Plows, Plagues and Petroleum

Plows, Plagues, and Petroleum: How Humans Took Control of Climate

William Ruddiman’s book Plows, Plagues, and Petroleum: How Humans Took Control of Climate has attracted a good deal of interest in the climate history world since it was published in 2005.

His major thesis is that even before the industrial revolution, human activity over a period of 8000 years was responsible for a significant rise in carbon dioxide and methane levels in the atmosphere.  After explaining orbital changes and their effect on ice-age cycles and monsoon cycles he turns to what he considers an anomalous rise in methane concentration in the atmosphere which began 5000 years ago – anomalous in that the naturally declining solar radiation would be expected to result in gradually lowering methane levels as wetlands diminished in size.   He patiently works his way through what can be inferred of early agriculture to a hypothesis that increasing rice irrigation was mainly responsible for the methane increase, with lesser contributions also from domestic grazing animals and biomass burning.  His next step is to look at CO2 changes, where he detects a similar anomaly beginning 8000 years ago when the natural downward trend was interrupted at around 260 parts per million to rise to around 280 ppm by the start of the industrial revolution.  In the case of CO2 he attributes the rise to deforestation for agriculture, aided perhaps by some peat and coal burning. This attribution is tested against the population levels and likely amount of deforestation resulting from agricultural activities; he explains the calculations which he undertook to establish its credibility.

If he is correct this would mean that the warm and stable climate of the last 8000 years has been due to unwitting human intervention which offset a natural cooling that would otherwise have gradually developed.  He sets out reasons for the conclusion that a degree of glaciation may by now have been occurring in Canada were it not for human farming activities.

His hypothesis has been challenged, as he expects and, as a scientist, welcomes. He responds in his book to two of the challenges, both of which he acknowledges to have merit.  One is that he did not go far enough back in the sequence of ice-age cycles when looking at the pattern of previous interglaciation periods for a comparison of what might be expected from natural processes today. The other is that humans could not possibly have cleared and burned enough forest to account for such a large CO2 anomaly.  He considers that with some adjustment his hypothesis survives these challenges.

He then considers the “wiggles” that have occurred in the CO2 increases over the 2000 years prior to the industrial revolution, particularly the so-called Little Ice Age, when the CO2 level dropped somewhat.  He doubts natural causes and looks instead for processes that might have reversed the slow deforestation which he has suggested responsible for the gradual CO2 increase.  He rules out war and famine as not disastrous enough on a large enough scale and settles on disease, especially the plague.  He theorises that as epidemics and pandemics caused major drops in population, reforestation occurred in abandoned farmland, there was a slowdown in new deforestation, and in China a decrease in the amount of coal burning.

The question Ruddiman then proceeds to address is why the relatively modest rise in greenhouse gases caused by humans before the Industrial Revolution led to so relatively large an increase in temperature – 0.8 degrees – while the relatively large rise in greenhouse gases since the Industrial Revolution has been accompanied by a still relatively small increase in temperature.  His answer lies in the response time required for the full effects to be felt and he explores this in some detail in relation to both land and ocean, showing how response times vary in different environments.

Ruddiman’s hypotheses continue to be debated by climate scientists.  In fact Wallace Broecker, one of the world’s leading experts on climate history describes them as “total and utter nonsense”, according to a September 2008 New Scientist article.  The article reports Broecker reckoning there’s a natural explanation for the CO2 rise. Deep-sea sediments record a drop in carbonate concentrations that could account for the rise in atmospheric CO2.  But others find Ruddiman at least worthy of further consideration.  His book is certainly a fascinating detective science story, readily accessible to a general reader.

But I enter a caveat in relation to his closing chapters where he looks at future warming prospects as the full effect of the large post-industrial revolution rise in greenhouse gases begins to be felt. His prognostications are more optimistic than many climatologists would be willing to offer today. He gives us a century or two to melt much of the world’s sea ice and mountain glaciers and push back the seasonal limits of snow cover, but considers the two great ice sheets will be largely intact. The book was published over three years ago. One wonders whether he would be as sanguine now.

When he wrote the book he was certainly disinclined to see climate change as an overwhelming challenge. In fact he is quite testy about what he describes as the alarmism of extreme environmentalists and their organisations. He doesn’t name them, but he accuses them of oversimplifying the complexities of the global warming issue. He should have identified the organisations he refers to. Maybe he has noticed more alarmist predictions than I have. Major environmental advocacy groups such as Greenpeace and WWF seem to me to stay well within the bounds of responsible science on climate change.

He finally states that the depletion of precious resources – naming water, topsoil and fossil fuel – poses a greater threat to the human future than the threat of global warming does.  There are certainly many serious threats to the continuance of human society, but he provided me with no grounds for relegating global warming to a secondary rank.

It’s comin’ on Christmas

A very merry Christmas from Hot Topic. Thanks to all regular readers and contributors — Bryan for his reading, especially. Meanwhile, I have a turkey to stuff…

Pip pip!

