Tag: CO2

The Long Thaw

The Long Thaw: How Humans Are Changing the Next 100,000 Years of Earth's Climate

The legacy of our release of fossil fuel CO2 to the atmosphere will be long-lasting. It will affect the Earth’s climate for millenia. We are becoming players in geologic time. That is the conclusion that climatologist David Archer shares with a general audience in his newly published book The Long Thaw: How Humans Are Changing the Next 100,000 Years of Earth’s Climate.

The author is a professor in the Department of The Geophysical Sciences at the University of Chicago and a contributing editor at Real Climate. His book is relaxed in style, almost conversational sometimes, repetitive on occasion, but nevertheless closely focused and packed with instructive detail. It was a pleasure for a non-scientist like me to read. He seems to understand how to illuminate processes for the general reader. For example, his chapter on the distribution of carbon in the atmosphere, the land and the ocean, and his explanation of the interactions between them in the carbon cycle, provided angles and information that pulled together satisfyingly the bits and pieces of my hesitant understanding.   Similarly what he writes about the acidifying of the ocean by CO2 and the part calcium carbonate plays in slowly neutralising its effect is a model of lucidity.

The book’s structure is simple.  There are three sections.  The first describes the situation we are in right now – meaning the 20th and 21st centuries.  The second section is about the past, investigated as a forecast for the future.  The final section looks into the deep future.

Archer produces no surprises about our current situation.  The basic physics of the greenhouse effect – that gases in the atmosphere that absorb infrared radiation could eventually warm up the surface of the earth – was described in 1827 by the French mathematician Fourier. Then in 1896 Swedish chemist Arrhenius estimated the amount of warming that the Earth would undergo on average from a doubling of the atmospheric CO2 concentration – what we now call the climate sensitivity. Such work sets the scene for the climate science which has exploded in the past few decades as global warming grew from a prediction into an observation.    He describes many aspects of our current understanding of global warming, with several particularly helpful sequences, such as that on the relative strengths of four external agents of climate change called climate forcings – greenhouse gases, sulfur from burning coal, volcanic eruptions, changes in intensity of the sun. The warming that is occurring cannot be explained by natural forcings.  Looking ahead in the present century he is very aware that sea level rise by 2100 may well be higher than predicted by the IPCC, as it begins to appear that the ice models used to forecast may be too sluggish to predict the behaviour of real ice.

In the second section he moves steadily back in time, starting with the last 100,000 years where the abruptness of some of the changes detected leads him to reflect that the IPCC forecast of a smooth rise in temperature from 0.5 degrees excess warmth today  to about 3.0 degrees excess warmth in 2100 represents a best-case scenario in that it contains no unfortunate surprises. He then treats the longer-term glacial climate cycles through the last 650,000 years, paying attention to orbital forcing and to the ups and downs of atmospheric CO2 through the cycles.  He envisages the ice sheets and CO2“entwined in a feedback loop of cause and effect, like two figure skaters twirling and throwing each other around on the rink.” His final step back is to the hothouse world of 50 million years ago and beyond that to transitions between hothouse and ice age climates over 500 million years. He selects the Paleocene Eocene Thermal Maximum event (recently discussed on Hot Topic) as an analogue for the global warming future.

The third section looks at that future.  In discussing the land’s and ocean’s ability to take up carbon being released from fossil fuels he considers it likely that there are limits to that process which will mean that a significant fraction of fossil fuel CO2 will remain in the atmosphere for millenia into the future.  There are calming effects from the carbon cycle, but there can also be opposite effects as seems likely to have been the case at times in the past.  Hopefully large scale methane hydrate release won’t be a large part of such feedbacks, but if the ocean gets warm enough it is possible and could double the long-term climate impact of global warming.

For now the carbon cycle is responding to the CO2 increase by inhaling the gas into the ocean and high-latitude land surface, damping down the warming effect. But on the timescale of centuries and longer the lesson from the past is that this situation could reverse itself, and the warming planet could cause the natural carbon cycle to exhale CO2, amplifying the human-induced climate changes.

The clearest long-term impact of fossil-fuel CO2 release is on sea level rise.  The book has a restrained chapter on this, but there is no escaping what will happen if the ice sheets melt. “We have the capacity to ultimately sacrifice the land under our feet.“

Have we averted an ice age?  Archer discusses this possibility, but finds the evidence uncertain.  He would in any case not put such a possibility forward as an argument in favour of CO2 emissions. All it means is that natural cooling driven by orbital variation is unlikely to save us from global warming – at this stage the much greater danger. Incidentally he mentions Ruddiman’s book Plows, Plagues, and Petroleum briefly and appreciatively in this section, but gives reasons for doubting its conclusions. (The book was reviewed on Hot Topic recently.)

