2/21/2016 A modern ark | The Economist Special report: Climate change Biodiversity A modern ark To save endangered species, move them to more congenial places Nov 28th 2015 | From the print edition ALONG THE BANKS of the Apalachicola river, near the border between Florida and Georgia, lives a rare tree called a stinking cedar. Once common, Torreya taxifolia seems to have got stuck in this tiny pocket as the continent warmed after the last ice age. It cannot migrate northward because the surrounding soils are too poor. Attacked by fungi, just a few hundred stinking cedars remain along the river. Rising temperatures now threaten to kill them off entirely. Spying a looming extinction, a group of people is engaged in a kind of ecological vigilantism. The self-styled \"Torreya Guardians\" collect thousands of seeds a year and plant them in likely places across the eastern United States. Stinking cedar turns out to thrive in North Carolina. The Torreya Guardians are now trying to plant it in colder states like Ohio and Michigan as well. By the time the trees are fully grown, they reason, temperatures might be ideal there. Some are dubious. The Torreya Guardians were at first seen as \"eco-terrorists spreading an invasive species\2/21/2016 Groupthink | The Economist Special report: Climate change Public opinion Groupthink People's views on climate change go hand in hand with their politics Nov 28th 2015 | From the print edition FOR ALL THE torrent of scientific reports, books and television documentaries on the subject, climate change commands a good deal less public attention than Kim Kardashian, a reality-TV star. Early in 2007 Google searches for Ms Kardashian's name overtook searches for \"climate change\". She has never fallen behind since. Even Bangladeshis Google her more than they do the forces that threaten their countryin English, at least. The rich are more concerned about climate change than the poor, who have many other things to worry about. A giant opinion-gathering exercise carried out by the United Nations finds that people in highly developed countries view climate change as the tenth most important issue out of a list of 16 that includes health care, phone and internet access, jobs, political freedom and reliable energy. In poor countriesand indeed in the world as a wholeclimate change comes 16th out of 16. Even in the rich world, interest flagged for a few years following the financial crisis of 2007. It is now recovering a little. But in America, another psephological trend is plain: attitudes to climate change have become sharply polarised along political lines (see chart). \"The partisan divide started in 1997,\" says Jon Krosnick of Stanford University. That was when a Democratic president, Bill Clinton, threw his weight behind the UN effort to introduce mandatory caps for greenhouse-gas emissions. It has since widened. YouGov, a pollster, found in http://www.economist.com/node/21678952/print 1/3 2/21/2016 Groupthink | The Economist 2013 that 70% of Democratic voters saw evidence of man-made climate change in recent weather patterns, whereas only 19% of Republican voters did. A similar, though smaller, divide was found in Britain. It is not that conservatives are ignorant. Knowledge of science makes little difference to people's beliefs about climate change, except that it makes them more certain about what they believe. Republicans with a good knowledge of science are more sceptical about global warming than less knowledgeable Republicans. The best explanation for the gap is that people's beliefs about climate change have become determined by feelings of identification with cultural and political groups. When people are http://www.economist.com/node/21678952/print 2/3 2/21/2016 Groupthink | The Economist asked for their views on climate change, says Dan Kahan of Yale University, they translate this into a broader question: whose side are you on? The issue has become associated with left-wing urbanites, causing conservatives to dig in against it. The divide will probably outlive Ms Kardashian's fame. From the print edition: Special report http://www.economist.com/node/21678952/print 3/3 2/21/2016 Hot and bothered | The Economist Special report: Climate change Climate change Hot and bothered Not much has come of efforts to prevent climate change so far. Mankind will have to get better at tackling itbut must also learn to live with it, says Joel Budd Nov 28th 2015 | From the print edition LOOKING BACK FROM the early 24th century, Charlotte Shortback suggests, half-jokingly, that modern human history can be split into distinct periods. The most exciting was the Accelerando, from about 2160 to 2200, when human lifespans were greatly extended and the terraforming of Mars was completed. That was followed by the Ritard, when the people of Mars lapsed into isolationism. Long before, though, came a strange spell, from 2005 to 2060, when people understood the science of climate change but did little to prevent it; nor did they try to colonise other planets. She dubs it the Dithering. Charlotte Shortback is a character in \"2312\2/21/2016 If all else fails | The Economist Special report: Climate change Geoengineering If all else fails Manmade global cooling is scary, but may become necessary Nov 28th 2015 | From the print edition THE SUM OF human tinkering with the climate since the beginning of the industrial era is sometimes likened to a planetary science experiment. That captures the magnitude of what is happening and the unpredictability of its results, yet it is also misleading. Global warming is not an experiment, because it is not intentional. Greenhouse-gas emissions are the unfortunate side effects of useful things like modern agriculture, electricity generation and convenient transport. Mankind has not really started experimenting with the climate yet. But perhaps, given the slow progress in keeping down emissions, it should. A small, underfinanced and somewhat obsessive group of scientists is working on ways of \"geoengineering\" the Earth to reverse global warming. Some of their proposals are absurdly costly; others are exceedingly dangerous. Still, geoengineering deserves much more serious consideration than it has so far received. Since climate change is mostly caused by greenhouse gases, the obvious way of reversing it is to remove those gases from the atmosphere. Removing carbon dioxide from the air would also help marine creatures: the oceans are becoming less alkaline as a result of dissolved carbon, which seems to be harming corals. Some scientists are exploring ways of speeding