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Paul Crutzen

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Welcome to the Anthropocene

Geology moves very slowly, and so do geologists. The Working Group on the Anthropocene was set up in 2009, but only presented its recommendation to the International Geological Congress in Cape Town last Monday. The Working Group’s experts have concluded that we are now living in a new geological epoch: the Anthropocene. That is, the epoch when human beings are reshaping the Earth.

Epochs (e.g. the Triassic, the Jurassic, or the Cretaceous) are usually big chunks of time: tens of millions of years. The Anthropocene, by contrast, is only about sixty-five years old, which is why many geologists are reluctant to accept it as a whole new epoch in the Earth’s history. But they probably will, in the end, because the evidence is already there in the rocks.

The radical idea of defining an entire epoch by the impact of human civilisation on the planet was advanced for the first time in 2000, by Nobel Prize-winning scientist Paul Crutzen. Modern human beings have been around for 200,000 years, he pointed out, but only in 1950 did our numbers and and the products of our science and industry grow so great that we became a dominant factor in the planet’s evolution.

Now we make the weather (by causing global warming with our greenhouse gas emissions). We are even melting the ice and raising the sea level.

We and our domesticated animals account for more than 90 percent of the total weight of all large land-dwelling animals (bigger than a chicken) on Earth. Our crops have pushed wild plants off most of the fertile land on the planet.

And if there are any geologists around a hundred million years from now, they will be able to detect our existence just by examining the rocks.

The acid test for defining a geological epoch is: are there clear differences in the make-up of the rocks? With us, it’s easy. In the 1950s, radioactive elements (radionuclides) from hundreds of open-air nuclear bomb tests appear in the sediments all around the world.

Even more ubiquitous are the tiny fragments of plastic, the particles of aluminum and concrete, and the tiny balls of unburnt carbon that pour out of our power stations, all embedded in the muds that will one day be rocks. The human race may or may not survive, but we have already left indelible evidence of our existence in the rocks.

The real goal of those who want to declare a new Anthropocene epoch, however, is not just to tidy up the geological record. They want to highlight the fact that, for better or worse, we are now in charge of the entire planet.

Paul Crutzen didn’t just propose a new epoch called the Anthropocene. In 2006, he was also the first scientist to go public and say that we may have to resort to “geo-engineering.” We are disabling the Earth’s natural mechanisms for maintaining a stable environment, he said, and in order to survive we may have to take responsibility for maintaining all the global cycles and balances ourselves.

That is not a good thing. In fact, it is a terrifying thing, because the Earth system is immensely complex and there are large parts of it that we do not even understand yet. It was another scientist, Jim Lovelock, who first pointed out what a huge and ultimately crushing burden we will have to shoulder.

Lovelock’s great insight, as important as Charles Darwin’s theory of evolution in the 19th century, was that the Earth’s living things, its atmosphere, its seas and its rocks are all part of a single interacting system. He boldly called it Gaia, but more timid scientists call it Earth system science. And in the very act of recognising it, he realised that it was breaking down.

Writing in 1979, he warned that if we disable Gaia’s natural functions, then one day we will wake up to find that we have inherited “the permanent lifelong job of planetary maintenance engineer. Gaia would have retreated into the muds, and the ceaseless intricate task of keeping all the global cycles in balance would be ours.

“Then at last we would be riding that strange contraption, ‘the spaceship Earth’, and whatever tamed and domesticated biosphere remained would indeed be our ‘life support system’.

“We can guess that at less than (ten billion people) we should still be in a Gaian world. But somewhere beyond this figure…lies the final choice of permanent enslavement on the prison hulk of the spaceship Earth, or gigadeath to enable the survivors to restore a Gaian world.”

So far we are only seven and a half billion people, but that’s no consolation. The world’s per capita energy consumption is so much higher than Lovelock foresaw in 1979 that we may be on the brink of that final desperate “choice” already. (And UN figures predict that we will be at ten billion by 2050 in any case).

Welcome to the Anthropocene.
To shorten to 725 words, omit paragraphs 2 and 5. (“Epochs…rocks”; and “We…planet”)

Geo-Engineering in Trouble

15 January 2014

Geo-Engineering in Trouble

By Gwynne Dyer

Bad news on the climate front. It was already clear that we are very likely to break through all the “do not exceed” limits and go into runaway warming later this century, because greenhouse emissions have not dropped, are not dropping, and probably will not drop. We did have a fall-back position, which was to counter the warming by geo-engineering – but now the leading technique for geo-engineering also looks like it will not work.

