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Chapter Three

The Climate Change Boundary

That climate change is a planetary boundary will come as a surprise to no one. What may come as a surprise however is that the target that has been advocated by not just governments, but environmentalists too, has for years been much too weak. More recently that has begun to change: now an extraordinary coalition of more than a hundred governments and dozens of campaigning groups is lining up squarely behind a safe target for carbon dioxide in the atmosphere, as proposed by the planetary boundaries expert group. Although powerful countries like the US and China are a long way from endorsing this target – and the world economy is even further away from meeting it – the fact that such a crucial planetary boundary has attracted such a strong level of support is a serious piece of good news and one that deserves celebration.

Previous chapters explained how humanity has risen to global prominence through a massive exploitation of fossil energy resources. Human civilisation remains over 80 per cent dependent on fossil fuels worldwide, and as the economy grows so does the rate at which the carbon dioxide resulting from the burning of coal, oil and gas accumulates in the air. On average the carbon dioxide concentration of the atmosphere rises by about 2 parts per million (ppm) every year, from a pre-industrial level of 278 ppm to about 390 ppm today. Whilst the precise level of temperature rise implied by higher CO₂ is always going to be uncertain, it is indisputable that – all other things being equal – global warming will result from the human emission of billions of tonnes of greenhouse gases, sustained over more than a century.

Arguments over what would be a ‘safe’ level of atmospheric CO₂ have raged for decades. Back in 1992 the UN Framework Convention on Climate Change required in its much-cited Article 2 that the objective of international policy should be to avoid ‘dangerous anthropogenic interference’ in the climate system – but without defining what ‘dangerous’ actually meant. The British government’s Stern Review on the Economics of Climate Change of 2006 suggested a stabilisation target of 550 ppm CO₂e (carbon dioxide-equivalent, implying a bundling together of all climate-changing gases rather than only CO₂). Two years earlier, the European Union had endorsed a target of limiting temperature rises to 2 degrees Celsius, implying – it was stated – a CO₂ target of 450 ppm. This latter objective was endorsed in my 2007 book about climate-change impacts, Six Degrees, where I suggested that 2 degrees and 450 ppm were necessary to steer away from large-scale dangerous tipping points in the climate system. Major environmental groups also lined up behind similar targets, and pushed them hard at international meetings.

It turns out we were all wrong. A fair reading of the science today, as this chapter will show, points strongly towards a climate change planetary boundary of not 450 ppm but 350 ppm for carbon dioxide concentrations – a level that was passed back in 1988, the year that NASA climate scientist and planetary boundaries expert group member James Hansen first testified to the US Congress that global warming was both real and already under way. Hansen has done more than any other scientist to put the 350 number on the map. He was one of the first to realise its importance, and has become a tireless advocate of the actions that are necessary to meet it. It was Hansen’s discussions with the American author and activist Bill McKibben, indeed, that led to the creation of the worldwide movement 350.org. McKibben calls 350 ‘the most important number in the world’, and he is right.

Never mind the enduring global-warming controversies in the media; these are a distraction. The climate change planetary boundary is the one that is best understood, and that we know most about how to achieve. Moreover, meeting the boundary is a basic requirement for any level of sustainable planetary management: if CO₂ continues to rise, and temperatures begin to race out of control, then the biodiversity boundary, the ozone boundary, the freshwater boundary, the land use boundary and ocean acidification boundaries cannot be met either, and the remaining planetary boundaries are also called into question.

The climate boundary is humanity’s first and biggest test that will reveal early on whether we are truly capable of managing our environmental impacts in a way that protects the capacity of the biosphere to continue to operate as a self-regulating system. It is a testament to our intelligence that we have developed our scientific understanding so far that we now know a great deal about how the climate system works, and can define with some confidence where the planetary boundary should lie. It is perhaps testament to our stupidity, however, that despite decades of research and advocacy on climate, all pointing at the need to control greenhouse gas production, human emissions today continue inexorably to rise.

Thankfully the technologies and strategies that humanity needs to achieve the climate boundary are today no mystery. We have all the tools necessary to begin a wide-scale decarbonisation of the global economy, and to achieve this at the same time as both living standards and population numbers are rising rapidly in the developing world. But environmentalism will need to change at the same time. Much of what environmentalists are calling for will either not help much or is actually thwarting progress towards solving climate change. It is time for a new – and far more pragmatic – approach, that does not hold climate change hostage to a rigid ideology.

