This Scientist Aims High To Save The World's Coral Reefs

Most scientists find a topic that interests them and keep digging deeper and deeper into the details. But Ken Caldeira takes the opposite approach in search for solutions to climate change. He goes after the big questions, and leaves the details to others.

We caught up with Caldeira on Australia's Great Barrier Reef, where he was conducting an experiment to measure how coral reefs are coping with increasing acidity in the world's oceans. People are causing this change by burning fossil fuels and putting carbon dioxide into the air. From there, it dissolves into the oceans, and makes them more acidic.

As a result, the world's coral reefs are in trouble. In a matter of decades, ocean water could become so corrosive that reefs may start dissolving faster than the coral can grow.

Caldeira works for the Carnegie Institution for Science, and he's based on the Stanford University campus. But throughout February, his base of operations was One Tree Island, Australia.

He spent many a day out on the reef, wearing a floppy sun hat, tattered shorts and a head-to-toe "rash guard" to block the intense sunlight. He and his team were pumping antacid onto a stretch of the reef to see if neutralizing some of the increased acidity would help the coral grow faster.

Nobody has ever tried this before. And Caldeira readily acknowledges that he may not get a clear answer himself. Over the course of one hourlong dose of antacid, he's hoping to measure changes in the amount of reef-building calcium carbonate the corals absorb. (See related story for more details.)

Caldeira has license to do this because he works at an unusual place. The Carnegie Institution for Science was endowed by industrialist Andrew Carnegie more than a century ago, so Caldeira worries less about money than other scientists do.

"My job offer letter said 'make important scientific discoveries,' " Caldeira says. "And they basically give me some resources and leave me alone to make important scientific discoveries."

This seems to have worked. More than 12,000 papers in the scientific literature refer to papers that Caldeira has written or co-authored.

Ken Caldeira of the Carnegie Institution for Science takes a water sample during his experiment on part of the Great Barrier Reef. The water is slightly pink because his team is using a dye to trace an acid-neutralizing chemical as it flows across the reef.

Science wouldn't really work if everyone tried to go after the flashy findings and not fret about chasing down all the details. But big-picture thinkers like Caldeira also help drive the field.

The reef expedition was a relatively rare foray; over the years, most of his work has been at a computer screen. He has calculated what it would take to cool the planet by spraying reflective particles into the atmosphere. He has wondered what would happen to global temperatures if all the trees near the Arctic were cut down. He has calculated just how much clean energy generation would be needed to replace all the fossil fuels we're using.

But for all that, he loves being out on a reef, doing firsthand research and taking risks on experiments that may simply not have enough power to detect the small changes he's looking for.

"This is how the science gets pushed forward, by people taking risks," he says. "And maybe we'll get lucky and it will work, and maybe it won't."

In a world where science is often driven by a researcher's ability to get government grants, taking a risk like this is a luxury.

But when Caldeira steps back to look at the big picture, it leaves room for some startling insights. For example, it might seem that our vast skies have an endless ability to hold the billions of tons of carbon dioxide we produce every year.

But here's how Caldeira visualizes it: "If you were to compress the entire atmosphere so it was the density of water, it would only be 30 feet deep, so all the stuff we're throwing into the atmosphere, it's like we're throwing it into an ocean that's only 30 feet deep." More

 

Sir John Beddington warns of major global crisis by 2030

One of Britain's leading scientists is warning that the growth of the world's population will reach crisis point by the year 2030.

John Beddington, the UK government's chief scientific adviser, says food and water supplies will come under severe pressure as the Earth's population swells to 8.5 billion people.

 

He says the answer is in embracing new agricultural technology.

 

Harry Smith reports.

 

'All That Has Been Done Is Too Late'

GENEVA (AP) — Former Soviet leader Mikhail Gorbachev painted a dim picture of the world's environmental progress on Thursday, two decades after he and a former Swiss lawmaker founded Green Cross International.

Mikhail Gorbachev

Shortly before the Soviet Union's demise in 1991, then-leader Gorbachev proposed a Red Cross for the environment that could also tackle threats from a nuclear arms race and the over-consumption of the world' resources from runaway population and development pressures.