up the natural processes that already do this. Carbon-absorbing minerals like olivine, which is in abundant supply, could be mined, crushed and spread out. Lime or limestone could be tipped into the ocean to react with dissolved carbon dioxide to create bicarbonate ions, allowing the water to http://www.economist.com/node/21678963/print 1/5 2/21/2016 If all else fails | The Economist absorb more carbon dioxide from the air. Iron and other nutrients could be added to the water to stimulate the growth of algae, which feed on carbon dioxide. Plants could be grown and then burnt in power stations capable of capturing the carbon that the plants had removed from the air; the gas could then be compressed and buried under the ocean. Carbon dioxide could be filtered out of the smoke that rises from factories and power stations, or even just out of the air. A Canadian firm, Carbon Engineering, has just opened a pilot plant that will do this. All methods of removing carbon dioxide from the atmosphere are even more challenging than they might seem at first sight. That is because the ocean and the land currently absorb about half of human emissions. If atmospheric concentrations were brought down, some carbon dioxide would naturally \"outgas\" from the seas and the land, adding to the amount that would have to be removed. And two fundamental (though contradictory) criticisms are levelled at the carbon-suckers. First, their methods are so costly that they could not possibly be deployed on the scale required to alleviate climate change. And second, if those methods could be made to work, they might introduce moral hazard. If greenhouse gases could magically be removed from the atmosphere tomorrow, why bother with cutting emissions today? The first objection is a good one. Carbon-removal techniques are indeed extraordinarily costly, and not just in a financial sense. Tim Kruger of the Oxford Martin School estimates that in order to remove just one gigatonne of carbon (roughly one-tenth of current annual emissions) from the atmosphere, 4.5 gigatonnes of lime would have to be dumped into the ocean. That would require 6.5 gigatonnes of limestone, or almost one tonne for every man, woman and child on Earth, and 4,500 factories to make it into lime. Alternatively, growing plants and then capturing their carbon would require enormous quantities of agricultural land to make much difference to the climate. Still, many of these technologies deserve to be tried out. The costs of some carbon-removal methods might come down in time, though others might turn out to be even more expensive than their proponents think. And at some point in the future one of them, or a combination, will have to be deployed if climate change is to be arrested. It will be impossible to prevent all greenhouse-gas emissions. There will always be individual national holdouts, and there will always be niche uses for gas and oil, such as powering passenger aeroplanes. The second objection to carbon removal, that it encourages recklessness, would be persuasive only if it could be done cheaply. At the moment it looks so costly and so tricky that it cannot be used to justify putting more greenhouse gases into the atmosphere. Indeed, it would be good to http://www.economist.com/node/21678963/print 2/5 2/21/2016 If all else fails | The Economist have more research into these technologies if only to see just how costly they would be. Most of the theoretical means of avoiding large-scale global warming assume that tens or even hundreds of millions of hectares of land can be given over to growing energy crops. It would be helpful to know how realistic that might be. At best, carbon-dioxide removal might turn out to be an expensive way of dealing with the chief cause of climate change. But there is another approach, which is to attack climate change directly. This could work out much cheaper. Indeed, it would almost certainly be cheaper than replacing fossil fuels with renewable sources of power. That is only one reason it is so unnerving. For all that human activities are perturbing the climate, those actions appear trivial when set beside the enormous heat engines that create the Earth's weather. Even doubling the concentration of carbon dioxide in the atmosphere would create a radiative forcing of only four watts per square metre, a number dwarfed by the 240 watts per square metre that pours into the Earth from the sun. That suggests a straightforward and highly appealing calculation. Four divided by 240 is 0.017. To offset the warming effect of a doubling of carbon dioxide, then, it might be necessary to intercept only about 1.7% of the solar radiation that currently reaches the Earth. Spray and pray Some early satellite pictures contained what appeared to be scratches, says John Latham, a scientist who lives in Colorado. These turned out to be ship trackslinear clouds that grow on aerosols emitted by ships as they traverse the seas (see image above). What has been done inadvertently could be done better deliberately. If ships were to create tiny salt particles from seawater in just the right places, water droplets would form on them. That would alter a type of cloud called a marine stratocumulus. With more droplets of a smaller size, the cloud would become lighter and thus more reflective. Seawater is innocuous; \"it's benign and it's infinite,\" explains Mr Latham. And marine stratocumulus clouds are so common that the Earth might be cooled substantially. Ship tracks are linear clouds that grow on aerosols emitted by ships. What has been done inadvertently could be done better deliberately The big technical problem so far has been to produce nozzles capable of consistently producing tiny droplets. Many ships would be needed to trundle up and down the best cloud-lightening corridors (the west coast of Africa is especially good). But these difficulties hardly seem insurmountable. A report published in 2012 for the Copenhagen Consensus Centre estimated that marine-cloud brightening would prevent global warming even more effectively than a carbon tax. http://www.economist.com/node/21678963/print 3/5 2/21/2016 If all else fails | The Economist If spraying seawater into the air would probably cool the Earth, spraying sulphur into the stratosphere would be almost certain to do so. It has been done, after all. Volcanoes spew out sulphur that creates particles which reflect sunlight back into space; those particles also bounce light around the atmosphere, producing wonderful sunsets. These can cool the Earth significantly, albeit briefly (see chart): within a year or