350: CURRENT EVIDENCE

First we need to establish whether 350 is actually the right number, and one that is supported by science. There are three broad lines of evidence that support the conclusion that atmospheric CO₂ concentrations need to be limited to 350 ppm. The first is the sheer rapidity of changes already under way in the Earth system, changes I never dreamt I would see so quickly when I started working on this subject more than ten years ago. These warn of looming danger. The second is modelling work suggesting that positive feedbacks – or thresholds, or tipping points, call them what you like – are getting perilously close. The third, and perhaps most conclusive, is evidence from the distant past linking temperatures with carbon dioxide concentrations in earlier geological epochs.

The best place to look for confirmation that our planet is gaining heat is not the air temperature at the ground, but the energy imbalance – the difference between incoming and outgoing radiation – at the very top of the atmosphere. There our sentinel machines, the satellites silently orbiting the planet twenty-four hours a day, show clearly that outgoing longwave heat radiation is increasingly being trapped at exactly those parts of the spectrum that correspond with the different greenhouse gases building up in the atmosphere below.¹ Natural variability is important in determining the average temperature each year, but recent records are revealing: the hottest year on record, according to NASA, is now tied between 2010 and 2005, with 2007 and 2009 statistically tied for second- and third-hottest.² Whatever the individual temperature records, the climatic baseline is visibly shifting: every year in the 1990s was warmer than the average of the 1980s, every year of the 2000s warmer than the 1990s average.³

There are now multiple lines of evidence pointing to ongoing global warming, some of which show that we are altering the characteristics of the atmosphere in unanticipated ways. Air-pressure distribution is changing around the world, with rises in the subtropics and falls over the poles.⁴ The stratosphere has cooled as more heat is trapped by the troposphere underneath,⁵ whilst the boundary between these two higher and lower atmospheric layers has itself increased in height.⁶ Even the position of the tropical zones has begun to shift as the atmosphere circulates differently in response to rising heat.⁷

A more energetic atmosphere also means more extreme rainfall events as the levels of water vapour in a warmer atmosphere increase: this too has been observed.⁸ The catastrophic flooding events that hit Pakistan in August 2010 and Australia in January 2011 are exactly the kind of hydrological disasters that will be striking with deadly effect more often in a warmer world. Whilst people in poorer countries are most vulnerable to the effects of floods, any country can be hit at any time: in the English Lake District the heavy rainfall event of 18–20 November 2009 had no precedent: rainfall totals outstripped previous all-time records in over 150 years of measurements.⁹

Perhaps the clearest indicator of current danger – Ground Zero for global warming – is the rapid thaw of the Arctic. Few experts argue any more about whether the sea ice sheet covering the North Pole will melt completely; merely when. In recent years the Arctic ice cap has entered what Mark Serreze, a climatologist at the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado, calls a ‘death spiral’.¹⁰ The extent of Arctic ice is plummeting, and what remains is thinner and more vulnerable to melt than before. In terms of volume, less than half the ice cap of the pre-1980 era remains; more than 40 per cent of the volume of multi-year ice (the thicker stuff that lasts through the summer) has disappeared since only 2005.¹¹ Even the wintertime ice coverage is in decline: in January 2011 the NSIDC announced that the sea ice extent for that month was the lowest in the satellite record, with the Labrador Sea and much of western Greenland’s coast remaining completely unfrozen.¹² The year of what I call A-Day, the late-summer day at some time in the future when not a fleck of the North Polar floating ice remains, has been suggested by one modelling study as likely to arrive in 2037, but if recent years are anything to go by this could shift closer by as much as a decade.¹³