In a paper published this month in “Environmental Research Letters”, three researchers at Reading University in England have shown that trying to cool the planet by putting large amounts of sulphur dioxide into the stratosphere would lead to a 30 percent decline in rainfall in most of the tropics. That would mean permanent drought conditions in countries like Indonesia, and millions would starve.

Starvation is the main impact that higher average global temperatures will have on human beings, as they will cause a big loss in food production, particularly in the tropics and sub-tropics. But the standard assumption was that there would still be as much rain in the tropics as before. Maybe even too much rain, as the heat would mean higher rates of evaporation and more powerful tropical storms.

What Drs. Angus Ferraro, Ellie Highwood and Andrew Charlton-Perez have done is to use several climate model simulations to examine the effect of geo-engineering on the tropical overturning circulation. This circulation is largely responsible for lifting water vapour that has evaporated at the surface high enough up into the atmosphere that it turns back into water droplets and falls as rain. If the circulation gets weaker, so does the rainfall.

Putting sulphur dioxide into the stratosphere to cut the amount of incoming sunlight and reduce heating at the surface was first suggested by Paul Crutzen, a Nobel Prize-winning atmospheric chemist, in 2006. At that time, talking about geo-engineering was taboo among scientists, because they feared that if the general public knew that the heating could be held down that way, they’d stop trying to curb their greenhouse gas emissions.

Crutzen violated the taboo because countries and people were NOT cutting their emissions, and there was no reasonable prospect that they would. (This is still largely the case, by the way.) So the world definitely needed a Plan B if we did not want to see a planet that is 4 degrees C hotter (7 degrees F) by the end of the century.

Crutzen pointed out that large volcanoes, when they explode, put substantial amounts of sulphur dioxide gas into the stratosphere. That causes significant cooling at the surface for one or two years, until it all comes down again – and it does no apparent harm in the process. The last big volcano to explode, Mount Pinatubo in the Philippines in 1991, reduced the average global temperature at peak by half a degree C (one degree F).

Human beings could also put sulphur dioxide into the stratosphere (on a rather larger scale), to hold the temperature down, said Crutzen. The ice caps wouldn’t melt, our agriculture would continue to get the familiar weather it needs, and we would win ourselves more time to get our emissions down. We still have to get our emissions down in the end, he stressed, but it would be better not to have a global calamity on the way from here to there.

There was so much outrage at Crutzen’s suggestion that he had a nervous breakdown, but then lots of other scientists came out of hiding to admit that they also thought the human race needed a fall-back position. Various other proposals for holding the temperature down were put on the table, and by now there are dozens of them, but the idea of putting sulphur dioxide in the stratosphere still led the field. Until now.

But the Reading University scientists have discovered a hitherto unsuspected side-effect of this kind of geo-engineering. The sulphur dioxide particles don’t just reflect back a portion of the incoming sunlight from above. They also reflect a portion of the long-wave radiation (heat) coming back up from the surface, and that heats the top of the troposphere.

The troposphere is the lower part of the atmosphere, where all the weather happens. If you heat the top of the troposphere, you reduce the temperature difference between there and the surface, so the tropical overturning circulation weakens. That means less water vapour is carried up, and less rain falls back down. Result: drought and famine.

This is exactly the kind of scientific investigation that Crutzen wanted. He understood clearly that we were venturing into dangerous territory when we start intervening in a system as complex as the climate, and he stressed that what was needed was lots more research before we have to gamble on geo-engineering to halt an imminent disaster. But it’s a very discouraging conclusion.

The sulphur dioxide option was the cheapest and seemingly the best understood option for holding the temperature down. A great many people were glad that it was there, as a kind of safety net if we really don’t get our act together in time to halt the warming by less intrusive means. Now there’s no safety net.


To shorten to 725 words, omit paragraphs 9 and 12. (“There…now”; and “This…conclusion”)

Gwynne Dyer is an independent journalist whose articles are published in 45 countries.


Geoengineering Takes Off

21 September 2011

Geoengineering Takes Off

By Gwynne Dyer

Scientists who are working on various concepts for “geo-engineering” the climate are almost comically eager to stress that they are not trying to come up with a substitute for reducing carbon dioxide emissions, the main cause of man-made global warming. They are just researching back-up systems that we might need if the reductions don’t happen fast enough.