so the particles are washed out of the atmosphere. Sulphur could be sprayed at precisely the right height and in very fine droplets, which would reflect more light for longer. It might take only a small fleet of high-altitude aircraft flying in relays to put enough in the stratosphere to cancel out the entire temperature rise resulting from human greenhouse-gas emissions. The sulphur would eventually fall as acid rain, but not in alarming quantities: the amount of sulphur required would be much less than is currently thrown up into the air by vehicles and factories. Both marine-cloud brightening and stratospheric aerosols carry risks. One is that cooling the Earth without removing carbon dioxide does not quite return the climate to normal. The more carbon dioxide that is present in the air, the less plants perspire, affecting the water cycle. And the heat-trapping greenhouse effect would still operate, just with less heat in the system. With temperatures more evenly distributed in the atmosphere, there would be less convection and, presumably, less precipitation. So a cooler world with lots of greenhouse gases would probably be a drier world. Any country that suffered a drought would surely blame the geoengineers. But the biggest problem is what would happen if the engineering stopped. Assuming that greenhouse-gas emissions continued while the ships or aeroplanes were doing their work, abruptly ending the artificial shielding would lead to a sudden jump in temperatures, which would be disastrous for people and the natural world alike. Ken Caldeira of the Carnegie Institution points out that an abrupt \"termination shock\" could be avoided if geoengineering were used only to slow global warming and then gradually wound down. But that assumes the nations of the world can agree on how to manage the climate. The history of United Nations climate talks suggests they can't. Still, these methods ought to be developed and evenvery carefullytested. The Earth might need a drastic intervention, particularly if it became clear that something alarming was about to happen, such as a breakdown of the Indian monsoon. Marine-cloud brightening could be deployed on a small scale to avert specific disasters. Mr Latham suggests that cooling just a few http://www.economist.com/node/21678963/print 4/5 2/21/2016 If all else fails | The Economist hundred square kilometres of ocean in the right place could make a hurricane less severe. If the climate-modellers are right that hurricanes will become more intense as the ocean warms, this will become increasingly tempting. Better the devil you know The most persuasive reason for investigating geoengineering further is that somebody is likely to try it. Countries will have different ideas about when global warming becomes truly dangerous: Britain, for instance, is a lot more sanguine than the Maldives. Some of the more skittish states might start injecting aerosols into the lower stratosphere, perhaps in a clumsy way. If no formal experiments had been carried out and thus scientists in other countries did not know what to look for, it might not be obvious for some time that this was going on. David Victor, who studies the politics of climate change at the University of California, San Diego, doubts that nations would ever formally agree to engineer the Earth's climate: their interests are too diverse. He thinks it much more likely that a country would just go ahead and try it. That would put the others in a quandary. Should they forcibly stop that country from acting, or should they step in with superior geoengineering techniques? Before long, Mr Victor says, they could find themselves acting as zookeepers to the planet. From the print edition: Special report http://www.economist.com/node/21678963/print 5/5 2/21/2016 If you can't stand the heat | The Economist Special report: Climate change Adaptation If you can't stand the heat How farmers in poor countries are responding to climate change Nov 28th 2015 | From the print edition IN THE BRACKISH coastal districts of southern Bangladesh, weather can be measured in centimetres. Women in Bujbunia, 140km (about 90 miles) south of Dhaka, hold their hands at knee height to show how deeply the village flooded during the most recent big cyclonic storm. Aila swept northward through the Bay of Bengal and hit Bangladesh in May 2009. The country had seen much bigger weather events; in 1991 a huge cyclone killed about 140,000 people. Still, Aila's storm surge brought enough seawater to inundate villages and wipe out rice crops. The inhabitants of Bujbunia still wince when they recall how hungry they were afterwards. Few countries of any size are more gravely threatened by climate change than Bangladesh (which has more than 110m people). Sarder Shafiqul Alam of the International Centre for Climate Change and Development in Dhaka checks off the many hazards. North-west Bangladesh seems to be turning drier. In the north-east and central parts of the country, flooding is a growing danger. The south and east are vulnerable to cyclones, which will probably intensify as the planet heats up (the higher the temperature, the more energy in the weather system). The south is also becoming saltier, partly because the sea is rising and partly because many farmers are inundating their fields with seawater so they can grow shrimp. To counter the most spectacular threat to human life, Bangladesh's government has built several thousand cyclone sheltersat best, sturdy buildings sitting atop pillars of reinforced concrete, which in normal times are often used as schools. One new shelter a few kilometres from http://www.economist.com/node/21678962/print 1/5 2/21/2016 If you can't stand the heat | The Economist Bujbunia could accommodate more than 1,000 people if they were to press closely together, and might even hold a few hundred cows on the ground floor. Women and children will rush there if a big cyclone threatens; men will head for the nearest brick-built mosque. Farmers are also preparing for storm surges in a humbler way. Scooping up greyish mud, they build plinths up to a metre high. Levelled and packed down, these become the floors of their homes; walls and roofs are made of palm fronds, bamboo and corrugated iron. The aim is to build the plinth higher than the flood waters will reach, to prevent the family's food and possessions being swept away. Even stoves would be destroyed; they are only made of earth. Whereas the global attempt to avert global warming by cutting emissions is not exactly racing forward, adaptation to climate change is well under way. Between 