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

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СКАЧАТЬ 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 СКАЧАТЬ