You might think that measuring the levels of greenhouse gases in the atmosphere would be a priority. If you did think that, though, you would be wrong.

In negotiations on nuclear weapons the preferred stance is “Trust but verify”. In negotiations on climate change there seems little opportunity for either. Trust, as anyone who attended last year’s summit in Copenhagen can attest, is in the shortest of supplies. So, too, is verification.

Barack Obama was asked when he was in Copenhagen whether a provision by which countries could peek into each others’ assessment processes was strong enough to be sure there was no cheating. He answered reassuringly that “we can actually monitor a lot of what takes place through satellite imagery”. That statement conjured up thoughts of the sort of cold-war satellite system that America used to identify and count Russian missiles. But the president was being a bit previous; at the moment, no such system exists, because America’s Orbiting Carbon Observatory (OCO), a satellite that would have fulfilled the role, was lost on launch this time last year. The purpose of OCO was to work out the fate of carbon dioxide that is emitted by industrial processes but does not then stay in the atmosphere—about 60% of the total.

America is planning to build a new OCO. In the meantime, however, a small group of scientists labours away on Earth, doing its best to monitor emissions at ground level. At the end of February a number of these researchers met at the Royal Society in London, to discuss what they were up to.

Measuring gas levels day in, day out can look a little humdrum to outsiders, including those who hold the purse strings. They tend to prefer scientists to experiment and test hypotheses, not just tally things. But that attitude galls the greenhouse-gas measurers, and not only because it denies them money. It also ignores the fact that careful measurement is a way of discovering new things, not just of checking the status quo. Monitoring is not just a necessary handmaiden of science—it is the real thing.

De bas en haut

Governments are required by treaty to inform the world about their greenhouse-gas emissions. To do this, they take a bottom-up approach, using data about how much of the relevant gases all sorts of activities, from steelmaking to dairy farming, are expected to produce and how much of each of those activities is going on. The researchers at the meeting work top down, looking directly at what is in the atmosphere, and how quickly it accumulates.

Ray Weiss of the Scripps Institution of Oceanography in La Jolla, California, has been studying the difference between these approaches. In most cases, he has found that the top-down estimates are appreciably higher. In some, such as that of sulphur hexafluoride, a powerful greenhouse gas that is used as an insulator in high-voltage electronics, the trends as well as the values are different: bottom-up accounts say emissions are falling; top-down analysis says they are going up.

Andreas Stohl of the Norwegian Institute for Air Research and his colleagues have been looking at weather patterns to discover where some of these gases are emitted. The level of a gas seen at a particular monitoring station depends on where it came from and which way the wind was blowing, so if you have a number of stations and some data on how their readings change with wind directions, you can have a good guess at the source.

Among Dr Stohl’s conclusions is the positive one that China now seems to be emitting less HFC-23, a powerful greenhouse gas produced by the refrigeration industry, than it did in 2005. This suggests that the large amounts of money invested through carbon markets in reducing such emissions may be having an effect. More detailed studies might show precisely which industrial regions the gases are coming from, and thus reveal what is going on with specific HFC-23-mitigation projects.

For gases that are sometimes or always produced biologically, such as carbon dioxide and methane, a less geographic way of assigning sources is possible. Living things treat carbon atoms of different weights slightly differently, and these differences show up in the weights of the gases they churn out. So it is possible to distinguish, for example, between methane that has been stored in permafrost and methane that is made by rotting vegetation.

This is the sort of technique with which one could evaluate the release of methane from permafrost beneath the warming Arctic Ocean, a phenomenon that was reported in this week’s Science by Natalia Shakhova of the University of Alaska and her colleagues. If, that is, one had the chance. Euan Nisbet of Royal Holloway, part of the University of London, who was one of the organisers of the meeting, has not had his funding for work on monitoring Arctic methane renewed.

Indeed, for all the noise that is made about climate change, much of this research is done with next to no money. Asked how she paid for her monitoring of various greenhouse gases in Baden Württemberg, Ingeborg Levin of Heidelberg University replied “by stealing”—meaning not that she robs banks, but that the monitoring work is cross-subsidised by grants intended for other studies.

That is slowly changing. A European project called the Integrated Carbon Observation System, which will set up a network of monitoring stations, is on the verge of being approved by the European Union, though individual member states (which will have to cough up most of the money) have yet to give it the nod. One of the benefits of systems like ICOS is that their measurements will provide “ground truth” to calibrate the readings of the reborn OCO.