Tear-stained letter #2

pottypeer.jpg Some summer reading for NZ prime minister John Key: Christopher, Viscount Monckton of Brenchley (“I’m no potty peer”) has penned another of his dippy epistles — an “open letter” in the next issue of Free Radical, an NZ libertarian publication. His last, to John McCain, was a triumph of hilariously overblown climate crank nonsense. This looks to be no more succinct, but has the publishers of FR chortling with excitement. From Not PC:

This is pure gold; the world’s leading climate ‘skeptic’ explains to NZ’s new Prime Minister that the apocalyptic vision of catastrophic anthropogenic climate change is a lurid and fanciful account of imagined future events that was always baseless, was briefly exciting among the less thoughtful species of news commentators and politicians, and is now thoroughly and scientifically discredited.

Thoroughly and scientifically? How exciting. Let’s take a look.

Continue reading “Tear-stained letter #2”

Climate Wars

Climate Wars

Gwynne Dyer’s new book Climate Wars explores the all-important political dimension of addressing climate change. Military history is Dyer’s speciality. One origin of this book was his dawning awareness that, in a number of the great powers, climate-change scenarios are already playing a large role in the military planning process. The other factor persuading him to write the book was the realisation that the first and most important impact of climate change on human civilisation will be an acute and permanent crisis of food supply.

He produces scenarios of his own to introduce each of the book’s seven chapters, positing in coming decades dangerous geopolitical developments in response to food shortages, with massive levels of human deaths. The scenarios range through many eventualities: dangerous confrontation on the Sino-Russian border;  nuclear conflict between India and Pakistan; the collapse of the European Union under the stress of south-north mass migration; a lethally effective border barrier between the US and Mexico with disastrous consequences for Mexico and the alienation of Hispanic-Americans within the US; a unilateral geo-engineering project gone wrong; and much else. His final scenario is different in that it looks much further ahead to a possible major extinction as a result of global warming effects on the oceans, drawing on the hypotheses in paleontologist Peter Ward’s recent book Under A Green Sky.

Dyer claims no certainty for his scenarios of course, but there is no denying their underlying credibility. As the main chapters of the book make apparent, the climate changes on which the scenarios are based are inescapable if we carry on with business as usual.  The book is as much about climate science as about the political and strategic consequences of climate change. Dyer is conversant with the major themes of  current science, and well understands the feedback mechanisms which threaten to accelerate the warming already under way.  He serves the general reader well in his this respect. He knows how to explain to lay people the complexities in which the experts deal.

He also spends a good deal of space canvassing mitigation possibilities and the likelihood or otherwise of their being adopted.  “We Can Fix This…” says one chapter, “…But Probably Not in Time” says the next, which is why he goes on to consider geo-engineering measures as an emergency fall-back option if the political process doesn’t deliver the goods on time.

As a respected journalist he has had access to numerous scientists, soldiers, bureaucrats and politicians. Extracts from their interviews are a core element of the book.  They lift his material clearly out of the realm of journalistic conjecture into the sober realms of the everyday working life of those he speaks with. The interviews have the further advantage of being recent and the book consequently takes us to where things stand right now. There is little doubt that they are worse than hitherto predicted.

Neither optimistic nor pessimistic, Dyer looks for realism. His final chapter centres partly on James Lovelock whom he sees as the most important figure in both the life sciences and the climate sciences for the past half-century; indeed he has him up there with a figure like Charles Darwin in the pantheon of scientific heroes.  But he finds the resolve to differ from Lovelock’s belief that irreparable damage has already been done. Dyer’s hope is that we will move sufficiently quickly towards decarbonising our economies to avoid the worst prospects of conflict and famine portrayed in his scenarios. He reflects on the small miracle that “at exactly the same time when it became clear we have to stop burning fossil fuels, a wide variety of other technologies for generating energy became available.”  But to make use of the opportunity we have within the next few decades, we will need, he concludes, the grown-up values of self-restraint and the ability to cooperate. One hopes this is not too much to ask.

Cold moments

arcticmethane.jpgMore data on the state of the methane hydrates on the Siberian shelf emerged during the American Geophysical Union’s Fall meeting in San Francisco this week. At a press conference covering recent work in the Arctic, Igor Semiletov, the leader of the team working on the Yakov Smirnitsky last (Arctic) summer, told reporters:

“The concentrations of the methane were the highest ever measured in the summertime in the Arctic Ocean,” Semiletov said. “We have found methane bubble clouds above the gas-charged sediment and above the chimneys going through the sediment.” [Science Daily, e! Science News]

A reporter at the press conference, who blogs at A Change In The Wind, asked Semiletov if the increase in methane release his team had discovered constituted “a global emergency”. In his blog entry he writes:

[…] his struggle with the question was evident. I tracked him down later, and asked if he felt he was the wrong person to be answering such a huge question. He admitted his discomfort, but said he thought it was the best question he was asked, and insisted:

“I am the person responsible for this research, and I think we have to tell people that something is happening now with the subsea permafrost.”

Why? A Change In The Wind explains:

Semiletov thinks that if just 1% of the ESAS methane is released, it will push total atmospheric methane up to 6 parts per million, and cites researchers such as David Archer in arguing that this would push us past the point of no return, towards runaway global warming.

Six ppm methane is a little over three times the current level, and with a global warming potential of 25, is equivalent to 150 ppm CO2, or 50 years worth of current annual CO2 emissions. There’s no reference to any time scale for this release, but the possibility should be enough to ring alarm bells — and loudly.

[There’s plenty of other Arctic/climate related material to blog from the Fall AGU meeting, and I’ll get to some of it soon, but for the time being Christmas shopping looms…]

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