“A sustainable perestroika is needed to revolutionize how people value life: their own, those of their children, and critically that of the one planet we share.”

Reflecting on the 20 years since he and Roland Wiederkehr launched the Geneva-based organization, the 82-year-old Gorbachev admits to deep frustrations as an environmental crusader.

"All that has been done is too late, and it's not enough," Gorbachev, speaking in Russian, told reporters in Geneva by video link.

Gorbachev railed against governments for falling short on nuclear disarmament, broader security, waste, development and climate change.

He urged governments to use his policies of "perestroika" (restructuring) and "glasnost" (openness) — which ushered in democratic changes that led against his will to the collapse of the Soviet Union — to address climate change and overconsumption of resources.

Gorbachev said world leaders have largely failed to do enough to aid nations in ecological trouble by taking meaningful steps to reduce widespread suffering and poverty.

"Such population pressure, coupled with a crumbling world economy and unchecked exploitation of natural resources, will only foment human suffering, spread poverty, reduce human security, cause more conflicts, and further degrade the environment," he said. "A sustainable perestroika is needed to revolutionize how people value life: their own, those of their children, and critically that of the one planet we share." More

 

 

Capitalism Is Great, But It Assigns No Value To Your Grandchildren, GRANTHAM

It started [in the mid-1990s] with a visit to the Amazon and to Borneo with the kids. And without thinking about it you start talking about the logs along the side of the river and the lack of mature forests in Borneo.

Jeremy Grantham

We were on family trips and happened to do a couple of tropical forests back to back. I'm sure that played a role, but we didn't treat it as an epiphany. I would argue that one of our children got there first. While we were environmentalists, but low key, one of my sons happened to get a job which saw him end up in a dry tropical forest in Paraguay for five years and then off into the forestry business. Shortly behind that, we [his investment company GMO] began to follow that interest in forestry. We started our own forestry operation 15 years ago [at GMO] because our interest in forestry and of our realisation that land is so important. Forests were mispriced and were an attractive investment. My interest in forestry at that point was entirely commercial and then it began to morph into a decent investment, plus, "look how important these forests are to maintain fresh water, carbon sequestration, etc"…

I picked up none of that [James Hansen's 1988 testimony before Congress on climate change and the 1992 Rio Earth Summit]. No. Absolutely not. I was following along afterwards [once the foundation launched in 1997] asking the big NGOs where was the leverage for the birds flying through Costa Rica and Panama. Let's put our money there. Where were the hotspots? The climate question wasn't there for me at that time. Now it is at least half of the focus for the foundation. And in the other half it brushes up against climate all the time. We are late arrivals to all this and I have nothing but admirations to those who beat me to the punch by a few decades.

On why his environmental interests moved beyond habitat conservation:

I was a moderate environmentalist 10-15 years ago. But then I started to get embroiled in resources and that [the rise in price of] oil was the first paradigm shift that we'd ever come across in an important asset class, and nothing is more important than oil. I realised that the price of oil had changed forever and is not going back to the old $15 a barrel. There had been a majorly important shift. That led us to asking the question, why only oil? Why not every finite resource? And so we ended up about four years ago saying, "watch out, we seem to be running out of things". Two years ago, we did a very detailed paper which took on a life of its own and helped to put these issues onto institutional agenda items, I think. That led me to the realisation, by looking at the data, that between population growth and China gobbling up the world that the world had changed – and dangerously so – and hidden under that that oil and food were the two most dangerous components and within that [the availability of] phosphorous was perhaps the most dangerous long-term issue of all. Digging into the phosphate problem, you realised that it can be handled, but only if the great majority of the world is fed via sustainable farming which means nurturing the soil and having it once again full of micro-organisms. If you kill them every year with herbicides and pesticides then you're dealing basically with sand. You've got to restore and renew the ability to grow by re-applying all the nutrients in very big, expensive doses every year. This is in contrast to well-nurtured soil. There's a 30-year patch in Pennsylvania at the Rodale Institute where they've never put on any phosphorous at all and they are getting productivity equal to regular farming up the road.