1993 and 2009 the proportion of American households with air-conditioning rose from 68% to 87%. Californian cities are coping with an epic four-year drought, which may have been exacerbated by climate change, by buying water rights from farmers and recycling more waste water. San Diego is building an expensive desalination plant. In sub-Saharan Africa many farmers are diversifying from growing wheat to sorghum and other crops. Few of the people making such adjustments are thinking explicitly about global warming; they are simply trying to make themselves more comfortable and secure. Yet their actions add up to the most profound and intelligent response to climate change so far. http://www.economist.com/node/21678962/print 2/5 2/21/2016 If you can't stand the heat | The Economist Bringing down emissions of greenhouse gases asks a good deal of people, not least that they accept the science of climate change. It requires them to make sacrifices today so that future generations will suffer less, and to weigh the needs of people who are living far away. Adaptation requires none of these things. \"Because of the free-rider problem, each of us has very weak incentives to alter our behaviour,\" says Matthew Kahn, of the University of California, Los Angeles. \"But we have very strong incentives to respond to whatever the climate throws at us.\" Bewket Amdu, Azemeraw Ayehu and Andent Deressa have surveyed almost 400 villagers in the upper catchment of the Blue Nile in Ethiopia and found that almost everybody believes temperatures are rising. Most villagers also think less rain is falling, although some are convinced the weather has become wetter. They have responded by tweaking their farming techniques. The villagers now plant potatoes two to three weeks later than they used to and harvest them a week earlier. The growing seasons for wheat and barley have also contracted by about a month. Yields are lower, but that is preferable to losing an entire crop to flooding or drought. To save farmers from having to make such dismal trade-offs, laboratories in Africa and elsewhere are developing crops that can survive more extreme weather. One poetically nicknamed innovation is \"scuba rice\2/21/2016 Second-best solutions | The Economist Special report: Climate change The way forward Second-best solutions If the best method for tackling climate change is not on offer, try something else Nov 28th 2015 | From the print edition ECONOMISTS LIKE TO argue, about climate change as much as anything else. Some of the fiercest rows are over the discount ratehow to weigh the likelihood that future generations will be richer than the current one when deciding how much to spend on averting climate change todayand over how to price catastrophic but unlikely events such as the collapse of the Greenland ice sheet. But on the biggest issue of all they nod in agreement, whatever their political persuasion. The best way to tackle climate change, they insist, is through a global http://www.economist.com/node/21678959/print 1/4 2/21/2016 Second-best solutions | The Economist carbon tax. Politicians tend to assume that subsidising clean energy has the same effect as taxing carbon, says Ottmar Edenhofer, an economist at the Potsdam Institute for Climate Impact Research. It does not. Subsidies for wind, solar and nuclear power increase the supply of wind, solar and nuclear energy, but they do not squeeze the polluters. Indeed, as has been shown earlier in this report, green-power subsidies can actually boost the most polluting fossil fuels. A carbon tax would bear down on the thing that most needs to be suppressed. Carbon taxes have their problems, though, beginning with the word \"tax\". New levies are never popular. Even if governments promised to cut other taxes, so that a carbon tax would be fiscally neutral, they would make enemies. It is a sound rule of politics that the winners from any reform are less delighted than the losers are angry. And no government could guarantee that carbondioxide emissions would fall by a specific amount. A carbon tax represents certain pain for uncertain gain. Instead, many countries have adopted \"cap-and-trade\" schemes. These specify the quantity of carbon that can be emitted and hand out, or auction, permits to pollute up to that limit. Polluters can buy and sell permits, which in theory means that the cheapest methods of reducing emissions are deployed first. By far the biggest cap-and-trade scheme was launched in 2005 by the European Union. It covers not only carbon dioxide but also nitrous oxide and perfluorocarbons, and includes emissions from commercial aircraft. California also has a capand-trade scheme, which is linked to projects run by some Canadian provinces. Earlier this year South Korea set one up. China, which already has six regional schemes of this sort, has promised a national one. Capping and trading pollution is less good than taxing it. Under pressure from heavy industry, governments tend to hand out too many pollution credits, so the price is invariably too low to alter behaviour. As this report went to press, carbon was trading in Europe for less than 10 a tonne. And cap-and-trade schemes can encourage free-riding. If a country covered by an international emissions-trading scheme decides to enforce stricter regulations, the market will be flooded with cheap pollution credits, encouraging others to pollute more. It helps to set a minimum carbon price and keep raising it, as California is doing. The big problem afflicting carbon taxes and cap-and-trade schemes alike is that not everybody wants to join the club. Carbon is best priced globally, partly because popular support will ebb if jobs move from virtuous countries to less virtuous ones, and partly because such schemes work much better on a large scale. William Nordhaus, a climate economist at Yale University, calculates that if every country in the world were to tax carbon, temperatures could be held to 2C above pre-industrial levels at a cost of 1-2% of world income per year. If the scheme were http://www.economist.com/node/21678959/print 2/4 2/21/2016 Second-best solutions | The Economist confined to countries representing only half of global emissions, the two-degree target would be almost impossible to hit. The obvious way to get countries to join a climate club is by threatening their exporters. Taxing imports at the border according to their carbon content, but giving credits for any carbon taxes already paid at home, might encourage exporting countries to levy their own taxes. But this would be brutally difficult to