In his epilogue on economics and ethics, where he ponders whether we are likely to turn away from the path we are currently on, he offers a comparison with slavery, another ethical issue: “Ultimately it didn’t matter whether it was economically beneficial or costly to give up. It was simply wrong.”

James Hansen describes the book as the best about carbon dioxide and climate change that he has read.  “David Archer knows what he is talking about.” To which I would add that he also knows how to explain it clearly to anyone prepared to give him reasonable attention.

Carbonscape and the charred potato

This column was published in the Waikato Times on 20 January

A couple of months ago a young company called Carbonscape opened a new plant in Marlborough. It makes charcoal from wood waste, hardly an exciting matter one might think. But beyond its traditional use as a fuel, charcoal may hold enormous potential for a sustainable future, for several reasons.

Soil fertility is one. Charcoal added by humans to the soil in pre-European times in the Amazon region has produced a much higher level of fertility than normal in the relatively poor soils of the region.  Modern experiments indicate that at least some soils benefit greatly from having porous charcoal added to them. Our neighbour Australia is finding this in soils which are lower in carbon content than optimal. The biochar, as it is called, seems to act as a catalyst to increase soil fertility. Less fertiliser is required. Microbial and fungal activity is increased. Water retention is improved. Leaching of nitrate and phosphate to waterways is reduced. Crop growth is greater, sometimes considerably so. And the biochar itself lasts for many centuries, being a very stable form of carbon.

Continue reading “Carbonscape and the charred potato”

Baby, it’s cold outside

Pegsnow.jpg In the make-believe world of Climate Debate Daily, where there are two sides to a great “debate” on the reality of climate change (there aren’t), a great gulf is opening between the opposing teams. Cranks are investing a great deal of (wasted) time and effort into spreading the idea that the world is cooling, while climate scientists think a new record high global temperature can’t be far away.

In The Australian today, The Great Communicator (for it is he!) runs the cooling argument for all its worth:

Thus, using several fundamentally different mathematical techniques and many different data sets, seven scientists all forecast that climatic cooling will occur during the first decades of the 21st century. Temperature records confirm that cooling is under way, the length and intensity of which remains unknown. […] Perhaps a reassessment will finally occur when two-metre thick ice develops again on Father Thames at London Bridge, or when cooling causes massive crop failure in the world’s granary belts.

Meanwhile, in an interview with Robin McKie in The Observer, Jim Hansen nails his colours to the mast:

Deniers should show caution, Hansen insisted: most of the planet was exceptionally warm last year. Only a strong La Niña – a vast cooling of the Pacific that occurs every few years – brought down the average temperature. La Niña would not persist, he said. “Before the end of Obama’s first term, we will be seeing new record temperatures. I can promise the president that.”

There’s a collision coming…

Continue reading “Baby, it’s cold outside”

The heater

global_energy_budget_in.png While some on the crank fringe fixate over a “global cooling” (that ain’t happening), the imbalance in our planet’s heat budget has inevitable — and inexorable — consequences for our climate. More heat’s coming into the system than can leave, as this excellent new article at NASA’s Earth Observatory spells out. It’s an easy to follow, but not dumbed-down explanation of how the earth and its atmosphere respond to energy arriving from the sun, with some superb illustrations — and astronaut photographs. Well worth a read, and a useful reference on the complex reality of the “greenhouse” we live in.

[Mutton Birds]

Fixing Climate

Fixing Climate: The Story of Climate Science - and How to Stop Global Warming

Wallace Broecker is a distinguished scientist in the field of climate history, and he’s been at it for over 50 years. He was one of the first scientists to warn of the dangers of global warming, as long ago as 1975. In a book published last year he teamed up with science journalist Robert Kunzig.  Fixing Climate: The Story of Climate Science – and How to Stop Global Warming is a highly readable narrative of how the modern scientific understanding of climate change has developed since it dawned on a few 19th century observers that there was evidence in the Swiss mountains of vast areas of past glaciation.  The book makes it very apparent that understanding climate in the past is the key to realising what is happening in the present and what it will lead to.

It’s a packed book, though it rarely seems so in the reading.  It ranges from relaxed stories about the scientists at work to closely explained accounts of the processes they investigate or uncover. The work of Broecker himself is often of considerable significance.  He was early engaged in the field of carbon dating, which proved a useful tool in establishing the abrupt (geologically speaking) end of the last ice age. He did recalculations of Milankovich’s theories on the earth’s orbital cycles and established their importance in affecting ice age climates, but only as part of the explanation – feedbacks must also be at work. He is known for his idea that ocean currents might rapidly change climate by switching on and off, and he came up with the name of conveyor belt to describe the ocean’s globe-spanning thermohaline circulation which transports heat into the North Atlantic and salt out. The section of the book explaining this is a model of clarity and interest for the general reader.  As indeed are many other sections like those on CO2 and on what portion of the carbon in the atmosphere goes into the sea or is taken up on land – so far at least.

