the fundamentalist doomsayers on global warming who ignore the above and either focus on micro events or simply strive to outbid their fellow travellers with more and more extreme and alarmist forecasts of the end of life as we know it, unless we reduce carbon dioxide levels.

Are there no climate scientists out there with open minds and a commitment to scientific honesty? The recent publication of Heaven and Earth by Professor Ian Plimer, which I am struggling through, provides extensive evidence that the hypothesis that rising carbon dioxide levels lead to global warming is simply not true.

He also makes the interesting observation that rising temperatures usually result in higher carbon dioxide levels and correlate well with periods of better than average crops and food production, which support population growth and rapid development of civilisation.

On the other hand, he portrays the ice ages as rather miserable periods in the history of mankind. I would hope that future debate on this subject focuses on the evidence presented by Plimer and not on the individual, as some recent comments have done.

Michael Sage, Weetangera

My reply appeared in the May 13 edition:

Michael Sage (Letters, 11 May) asks where the climate researchers with open minds are.  The simple answer is that they are to be found in CSIRO, the Hadley Centre, the National Oceanic and Atmospheric Administration, all over the world in their thousands.

They devote their working lives to understanding and improving climate science, studying the enormous and ever-increasing data involved.  It overwhelmingly supports that global warming is a reality, and that it’s entering a very dangerous stage indeed.

Michael cites Ian Plimer repeatedly; a little investigation will reveal comprehensive descriptions of the extraordinary number of serious errors, omissions, and misrepresentations in Plimer’s work. Other writers in the same vein have similarly been exposed as deeply erroneous and at times apparently fraudulent. I strongly recommend putting Plimer’s shameful book aside and doing some independent investigation into the big picture.

For instance, a little non-partisan exploration will reveal that mainstream climate science does not in fact regard CO2 as the only greenhouse gas.  It will also show that the IPCC predictions have not actually been proved incorrect at all (current temperatures are well within the 95% confidence band of prediction).  Every other criticism raised by Plimer and others has been comprehensively answered, and these answers are easily available.

It’s sad to see that many who question global warming do so with little apparent knowledge of what mainstream climate science is saying, and what the supporting evidence is, rather than simply accepting the highly distorted picture presented by a few.

Read some real climate scientists first: get Barry Pittock’s recent book, or take a look at websites such as realclimate.org where climate scientists write about these issues.

Matt Andrews, Aranda

There was another reply published on the same day:

Michael Sage (Letters, May 11) asks how meteorologists can forecast global warming decades ahead when they can’t reliably predict the weather in a few days time.

They can do this in the same way that they can reliably tell you it will be warmer in January then now, but not how hot it will be in a fortnight, or what the average annual rainfall in Canberra is likely to be 2010-20, but not whether December will be wet or dry.

Almost all series of natural and social phenomena involve being able reliably to discern fundamental long-term trends or probabilities, but not being able to predict random short-term fluctuations.

Sage’s contention that climate scientists make global warming forecasts with no probabilities attached is puzzling because the IPCC conclusions on this are made with probabilities. For instance, it publishes a range for the likely increase in global temperatures with probabilities, not one figure. In fact the global consensus that has been reached on global warming, after decades of completely open scientific debate by thousands of scientists in many areas, is not that it is a certainty, but that it is a risk, even a small degree of which makes mitigation action worthwhile.

It is those whose apparent view is that anthropogenic global warming simply cannot be a problem requiring action, who seem to be attached to certainties rather than to probabilities and a rational insurance approach to risk-minimisation.

Paul Pollard, O’Connor

On 15 May Michael Sage replied:

Matt Andrews and Paul Pollard (Letters, May 13) are clearly committed to the view that global warming is real, poses risks to our future and that the science is solid.

Nevertheless, there is no attempt to answer my question (Letters, May 11) regarding the explanation for the fall in global temperatures for nearly three decades in the mid-20th century, while carbon dioxide levels continued to rise.

This inconvenient truth would seem to undermine the theory that rising carbon dioxide levels drive global warming.

I am yet to see any attempt to explain this anomaly, let alone a rational and compelling argument in support of the theory.

If, as Andrews claims, the answers are easily available, why has nobody produced them for examination?

Andrews also suggests that I cited Ian Plimer repeatedly, which I think is something of an overstatement, given a couple of general references.

The interesting situation regarding Plimer’s Heaven and Earth is that it has attracted much criticism in general (Andrews calls it shameful), but no one has offered any detailed rebuttal of even two or three of his central claims.