A-Day will be a momentous date for the Earth, for it will be the first time in at least five thousand years that the Arctic Ocean has been without any summertime sea ice.¹⁴ This will in turn alter the heat balance of the planet and the circulation of the atmosphere: without its shiny cap of frigid ice, the Arctic Ocean can absorb a lot more solar heat in summer and release much more in winter, changing storm tracks and weather patterns. The resulting prognosis is not for straightforward warming everywhere: one model projection by scientists working in Germany, published in November 2010, suggested that disappearing sea ice in the Arctic Ocean north of Scandinavia and Siberia could in fact drive colder winters in Europe. The researchers proposed that warmer unfrozen waters in the north could drive a change in wind patterns that allows cold easterly winds to sweep down into Europe and Russia, and that this may have helped cause the colder winters of 2005–6, 2009–10 and 2010–11 in both Europe and eastern North America, which have seen snowstorms and frosts even as the Arctic basked in unprecedented winter warmth. ‘Our results imply that several recent severe winters do not conflict [with] the global warming picture but rather supplement it,’ they concluded in the Journal of Geophysical Research.¹⁵

The disappearance of the Arctic ice will eliminate an entire marine ecosystem. Currently algae growing on the underside of floating ice are the base of a unique food chain, feeding zooplankton that in turn support large populations of Arctic cod.¹⁶ Rapidly diminishing ice spells disaster for ice-dependent species like ringed seals, walrus, beluga whales and, of course, polar bears. This may not necessarily mean outright extinction for the latter, but it will lead at best to a substantial reduction in their habitat.¹⁷ In May 2008 the polar bear was listed as ‘threatened’ under the US Endangered Species Act thanks to climate change.¹⁸

Given its current rate of precipitous decline, there is little hope that the Arctic ice cap’s death spiral can be arrested. But it is theoretically still possible to save or restore the frozen North Pole – by urgently retreating back within the 350 ppm climate boundary, and, as I will set out in a future chapter, by reducing emissions of other warming agents like black carbon. As NASA’s James Hansen, a member of the planetary boundaries expert group, writes: ‘Stabilisation of Arctic sea ice cover requires, to first approximation, restoration of planetary energy balance.’¹⁹ Reducing carbon dioxide levels to between 325 and 355 ppm would achieve this initial outcome, Hansen suggests – however, a further reduction, with CO₂ down between 300 and 325 ppm, ‘may be needed to restore sea ice to its area of 25 years ago’.

Serious climate impacts have of course also been identified outside the polar regions. In a June 2010 piece for Science magazine, climate experts Jonathan Overpeck and Bradley Udall – based at the universities of Arizona and Colorado respectively – wrote that ‘it has become impossible to overlook the signs of climate change in western North America’. These signs include ‘soaring temperatures, declining late-season snowpack, northward-shifted winter storm tracks, increasing precipitation intensity, the worst drought since measurements began, steep declines in Colorado River reservoir storage, widespread vegetation mortality, and sharp increases in the frequency of large wildfires’.²⁰ As with the melting of the Arctic, Overpeck and Udall reported that the impacts of global warming in western North America ‘seem to be occurring faster than projected’ in mainstream climate assessments like the IPCC’s 2007 report. In the Rockies higher temperatures mean that more winter precipitation is falling now as rain, and what snow does lie is melting earlier and faster. Peak stream-flow in the mountains of the American west now occurs up to a month earlier than it did half a century ago.²¹

One of the most worrying climate impacts mentioned by Overpeck and Udall in the western US is the rapid increase in tree death rates: more than a million hectares of piñon pine died recently due to drought and warming, and even desert-adapted species, that should be able to cope with ordinary dry weather, are ‘showing signs of widespread drought-induced plant mortality’. This climate-related forest die-off seems to be part of a serious global trend, which has seen widespread tree death observed in places as far apart as Algeria and South Korea, and dramatic reductions of forest cover even in protected areas like national parks.²² In some cases insect infestations are the immediate cause of the die-offs: in British Columbia beetle outbreaks have killed such extensive areas of boreal forest that experts estimate 270 million tonnes’ worth of carbon sink have been eliminated.²³

All over the world ecosystems face being wiped out as their climatic zones shift rapidly elsewhere – or disappear altogether. Just as polar animals are effectively pushed off the top of the world by the rising heat, so mountain-dwellers are confined to ever-shrinking islands of habitat on the highest peaks. Indeed, what is possibly global warming’s first mammal victim – the white lemuroid possum – may already have disappeared from its habitat of just a few isolated mountaintops in tropical Queensland, Australia. ‘It was quite depressing going back on the last field trip a couple of weeks ago, going back night after night thinking, “OK, we’ll find one tonight,”’ biologist Steve Williams told the Australian Broadcasting Corporation. ‘But no, we still didn’t find any.’²⁴ In Madagascar, another global biodiversity ‘hotspot’, mountain-dwelling species are already being displaced uphill, and some species of frog and lizard may now be extinct because of the changing climate.²⁵