implement. Besides, border taxes on carbon would suppress trade, just as other tariffs do. And they might well prove illegal. Count to three A global carbon taxor even one involving many countriesis likely to remain an economic theory for a long time. Certainly, nothing of the sort will be seriously discussed in Paris. Even so, there are three perfectly good things everybody could be getting on with right away. Two are humdrum, though no less worthwhile for that. The third requires greater ambition. First, countries should be nudged to upgrade their promises for cutting emissions. In advance of the Paris conference, an untidy mess of pledges has been dumped on the table. Some countries say, fairly straightforwardly, that they will cut greenhouse-gas emissions by such-and-such a percentage compared with a particular year. But they pick different base yearsinvariably ones in which their emissions were very highto make their promises look better. Australia goes for 2005; Russia plumps for 1990, just before its heavy industries collapsed. Other countries do not even propose to hold emissions to a specific level. Some countries go in for statistical tricks, arguing, for example, that their efforts to prevent deforestation should be weighed more generously. The pledges should be made more comparable. A good second move would be to ditch the carbon monomania. Tackling carbon dioxide, the most important greenhouse gas, is essential. Yet aside from its effect on ocean chemistry and the fact that it is warming the world, though so gradually that most people cannot detect it, carbon dioxide is innocuous. And the effects of emissions persist in the atmosphere for so long that even a drastic cut would have only a slight effect on climate change in the short term. Carbon dioxide is not, however, the only greenhouse pollutant. Methane, black carbon (ie, soot) and hydrofluorocarbons also warm the world a good deal. It has been estimated that if strong action were taken to suppress them, the world might be 0.6C cooler by 2050 than it would otherwise bea quick, fairly noticeable change. There is talk of regulating hydrofluorocarbons under the Montreal Protocol, which cracks down on ozone-depleting chlorofluorocarbonsan excellent idea. More research on cheap, clean stoves for developing countries would be money well spent http://www.economist.com/node/21678959/print 3/4 2/21/2016 Second-best solutions | The Economist The best target is black carbon, which comes off open wood fires and out of the exhaust pipes of unsophisticated diesel vehicles. This is an immediate killer, and it is easier to tackle than carbon dioxide. California cut black-carbon emissions by half in 20 years, mostly by cracking down on vehicles. More research on cheap, clean stoves for poor countries would be money well spent. The most important thing of all is to innovate. Bill Gates, the philanthropist, laments that in all the discussions about climate change around the UN, almost nothing is said about research. Yet there is a crying need to develop technologies that are cheaper and more dependable than today's wind turbines and solar farms. Mr Gates has invested in new types of nuclear reactor but he also holds out hope for artificial photosynthesis, which uses solar energy to make hydrogen from water. \"It's not like the Manhattan Project,\" he says. \"There are maybe a hundred different paths.\" Mr Gates points out that annual spending on energy research in America is only about $6 billion, compared with $30 billion on medical researchand America is much more openhanded than many other countries. Energy firms do not spend a lot on research because there is no product differentiation in energy (electrons are electrons) and thus nothing exciting to sell until the price falls below that of the existing technology. So taxpayers will have to stump up most of the cash. If more money were forthcoming, a good deal of it would be wasted on dead-end projects. But that is the nature of research and development. Only a few successes would be needed in order to avert calamitous climate change. And the funds that governments are currently pouring into subsidies for things like offshore wind farms are not doing much good. \"We're spending almost all our money on wind turbines and solar panels that we know are not effective,\" says Bjorn Lomborg of the Copenhagen Consensus Centre. But then, he points out, people are used to doing things that make them feel good about climate change, rather than things that actually do good. From the print edition: Special report http://www.economist.com/node/21678959/print 4/4 2/21/2016 Seeing daylight | The Economist Special report: Climate change China Seeing daylight The world's biggest polluter cleans up Nov 28th 2015 | From the print edition WHEN THE NATIONS of the world first tried to cut a deal to reduce greenhouse-gas emissions, in the late 1990s, a gorilla A hazy prospect of cleaner air stood in the way. America, then the world's biggest polluter, would not consent to mandatory reductions, all but strangling the accord. These days China is the biggest polluter and the country without which no global agreement will stick. But it is not quite the climate pariah that it is often thought to be, and it has started to change. China emits more greenhouse gases than anywhere else in the world partly because it has a lot of people: 1.4 billion, compared with 800m for America and the EU put together. And much of the pollution it causes comes from making goods for other countries. The chart on the next page, which uses data from Michael Grubb of University College London, controls for both of these things. It shows that, once the pollution that goes into traded goods is assigned to the country that consumes them, the average Chinese person harms the planet less than does the average European and much less than the average American. He is catching up fast, though. China was responsible for three-quarters of the net coal-fired power-generating capacity added worldwide between 2000 and 2014. And the country's hunger for the black stuff is not limited to its power stations. At least a quarter of Chinese coal is used in what Laszlo Varro, a fossil-fuels http://www.economist.com/node/21678960/print 1/4 2/21/2016 Seeing daylight | The Economist expert at the International Energy Agency, calls a \"Dickensian\" manner. Burned, inefficiently, in boilers to heat buildings and power textile mills, it has fouled the air around Chinese cities, turning them into simulacra of 19th-century Manchester. Climate-change denial is strikingly rare among China's