Unfortunately, OCO is a one-off. Its potential successors, such as a European mission called CarbonSat that could identify and quantify emissions from large power plants around the world, remain, at the moment, on the drawing board. Dr Nisbet’s hope is that realising Mr Obama’s belief in remote verification means changing that, and will lead to a monitoring system with numerous ground-based and space-based components. Accurate measurement is the beginning of all science. It is a shame that so little attention has been paid to it in such an important field.

Source: The Economist

Still Pictures

Forests lock up a lot of carbon. Cutting them down accounts for around 20% of the world’s emissions of greenhouse gases. On paper, halting deforestation should be the simplest way to cut emissions. Achieving a similar reduction by building wind turbines or nuclear-power stations, or by mandating more fuel-efficient cars and buildings, would take years and cost billions. In practice, however, halting deforestation is hard: much of the world’s rainforest has already succumbed to loggers and farmers. That is because it is difficult to align the interests of people who live in forests (now 20m in the Brazilian Amazon) with those of the rest of humanity.

The best way of doing so involves a mixture of two ideas: establishing clear property rights over land and paying its owners not to cut down trees. If these policies are to work anywhere, it will be in Brazil, which possesses 60% of the world’s greatest tropical forest. Brazil has powerful motives for preserving the Amazon. Deforestation does terrible damage to the reputation of a country that is a pioneer in renewable energy. It also puts at risk the Amazon rain factory that enables Brazil to be one of the world’s biggest agricultural exporters.

Brazil now has a sophisticated system for monitoring deforestation from satellites and aeroplanes. It has set aside some 40% of the Amazon as national parks or Indian reserves. It has laws that restrict deforestation in the rest. The problem is enforcing those laws over a vast area where many of the inhabitants dislike the rules (see article). The first step is a proper land registry to confirm who owns what. Some 15-25% of the Amazon is private property, which is supposed to be kept 80% forested (though often is not). Most of the rest is nominally federal land, but in practice is up for grabs: title deeds are forged, people are killed and deforestation accelerates because of competing claims. Some farmers even clear trees as a way to solidify land claims: fines from Brazil’s environmental agency can create a paper trail that acts as proof of ownership.

A law approved this month by Brazil’s Congress aspires to end this mess—but at a price. It would grant title to all landholdings up to 1,500 hectares (3,700 acres) occupied before 2005 in the Amazon, comprising an area the size of France, and ban further land claims. The law entrenches injustice: it risks rewarding people who used violence to obtain land, including large landholders who occupy almost 90% of the area under discussion. Brazilian greens want to limit the measure to smaller plots, and to ban their resale for ten years.

Yet that risks defeating the object. Better for the government to complement this attempt to end battles over privately owned land with a decision to take the rest of the Amazon into public ownership, as parks or reserves. Countries with rainforests also need to have due regard for their preservation and for the Indians who live in them when allowing mining and oil exploration. The lack of such procedures was behind a bloody clash in Peru this month (see article).

Lay down that axe and you will get cash

At the moment it makes economic sense to cut down trees: those who do so can sell the timber and turn the land into farms or ranches. So the second idea for saving forests lies in changing economic incentives by paying people not to chop down trees—an idea known in the ghastly jargon of climate-change diplomacy as “reduction of emissions from deforestation and degradation” (REDD). Since many rich countries felled their forests as they developed it seems fair that they should pay some of the cost of this.

There are difficulties, though. One is that “avoided deforestation” is hard to define and quantify. Another, raised by officials in Europe who have chosen not to include REDD in the European carbon-trading scheme, is that the carbon market would be flooded with deforestation credits that will push down the price. Companies would then buy cheap credits and continue doing business as usual rather than cutting their own emissions. Further tricky issues abound: who should have the right to sell credits? How should the money be split between central governments, local governments and indigenous people? And should the money be paid in perpetuity?

REDD schemes will require careful monitoring to ensure that forests really are left intact and that carbon credits for an area are not claimed more than once. Murky goings-on in Papua New Guinea, one of the leading advocates of REDD, highlight such worries (see article).

Even so, it is worth trying, simply because avoiding deforestation is so effective in slowing carbon emissions. So REDD deserves a place in the world climate treaty to be negotiated in Copenhagen in December, to replace the Kyoto treaty when it expires in 2012. As with other forms of carbon credit, today’s voluntary and experimental REDD schemes will need to be replaced by more rigorously accredited and monitored schemes. But they have a chance of working only if the countries in which they operate define forest land rights clearly. Brazil’s flawed attempt to do this is a step forward.