Thermal stress also affects humans, of course, as increasingly intense and frequent heatwaves scorch our cities. Hundreds died in the August 2010 Moscow heatwave. Tens of thousands (and possibly as many as 70,000 in total²⁶) succumbed across continental Europe in the record-breaking summer of 2003. Very hot summers have already become more frequent across the Northern Hemisphere, and the risk of a repeat of the 2003 heat disaster has now doubled, thanks to global warming.²⁷ According to news reports, 2010 saw Japan endure its hottest-ever summer, whilst all-time heat records were smashed in 17 different countries.²⁸ Heatwaves have also increased in the Mediterranean region in number, length and intensity, according to the latest studies.²⁹ This warming and drying trend is repeated across much of the world: in southwestern Australia, for example, rainfall has fallen by a fifth since the 1970s, leading to permanent water shortages in Perth.³⁰

All these lines of evidence – of rising temperatures, thawing ice caps, shifting weather patterns and increasingly dangerous impacts – emphasise that limiting CO₂ concentrations at 350 ppm in order to prevent substantial future global warming is the only sensible option. Getting back within this planetary boundary would potentially restore the Arctic to health and prevent the complete thawing of mountain glaciers in the Andes and Himalayas that help sustain freshwater supplies to many millions of people. Limiting the speed and magnitude of the future temperature increase to just a degree and a half this century, the most likely outcome of a 350 ppm pathway, would keep global warming slow enough to allow both natural ecosystems like coral reefs and human societies to adapt to climate change.

350: MODELLING EVIDENCE

Observing the present allows us to extrapolate using educated guesswork towards the future. But perhaps a more scientifically rigorous way to project future climate change is to look at the output of complex computer models that simulate the way the climate operates in incredible detail. Taking months of supercomputer time to crunch all their complex equations, these modelling studies allow scientists to simulate changing conditions on Earth as CO₂ rises, ice melts and temperatures climb inexorably. Although computer models are always going to be an imperfect representation of the real planet we live on, they are the only way to run experiments into the future – other than sitting back and watching what really happens to the Earth, by which time it will be too late to do anything about it.

The point of setting a planetary boundary on climate is to enable humanity to keep on the right side of potential tipping points that could mark dangerous and potentially irreversible shifts in the way the biosphere operates. With that objective in mind, two members of the planetary boundaries expert group, Tim Lenton and Hans Joachim Schellnhuber, were co-authors of a landmark study published in 2008 that tried to identify the different tipping points that might exist in the climate system and get some idea of what level of temperature rise might trigger them.³¹ Top of the list was Arctic sea-ice loss. This is because the Arctic melt is self-reinforcing: as ice disappears, its highly reflective surface is replaced by darker sea or land, that absorbs more of the sun’s heat, allowing the melt of even more ice. The problem here is that models generally underestimate the observed loss of ice – in other words, what is happening in the real world tends to be worse than anything projected by the models. Given this, the experts concluded, ‘a summer ice-loss threshold, if not already passed, may be very close’. Only a 350 ppm target would likely prevent it, corresponding to 0.5 to 2˚C future global warming. But even this may not be enough.

Second on the tipping points list came the melting of Greenland’s vast ice sheet. Thick enough to raise the global oceans by seven metres if it melted entirely, the stability of Greenland matters hugely to faraway nations like Bangladesh and the Maldives, which face partial or total inundation (in the case of the latter) if it melts because of global warming. So where does the tipping point lie that might doom the Greenland ice cap to eventual destruction? Between just 1 and 2 degrees above today’s temperatures, the experts concluded, meaning that a 350 ppm trajectory is once again the least we will need to achieve to protect it. Here too the process could become self-reinforcing. The centre of Greenland is extremely cold because the thickness of the ice sheet means that it extends into high altitude: Greenland’s Summit Camp is located 3,200 metres above sea level. But as global warming nibbles away at the edges of this enormous ice body, more of it comes into the lower altitude zone, exposing the ice to higher temperatures and increasing the melt rate. Although eliminating a whole continent’s worth of ice will take time, the process could be completed in as little as three centuries, dramatically changing the coastal geography of the planet. Once again, this is a tipping point that humanity would be wise not to trigger.

