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Category — Carbon Dioxide

More CO2 limits plants’ protein output

Tim Radford

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The Mojave desert: As CO2 levels rose, it took up unexpectedly large amounts of the gas. Image: Rennett Stowe via Wikimedia Commons

With increasing warmth drying more of the Earth, arid soils may absorb more carbon dioxide – but that in turn is likely to limit protein production.

As global temperatures rise, more than one third of the land surface may become more arid. Although there will be changes in rainfall patterns, heat – and the attendant evaporation of the soil – could extend ever drier conditions to more and more farmland and cities, according to research in the journalClimate Dynamics.

The new study – which excludes Antarctica – is led by Benjamin Cook, a climate scientist both with the University of Columbia’s Lamont-Doherty Earth Observatory and the US space agency Nasa. It is based on climate simulation, and forecasts that 12% of the land surface will be subjected to drought by 2100 just through changes in rainfall. Throw in the increased heat, though, and the drying effect will be spread to 30% of the land.

Even those regions that might be expected to get more rain will be at greater risk of drought. This would be very bad news for the wheat, corn and rice belts of the south-western US and south-eastern China.

“For agriculture, moisture in the soil is what really matters,” said Cook’s co-author, Jason Smerdon. The research confirms previous studies, and the more recent warnings from the Intergovernmental Panel on Climate Change, and other studies, have predicted that extremes of temperature will be bad news for farmers anyway, with yields  likely to be affected.

But nothing in climate research is simple. The extra warming will be a direct consequence of ever-higher levels of carbon dioxide in the atmosphere. A study in Nature Climate Change has just revealed that arid zones offer an unexpected source of what engineers call negative feedback. [Read more →]

April 12, 2014   No Comments

Livestock diet ‘can cut GHG emissions’

Tim Radford

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Better livestock diets could mean greenhouse gas cuts of 23% by 2030, the researchers say. Image: Fir0002/Flagstaffotos via Wikimedia Commons

Limiting changes in the way we use land may be a better way slowing the contribution of livestock to climate change than reducing meat consumption, an international research team says.

Here’s a way to make cattle emit lower volumes of methane through their digestive tracts: give the beasts a higher-quality diet. That way, you get more stock on less grassland, get improved yields per hectare and at the same time reduce greenhouse gas emissions, according to new research in theProceedings of the National Academy of Sciences.

“There is a lot of discussion about the reduction of meat in the diet as a way to reduce emissions,” says Petr Havlik of the International Institute for Applied Systems Analysis in Austria. “But our results show that targeting the production side of agriculture is a much more efficient way to reduce greenhouse gas emissions.”

This will provoke some argument, and in any case seems counter-intuitive. Campaigners have been arguing for decades that livestock farming is in many though not all regions an inefficient way to produce nourishment: grain, pulses, fruits and vegetables deliver greater outputs of calories and proteins at much lower overall costs in water, energy and emissions.

Farm animals are responsible for 12% of greenhouse gas emissions and, as the poorer nations develop, demand for meat and dairy protein tends to rise, so emissions are expected to increase. [Read more →]

February 26, 2014   No Comments

Tree roots ‘are natural thermostat’

Tim Radford

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In sight of the Carpathians: Mountain forests can cool – and warm – the Earth. Image: Horia Varlan from Bucharest, Romania, via Wikimedia Commons

Trees can influence the climate in unexpected ways, and British researchers say their roots are an important way of helping rocks to weather and drawing carbon dioxide from the atmosphere.

Trees have become a source of continuous surprise. Only weeks after researchers demonstrated that old forest giants actually accumulate more carbon than younger, fast-growing trees, British scientists have discovered that the great arbiters of long-term global temperatures may not be the leaves of an oak, a pine or a eucalypt, but the roots.

The argument, put by a team from Oxford and Sheffield Universities in the journal Geophysical Research Letters, begins with temperature. Warmer climates mean more vigorous tree growth and more leaf litter, and more organic content in the soil. So the tree’s roots grow more vigorously, say Christopher Doughty of Oxford and colleagues.

