The God Species: How Humans Really Can Save the Planet.... Mark Lynas

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      Work by Archer and colleagues modelling the Earth’s response to climate change suggests that methane hydrate release could add another half-degree or so to the total warming, but only over several thousand years, and only if the released methane is not dissolved or oxidised first in the ocean before it has time to escape into the atmosphere.⁴⁴ This is a ‘slow tipping point’, Archer concludes: it takes a long time for warming to penetrate the oceans, even longer for this to melt and release hydrates, and longer still for this methane to warm the atmosphere and the oceans further in a positive feedback loop. Happily, this is a tipping point we have still not crossed – ‘We have not yet activated strong climate feedbacks from permafrost and CH₄ [methane] hydrates,’ reported a team of scientists in 2009.⁴⁵ In the case of methane hydrates, respecting the climate boundary is not necessarily about protecting ourselves or even our children, but the stability of the Earth system over the very long term – for this tipping point, while slow to activate, would be essentially irreversible once crossed.

      350: PAST EVIDENCE

      If current observations of accelerating climate change and worries about tipping points in the future make two very good reasons why 350 ppm is the right place for a climate change planetary boundary, even stronger evidence comes from the Earth’s more distant climatic past. Climate models projections such as those published by the IPCC tend to project nice smooth – albeit upward-pointing – curves of likely future temperature trends. But a glance back in time, courtesy of ice-core records drilled in Greenland and Antarctica, shows that gentle, slow changes are far from being the norm in the Earth’s past. Instead, these records of past climate – which now reach back almost a million years – show climatic swings of extraordinary and terrifying abruptness. One extremely sudden warming took place in Greenland 11,700 years ago; it involved a temperature rise of 10 degrees Celsius within just three years.⁴⁶ Rapid shifts are observed elsewhere too: 12,679 years ago, according to sediments recovered from a lake in western Germany, the European climate saw a sudden transition to more stormy conditions between one year and the next.⁴⁷ The lesson is clear. Abrupt climate change is not the exception in the past, it is the norm. As the veteran oceanographer Wally Broecker says: ‘The climate is an angry beast, and we are poking it with a stick.’

      Although current CO₂ levels are higher than they have been for a million years, if we look even further back into the geological past there are episodes when both carbon dioxide and temperatures were far above where they are now. But rather than suggesting we have nothing to worry about, they further strengthen the evidence for counting 350 ppm as the crucial planetary boundary. For example, during the Pliocene epoch, about 3 million years ago, sea levels were 25 metres higher than today because the major ice sheets were much smaller than now due to a warmer climate. The CO₂ concentration then? About 360 ppm – a line we crossed in 1995.⁴⁸

      The Earth was completely ice-free – and sea levels 80 metres or more higher – until about 33 million years ago, early in the geological epoch called the Oligocene. After having been at 1000 ppm or higher throughout the Cretaceous, Eocene and Paleocene, this was the moment when CO₂ levels dropped past a crucial threshold allowing continental-scale ice sheets to form on Antarctica for the first time in perhaps a hundred million years.⁴⁹ This CO₂ level was 750 ppm, a level expected to be crossed again in about 2075 if carbon emissions continue to rise unabated. For the following 31 million years, only Antarctica held substantial ice sheets – until, late in the Pliocene, the more recent ice-age cycles began. There was another CO₂ threshold at play here, one that allowed Northern Hemisphere ice sheets (such as the current one on Greenland) to form for the first time. That level was 280 ppm, which we crossed right at the start of the Anthropocene at the turn of the nineteenth century. Were Greenland to be ice-free at the moment, in other words, CO₂ levels are already too high for an ice sheet to form. Once again, 350 ppm seems to be the minimum necessary to protect the big polar ice sheets over the longer term.⁵⁰,⁵¹

      NASA’s James Hansen (a member of the planetary boundaries expert group) wrote in the introduction to his landmark 2008 paper ‘Target Atmospheric CO₂: Where Should Humanity Aim?’ (published with nine co-authors in the open-source journal Open Atmospheric Science Journal): ‘If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO₂ will need to be reduced from its current 385ppm to at most 350ppm, but likely less than that.’⁵² Hansen and his colleagues reject a target of 450 ppm, for long the objective of both many governments and environmental groups. ‘A CO₂ amount of order 450ppm or larger, if long maintained, would push Earth toward the ice-free state,’ they maintain. And although the inertia of the climate system and slow response-times of ice sheets would limit the speed of this change, ‘such a CO₂ level likely would cause the passing of climate tipping points and initiate dynamic responses that could be out of humanity’s control’.

      TOWARDS A TECHNOFIX?

      Having said all that, solving climate change is actually a lot simpler than most people think. Global warming is not about overconsumption, morality, ideology or capitalism. It is largely the result of human beings generating energy by burning hydrocarbons and coal. It is, in other words, a technical problem, and it is therefore amenable to a largely technical solution, albeit one driven by politics. I often receive emails telling me that fixing the climate will need a worldwide change in values, a programme of mass education to reduce people’s desires to consume, a more equitable distribution of global wealth, ‘smashing the power’ of transnational corporations or even the abolition of capitalism itself. After having struggled with this for over a decade myself, I am now convinced that these viewpoints – which are subscribed to by perhaps a majority of environmentalists – are wrong. Instead, we can completely deal with climate change within the prevailing economic system. In fact, any other approach is likely doomed to failure.

      Here are two options that certainly won’t work. First, we could try to reduce the global population. Certainly, fewer people by definition means lower emissions. But getting to 350 ppm by reducing the number of human carbon emitters on the planet is impossible as well as undesirable: at a first approximation it would require the number of people in the world to be reduced by four-fifths down to just a billion souls or less. Short of a programme of mass forced sterilisation and/or genocide, there is no way that this could be completed within the few decades necessary. Certainly there are a multitude of reasons why giving people access to family planning is a good idea, but climate-change mitigation is not among them. The best reason for promoting birth control is that people want it, and everyone should be able to choose how many children they have. The future of the planet doesn’t come into it.

      The second option is to restrain economic growth, as GDP is very closely tied to the consumption of energy and therefore carbon emissions. No one disputes that recessions do tend to reduce emissions: the global financial and economic crisis that began in 2008 led to a fall in CO₂ emissions worldwide by 1.3 per cent within a year.⁵³ But imagine that the recession had been caused not by solvency problems within financial institutions but by government policies to tackle climate change. Jobless totals would be rising, government cutbacks in welfare services hitting the poor, and a new age of austerity dawning – all because of the tree-huggers. If you thought the debate on climate change was ill-tempered now, imagine that particular future and its implications.

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