Greenland is not the only vulnerable polar ice sheet, of course. Third on the list came the West Antarctic Ice Sheet, again of serious concern because – like Greenland – its loss could trigger multi-metre rates of sea-level rise. The West Antarctic also could be subject to a positive feedback process once a serious melt got under way, not just because of the change in altitude but because most of the ice sheet is actually grounded well below today’s sea level. As warming waters penetrate underneath the ice mass they could trigger a collapse that would be unstoppable, and would eventually raise global sea levels by another 5 metres. Here we may be on slightly safer ground, as the experts conclude that a global warming of 3–5˚C will likely be necessary to lead to complete collapse. So the 350 ppm boundary would appear to be well within the safety margin according to the models.

As with the Arctic sea ice, however, the real world may prove the models of Greenland and the West Antarctic to be overly conservative. The most recent satellite data from the GRACE (Gravity Recovery and Climate Experiment) mission shows a doubling in ice mass lost from both Greenland and Antarctica over the last decade³² – despite a thickening of Greenland’s higher interior where warmer winds have increased snowfall rates. Until recently the massive East Antarctic ice sheet was probably stable, but it too began losing ice in coastal areas after about 2006.³³ In total the Earth’s great ice sheets are now shedding a few hundred billion tonnes of ice annually, and sea levels rising by slightly more than 3 mm per year as a result – nearly double the rate for most of the twentieth century.³⁴ A rise in sea levels by 2100 of somewhere between 60 cm and 1.6 metres is now on the cards,³⁵ substantially more than was suggested just a few years ago by the IPCC.³⁶

A more familiar tipping point was examined next, one that has even been made into a dramatic Hollywood film. In The Day After Tomorrow, a sudden ice age is seen flooding and then freezing New York (why is it always New York?) after global warming destabilises the circulation of the Atlantic Ocean. Although the flash-freezing depicted in the movie is thermodynamically impossible, the scenario of a collapsing Atlantic current is not complete science fiction. All the models examined by the expert group led by Tim Lenton showed a tipping point in the North Atlantic where warmer, fresher waters could shut down the circulation pattern that brings comparatively balmy temperatures to the eastern US and high-latitude Western Europe. This shutdown would not trigger a new ice age, but temperatures in these regions could fall for several decades, causing serious impacts on societies and ecosystems alike.³⁷ Again unlike the Hollywood movie, which showed temperatures dropping in seconds, the full transition towards an Atlantic Ocean circulation shutdown would likely take a century or more. More good news is that avoiding this tipping point is still possible: the scientists conclude from studying their models that a global warming of 3–5˚C would be needed to put us in the danger zone, well above the 1.5˚C maximum warming implied by our 350 ppm planetary boundary.

Another candidate on the tipping-point list is the Amazonian rain-forest. For years now many scientists have warned that global warming could trigger a collapse of the forest if rising temperatures lead to severe drought in western Brazil. This scenario seems even more of a danger given the recent droughts experienced in Amazonia in both 2005 and 2010, where entire river systems in this normally wet forest dried up for hundreds of kilometres. The problem here is that models don’t concur: some show a warmer Amazon getting wetter, whilst the most pessimistic forecasts for Amazon die-back are based on the projections of just one model, the HadCM3 model produced by the UK Met Office’s Hadley Centre. However, half of the 19 different models examined by a team of scientists led by Oxford University’s Yadvinder Mahli in 2009 did show a shift towards more seasonal forest, and a quarter showed that the rainforest could dry out sufficiently to collapse into a savannah-type ecosystem instead.³⁸ Keeping global temperatures below 3˚C – very likely if our 350 ppm planetary boundary is achieved – should be enough to avoid this transition, but just as important will be respecting the other planetary boundaries on land use and biodiversity loss. The Amazon rainforest today is probably more threatened by deforestation and agriculture than it is by rising temperatures.

