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Geologists and climate change denial

Posted on 9 June 2011 by John Cook

This article was originally published at ABC Environment yesterday. I'm doing my best to respond to comments over there but it's not easy - perhaps SkS readers can help me out :-)

Of all the people that doubt the science of climate change, geologists seem to be the most vocal. But they, of all people, should be the most concerned.

I was headed to the Sydney ABC studio to talk about my new book on climate change denial. What was unique about this interview was my coauthor Haydn Washington and I would have the opportunity to answer questions from callers. Considering the topic at hand, we expected some demanding questions from those who doubt the climate science. On the way, I declared to Haydn I'd put money on someone bringing up past climate change. In every interview over the weeks following the launch of our book Climate Change Denial, the same question always arose: "Climate has changed naturally in the past so how do we know current climate change is caused by humans?"

Haydn wisely didn't accept the wager. And sure enough, the first caller (listen) introduced himself as a geologist and proceeded to discuss past climate change. Afterwards, I reflected on geologists and the perception that they tend to be sceptical about human-caused global warming. Australia's most well known skeptic, Ian Plimer, is a geologist, as is another well known sceptic Bob Carter. But is the characterisation that geologists are mostly sceptics accurate?

One survey of earth scientists found that while 97 per cent of actively publishing climate scientists agree humans are changing global temperatures, only 47 per cent of economic geologists (those who study geology with a view to its commerical exploitation) concur (pdf). In fact, among all earth scientists, economic geologists are the most sceptical.

Similarly, in response to the consensus on global warming, the American Association of Petroleum Geologists "respects these scientific opinions but wants to add that the current climate warming projections could fall within well-documented natural variations in past climate and observed temperature data". You'd call that type of endorsement damning with faint praise.

However, the broader community of geologists seems convinced by the evidence that humans are causing global warming. The European Federation of Geologists says climate change is predominantly caused by anthropogenic emissions of CO2 and poses significant risks to human civilisation. The Geological Society of America concurs that "greenhouse gases have been an increasingly important contributor [to global warming] since the mid-1800s and the major factor since the mid-1900s". The Geological Society of London states that "evidence from the geological record is consistent with the physics that shows that adding large amounts of carbon dioxide to the atmosphere warms the world and may lead to: higher sea levels and flooding of low-lying coasts; greatly changed patterns of rainfall; increased acidity of the oceans; and decreased oxygen levels in seawater".

So climate scepticism seems strongest among geologists closely linked to the mining and fossil fuel industries. Perhaps the words of Upton Sinclair shine some understanding on the forces at play here: "It is difficult to get a man to understand something, when his salary depends upon his not understanding it."

Regardless of motive, the question of past climate change is certainly an important one that provides much insight into how our climate behaves. Plimer's conceit is that as a geologist, he has taken into account Earth's past while climate scientists have ignored it. This is a curious position considering there is an entire field of climate science, paleoclimatology, that examines past climate change. What do they find?

Climate has changed in the past. Sometimes it changes quite dramatically. Why? When something causes a change in global temperature, such as varying solar activity or changes in the Earth's orbit, feedbacks amplify these changes. The atmosphere grows more humid and as water vapour is a greenhouse gas, this traps more heat. Arctic sea ice melts, causing the exposed ocean to absorb more heat. The feedbacks aren't so large that they lead to runaway warming but they are enough to amplify one degree of greenhouse warming to three degrees of total warming. Many different periods throughout Earth's history, from the last few millennia to millions of years ago, yield remarkably consistent results establishing this amount of climate feedback.

When geologists bring up past climate change, they're actually citing evidence for climate feedback. Dramatic swings in global temperature, dragging the planet in and out of ice ages, are possible because of these feedbacks. Renowned paleoclimatologist Wally Broecker sums it up beautifully: "The paleoclimate record shouts out to us that, far from being self-stabilising, the Earth's climate system is an ornery beast which overreacts to even small nudges."

We have already given our climate a big nudge. How do we know it's us causing the warming and not natural causes? Because we've directly measured it. Satellites measure reductions in heat escaping to space - direct empirical evidence that carbon emissions are trapping heat. Surface measurements measure more heat returning to Earth, confirming the increased greenhouse effect. We see many signatures of greenhouse warming such as winters warming faster than summers, cooling upper atmosphere with warming lower atmosphere and nights warming faster than days. The case for human-caused warming is based on many independent lines of evidence.

The feedbacks that amplified past climate change are now amplifying the warming caused by our carbon emissions. We're measuring more water vapour in the atmosphere, a strong feedback. Arctic sea ice is disappearing and satellites measure less sunlight reflected back to space - another significant feedback. The Earth's past and modern measurements all paint a consistent picture - our climate is already overreacting to our "nudge".

The peer-reviewed literature on past climate change sends a strong message, in stark contrast to what we hear from petroleum geologists. Past climate change is not a source of comfort. It's a cause for concern.

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Comments 101 to 108 out of 108:

  1. Devil's advocate here (non-economic geologist!). You state that increased radiative output from Earth is proof that rising CO2 causes warming, but suppose it's not really rising CO2 that has caused the warming, but something entirely different, such as anthropogenic chlorine photodissociated from CFCs depleting the ozone layer and admitting more high-frequency UV-B. What actual hard-data proof is there that CO2 is actually responsible for the observed warming and not something else? Tx.