“It’s hard to imagine a situation except a dire emergency where this will be used, but in order to have that conversation sensibly we need to provide some evidence-based research,” Dr Matt Watson of Bristol University told the British Science Festival in Bradford last week. He is planning to test the feasibility of an “artificial volcano” that injects sulphur dioxide into the stratosphere, so where better to try it than in the pancake-flat county of Norfolk?

Interestingly, he has the implicit blessing of the British armed forces, which take the threat of climate change very seriously. His experiment will be carried out at Sculthorpe airfield, a bomber base during the Second World War and still an active Royal Air Force facility. The goal is to find out whether non-rigid balloons (blimps) could be used to spray sulphur dioxide particles into the air and cool the planet’s surface.

Why an “artificial volcano”? Nobel Prize-winning atmospheric chemist Paul Crutzen, who first suggested this method of cooling the planet five years ago, pointed out that big volcanic explosions inject millions of tonnes of sulphur dioxide into the stratosphere, where they remain on average for a couple of years. During that time, they reflect enough incoming sunlight to lower the temperature at the surface appreciably.

The Mount Pinatubo explosion in the Philippines in 1991 put enough sulphur dioxide in the upper atmosphere to lower the average global temperature by half a degree Celsius (almost one degree Fahrenheit) for two years. No mass extinction or global famine ensued, so we can tentatively assume that human beings could also put sulphur dioxide into the stratosphere without causing instant global disaster.

We cannot assume that there would be no negative side-effects, however, which is why some scientists have been urging that we carry out small-scale experiments to learn more about the process. They also want to investigate how we could put such a large volume of sulphate particles into the stratosphere, for the task might turn out to be too expensive or just impossible.

That is the goal of a three-year project called Stratospheric Particle Injection for Climate Engineering (Spice), which is being supported by the universities of Bristol, Cambridge, Edinburgh and Oxford. The first phase of the project involves testing a blimp that will lift a reinforced hosepipe to an altitude of one km. (one thousand yards) and spray water into the air.

It’s purely about delivery methods: will a balloon tethered to the ground be stable enough to support such a length of hose, or will it become uncontrollable in the wind? If it passes that test, then the long process begins of scaling up to a blimp big enough to support a 20-km (12-mile) hose, for that is the height at which the sulphate particles must be dispersed in order to stay up for a long time.

A blimp big enough to do that would be the size of a football stadium, and the Spice researchers estimate that it would take about twenty of them, moored over the ocean, to cool the planet by 2 degrees C. It would cost, they think, as little as $7 billion or as much as $75 billion dollars, but even the latter sum would look affordable to a government in a panic – the kind of panic that would occur if the planet got 2 degrees C (3.5 degrees F) hotter.

This is the first time that a geo-engineering idea has moved out of the lab and into the real world, and it is bound to attract some very hostile attention. You still hear the argument that we should not even discuss geo-engineering techniques, for the knowledge that they might exist will lessen the pressure to cut carbon dioxide emissions quickly. But the cat is out of the bag, and the best we can do is to figure out whether they are really a viable option.

Nobody is claiming that geo-engineering measures are a substitute for reducing our greenhouse gas emissions. But for all the talk about cutting emissions, they are still increasing, and it is highly unlikely that we will turn that trend around in time to avoid passing through 2 degrees C hotter – after which the risk of uncontrollable, runaway warming gets very big.

The scientists who are investigating geo-engineering are not reckless. They are actually the cautious ones, who want to have some fall-back plan available in case all the promises of future emissions cuts do not come true, just like all the past promises of emissions cuts failed to come true. We will get our emissions down eventually, no doubt, but it would be nice not to have a climate catastrophe in the meantime.

Can geo-engineering avert catastrophe? Nobody really knows, and that’s the point. “It may turn out that this whole strategy is a bad strategy,” as Dr Hugh Hunt of Cambridge University, who is leading the field test at Sculthorpe, told The Independent newspaper. “That’s what we’re trying to find out.”


To shorten to 725 words, omit paragraphs 11 and 12. (“Nobody…meantime”)

Time for Geoengineering?

26 September 2008

Time for Geoengineering?