If the Amazon rainforest did collapse, huge quantities of carbon would be released in the process, giving a further boost to global warming. But the biggest carbon stores of all lie not in the tropics, but in the sub-polar continental regions where frozen permafrost holds enormous carbon stores tens of metres thick in Siberia and other high-latitude land areas. The threat to permafrost stability is possibly global warming’s biggest tipping point, because if this frozen carbon store begins to thaw, vast quantities of both carbon dioxide and methane will be released. According to a 2008 study in the journal BioScience, the carbon locked up in the Northern permafrost zone totals more than 1.5 trillion tonnes, double the entire carbon content of the atmosphere.³⁹ Even if only 10 per cent of this permafrost thaws, another 80 ppm of CO₂ will have accumulated in the atmosphere by 2100, raising the planet’s temperature by an additional 0.7 degrees⁴⁰ – and making the eventual attainment of the 350 ppm climate change boundary much more difficult.

Scientists have already begun watching with some alarm a recent upward trend in atmospheric methane, some of which may be coming from the Arctic.⁴¹ Not all this methane – a greenhouse gas 25 times more potent than CO₂ – is likely to bubble out of swamps on land; vastly more is contained in subsea sediments in the form of ice-like methane hydrates. If these hydrates melt rapidly as the oceans warm up, then all global warming bets are off – a scenario that has already sparked scary newspaper headlines. So how afraid should we be? Researchers have already reported seeps of methane leaking from the seabed offshore from eastern Siberia and the Norwegian Arctic islands of Svalbard, in both cases possibly in response to warmer ocean waters.⁴² But the experts are cautious. ‘Methane sells newspapers, but it’s not the big story,’ writes David Archer on the excellent RealClimate blog.⁴³ ‘CO₂ is plenty to be frightened of, while methane is frosting on the cake.’

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.

Greens have for years called into question GDP as a measure of true progress, but the reality is that increasing prosperity – measured in material consumption – is non-negotiable both politically and socially, especially in developing countries. This may one day need to change, but that is a different debate, and one that needs to be had for different reasons. As the climate scientist Roger Pielke Jnr writes in his 2010 book The Climate Fix, ‘if there is an iron law of climate policy, it is that when policies focused on economic growth confront policies focused on emissions reductions, it is economic growth that will win out every time.’ Greens may despair, but I think Pielke Jnr is right. The implication, however, is not that we are all doomed, but that any successful policy to decarbonise the global economy ‘must be designed such that economic growth and environmental progress go hand in hand’.⁵⁴

In a related sense, although Greens often insist that energy is too cheap, this too is incorrect. Energy is actually too expensive, certainly for the 1.5 billion poor people in the world who lack access to electricity because they do not have the purchasing power to demand it. Well-fed campaigners in rich countries may fantasise romantically about happy peasants living sustainably in self-reliant African villages, but the fact is that people across the developing world are desperate to increase their economic opportunities, security and wealth. They want to have enough to eat, they want to have clean water and they want their young children not to die of easily treatable diseases – and that is just for starters. They want the benefits of being part of the modern world, in other words, which is why so many young people across the developing world are moving to cities in search of a job and a better way of life. And this better way of life is coming, as the soaring rates of economic growth in China, India, Brazil and many other developing countries demonstrate. The fact is that most of the world needs more growth, not less: China has lifted 300 million people out of poverty in the last couple of decades due to its economic miracle. Hundreds of millions more, in Africa now too as well as Asia and Latin America, are determined to follow, as they have every right to.

By mid-century, in other words, we will see a world of many more, much richer people. Most Greens view this prospect with dread, for how can the world possibly reduce carbon emissions under such a scenario? The London-based New Economics Foundation (NEF), for example, writes in a recent report: ‘If everyone in the world lived as people do in Europe, we would need three planets to support us.’⁵⁵ This is nonsensical, for everyone in the world is going to live like Europeans within this century (and Europeans too will also get richer) whether NEF likes it or not, and we will still only have one planet. NEF’s ‘Happy Planet Index’ was recently topped by Costa Rica (with the Dominican Republic in second place and Jamaica in third), apparently suggesting that the best country in the world to live is one where 10 per cent of the population still survive on just $2 a day.⁵⁶ Certainly, the fact that GDP does not necessarily equate to happiness is an important point to make. But it won’t cut much ice with the billions of people – a majority of humanity – who are poor, insecure or malnourished in today’s world. For them economic growth is not a choice but a necessity.