Source: The Economist

Still Pictures: Try counting the trees

The human impact of climate change “is difficult to assess reliably”, say the authors of a new report from the Global Humanitarian Forum, a think-tank run by Kofi Annan, a former United Nations secretary-general, aided by a raft of eminent folk. But they make a stab, reaching the conclusion that 325m people around the world are seriously affected by climate change every year and that this number could more than double, to around 660m, by 2030.

As in so many reports of this kind, the trend looks plausible, but there seems little basis for the exact numbers. For example, the authors attribute two-fifths of an expected increase in weather-related disasters to climate change and use this as a basis for all their other sums. But they offer no convincing rationale for this approach, and admit with refreshing candour that “the real numbers may be significantly lower or higher.”

On slightly firmer ground, the authors elaborate on the familiar point that most of the damage from a changing climate will be felt in poor countries. Warmer temperatures are actually leading to increased crop yields in some parts of North America and Russia. But areas where yields are falling because of climate change include sub-Saharan Africa and South Asia, where the victims are small farmers eking out an already meagre living. And the countries seen as most vulnerable to climate change are all poor: they include Somalia, Burundi, Niger, Eritrea, Afghanistan and Chad.

Nor are people in those countries well placed to adapt to change. As their livelihood vanishes, they are more likely to fuel the ranks of the temporarily or permanently displaced. The eminent writers duly propose a huge (nay, hundredfold) boost in funding to help the poor cope with a shifting climate—through drought-resistant crops, for example.

In another haphazard estimate, the authors of “Human Impact Report: Climate Change—Anatomy of a Silent Crisis” say 26m people have already been displaced by climate change. But here again, accuracy is impossible. Should Cyclone Aila, which hit Bangladesh and India on May 25th and affected hundreds of thousands of people, be classified as a climate-change event? Even if scientists could agree on the contribution of global warming to the rising frequency of such disasters, it would still be hard to classify the causes of any given catastrophe. Nor is it easy to disentangle the effects of climate change from those of avoidable failures in policy.

In South Asia, for example, climate change is likely to bring more water to a perennially thirsty region. A blessing in disguise, then? No, because so little progress has been made on ways to trap and use this water when it cascades down in a short space of time. Given that governments have missed so many obvious tricks, is there any reason to assume that more money thrown at the problem will be spent wisely? Coping with climate change will certainly cost money—it is anyone’s guess how much—but plenty of wisdom will be needed too.

Source: The Economist

In 2006 Mario Lebrato and Daniel Jones of the National Oceanography Centre in Southampton, England, were using a remotely operated deep-sea vehicle to study the sea floor near an oil pipeline off Côte d’Ivoire. What they found surprised them. It was a thaliacean graveyard. And its discovery throws into question the received wisdom about one important aspect of climate change, namely how much carbon from the atmosphere ends up at the bottom of the sea.

Despite their unfamiliarity to most people, thaliaceans (a colony of which is pictured) are abundant creatures in many parts of the ocean. Their bodies are transparent and gelatinous, like those of jellyfish. They are not jellyfish, though. They are actually chordates—in other words, part of the same group of animals as humans, even though they do not have backbones. The thaliacean graveyard off Côte d’Ivoire came as a surprise because not much was known at the time about what happens to animals with gelatinous bodies, whether chordates or jellyfish, after they have died. And it set Mr Lebrato and Dr Jones thinking, because if thaliaceans are falling to the bottom of the sea in large numbers, they might be taking a lot of carbon with them.

Until then gelatinous animals had largely been ignored by researchers studying the carbon cycle (the way that element moves through land, sea, air and living creatures) because gelatinous bodies were thought to contain a lot of water and thus relatively little carbon. However, as Mr Lebrato and Dr Jones report in Limnology and Oceanography, when they analysed thaliacean tissues they found that the creatures were one-third carbon by weight. That was much more than they expected. Jellyfish, by comparison, are 10% carbon, and diatoms (single-celled algae that are common in plankton) 20%. It also helps explain why thaliaceans are so dense—and thus sink so quickly after they die.