We arrived at all this just by looking at the numbers and the more I did the more I became concerned that we were already deep into a food crisis. Arab Spring countries were already getting throttled a bit by rising price of energy and food. They don't spend 8-10% of their budget on these, they spend 40%. So when that starts to double on you, you can see how quickly why people take to the streets. And that's where we are. The rich countries are really not that concerned and their casual behaviour is only serving to push up the price which is not that big a deal to them, certainly not the movers and shakers who make all the money. But it's a terrible deal for the poor half of the world and a disaster for the poorest 10% or so. That's the world we're in and it could lead to country after country being destabilised.

It has forced me to go back and read all the classics. On my iPad I think I have 40 or so books now. I recommend a book by a scholar who summarises all these works back to Gibbon's Decline and Fall of the Roman Empire. It's calledImmoderate Greatness: Why Civilisations Fail by William Ophuls. And then there's perhaps my favourite book of a more detailed type which is called Dirt: The Erosion of Civilisation [by David R Montgomery]. That's a really good read. Then there's Collapse by Jared Diamond, which seems to have done quite well and is reasonable. A lot of details are queried by the experts in the field, but I thought it was fine. Then there are books on peak oil and shortages of raw materials. Books on the whole package of long-term growth on a finite planet, going back to the Limits to Growth and a book by one of the co-authors that looks at the next 40 years. That's called 2052 [by Jorgen Randers]. And so on and so forth.

On the strengths and weaknesses of capitalism:

Capitalism does millions of things better than the alternatives. It balances supply and demand in an elegant way that central planning has never come close to. However, it is totally ill-equipped to deal with a small handful of issues. Unfortunately, today, they are the issues that are absolutely central to our long-term wellbeing and even survival. It doesn't think long-term very well because of high discount rate structure. If you're a typical corporation anything lying out 30 years literally doesn't matter. Or, as I like to say: QED, your grandchildren have no value. And they usually act as if that was true, even though I'm sure they are actually very kind to their grandchildren. More

 

There’s Only One Real Option for Averting Economic and Ecological Ruin

The following excerpt is reprinted from the new book Energy: Overdevelopment and the Delusion of Endless Growth, edited by Tom Butler and George Wuerthner, published by Post Carbon Institute and Watershed Media, in collaboration with the Foundation for Deep Ecology.

Energy conservation is our best strategy for pre-adapting to an inevitably energy-constrained future. And it may be our only real option for averting economic, social, and ecological ruin. The world will face limits to energy production in the decades ahead regardless of the energy pathway chosen by policy makers. Consider the two extreme options—carbon minimum and carbon maximum.

If we rebuild our global energy infrastructure to minimize carbon emissions, with the aim of combating climate change, this will mean removing incentives and subsidies from oil, coal, and gas and transferring them to renewable energy sources like solar, wind, and geothermal. Where fossil fuels are still used, we will need to capture and bury the carbon dioxide emissions.

We might look to nuclear power for a bit of help along the way, but it likely wouldn’t provide much. The Fukushima catastrophe in Japan in 2011 highlighted a host of unresolved safety issues, including spent fuel storage and vulnerability to extended grid power outages. Even ignoring those issues, atomic power is expensive, and supplies of high-grade uranium ore are problematic.

The low-carbon path is littered with other obstacles as well. Solar and wind power are plagued by intermittency, a problem that can be solved only with substantial investment in energy storage or long-distance transmission. Renewables currently account for only a tiny portion of global energy, so the low-carbon path requires a high rate of growth in that expensive sector, and therefore high rates of investment. Governments would have to jump-start the transition with regulations and subsidies—a tough order in a world where most governments are financially overstretched and investment capital is scarce.

For transport, the low-carbon option is even thornier. Biofuels suffer from problems of high cost and the diversion of agricultural land, the transition to electric cars will be expensive and take decades, and electric airliners are not feasible.