political leaders, some of whom trained as engineers. They understand that their country is expected to suffer some of the worst consequences of global warming: northern China, which is increasingly hot and dry, will probably become hotter and drier still. The politicians are also well aware that their country's urbanites are fed up with breathing toxic air. Earlier this year an online documentary film about air pollution, \"Under the Dome\2/21/2016 Supermodels | The Economist Special report: Climate change The science of climate change Supermodels What is known about global warmingand what remains dark Nov 28th 2015 | From the print edition IN AN APPROPRIATELY sweltering lecture theatre at the University of Pierre and Marie Curie in Paris, scientists gathered earlier this year to discuss a phenomenon called the global-warming hiatus. Between 1998 and 2012 humans pumped unprecedented quantities of greenhouse gases into the atmosphere, but the average global temperature barely rose. Why? Because much energy went into melting ice, explained one. Because it was absorbed by the oceans, said another. Because many small volcanic eruptions threw particles into the atmosphere, deflecting solar radiation, explained a third. Nonsense, said a fourth. There was no hiatus at all1998 was a freakishly hot year, so it was hardly surprising that temperatures bumped around the same level for a few years. At the end, the moderator summed up: \"Well, that's science!\" This sort of thing drives green-minded politicians mad. It is hard enough to persuade voters that global warming is a serious danger that they must pay to avoid, in the form of higher energy bills and unsightly wind farms. If the scientists seem unsure, the task becomes impossible. Despite appearances, though, key parts of climate science are settled. Although the remaining uncertainties are a little larger than green groups generally admit, they are not nearly as big as global-warming sceptics suppose. The greenhouse effect itself is straightforward; it just does not work much like a greenhouse. http://www.economist.com/node/21678953/print 1/4 2/21/2016 Supermodels | The Economist About one-third of the energy that pours into the Earth from the sun reflects off clouds and the planet's surface and heads back into space. Much of the rest is absorbed by the land and the oceans, which then emit it largely in the form of infra-red radiation. This is absorbed by trace gases in the atmosphere, which in turn release infra-red upwards, sideways and downwards to the Earth's surface. It is this bouncing around of energy that is known as the greenhouse effect. It is essential to life on Earth; without it, the average temperature at the Equator would be -10C. The most important greenhouse gas is water vapour. Were there no water vapour or clouds, the greenhouse effect would be only about one-third as powerful as it is. Carbon dioxide is the second most important, followed by methane, then chlorofluorocarbons (CFCs), industrial chemicals that were cracked down on in the 1980s and 1990s because of their ozone-depleting properties but are still hanging around. These gases are more or less potent and durable. Tonne for tonne, methane is a much more powerful greenhouse gas than carbon dioxide, but it breaks down more quickly. Carbon dioxide, which reaches its maximum warming effect about ten years after being released, is so stable that even 1,000 years after a bump in emissions, atmospheric levels will still be substantially higher than normal. The basic science is hardly novel. In the 1890s a Swedish scientist, Svante Arrhenius, ran some \"tedious calculations\" on the greenhouse effect and went on to explain how burning fossil fuels might intensify it (living in a cold country, he thought this a thoroughly good thing). Things get complicated when scientists try to work out what happens to the extra energy that remains in the Earth system and how other human activities, beyond emitting greenhouse gases, might also affect the climate. Beware the feedback loops Greenhouse warming sets off a cascade of effects known as feedbacks, which are harder to measure. On balance, warming begets more warming. Higher temperatures enable the atmosphere to hold more water vapour. Oceans absorb huge amounts of carbon dioxide, keeping a lid on climate changebut as they warm up, their absorption capacity declines. Melting ice produces dark pools of water that absorb more energy. Partly for this reason, the Arctic is warming faster than other places. Inadvertently, though, humans also cool the Earth. Although the overall effect of deforestation is to warm the planet, replacing trees with crops or grassland makes the land paler and more reflective. Particles created from sulphur dioxidethe cause of acid rainreflect lots of light back into space. China has probably been shielded from higher temperatures by air pollution, and might heat up quickly if it gets serious about scrubbing its skies. The greatest mystery is the effect of human activity on clouds. Because clouds grow on aerosol http://www.economist.com/node/21678953/print 2/4 2/21/2016 Supermodels | The Economist particles, more of them are likely to form in a more polluted atmosphere. Clouds are also affected by temperature changes. But precisely how is unclearand this matters, because whereas high clouds tend to keep the Earth warm, low clouds tend to cool it. Part of the problem in measuring their effect is that many clouds are small. Climate models tend to simplify the world by dividing the atmosphere and the oceans into boxes, perhaps 50km by 50km in the horizontal plane, and treating these as pixels in a giant three-dimensional computer simulation. To capture cloud processes properly might require climate models with cells just tens of metres square. No computer in the world could handle that. Add up all these difficulties, throw in some problems with measuring temperatures, and you get a lot of uncertainty. The chart on the previous page, which shows the estimates by the International Panel on Climate Change (IPCC) of \"radiative forcing\"perturbations to the Earth's energy system from human and other activitiescontains black bars showing 95% confidence ranges. Some of those bars are long. It is especially hard to be sure of the effect of aerosols. If the past is a little hazy, the future is more so. Not only does it depend on the outcome of physical processes that are inadequately understood. It also depends on human actions. How many people will be living in 2100? How rich will they be? Will they make strenuous efforts to cut