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

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      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 СКАЧАТЬ