Hitherto it was assumed that the main way carbon gets from the top to the bottom of the ocean was as part of dead planktonic algae sinking to the seabed. But the discovery of just how carbon-rich and prone to sinking thaliaceans are may change that assumption. Because they gather by the billion in feeding swarms around the world (they eat single-celled algae), the amount of carbon thaliaceans are taking to the bottom of the sea is by no means trivial, according to Mr Lebrato. He admits it is difficult to make accurate comparisons, because the research is still in its infancy. But he estimates that the “jelly pump”, as he refers to it, sinks almost twice as much carbon as algae do.

The question is, does that carbon stay down once it has arrived? That is unclear. The one sure way of keeping carbon on the seabed is in the form of calcium carbonate, the main ingredient of most animal shells. But thaliaceans have no shells. Nevertheless, some thaliaceans get buried before they have completely decomposed, and other researchers have found evidence that dead jellyfish sometimes accumulate in trenches without much decomposition, so perhaps thaliaceans do, too.

Even if the carbon is not permanently buried, the lack of mixing between deep and shallow water in the ocean means that it is likely to stay down there for a long time—something that will have to be added to computer models of how the climate works. The carbon cycle has thus acquired another epicycle, and become even more complicated to understand than it was.

Source: The Economist

Alamy

Anthony Giddens, a professor at the London School of Economics, is a sociologist most famous for developing the “Third Way”, the centre-leftish political philosophy espoused by Tony Blair and Bill Clinton. His book argues that the scale of the climate-change problem and the difficulty of reconciling greenery with development demands a new political approach.

The result is a wide-ranging book that covers everything from renewable energy to carbon trading and the practicalities of adapting to a world with deeper seas and fiercer weather. Lord Giddens (he was ennobled in 2004) gives much good advice. He chastises eco-warriors for their relentlessly downbeat message, arguing that people are more likely to change their habits if offered a happy future to look forward to rather than a bleak one to avoid. He rejects the hair-shirt ideals of many greens as unlikely ever to appeal to most voters. And he argues against the idea that climate change is too big a problem for a democratic system to deal with.

But the price of breadth is a lack of depth that may leave curious readers frustrated. Part of the problem is a tendency to affectation. The rather pedestrian observation that distant, abstract crises tend not to change people’s behaviour even if the consequences are extremely unpleasant is christened “Giddens’ paradox”, and the opening chapter mentions every fashionable meme from the internet and social networks to Barack Obama’s “yes we can” campaign slogan. Overall, there is little in the book that is truly original. But it is conveniently packaged and Lord Giddens’s reputation among policy wonks (as well as an endorsement from Mr Clinton) will propel it onto shelves in high places.

Those who crave something less woolly will prefer Sir Nicholas Stern’s book. Sir Nicholas is a former chief economist at the World Bank and author of an influential study of climate-change economics for the British government. His book addresses the argument in cost-benefit terms, and concludes that spending 1-2% of global output to avoid a significant temperature rise is a bargain worth taking—a similar conclusion to that in his original 2006 study. But the book is written for a wider audience than the official report, and incorporates some more recent (and worrying) findings from climate science.

Least woolly of all is David MacKay’s book (which can be bought or downloaded free from www.withouthotair.com). Irritated by the waffle that often surrounds discussions of energy and climate change, Mr MacKay, a physicist at Cambridge University, has chosen to illustrate the challenge of breaking our fossil-fuel addiction armed only with the laws of physics, reams of publicly available information and the back of an envelope.

Mr MacKay favours no particular technology. He is concerned only that proposals to decarbonise the economy should add up. But his refreshingly hard-headed approach (confined to Britain, but easily adapted to other countries) comes to some sobering conclusions. Meeting Britain’s energy needs from onshore wind power would require covering literally the entire country in turbines, even assuming that the wind was guaranteed to blow. If only 10% of Britain were covered then wind could provide roughly a tenth of total demand. Switching every piece of agricultural land to biofuel production would provide just 12% of the requisite juice.

It is a similar story for offshore wind, tidal and wave energy, all of which make the claims of green advocates that Britain has a “huge” renewable resource look somewhat hollow, especially since the book ignores questions of costs and focuses purely on physical limits. To make a dent in fossil-fuel consumption without using nuclear power, renewable-energy facilities will have to be “country-sized”, with offshore wind farms bigger than Wales and huge solar-power arrays in sunny deserts piping power to cloudier nations.

Although Mr MacKay’s conclusions are fascinating, much of his book’s appeal lies in its methods. Ballpark calculations are a powerful way of getting to grips with a problem. The book is a tour de force, showing, for example, how the potential contribution of biofuels can be approximated from just three numbers: the intensity of sunlight, the efficiency with which plants turn that sunlight into stored energy and the available land area in Britain. As a work of popular science it is exemplary: the focus may be the numbers, but most of the mathematical legwork is confined to the appendices and the accompanying commentary is amusing and witty, as well as informed.