New Zealand is there. A six-page section of the book begins with the words: “Outside the little town of Methven…”  George Denton and his team have spent a decade identifying and dating moraines all over the Southern Alps and recording their results on detailed maps.  Denton had spent decades working in Antarctica and Alaska when Broeckner convinced him to move his fieldwork into mid-latitude New Zealand.

Do we need to worry about what is happening?  The authors think so. They dissociate themselves, albeit respectfully, from the arguments of Al Gore and other environmentalists that it is a threat to western civilisation, considering that western civilisation is more resilient than that and that such “grandiose rhetoric” converts many reasonable people into sceptics. Their logic escapes me here, but never mind, for they go on to identify two dangers which strike them as particularly urgent – prolonged, catastrophic drought in some regions, and a rising sea level. Both dangers are explained in illuminating detail.

The last fifty pages of the book swing between pessimism and hope.  Although the authors recognise that we need to stop the increase in atmospheric CO2, they see no sign that we are capable of weaning ourselves from fossil fuels and are pessimistic of that obvious solution being applied. They sympathetically canvass the various green technologies but dismiss them as inadequate to the magnitude of the task and as too expensive in relation to cheap fossil fuels. For some time adaptation seemed the only option.  But then Broecker met Klaus Lackner, a theoretical physicist who considered that it was possible to scrub CO2out of the atmosphere, not just capture it in the industrial settings where it is produced. By 2001 Lackner was on the staff at Colombia, Broecker’s university. He has worked with engineer partner Allen Wright on designing a carbon scrubber which can work anywhere taking CO2 from the air for sequestration.  The process is described in some detail and estimates made of the number of extractors required to have a substantial effect on the levels of CO2 in the atmosphere. It would be a large undertaking but by no means beyond our capacity.

Scrubbing the carbon is one matter, but how is it to be disposed of?  The book covers a range of possibilities for sequestration: deep in the ocean; old oil wells; saline aquifers; layers of volcanic basalt; and eventually, because Lackner does not consider these forms adequate in the long term, mineral sequestration – accelerated geochemical weathering made possible by reducing immense quantities of igneous rock to a fine powder and reacting it with CO2.

Scrubbing CO2 from the air would not supplant capturing emissions from stationary sources, such as power plants, directly at the smokestack. It is an additional means of capture. It has the great advantage of being able to be carried out close to the intended place of sequestration.

The authors are very serious about the prospects for this technology. One can almost hear their sigh of relief that it has turned up. I notice they have just published an article in New Scientist further exploring it not only in relation to Lackner but also to teams working on lab-scale units at the University of Calgary in Alberta and at the Swiss Federal Institute of Technology in Zurich. In this article they allow themselves a little more room for hope in alternatives — solar, wind or nuclear — than is apparent in their book. But if we can’t avert a climate crisis through a massive switch to those means then air scrubbers could be the last-ditch lifeline.  I was mollified by the New Scientist article because I thought their book’s assertion that green technologies wouldn’t be adequate was reached too quickly, as was their belief that humankind would not turn from fossil fuel use while it remained available. At this point they had moved from science to politics and policy where it seems to me premature to declare failure — though of course it looms as a possible outcome.  But in any case the technology of removing CO2 directly from the atmosphere could meanwhile have a very useful function as one of the means by which we battle climate change and which can be rapidly scaled up if necessary. If it is a feasible process it must surely have a significant part to play.

In the final section of the book, Broecker and Kunzig examine some of the more drastic geo-engineering possibilities, such as putting sulfur dioxide in the atmosphere or iron in the ocean, and express reservations about them. The process of  taking CO2out of the atmosphere they do not see as geo-engineering. It is much more conservative. It is merely cleaning up after ourselves. They conclude, sounding something of a recurrent theme in recent writing, that the planet has become ours to run, and we can’t retreat from the responsibility to run it wisely. This might seem an overweening claim: nature has hardly surrendered the reins.  But there is at least a metaphorical truth to it. It highlights the immensity of the effect on Earth’s climate of our releasing so much extra CO2 into the atmosphere, and the concomitant responsibility we bear for managing that. Sequestration schemes seem a sensibly modest approach which respects the natural cycles.  The authors are too respectful of the complexities of the Earth’s systems to want to go further than that.