They get into the bedrock, and break up it up into its constituent minerals. Once that happens, the rock starts to weather, combining with carbon dioxide. This weathering draws carbon dioxide out of the atmosphere, and in the process cools the planet down a little. So mountain ecosystems – mountain forests are usually wet, and on conspicuous layers of rock – are in effect part of the global thermostat, preventing catastrophic overheating.

The tree is more than just a sink for carbon, it is an agency for chemical weathering that removes carbon from the air and locks it up in carbonate rock.

That mountain weathering and forest growth are part of the climate system has never been in much doubt: the questions have always been about how big a forest’s role might be, and how to calculate its contribution. [Read more →]

February 18, 2014   No Comments

Carbon output ‘will climb 29% by 2035′

Alex Kirby

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Spelling it out: A French “non” to the prospect of shale oil and gas. Image: Eva Joly 2012 via Wikimedia Commons

Climate scientists agree that global carbon dioxide emissions need to be sharply cut. A prominent player in the energy industry predicts they will go in the opposite direction.

The good news, from the climate’s standpoint, is that while global demand for energy is continuing to grow, the growth is slowing. The bad news is that one energy giant predicts global carbon dioxide emissions will probably rise by almost a third in the next 20 years.

The Intergovernmental Panel on Climate Change says greenhouse gas emissions need to peak by 2020 and then decline if the world is to hope to avoid global average temperatures rising by more than 2°C over pre-industrial levels. Beyond 2°C, it says, climate change could become dangerously unmanageable.

But BP’s Energy Outlook 2035 says CO2 emissions are likely to increase by 29% in the next two decades because of growing energy demand from the developing world.

It says “energy use in the advanced economies of North America, Europe and Asia as a group is expected to grow only very slowly – and begin to decline in the later years of the forecast period”.

But by 2035 energy use in the non-OECD economies is expected to be 69% higher than in 2012. In comparison use in the OECD will have grown by only 5%, and actually to have fallen after 2030, even with continued economic growth. The Outlook predicts that global energy consumption will rise by 41% from 2012 to 2035, compared with 30% over the last ten. [Read more →]

February 7, 2014   No Comments

Few would welcome geo-engineering

Tim Radford

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Simplest is often best: Biochar, made from vegetable matter, arouses fewer objections. Image: K.salo.85 via Wikimedia Commons

Trying to avert dangerously high global temperatures by modifying the climate – geo-engineering – may or may not be possible. It certainly won’t be popular, researchers say.

Geo-engineering – the frustrated climate scientist’s last-ditch solution to global warming – is not likely to be a very popular choice. Members of the public have “a negative view” of deliberate large-scale manipulation of the environment to counteract climate change, according to new research inNature Climate Change.

Geo-engineering has been repeatedly proposed as a response to the steady build-up of carbon dioxide in the atmosphere, and increasingly cited as a potential necessity as global emissions from fossil fuels have continued to increase. If political action fails, some scientists reason, then perhaps technology could stop global average temperatures from getting too high.

Among these options is the injection of aerosols into the stratosphere to block or dim the sunlight, or the release of reflecting devices in Earth orbit to actually reflect sunlight away from the planet, on the principle that if you can’t turn down the atmospheric temperature, you could at least put up a sunscreen to cool the planet a little.

Such ideas have failed to find universal favour in the scientific community, if only because such action could seriously upset rainfall patterns and trigger disaster in the arid parts of Africa. [Read more →]

January 17, 2014   No Comments

2013 ‘will mark continued rise of CO2′

Tim Radford

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The coal-fired power station at Drax in the North of England: Coal is still the world’s biggest source of CO2. Image: Paul Glazzard via Wikimedia Commons

The world’s emissions of the main greenhouse gas produced by human activities, carbon dioxide, in 2013 are expected to be nearly two-thirds higher than in 1990.

Global carbon dioxide emissions are likely to hit 36 billion tonnes in 2013, according to new research from the University of East Anglia in the UK. This is a small rise – an estimated 2.1% – on 2012, but it will be 61% above the levels in 1990, which is the baseline year for the Kyoto Protocol.

The Kyoto Protocol was agreed by most of the world’s concerned nations, anxious to reduce carbon dioxide emissions and contain warming to a global average of 2°C. So the 2013 carbon budget is not being hailed as a great success.