With global climate-change and energy policy consisting mostly of feel-good rhetoric rather than action, Mr MacKay’s reminder that the natural world does not care for political expediency—summed up in Richard Feynman’s famous observation that “nature cannot be fooled”—should be engraved on environment-ministry doors the world over. For anyone seeking a deeper understanding of the real problems involved, “Sustainable Energy—Without the Hot Air” is the place to start.

Sustainable Energy: Without the Hot Air.
By David MacKay.
UIT Cambridge; 384 pages; $49.95 and £45

The Global Deal: Climate Change and the Creation of a New Era of Progress and Prosperity.
By Nicholas Stern.
Public Affairs; 256 pages; $26.95. Published in Britain as “Blueprint for a Safer Planet”; The Bodley Head; £16.99

The Politics of Climate Change.
By Anthony Giddens.
Polity Press; 264 pages; £50. To be published in America by Polity next month

One of the most impressive monuments to Franklin D. Roosevelt’s New Deal is the network of dams that stud the Tennessee River valley, built to provide work and to modernise a backward corner of America during the Great Depression. Seventy-five years later and on the other side of the Atlantic, work is once again growing scarce and an economy is in need of modernisation, this time to secure energy supplies and slash the release of planet-heating greenhouse gases. The British government has been playing up the parallels, with much ministerial talk of a “Green New Deal”. In March Gordon Brown promised the creation of a “low-carbon economy” for Britain that would provide jobs and clean up industry. Lord Mandelson, his business secretary, talked of a new industrial revolution and said that there was “no high-carbon future”.

It is a seductive vision. If Keynesian stimulus is to be the order of the day, greenery seems a good sector in which to apply it. There are benefits besides decarbonisation. Much of the contribution would come from changing the way electricity is generated, and many of Britain’s old power plants need replacing anyway. A switch to renewable power would cut dependence on oil and natural gas as national production of both dwindles. Windy, storm-lashed Britain is a good place to harness the weather; boosters talk excitedly of a splurge on renewable electricity and the possibility of capturing the market for offshore wind turbines or wave-power machines, creating tens of thousands of jobs. On April 1st Statkraft, a state-owned Norwegian firm, said it was investing £500m ($715m) in a Scottish wind-farm project.

Not everyone is convinced. Green rhetoric in Britain has traditionally soared far above reality. Greenhouse-gas emissions are more or less unchanged since Labour came to power in 1997 (a better record than many countries, but hardly the promised transformation). Less than 5% of British electricity came from renewable sources in 2006, compared with 26% in Denmark and 48% in Sweden. Ambitious goals to derive 30-35% of electricity from renewable sources by 2020 are widely considered impossible. A related pledge that 15% of total energy consumption (of which electricity accounts for roughly a third) will be renewable by that date looks even less plausible.

Mr Brown’s green New Deal looks similarly flimsy. On March 31st HSBC, a big bank, published a report ranking countries by how green their economic-stimulus packages were. The bank reckons that Britain is allocating just 7% of its fiscal stimulus to greenery, compared with 12% in America, 34% in China and a whopping 81% in South Korea (see chart). A separate report prepared for Greenpeace, a pressure group, by consultants at the New Economics Foundation (NEF) considers only genuinely new funding and arrives at a figure of just 0.6%, or £120m.

Private-sector caution reflects this official inaction. Lower oil prices, sagging demand for energy and hard-to-get credit have caused many firms to cut back on renewables worldwide. But there are particular problems in Britain, not least the falling pound (most of the wind turbines installed there, for example, are built in continental Europe).

Energy companies such as Centrica and EDF, a French firm, are re-evaluating their British renewables projects. Lord Browne, a former boss of the big British oil firm BP, doubts that Britain’s laissez-faire energy policy is up to the job of decarbonising the economy, and wants state-owned banks directed to finance green-energy projects. (BP has opted out of the British renewables market because it expects low returns.) And last year Royal Dutch Shell pulled out of a £3 billion wind-farm in the Thames estuary.