Carbon capture and storage will also be costly and will likewise take decades to implement on a meaningful scale. Moreover, the energy costs of building and operating an enormous new infrastructure of carbon dioxide pumps, pipelines, and compressors will be substantial, meaning we will be extracting more and more fossil fuels just to produce the same amount of energy useful to society—a big problem if fossil fuels are getting more expensive anyway. So, in the final analysis, a low-carbon future is also very likely to be a lower-energy future.

What if we forget about the climate? This might seem to be the path of least resistance. After all, fossil fuels have a history of being cheap and abundant, and we already have the infrastructure to burn them. If climate mitigation would be expensive and politically contentious, why not just double down on the high-carbon path we’re already on, in the pursuit of maximized economic growth? Perhaps, with enough growth, we could afford to overcome whatever problems a changing climate throws in our path.

Not a good option. The quandary we face with a high-carbon energy path can be summed up in the metaphor of the low-hanging fruit. We have extracted the highest quality, cheapest-to-produce, most accessible hydrocarbon resources first, and we have left the lower quality, expensive-to-produce, less accessible resources for later. Well, now it’s later. Enormous amounts of coal, oil, gas, and other fossil fuels still remain underground, but each new increment will cost significantly more to extract (in terms of both money and energy) than was the case only a decade ago.

After the Deepwater Horizon oil spill of 2010 and the Middle East–North Africa uprisings of 2011, almost no one still believes that oil will be as cheap and plentiful in the future as it was decades ago. For coal, the wake-up call is coming from China—which now burns almost half the world’s coal and is starting to import enormous quantities, driving up coal prices worldwide. Meanwhile, recent studies suggest that global coal production will max out in the next few years and start to decline.

New extraction techniques for natural gas (horizontal drilling and “fracking”) have temporarily increased supplies of this fuel in the United States, but the companies that specialize in this “unconventional” gas appear to be subsisting on investment capital: Prices are currently too low to enable them to turn much of a profit on production. Costs of production and per-well depletion rates are high, and energy returns on the energy invested in production are low. Recent low prices resulted from a glut of production produced by rampant drilling in 2005–2007, which only made economic sense when gas prices were much higher than they are now. All of this suggests that rosy expectations for what “fracking” can produce over the long term are overblown.

Exotic hydrocarbons like gas hydrates, bitumen (“tar sands”), and kerogen (“oil shale”) will require extraordinary effort and investment for their development and will entail environmental risks even higher than those for conventional fossil fuels. That means more expensive energy. Even though the resource base is large, with current technology the nature of these materials means they can be produced only at relatively slow rates.

But if the hydrocarbon molecules are there and society needs the energy, won’t we just bite the bullet and come up with whatever levels of investment are required to keep energy flows growing at whatever rate we need them? Not necessarily. As we move toward lower-quality resources (conventional or unconventional), we have to use more energy to acquire energy. As net energy yields decline, both energy and investment capital have to be cannibalized from other sectors of society in order to keep extraction processes expanding. After a certain point, even if gross energy production is still climbing, the amount of energy yielded that is actually useful to society starts to decline anyway. From then on, it will be impossible to increase the amount of economically meaningful energy produced annually no matter what sacrifices we make. And the signs suggest we’re not far from that point.

In one sense it matters a great deal whether we choose the low-carbon or the high-carbon path: One way, we lay the groundwork for a sustainable (if modest) energy future; the other, we destabilize Earth’s climate, shackle ourselves ever more tightly to energy sources that can only become dirtier and more expensive as time goes on, and condemn myriad other species to extinction.

However, in another sense, it doesn’t matter which path we choose: With human population numbers growing and energy constraints looming, we will have less energy to burn per capita in the future. Plot any scenario between the low-carbon and high-carbon extremes and that conclusion still holds, which means less energy for transport, for agriculture, and for heating and cooling homes. Less energy for making and using electronic gadgets. Less energy for building and maintaining cities.