So reducing human population and economic growth is neither possible nor desirable. Luckily there is a third way: we can reduce the carbon intensity of the economy, so that for each unit of GDP produced, less and less carbon needs to be emitted. This means deploying low-carbon technologies across the board so that the energy that is needed to drive economic activity can be generated without additional greenhouse gases. What we need, in other words, is an economy-wide technofix.

TECHNOLOGIES FOR 350

My own perspective on tackling climate change has shifted since I was appointed adviser to President Nasheed of the Maldives in 2009. The president, whose country is of course early on the list of those liable to be wiped out by rising sea levels, had just announced his ambition for his nation to become the first carbon-neutral country in the world, by 2020. Suddenly, having spent most of my life as a journalist, I was confronted with the challenges of real energy supply in a real developing country. All my Green ideology – of tackling corporate power, reducing consumption, challenging economic growth and so on – was going to be of little help with this intensely practical challenge. To be carbon-neutral the Maldives would have to stop burning diesel in electric generators on every one of its 300 or so inhabited islands, and shift instead to an energy system entirely based on renewables. It would have to do this in a way that would not raise people’s energy bills, and would provide opportunities for new business. I found myself in a world where discussions of wind and solar hybrids, battery storage options, biomass and waste-to-energy, and electrical grid load-balancing came to the fore. I began to think less like an ideologue and more like an engineer.

This, on a far grander scale, is the same challenge that confronts the world. To achieve the planetary boundary of 350 ppm, the global economy needs to be carbon-neutral by mid-century and carbon-negative thereafter. Meeting this target means we all – Greens included – need to start thinking like engineers. This is a huge industrial building project, converting the energy basis of civilisation from fossil fuels to a variety of cleaner sources. If we do it right, it will not be a burden or a cost to the world’s economy, but a source of enormous potential future growth, innovation and job creation. The sheer amount of economic activity implied by the transition is staggering: to reduce the emissions of the United States by a third, for example, would (using current technologies) involve constructing 145 nuclear plants, 33,000 solar thermal power stations and 130,000 large wind turbines. In Germany, the same ambition of a 30 per cent emissions cut implies 21 nuclear plants, 4,800 solar stations and 20,000 additional windmills.⁵⁷

Different technologies can be substituted according to different circumstances or national preferences, of course. The Austrians, for example, despise nuclear power. (The country spent $1 billion building a nuclear plant, and then had a referendum in 1978 that was won by the anti-nuclear lobby. The plant, called Zwentendorf, was never opened, and coal-burning power stations built instead.) For the Maldives I would not suggest any nuclear power stations, because each island operates as a separate independent energy entity and nuclear plants are simply too big to be appropriate. Moreover, the country is drenched in solar radiation for most of the year – its main constraint, in fact, is the land space needed to capture the sun’s energy. But very large, densely populated nations outside the tropics are likely to need substantial nuclear generation. This may be difficult for many Greens to swallow, but as I will show in future chapters, nuclear power is nothing like the environmental threat it has long been made out to be. Instead, by displacing coal from our energy mix, it can be a net win for the biosphere. China, for instance, has 13 operational nuclear plants and 150 more under construction or on the drawing board.⁵⁸ Each 1-gigawatt nuclear plant will displace 6 million tonnes of annual CO₂ emissions, making this one of the best pieces of climate-related news anywhere in the world.⁵⁹ That should be the end of the matter so far as environmentalists are concerned: nuclear is Green.

To cut global emissions in half by 2050 (with growing energy consumption in the meantime) would require the construction of 12,000 nuclear power stations – with one plant coming online every single day between now and then (assuming we start in 2015). I mention this only as an illustrative exercise, for no one – not even the nuclear industry – suggests that we try to deal with climate change using nuclear power only. Such a level of new-build sounds impossible, but consider that over the last fifty years humans have constructed two large dams per day, half of those in only one country – China.⁶⁰