Andrews also acknowledges that carbon dioxide is not the only greenhouse gas; I agree it’s not even a major one.

Pollard seems to take an each-way bet on climate prediction, suggesting that summer is likely to be hotter than winter, but little else can be predicted with confidence.

He also concedes that global warming is not certain, but is a risk worth consideration.

I tend to agree with these moderate views. It is the translation from risk to certainty and then to massive overreaction that is of concern. There are countless examples of simple, scientific solutions leading to unwelcome, unintended consequences.

We would all benefit from a debate based on evidence, not on generalities and personal criticism.

Michael Sage, Weetangera

We then had two responses on May 18:

Matt Andrews (Letters, May 13) must surely have been referring to Al Gore’s Inconvenient Truth, not Ian Plimer’s Heaven and Earth, when he wrote that a little investigation will reveal comprehensive descriptions of the extraordinary number of serious errors, omissions, and misrepresentations. A British court ruled that Gore’s work could not be shown in schools unless eleven inaccuracies were specifically drawn to the attention of children.

Andrews urged people to read some real climate scientists at websites such as realclimate.org, the blog started by Dr Michael Mann and his colleagues.

Mann was the lead author of the infamous Hockey Stick study that was the poster child of the IPCC’s Third Assessment Report, but was subsequently discredited and unceremoniously dumped from the Fourth Assessment Report.

The Hockey Stick pretended to show that the modern warm period was unprecedented by rewriting history to remove the Medieval Warm Period and the Little Ice Age that followed.

In the very next letter, Paul Pollard wrote that meteorologists could predict the climate in a few decades’ time in the same way as they could predict that January will be warmer than now.

We know that weather varies on fairly predictable daily and annual cycles, but we also know that it varies on irregular decadal cycles that we can’t predict or explain.

We’ve seen in the last decade or so that whatever is responsible for these cycles is able to swamp any relatively minor anthropogenic influence on climate. Global warming might be a reality, but its certainly far from simple.

D. Zivkovic, Aranda

… and …

Michael Sage (Letters, May 15), the reason for the ”cooling” in the middle of last century is readily available. It only went on for about seven years, and then there was a period of relative stability for two decades.

The cause was man-made aerosols. These particles reflect sunlight, thereby cooling the planet if they are in the atmosphere. There was surge in the production of these particles during and in the recovery from World War II.

The downside of these particles is that they cause acid rain, which is why they are no longer acceptable.

Aerosols have the largest responsibility in masking temperature rises during the middle of the last century. Fortunately, aerosols have a relatively short lifetime in the atmosphere.

Carbon dioxide, on the other hand, remains in the atmosphere for centuries. That it has such a long stable lifetime, and the fact that the warming it causes is cumulative, are the reasons for targeting carbon dioxide so strongly, even though there are stronger greenhouse gases.

Venus is a rather Earth-like planet, but it has huge concentrations of carbon dioxide in its atmosphere and a surface temperature many hundreds of degrees above the Earth’s.

Earth’s current climate is very different from that when it was formed, and is the result of millennia of tiny organisms producing oxygen as a waste product. To think that organisms (humans) are incapable of causing planet-wide changes is thus folly.

You’d do better to not rely on the writings of a man whose arguments had been repeatedly debunked before he gathered them together in a book, which is sad as that is the exact behaviour he condemns in creationists.

Arved von Brasch, Aranda

My reply was published on 21 May:

D. Zivkovic (Letters, May 18) tries to dismiss Al Gore’s An Inconvenient Truth because a British court found some inaccuracies.

However, Zivkovic fails to mention that the court also acknowledged that Gore’s central thesis that climate change is mainly attributable to man-made emissions of greenhouse gases was completely sound and was strongly backed up by peer-reviewed science.

Ian Plimer’s Heaven and Earth has yet to be subjected to judicial analysis, but the scientific response to the book has been devastating.

Several detailed assessments are available online (see http://tinyurl.com/plimer as a starting point), but this observation from climate scientist Barry Brook sums it up nicely: ”Ian Plimer’s book is a case study in how not to be objective. Decide on your position from the outset, and then seek out all the facts that apparently support your case, and discard or ignore all of those that contravene it.”

Global warming is not a certainty; in a complex system like climate it’s all about the balance of probabilities.

The trouble is that the impacts of global warming are potentially so severe that, even if there was only 10 per cent risk of a rise of over two degrees this century, it would warrant massive precautionary efforts to avoid the risk.

