Global Warming Close To Becoming Irreversible: Scientists

Nina Chestney PlanetArk 27 Mar 12;

The world is close to reaching tipping points that will make it irreversibly hotter, making this decade critical in efforts to contain global warming, scientists warned on Monday.

Scientific estimates differ but the world's temperature looks set to rise by six degrees Celsius by 2100 if greenhouse gas emissions are allowed to rise uncontrollably.

As emissions grow, scientists say the world is close to reaching thresholds beyond which the effects on the global climate will be irreversible, such as the melting of polar ice sheets and loss of rainforests.

"This is the critical decade. If we don't get the curves turned around this decade we will cross those lines," said Will Steffen, executive director of the Australian National University's climate change institute, speaking at a conference in London.

Despite this sense of urgency, a new global climate treaty forcing the world's biggest polluters, such as the United States and China, to curb emissions will only be agreed on by 2015 - to enter into force in 2020.

"We are on the cusp of some big changes," said Steffen. "We can ... cap temperature rise at two degrees, or cross the threshold beyond which the system shifts to a much hotter state."


For ice sheets - huge refrigerators that slow down the warming of the planet - the tipping point has probably already been passed, Steffen said. The West Antarctic ice sheet has shrunk over the last decade and the Greenland ice sheet has lost around 200 cubic km (48 cubic miles) a year since the 1990s.

Most climate estimates agree the Amazon rainforest will get drier as the planet warms. Mass tree deaths caused by drought have raised fears it is on the verge of a tipping point, when it will stop absorbing emissions and add to them instead.

Around 1.6 billion tonnes of carbon were lost in 2005 from the rainforest and 2.2 billion tonnes in 2010, which has undone about 10 years of carbon sink activity, Steffen said.

One of the most worrying and unknown thresholds is the Siberian permafrost, which stores frozen carbon in the soil away from the atmosphere.

"There is about 1,600 billion tonnes of carbon there - about twice the amount in the atmosphere today - and the northern high latitudes are experiencing the most severe temperature change of any part of the planet," he said.

In a worst case scenario, 30 to 63 billion tonnes of carbon a year could be released by 2040, rising to 232 to 380 billion tonnes by 2100. This compares to around 10 billion tonnes of CO2 released by fossil fuel use each year.

Increased CO2 in the atmosphere has also turned oceans more acidic as they absorb it. In the past 200 years, ocean acidification has happened at a speed not seen for around 60 million years, said Carol Turley at Plymouth Marine Laboratory.

This threatens coral reef development and could lead to the extinction of some species within decades, as well as to an increase in the number of predators.

As leading scientists, policy-makers and environment groups gathered at the "Planet Under Pressure" conference in London, opinions differed on what action to take this decade.

London School of Economics professor Anthony Giddens favours focusing on the fossil fuel industry, seeing as renewables only make up 1 percent of the global energy mix.

"We have enormous inertia within the world economy and should make much more effort to close down coal-fired power stations," he said.

Oil giant Royal Dutch Shell favours working on technologies leading to negative emissions in the long run, like carbon capture on biomass and in land use, said Jeremy Bentham, the firm's vice president of global business environment.

The conference runs through Thursday.

Shadow of 'Anthropocene' falls over Rio Summit
Richard Ingham (AFP) Google News 26 Mar 12;

LONDON — Man's catastrophic damage to the environment and disparities between rich and poor head the daunting challenges facing the Rio Summit in June, experts said on Monday.

The summit must sweep away a system that lets reckless growth destroy the planet's health yet fails to help billions in need, they said.

"This century is special in the Earth's history. It is the first when one species -- ours -- has the planet's future in its hands," said Martin Rees of the Royal Society, Britain's academy of sciences.

"We've invented a new geological era: the Anthropocene," he said referring to an epoch shaped by Man, not nature.

The four-day London meeting gathers 2,800 scientists, economists, business executives and policymakers in the goal of issuing a snapshot of the planet's health ahead of Rio.

The June 20-22 UN conference is the 20-year followup to the famous Earth Summit.

That year, political leaders declared they would nail sustainable development to their agenda and set up two UN institutions for tackling global warming and species loss.

But many experts on Monday painted a grim tableau of threat and called on governments to ditch strategies based obsessively on GDP growth.

The drivers of the peril are a world population set to balloon from seven billion today to nine billion by mid-century -- but also voracious, inefficient and damaging consumption of resources, they said.

Will Steffen, head of the Climate Change Institute at the Australian National University, said the Anthropocene was pushing several of Earth's ecological systems towards "tipping points."

Within a few decades, these vital buffers could suffer lasting or irreversible damage through man-made warming, he said.

Worry spots include the Greenland icesheet, the Amazonian forest as well as Siberia, where billions of tonnes of natural greenhouse gas could be freed from melting permafrost. The Arctic Ocean would probably become ice-free "this century," he said.

"Under a worst-case scenario, it's very likely, I think, that the Earth's system will move to a new state of some sort, with a very severe challenge to contemporary civilisation," said Steffen. "Some people have even talked about a collapse."

Twenty leading figures and organisations, all of them past winners of the prestigious Blue Planet Prize for environmental work, called for Rio to look at problems through fresh eyes.

The UN's goal of limiting global warming to two degrees Celsius (3.6 degrees Fahrenheit) is already out of reach, said Bob Watson, former head of the UN's climate panel and chief advisor to Britain's environment ministry, as he presented the laureates' study.

"If you look at the commitments today from governments around the world, we've only got a 50-50 shot at a 3 C (5.4 F) world, almost no chance of a 2 C (3.6 F) world, and to be quite honest I would say it's not unlikely that we will hit a 5 C (9.0 F) world," said Watson.

"That is clearly a world with significant adverse consequences for ecological systems, for socio-economic systems and for human health."

He added: "We have to realise that we are looking at a loss of biodiversity that is unprecedented in the last 65 million years... We are clearly entering the (planet's) sixth mass extinction."

"The challenges we face today are exactly the same challenge of Rio 20 years ago," Watson said bluntly.

"We just have not acted. The need for action is becoming more and more urgent with every day that passes."

Diana Liverman, a professor at the University of Arizona, said the news was not entirely bleak.

Since 1950, "we have have seen a great acceleration in human impacts but there are some signs that some drivers are slowing or changing," she said.

Liverman pointed to a slowdown and eventual stabilisation in population growth, gains in energy efficiency and reforestation in some countries.

But, she added, "many people still struggle to meet basic needs. Many of them see a profoundly unequal world. And many still aspire to increase their consumption."