Convinced that these are short-term problems, fans of renewables want government cash to see projects through the tough times. But there are longer-term reasons for Britain’s comparative sluggishness. Its subsidy regime, under which green power stations generate tradable certificates, is unwieldy compared with traditional cash handouts in other countries. In the past, all technologies were subsidised equally, so most investment went into onshore wind, the cheapest source of renewable energy. But windy spots tend to be beautiful spots, and local opposition bogged down projects. There have been reforms: planning changes have made local objections easier to ignore, and the subsidy scheme was tweaked on April 1st to give extra cash to more expensive technologies, such as offshore wind turbines. An independent Climate Change Committee is supposed to advise on and police legally binding emissions-reduction targets, but it is new and its powers untested.

One fear shared by many enthusiasts of renewables, says Andrew Simms, policy director of the NEF, is that the government is simply losing interest in them. It has moved speedily to revive the nuclear-power industry, by contrast. From a position of cordial dislike in 2003, the government announced itself in favour of new nuclear plants in principle as early as 2006.

More recently ministers have been positively prescriptive, suggesting how many plants might be built and where. A takeover of British Energy, which runs most existing nuclear plants, by EDF, keen to build more, took place last year. A new nuclear laboratory has been founded, schemes to train workers set up and the vexed issue of waste disposal re-examined.

Nuclear-power stations take many years to build, so new ones will not help Britain meet its 2020 targets for curbing emissions. But the technology is well understood. Politicians may have calculated that a few nuclear-power stations will be easier to sell the public than thousands of wind turbines. And energy does not have to be renewable to be low-carbon.

Source: The Economist

Messing around with ecosystems is an unpredictable business. That proved true again this week when a group of Indian and German researchers gave their first report from the biggest ever experiment in geo-engineering: an expedition to pour iron into the Southern Ocean, a vast area that encircles Antarctica, to stimulate a giant bloom of phytoplankton.

We did!

Phytoplankton are tiny algae that absorb carbon dioxide when they grow and then lock up some of the greenhouse gas when they die and sink to the seabed. Stimulate the growth of more phytoplankton, the theory goes, and you might send more CO2 to the bottom of the ocean, where it cannot contribute to global warming. But the experiment did not quite turn out like that.

The voyage, a joint venture by India’s National Institute of Oceanography and the Alfred Wegener Institute for Polar and Marine Research in Germany, was controversial from the start. Some environmental groups claimed it was akin to pollution, and thus illegal. At one point, therefore, the German government ordered the Wegener Institute to suspend operations while it looked into the matter. Eventually, permission to continue was given and the research ship Polarstern made a two-and-half-month passage through stormy seas following the bloom that the researchers had created.

The growth of phytoplankton is kept in check by the amount of sunlight available for photosynthesis and the supply of crucial nutrients such as iron. In the Southern Ocean, iron is indeed often the limiting nutrient. As a result, when iron levels increase naturally (for example when a dust storm dumps large amounts of it into the sea) giant blooms of phytoplankton can suddenly appear. Previous studies have shown that adding iron artificially can also create algal blooms. The expedition’s researchers wanted to find out how many of the extra algae end up on the sea bed.

Those researchers, led by Wajih Naqvi and Victor Smetacek, created a bloom of phytoplankton by fertilising an area of 300 square kilometres with six tonnes of iron sulphate, which dissolves in water. In two weeks the bloom’s mass doubled. But it also proved to be extremely tasty for small crustaceans called copepods, which gobbled the phytoplankton up so quickly that even with further iron fertilisation the bloom stopped growing. As a result, only a small amount of CO2 was dispatched to the ocean floor.

The problem lay with the species of phytoplankton in the bloom. In previous experiments the blooms had consisted of a group of algae known as diatoms. As diatoms have shells made of silica they are protected from copepods and so are more likely to die without being eaten and thus take take their carbon to the ocean floor. But in the area where the researchers were working natural blooms had already depleted much of the silicic acid, which the diatoms use for shellmaking. The result was that the beneficiaries of the iron were instead groups of algae such as Phaeocystis, which are among the most heavily grazed by copepods.

Since silicic-acid levels are naturally low across about two-thirds of the Southern Ocean, the expedition’s results suggest that iron-fertilisation would remove less CO2 from the atmosphere than optimists had hoped. Although that is a setback for proponents of large-scale iron-fertilisation, the results from the Polarstern expedition have given researchers lots to work on, including the role predators play in reducing algal blooms. And the results in one part of the ocean may be different from those in another because, as Ulrich Bathmann of the Wegener Institute points out, ecosystems in the sea are at least as diverse as those on the land. So the team may make another voyage to discover more.

Source: The Economist