Matt Andrews, Aranda

This thread basically died off at that point, and another began on 29 May, reacting to a statistic given in a green-energy article:

Fiona Wain (“Industries and jobs need climate action now”, May 28, p23) has the atmospheric concentration of CO2 wrong. It is 387 parts per million by volume (ppmv) not 455 as she claims.  It is increasing by about 2ppmv a year, mostly through natural causes. Man contributes between 1 per cent and 3 per cent of that increase.  Man’s CO2 contribution causes about 0.2 per cent of the greenhouse effect. Could Wain possibly have a vested interest?

John McKerral, Batemans Bay

My reply was printed on 3 June:

John McKerral (Letters, 29 May) states that current CO2 levels are 387 parts per million, rising by 2 ppm each year, which is perfectly correct. However, he also claims that only 1 to 3 percent of the rise is due to human causes, which is completely wrong.

The source is probably an infamous howler of a paper in 2006 by couple of petroleum engineers named Khilyuk and Chilingar, which tried to minimise human-caused emissions by comparing them against the cumulative total of billions of years of natural emissions.  Amazingly, this meaningless figure is repeated uncritically by Ian Plimer in his recent Heaven and Earth, a widely debunked anti-science book which contains dozens of fundamental errors, omissions and misleading statements. In reality, human activities are responsible for almost all of the current rate of increase in CO2.

This is comprehensively demonstrated by mainstream climate science – the details are easy to find if you’re prepared to take a few minutes to search for them.

Matt Andrews, Aranda

A reply appeared on 6 June:

Matt Andrews (Letters, June 3) rightly corrects the claim in a previous letter that only 1-3 per cent of atmospheric CO2 is due to human causes, and points out the origin of the claim.However, he falls into the trap in the warmists v the sceptics dialogue by making a list of possible errors and omissions in one version of the sceptic argument without addressing any of them. He assures a few minutes on the internet will furnish the evidence.

I think this greatly diminishes the scientific argument for either case.

If someone makes a claim they should give the evidence in the letter, not lazily refer the reader to a search of the internet where verification is difficult, often not possible, and to many not understandable.

My fear is government decisions will skirt around the scientific evidence for and against the magnitude of increased CO2 impacts, with policy statements continuing to be determined by lobby groups using similar unsupported comment.

Joe Walker

On 6 June I emailed the Canberra Times a response (not yet published):

Joe Walker (Letters, June 6) rightly pulls me up for not including a direct source clarifying the extent to which human activities are causing the rise in CO2 emissions.  As the Intergovernmental Panel on Climate Change (bit.ly/ipccwg1) says, “the primary source of the increased atmospheric concentration of carbon dioxide since the pre-industrial period results from fossil fuel use, with land-use change providing another significant but smaller contribution.”  A good introduction to the big picture of global carbon flows can be found at bit.ly/humanco2 (New Scientist).

Joe also protests that I did not include any specific details of the errors, omissions and misleading statements in geologist Ian Plimer’s book “Heaven and Earth”.  I didn’t attempt it here, because the number and depth of the book’s spectacular flaws are such that it’s impossible to do it justice in just 250 words. One review is at bit.ly/klambeckplimer (by Kurt Lambeck, president of the Australian Academy of Science), another is at tinyurl.com/plimer (by climate scientist Barry Brook), and at bit.ly/plimer I have listed a number of other detailed commentaries. It would be useful if the Canberra Times website allowed comments (with links) on letters.

I share Joe’s concern that the current national government climate policy appears to be based on unsupported assertions.  The proposed Carbon Pollution Reduction Scheme has a target of only 5% reduction in emissions by 2020 – far weaker than the action which current science indicates is necessary.  The CPRS as proposed appears to have been rendered almost completely ineffective by the government’s caving in to the demands of polluters: free permits, exemptions and other flaws mean that big polluters would start off paying an effective carbon price of just 50 cents per tonne of CO2.  A price closer to $40 per tonne is probably needed to start making significant shifts in the economy towards renewable energy.  Even if the free permits and other flaws were removed, a cap-and-trade system with a weak target is probably worse than useless, by locking in a dangerously inadequate framework while allowing the government to pretend it is taking effective action.  Fortunately this “Continue Polluting Regardless Scheme” is now politically dead, and hopefully a more responsible, evidence-based and sensible policy will quickly emerge from the ashes.