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  2. davidbennettlaing... One would be to look at the relative radiative forcing of all the potential factors. As here: 

    (larger version here)

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  3. Also David, we are measuring the change in the incoming radiation (or outgoing radiation) and it has the spectral signature of CO2. The match between calcuated radation spectra and intensity for the CO2 increase and the measurement is extremely good. See the papers on this discussed here.

    Unless you wish to abandon conservation of energy and Plancks Law, then you need explain why that measured increase in radiation from CO2 has not caused warming if you want argue for other causes.

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  4. David

    Some extra points. If it were a further breakdown of the ozone layer, that wouldn't change the amount of sunlight absorbed, just where it is absorbed. The UV would still be absorbed, just now it would be in the lower atmosphere. And nobody has reported any such change and since the advent of the ozone hole, we are monitoring that kind of stuff.

    Also we are seeing cooling throughout the stratosphere, not just the ozone layer. This is a signature of more GH gases, particularly CO2.

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  5. I have had several thoughts about the climate change issue:

    1. The shutting down of debate is counterproductive; it does nothing to convince deniers & possibly swings abstainers to the denial side. Reasoned discussion is essential, even if it does become tiresome repeating the same points over & over.

    2. If a small human-made change to climate can be amplified to produce a large effect, then that implies that a small reverse adjustment could also easily fix the climate later.

    3. The lack of any clear explanation of how the massive climate changes of the last 100 million years fits with recent climate history. This suggests we're doomed anyway within the next 1000-2000 years when the next ice-age kicks-in.

    4. If we are about enter a new ice-age within the next 500-2000 years... is it possible that human-made global warming could be used to stabilise global climate to prevent a new ice-age from happening at all?

    5. The more alarming the climate scientists warnings become, the more I hope they are mistaken, because I believe economic/political forces will prevent any effective action until it is too late.

    I'm genuinely interested to hear peoples responses to my points above.

    PS - I'm not a climate change denier, or even a skeptic, more of a climate agnostic... :)

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  6. ad1mt@105,

    My thoughts regarding your points:

    1. Reasoned discussion leads to common understanding when there is substantial amounts of evidence available. The fundamentals of climate science identifying the need for the current generation to rapidly end the burning of fossil fuels, and even to start unprofitably and safely removing CO2 from the atmosphere, is not debatable. It hasn't been debatable for a very long time (decades). The debates need to be about why some leaders still try to claim that it, or the need to rapidly unprofitably and unpopularly correct the unacceptable activity that has developed, should be debated.

    2. The human impact that has rapidly increased atmospheric CO2 from 280 ppm to over 400 ppm is not small. And much of the new Carbon imposed on the environment has been harmfully absorbed into the oceans (or there would be even more still in the atmosphere), significantly rapidly changing the ocean acidity. Removing CO2 from the atmosphere would not reverse the ocean chemistry changes. And it is unacceptable to excuse making a problem for future generations by claiming that they will develop the ability to fix it, or can adapt to the harsh new climate realities.

    3. The natural changes of the planet are not the issue. The rapid changes created by human activity are the issue.

    4. The fossil fuels already burned up could have been very helpful in the future. A controlled future burning could have moderated a natural cooling period. It is also possible that a massive rapid burning could help mitigate the chilling results of an asteroid impact (a small enough one to dust up the atmosphere without massive damage done).

    5. The climate scientists' warnings are becoming 'more alarming' because they never were mistaken. People preferring leaders who told them what they wanted to believe led to winners in popularity and profitability competitions that have continued to make the problem worse.

    Science is about awareness and understanding, not beliefs. People either want to understand it or want to doubt it. You appear to want to understand. Others want to doubt, and repeatedly debating with a deliberate doubter is a waste of time.

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  7. ad1mt,

    Reasoned discussion is not possible with people who argue in bad faith. There was a contributor on this site who participated for some time and claimed he was a retired lawyer for Cabadian fossil fuel interests. His approach to the evidence was that of a lawyer; it included minimizing what was not going his preferred direction, repeatedly re-using arguments that had been shown to have no validity, establishing premises as facts when they weren't, etc, etc. It is impossible to read his posts over time and not come to the conclusion that he was arguing in bad faith.

    I strongly object to the use of the word "agnostic", which suggests that this is all  matter of faith. There is enough scientific knowledge available on the subject to not have to rely on faith. The only way one can fall back on faith is if they are unable to think quantitatively or so deep in denial that all rational thought is abandoned. If any debate is to be had, it is not about the reality of what is happening; that is the terrain for pseudo debates, indulging those who are incompetent, uninformed, misinformed, overwhelmed by emotional attachment to ideology, or simply dishonest.

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  8. So I ask the question of causes of past climate nudges.... solar intensity, cosmic impacts, super vulcanism, tectonic forces, supercontinant creation/disintegration, chemical weathering of rocks.... so I don't recall any of these happening in the last 100 years, yet all the indicator of such an influence are present. Humans are impacting the planets systems to the same extent as a comet impact on a huge oil field or permafrost methane hydrate province.... 

    Which past event corolates to what we are seeing today? 

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