greenhouse-gas emissions, do nothing, or something in between? If mankind makes heroic efforts, the Earth system will remain within familiar bounds, making predictions easier. If concentrations of greenhouse gases increase steeply, though, things become highly unpredictable. Passing irreversible tipping points, such as the collapse of the Greenland ice sheet, becomes more likely. If nothing were done to avert climate change by 2200, the IPCC estimates, the world would probably warm by between 3C and 10C. That enormous range is manageable at one end, unimaginable at the other. Much remains unknown, then. But, equally, much has been settledit is just that the settled stuff generates fewer papers and conference panels, because researchers have moved on. Some possibilities that seemed troubling a few years ago have been probed and revealed to be less so. It now appears unlikely, for example, that climate change will lead to the irreversible collapse of the Gulf Stream. Melting permafrost will emit methane, but not as much as some once feared. Even those mysterious clouds are giving up some of their secrets. Satellite-based radar and laser measurements have enabled scientists to peer into clouds; small-scale models designed to capture their behaviour have been refined and plugged into global models. It seems increasingly likely that low cloud cover will diminish as the Earth warms, speeding the process. Most important, the basic proposition of climate changethe causal relationship between http://www.economist.com/node/21678953/print 3/4 2/21/2016 Supermodels | The Economist greenhouse-gas emissions and higher temperatureshas become almost unassailable. As it happens, the interesting debate about the global-warming hiatus has a boring coda: 2013 turned out slightly hotter than 1998, and 2014 was roasting, setting a new record. That will not stand for long. From the print edition: Special report http://www.economist.com/node/21678953/print 4/4 2/21/2016 When the wind blows | The Economist Special report: Climate change Energy When the wind blows Renewable power is good. More renewable power is not always better Nov 28th 2015 | From the print edition ON A BREEZY, sunny day in north-east Germany it seems as though the world is running on renewable energy. Near Altentreptow 50-odd giant wind turbines, the tallest 200 metres high, spin above a potato field, making a gentle swishing sound. The hum from the base of each turbine is the sound of electricity being generated, much of it bound for Berlin. The view from the wind farm, across flat fields, is of another wind farm. Sadly, this is not how the world's power is generated. In truth, the view from Altentreptow does not even properly reflect how Germany's power is generated. The battle to drive carbon dioxide out of the world energy system, which accounts for about two-thirds of human greenhouse-gas emissions, has seen some heartening and visible advances. But clean energy is still being soundly thrashed by the dirty sort. Even as the wind turbines and solar panels began to spread across the fields of Europe, an ancient black fuel was making a comeback (see chart). In 2000 the world's coal-fired power stations were capable of producing 1,132 gigawatts of electricity between them, according to Enerdata, a Paris-based research firm. By 2014 so many new power stations had been built that they could put out 1,980 gigawatts. Coal, which is about twice as polluting as natural gas, now supplies 41% of the world's electricity and 30% of its overall energy needs. The biggest single cause of the fossil-fuel boom is China, which is examined in the next article. http://www.economist.com/node/21678955/print 1/5 2/21/2016 When the wind blows | The Economist But rich Western countries are more culpable than they think. They have transformed their rural landscapes with wind farms and pushed up electricity prices for consumers, yet have managed to drive surprisingly little carbon out of the energy system. The record would look even worse if Western countries had not simultaneously exported much of their heavy industry, and thus much of their pollution, to China and other emerging countries. The large wind farm near Altentreptow is one of hundreds in Germany. Helped by some big storms, these turbines produced 41,000 gigawatt-hours of electricity in the first half of this year, 15% of Germany's total electricity output. Add hydro-electric power stations, solar farms and biomass, and the country derived 35% of its electricity from renewable sources. Germany has become a world leader in green power, but also a warning about what can go wrong. Wind and sunshine have two big drawbacks as sources of power. First, they are erratic. The sun shines weakly in winter when it shines at all, and the wind can drop. On January 20th this year the output from all of Germany's solar and wind farms peaked at just over 2.5 gigawattsa small proportion of the 77 gigawatts Germany produced that day. A few months later, during a sunny, windy spell in early June, the combined wind and solar output jumped to 42 gigawatts. The second problem with wind and solar energy, oddly, is that it is free. Wind turbines and solar panels are not free, of course. Although the cost of solar photovoltaic panels has plunged in the past few years, largely because Germany bought so many, wind and solar farms still tend to produce more expensive electricity than coal or gas power stations on a \"levelised cost\" basis, which includes the expense of building them. But once a wind or solar farm is up, the marginal cost of its power output is close to zero. The problem lies with the effect of renewables on energy markets. Because their power is free at the margin, green-power producers offer it for next to nothing in wholesale markets (they will go on to make money from subsidies, known as feed-in tariffs). Nuclear power stations also enter low bids. The next-lowest bids tend to come from power stations burning lignite coala cheap but especially dirty fuel. They are followed by the power stations burning hard coal, then the gasfired power stations. The energy companies start by accepting the lowest bids. When they have filled the day's requirements, they pay all successful bidders the highest price required to clear the market. The surge of solar and wind power is pushing down the clearing price and bending Germany's energy market out of shape. Power stations burning natural gas increasingly find no takers for http://www.economist.com/node/21678955/print 2/5 2/21/2016 When the wind blows | The Economist their electricity, so they