“Governments meeting in Warsaw this week need to agree on how to reverse this trend,” said Corinne Le Quéré of the university’s Tyndall Centre for Climate Change, who led the Global Carbon Budget report for 2013, compiled by 49 authors from 10 countries. She was speaking before the start of last month’s UN climate talks in the Polish capital.

“Everyone can explore their own emissions, and compare them with their neighbouring countries…”

“Emissions must fall substantially and rapidly if we are to limit global climate change to below two degrees. Additional emissions every year cause further warming and climate change.”

The Tyndall Centre has also launched the Global Carbon Atlas, an online platform that identifies the biggest carbon emitters. “Everyone can explore their own emissions, and compare them with their neighbouring countries – past, present and future,” said Professor Le Quéré.

China is the biggest contributor, with 23%, followed by the US at 14% and the European Union at 10% and India at 6%. Emissions per person put these figures into another perspective: people in China and in the EU each released seven tonnes per head in 2012. The US remains the highest emitter with 16 tonnes per capita; people in India, by comparison, release only 1.8 tonnes each.

Coal remains the biggest source of carbon dioxide at 43%; oil 33%, gas 18% and cement 6.3%. Since 1870, humans have released 2,105 billion tonnes of carbon dioxide into the atmosphere – 70% from fossil fuels and 30% by chopping down forests and changing the patterns of land use.

December 31, 2013   No Comments

Climate imperils Peru’s poverty drive

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A garbage picker in Peru: Rising temperatures may endanger the country’s anti-poverty policies. Image: Alex Proimos from Sydney, Australia, via Wikimedia Commons

Peru’s efforts to reduce poverty are at risk from the effects of climate change, one example of the problems facing the wider Amazonia region in a warming world.

Peru is the country chosen to host the 2014 UN climate conference, a key meeting for trying to advance an ambitious plan to rein in greenhouse emissions which is planned for agreement in 2015.

But the country has recently earned a rather more dubious distinction. In 2012, for the first time, the Peruvian Amazon became a net emitter of carbon dioxide rather than oxygen, according to the latest human development country report of the UN Development Programme (UNDP).

The Amazon rainforest usually acts as a carbon sink, absorbing atmospheric CO2 rather than releasing it. Scientists think this reversal of its normal behaviour results from the droughts in the western Amazon in 2005 and 2010 and say it shows Peru’s vulnerability to climate change.

Peru has more than halved its poverty rate in the last decade, from 48.5% in 2004 to 25.8% in 2012. But the 2013 UNDP report said its vulnerability to a warming climate could cancel the progress it has made in directing economic growth into sustained poverty reduction. [Read more →]

December 26, 2013   No Comments

Earth ‘may be doubly sensitive’ to CO2

Alex Kirby

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Bad news for bears – snd for us: Geological evidence as well as models prove rising CO2 is melting polar ice. Image: Alastair Rae via Wikimedia Commons

The sensitivity of the Earth system to a doubling of atmospheric carbon dioxide may be twice as great as scientists had thought, new climate records from the distant past suggest.

You may think the prospect of climate change is alarming, a call to action to slow down our emissions of carbon dioxide and other greenhouse gases.

You’re almost certainly right. But some scientists are now suggesting you should be much more concerned than you are, because they think we may be seriously underestimating the problem.

The Geological Society of London (GSL) says the sensitivity of the Earth’s climate to CO2 could be double earlier estimates.

The Society has published an addition to a report by a GSL working party in 2010, which was entitledClimate change: Evidence from the Geological Record.
The addition says many climate models typically look at short term, rapid factors when calculating the Earth’s climate sensitivity, which is defined as the average global temperature increase brought about by a doubling of CO2  in the atmosphere.

Scientists agree that a doubling of atmospheric CO2 levels could result in temperature increases of between 1.5 and 4.5°C, caused by rapid changes such as snow and ice melt, and the behaviour of clouds and water vapour.

But what the GSL now says is that geological evidence from palaeoclimatology (studies of past climate change) suggests that if longer-term factors are taken into account, such as the decay of large ice sheets, the Earth’s sensitivity to a doubling of CO2 could itself be double that predicted by most climate models. [Read more →]

December 11, 2013   No Comments