Efficiency can help us obtain greater services for each unit of energy expended. Research has been proceeding for decades on how to reduce energy inputs for all sorts of processes and activities. Just one example: The electricity needed for illumination has declined by up to 90 percent due to the introduction first of compact fluorescent light bulbs, and now LED lights. However, efficiency efforts are subject to the law of diminishing returns: We can’t make and transport goods with no energy, and each step toward greater efficiency typically costs more. Achieving 100 percent efficiency would, in theory, require infinite effort. So while we can increase efficiency and reduce total energy consumption, we can’t do those things and produce continual economic growth at the same time.

Humanity is at a crossroads. Since the Industrial Revolution, cheap and abundant energy has fueled constant economic growth. The only real discussion among the managerial elite was how to grow the economy—whether in planned or unplanned ways, whether with sensitivity to the natural world or without.

Now the discussion must center on how to contract. So far, that discussion is radioactive—no one wants to touch it. It’s hard to imagine a more suicidal strategy for a politician than to base his or her election campaign on the promise of economic contraction. Denial runs deep, but sooner or later reality will expose the delusion that endless growth is possible on a finite planet. More

 

 

Jeremy Grantham, environmental philanthropist: 'We're trying to buy time for the world to wake up'

You've probably never heard of him, and for years Jeremy Grantham liked it that way. But now the man who made billions by predicting every recent financial crisis is speaking out.

Jeremy Grantham

One icy morning in February, a train pulled into Washington DC. It was loaded with environmentalists planning to handcuff themselves to the gates of the White House, in protest at the building of a 3,500km oil pipeline from Canada to the Gulf of Mexico. Amid the hundreds of placard-carrying protesters stood a somewhat incongruous figure in a suit – Jeremy Grantham, a 74-year-old fund manager. "What we are trying to do is buy time," he told reporters. "Buy time for the world to wake up."

Grantham – who occupies a legendary place in the world of finance for predicting all the major stock market bubbles of recent decades (and doing very well in the process) – had decided, after 15 years of low-key environmental philanthropy, to, as he puts it, "walk the walk".

"I was committed to getting arrested," says Grantham, a tall, slight man, as he looks out across the City from his London office on the 15th floor of a glass-and-steel tower next to the Bank of England. He speaks machine gun-quickly in a soft, mid-Atlantic accent. "But the day before [the protest] my wife checked with the lawyer, who said, 'Don't do that!'" It turned out that being arrested would give him serious problems when it came to travelling. "I've had a green card since completing my MBA at Harvard in 1964."

Grantham, co-founder and chief strategist of GMO, a Boston-based global investment group, manages $106bn (£69bn) of assets on behalf of 1,000 institutional investors, and employs 600 people, so he decided that the fallout would be too great. He was forced to stand back and watch as his daughter Isabel got arrested, alongside the actor Daryl Hannah, the US's highest-profile environmentalist Bill McKibben, and Nasa climate scientist James Hansen.

So he is speaking out instead. From where he stands, this bubble, the "carbon bubble", is the biggest he's seen. "We're already in a bad place. The worst accidents are [only] 20, 30, 40 years from now." Such apocalyptic talk is often the preserve of deep-green doom-mongers – the kind of talk that has led many to reject environmentalism. But Grantham insists he's guided "by the facts alone". On some issues (immigration and education) he "would be considered rightwing", but with the environment, he says he calls it as he sees it. He is disdainful of those who ignore the data, or worse, misinform the public.

"I find the parallels between how some investors refuse to recognise trends, and our reaction to some of our environmental challenges, very powerful," he says. "There is an unwillingness to process unpleasant data. In a bull market you want to believe good news. You don't want to hear that the market is going to go off a cliff." He finds climate sceptics – led by a "little army of non-scientific, persuasive loony lords", as he characterises them (a barely disguised reference to the former Conservative chancellor Lord Lawson and Ukip's Lord Monckton, both of whom promote, to varying degrees, climate-sceptic views) – a frustrating ideological phenomenon. "They have profound beliefs – as opposed to knowledge – that they are willing to protect by all manner of psychological tricks. So you have people who are very smart – great analysts and hedge-fund managers – who on paper know that their argument is wrong, but who promote it fiercely because they are libertarians. Anyone with a brain knows that climate change needs governmental leadership, and they can smell this is bad news for their philosophy. They are using incredible ingenuity to steer their way around facts they do not choose to accept."