By Gwynne Dyer

Scientists have their own way of putting things. This is how Dr Oerjan Gustafsson of Stockholm University announced the approach of a climate apocalypse in an e-mail sent last week from the Russian research ship “Jakob Smirnitskyi” in the Arctic Ocean.

“We had a hectic finishing of the sampling programme yesterday and this past night. An extensive area of intense methane release was found. At earlier sites we had found elevated levels of dissolved methane. Yesterday, for the first time, we documented a field where the release was so intense that the methane did not have time to dissolve into the seawater but was rising as methane bubbles to the sea surface.”

Gustafsson’s preliminary report, published in “The Independent” of 23 September, is a development far more frightening than the current financial crisis, although it will get only one-thousandth of the coverage. The worst that the financial crisis can bring is some years of recession. The worst that massive methane releases in the Arctic can bring us is runaway, irreversible global warming.

Molecule for molecule, methane gas is twenty time more potent than carbon dioxide as a warming agent. However, since methane doesn’t stay in the atmosphere as long — around 12 years, on average, compared to a hundred years for CO2 — and human activities do not produce all that much of it, concerns about climate change have mostly been focussed on carbon dioxide. The one big worry was that warmer temperatures might cause massive releases of methane from natural sources.

There are thousands of megatonnes of methane stored underground in the Arctic region, trapped there by the permafrost (permanently frozen ground) that covers much of northern Russia, Alaska and Canada and extends far out under the seabed of the Arctic Ocean. If the permafrost melts and methane escapes into the atmosphere on a large scale, it would cause a rapid rise in temperature — which would melt more permafrost, releasing more methane, which would cause more warming, and so on.

Climate scientists call this a feedback mechanism. So long as it is our emissions that are causing the warming, we can stop it if we reduce the emissions fast enough. Once feedbacks like methane release start to drive the warming, it’s out of our hands: we might even cut our emissions to zero, only to find that the temperature is still rising.

Fear of this runaway feedback is why most climate scientists (and the European Union) have set a rise of 2 degrees C (3.5 degrees F) in the average global temperature as the limit which we must never exceed. Somewhere between 2 and 3 degrees C (3.5 and 5.2 degrees F), they fear, massive feedbacks like methane release would kick in and take the situation out of our hands.

Unfortunately, the heating is much more intense in the Arctic region. The average global temperate has only risen 0.6 degree C (1.1 degree F) so far, but the average temperature in the Arctic is up by 4 degrees C (7 degrees F). So the permafrost is starting to melt, and the trapped methane is escaping.

That is what the research ship “Jakob Smirnitskyi” has just found: areas of the Arctic Ocean off the Russian coast where “chimneys” of methane gas are bubbling to the surface. What this may mean is that we have no time left if we hope to avoid runaway global warming — and yet it will obviously take many years to get our own greenhouse gas emissions down. So what can we do?

There is a way to cheat, for a while. Several techniques have been proposed for holding the global temperature down temporarily in order to avoid running into the feedbacks. They do not release us from the duty of getting our emissions down, but they could win us some time to work on that task without running into disaster.

The leading candidate, suggested by Nobel Prize-winning atmospheric chemist Paul Crutzen in 2006, is to inject sulphur dioxide into the stratosphere in order to reflect some incoming sunlight. (This mimics the action of large volcanic eruptions, which also lower the global temperature temporarily by putting huge amounts of sulphur dioxide into the upper atmosphere.)

Another, less intrusive approach, proposed by John Latham of the National Center for Atmospheric Research in Boulder, Colorado and Prof. Stephen Salter of Edinburgh University, is to launch fleets of unmanned, wind-powered vessels, controlled by satellite, that would spray seawater up into low-lying marine clouds in order to increase the amount of sunlight that they reflect. The great attraction of this technique is that if there are unwelcome side-effects, you can turn it off right away.

These techniques are known as “geo-engineering,” and discussing them has been taboo in most scientific circles because of the “moral hazard”: the fear that if the public knows you can hold the global temperature down by direct intervention, people will not do the harder job of cutting their emissions. But if large-scale methane releases are getting underway, the time for such subtle calculations is past.

Starting now, we need a crash programme to investigate the feasibility of these and other techniques for geo-engineering the climate. Once the thawing starts, it is hard to stop, and we may need them very soon.


To shorten to 725 words, omit paragraphs 6 and 13. (“Climate…rising”; and “These techniques…past”)