sit idle. Meanwhile the cheap, carboniferous lignite power stations burn on (see chart). Coal-fired power capacity has actually increased in the past few years. Coal is likely to become even more important to Germany's energy supply in future because the government is committed to phasing out nuclear power by 2022. One of Germany's biggest coal-fired power stations, Jnschwalde, sits near the border with Poland. Built in the 1980s, it burns 80,000 tonnes of lignite a day and can put out three gigawatts of power. Jnschwalde has also become ever more flexible, ramping up and down speedily as the weather changes. Lignite is proving to be an excellent partner for erratic wind and solar power, argues Olaf Adermann of Vattenfall, the firm that owns Jnschwalde. Sadly for the environment, he is right. Earlier this year a shamefaced German government moved to regulate lignite-burning power http://www.economist.com/node/21678955/print 3/5 2/21/2016 When the wind blows | The Economist stations out of existence, but after thousands of miners protested in Berlin, it dropped that policy. The country appears to be stuck with coal. It is likely to miss its self-imposed target for reducing greenhouse-gas emissions, reckons McKinsey, a consultancy. And because of generous feed-in tariffs for renewables that are guaranteed for 20 years, consumers in Germany are paying high prices for their not especially clean power. In the first half of this year households there paid 0.30 for a kilowatt-hour of electricity, whereas the French paid a mere 0.16. Germany has made unusually big mistakes. Handing out enormous long-term subsidies to solar farms was unwise; abolishing nuclear power so quickly is crazy. It has also been unlucky. The price of globally traded hard coal has dropped in the past few years, partly because shale-gasrich America is exporting so much. But Germany's biggest error is one commonly committed by countries that are trying to move away from fossil fuels and towards renewables. It is to ignore the fact that wind and solar power impose costs on the entire energy system, which go up more than proportionately as they add more. Many wealthy countries have too many power stations, the result of a building boom before the financial crisis. This oversupply, combined with the solar- and wind-power boom and the falling wholesale price of electricity, has crushed investment in modern, efficient power stations. It has also turned all energy producers into beggars. Owners of power stations burning coal and gas point out that if they are frequently undercut by wind and solar farms, their costs per watt of electricity produced rise. The government ought to compensate them for that, they say, otherwise they might have to close down. Terrified of looming blackouts, many Western governments are increasingly paying fossil-fuel power stations to stay open Terrified of looming blackouts, Western governments are increasingly paying fossil-fuel power stations to stay open. Some offer \"capacity payments\"money for standing by. Texas tries to keep the power stations open by promising higher prices at times of strong demand. These payments are a hidden cost of using more wind and solar energy. Moreover, in many countries, including America, renewable-power producers rely on coal- and gas-fired power stations to set the market price of electricity at a healthy level, points out Frank O'Sullivan, an energy researcher at the Massachusetts Institute of Technology. Solar farms that offer their power for next to nothing will eventually depress the market so much that they render themselves uneconomic without heavy subsidies. There are ways out of this mess. If governments were to levy a hefty tax on carbon, they would drive the most polluting power stations off the system. Germany does not do this: it relies on the European Emissions Trading System, which sets a rock-bottom carbon price. But Sweden does, and Britain has a floor price, which amounts to the same thing. Better still, says Mr Helm at http://www.economist.com/node/21678955/print 4/5 2/21/2016 When the wind blows | The Economist Oxford University, a heavy carbon tax could be combined with market reforms that would force renewable power producers to bear the costs of their intermittency. It would help if electricity grids were bigger and more efficient. The larger the grid, and the less power lost per kilometre of transmission, the less intermittency matters: cloudy and windless conditions rarely prevail across an entire continent. Denmark gets away with relying heavily on wind turbines because it has a connection to Norway, which can supply hydro-electric power on demand. But Germany's efforts to build long-distance transmission lines have been stymied by not-in-my-backyard protests. Better energy storage would help, too. Hydro-electric power stations have been used to store energy for decades. But there is not always an uphill reservoir handy, and other ways of storing energy, such as lithium-ion batteries, are expensive. More promising, probably, is automatic demand reduction. Smart meters can turn down household freezers and air-conditioning units briefly when power is in short supply and then power them up again, thereby shifting demand. Sia Partners, a consultancy, estimates that European countries could cut peak demand by 9% with such methods. But they can do only so much. Energy storage and demand-response technologies are good for matching supply with demand during the course of a single day. In a place like California, power demand is highest on sunny summer afternoons, when people turn up their air-conditioners. Solar farms produce most of their power around the same time, so with a bit of clever demand adjustment the peaks of supply and demand could be aligned. In northern Europe, however, electricity demand is highest in the early evening in winter, when solar farms are producing no power. Near Altentreptow, electricity from the wind farm is being used to turn water into hydrogen and oxygen. The hydrogen is stored in tanks and burned to produce power when the wind drops. The firm doing this, WIND-Projekt, just wants to be able to keep the lights on. The process is inefficient: 84% of the original electricity gets lost in being converted and reconverted. But perhaps the hydrogen could be sold directly to consumers, or the heat could be captured. At any rate, suggests Marcus Heinicke of WIND-Projekt, the days of being able to sell power only when the wind blows will not last for ever. From the print edition: Special report http://www.economist.com/node/21678955/print 5/5