Grantham, who was born in Hertfordshire and raised by his Quaker grandparents in Doncaster, freely admits to being a "late arrival to all this". After completing a degree in economics at the University of Sheffield in the early 1960s, he worked for a short stint at Shell before going to Harvard for an MBA. In 1977, he co-founded GMO [Grantham, Mayo, Van Otterloo]. Making his clients – and himself – wealthy filled his working days until the mid-1990s. And then he went on holiday with his children, to the Amazon and Borneo. "And without thinking about it, you start talking about the logs along the side of the river and the lack of mature forests in Borneo." He smiles, seeing the risk of being accused of being driven by emotion rather than rigorous statistical analysis. "That played a role, but we didn't treat it as an epiphany."

And he didn't preach. For years he has remained, Oz-like, behind the curtain of the environmental movement. He has shunned in-depth interviews and expressed his views only in quarterly newsletters published on GMO's website, where he writes of long-term risk, climate change and dwindling resources – not just oil, coal and natural gas, but also phosphorus and potash, whose use in modern farming methods "must be drastically reduced in the next 20–40 years or poorer countries will begin to starve".

At the same time, he has poured an ever-larger amount of his personal wealth into his Grantham Foundation for the Protection of the Environment, which he runs, with family input (his children are trustees) and minimal staff, out of GMO's Boston headquarters. The foundation's latest tax filing shows that in 2011 he increased the fund's coffers by $46m (£30m), bringing the total to something approaching $400m (£260m), up from $106m in 2006. Ever the wise moneyman, he has largely reinvested this money, in order to guarantee the foundation's long-term security. But he also spends about $17m annually on his chosen causes, in the process becoming, according to one magazine, the "world's most powerful environmentalist".

Run your finger down the tax document and you see why. In 2011 alone, his foundation gave $1m to each of the leading US conservation charities, the Sierra Club and Nature Conservancy, as well as $2m to the Environmental Defense Fund, where his German-born wife Hannelore is a trustee and where Isabel has also worked. He is perhaps best known in the green world for funding the London School of Economics' Grantham Research Institute on Climate Change and the Environment ($2.2m in 2011), and Imperial College London's Grantham Institute for Climate Change ($1.9m in 2011), but he funds climate researchers in India, too. He has written large cheques for the Carnegie Institute of Science, the Smithsonian, 350.org, WWF, Greenpeace and, keen to counter what he calls the "misinformation machine", funds environmental journalism at National Public Radio, the Center for Investigative Journalism, grist.org, Media Matters and the Yale Forum on Climate Change & the Media. Until last year (when he decided investigative and environmental journalism was "dying out" due to cutbacks), he funded the world's most lucrative journalism award, the annual $80,000 Grantham prize for environmental reporting.

In the past few months, however, there has been a conspicuous gear-shift in his activities. In addition to being more outspoken, he intends to support new research initiatives, particularly into "avant garde, sustainable" farming techniques. He talks of a "hybrid" form of farming that takes the best of organic farming and the best from "Big Ag". He doesn't rule out "compromises" such as genetic modification, which some environmentalists will find hard to swallow.

Having said that, his interest isn't entirely selfless. "Fifteen years ago, we started a forestry division [at GMO] because I had fallen in love with land and trees, and because I realised it was a mispriced asset class. We have done extremely well in that sector, outperforming the benchmark for 15 years."

Many deep-greens – who claim the root cause for our environmental woes is the slavish quest for economic growth – will recoil at the thought of a hard-boiled capitalist such as Grantham underpinning so much of the environmental movement. He is unconcerned. "Capitalism does millions of things better than the alternatives. It balances supply and demand in an elegant way that central planning has never come close to. However, it is totally ill-equipped to deal with a small handful of issues. Unfortunately, they are the issues that are absolutely central to our long-term wellbeing and even survival."

More awkwardly, he insists his substantial investments in oil and gas don't contradict his green views. "We need oil. If we took oil away tomorrow, civilisation ends. We can burn all the cheap, high-quality oil and gas, but if we mean to burn all the coal and any appreciable percentage of the tar sands, or even third-derivative, energy-intensive oil and gas, with 'fracking' for shale gas on the boundary, then we're cooked, we're done for."

He does think there's some cause for hope. For example, "the business mathematics of alternative energy are changing much faster [than many people] realise." Looming carbon taxes ("hopefully, in the not-too-distant future"), coupled with the increasing affordability of alternative energy, will mean that coal and oil from tar sands run the "very substantial risk of being stranded assets". There there's the "amazing" fall in fertility rates across the world ("the absolute minimum hope of survival is a gracefully declining population").

 

Dramatic Retreat of the Andean Glaciers Over the Last 30 Years

Apr. 8, 2013 — The glaciers in the tropical Andes shrunk between 30 and 50% in 30 years, which represents the highest rate observed over the last three centuries.

On the Antisana in Ecuador. (Credit: © IRD / B. Francou)

IRD researchers and their partners(1) recently published a summary which chronicles the history of these glaciers since their maximum extension, reached between 1650 and 1730 of our era, in the middle of the Little Ice Age*. The faster melting is due to the rapid climate change which has occurred in the tropics since the 1950s, and in particular since the end of the 1970s, leading to an average temperature rise of 0.7°C in this part of the Andes. At the current pace of their retreat, small glaciers could disappear within the next 10 to 15 years, affecting water supply for the populations.

For the first time, a study conducted by IRD researchers and their partners(1), recently published in the journal The Cryosphere, provides a retrospective of more than three centuries on glacier evolution in the entire tropical Andean region (3).

300 years of glacier history

Since their maximum extension, reached between 1650 and 1750, during the Little Ice Age*, the tropical Andean glaciers have gradually retreated. Over the last 30 years, however, their decline has taken dramatic proportions. This summary clearly shows the peculiarity of these last decades, with melting speeds that had never been reached before in 300 years: the surface areas of glaciers in Colombia, Ecuador, Peru and Bolivia were reduced from 30-50% since the end of the 1970s and up to 80-100% in extreme cases. This new study confirms the acceleration of climate change in this part of the world at the end of the 20th century.

Combined methods

Based on a study of moraines(4) deposited along the glacier sides, scientists were able to map and date the former positions of glaciers throughout their retreat from the 1730s. Furthermore, aerial photographs and satellite images reveal changes in glacial surfaces after 1950. At the same time, researchers modelled glacier responses to current fluctuations in temperature and rainfall, in order to determine the relationship between climatic conditions and ice retreat. Thus, they have been able to reconstruct shifts in the climate that might have led to fluctuations in the glaciers observed.

A common cause

All Andean glaciers respond to the same climatic variability mechanisms. Whereas rainfall has remained fairly stable, the atmospheric temperature in the tropical Andes has increased by 0.7°C, in conjunction with the warming of the tropical Pacific since the 1970s. At the same altitude, the temperature is not directly responsible for the melting, which is due mainly to the balance between the radiation absorbed and reflected by the glacier's surface. However, the temperature affects the type of rainfall (solid or liquid form), and therefore the conditions for maintaining (or not) the snow pack, which helps reflect the majority of the solar energy. A lack of snow pack leads to a considerable increase in the melting of the glacier. This occurrence of bare glaciers -- during summer in the tropics or during the equinoxes on the equator -- has become more frequent over the last few decades.

Small glaciers -- less than 1km² in size -- located within 5,400m of altitude appear to be the most affected. Should the rises in temperature projected for the end of the century(5) by climatic models be confirmed, most glaciers in this part of the Andes (whether large or small) could disappear, as was the fate of the Chacaltaya glacier above the city of La Paz in Bolivia in 2010. More