Tag Archives: Warming

Political will is only barrier to 100% renewables

Wind turbines in Germany's Rhein-Hunsrück district, a world leader in renewables Image: Markus Braun via Wikimedia Commons
Germany’s Rhein-Hunsrück district already exceeds100% electricity from renewables
Image: Markus Braun via Wikimedia Commons

By Paul Brown

A report published ahead of next week’s UN Climate Summit illustrates that poor and prosperous nations, tiny islands and great cities, can achieve all their energy needs from renewables.

LONDON, 20 September, 2014 − A new handbook shows how forward-looking communities around the world are already moving away from reliance on fossil fuels and generating their own power with 100% renewables − while also becoming more prosperous and creating jobs.

The report, How to Achieve 100% Renewable Energy, is being released today, ahead of the UN Climate Summit in New York next Tuesday (September 23), when the UN Secretary-general, Ban Ki-Moon, will call on world leaders to make new commitments to cut fossil fuel use.

The World Future Council, based in Hamburg, Germany, has issued the report to show that it is only lack of political will that is preventing the world switching away from fossil fuels. It believes that the leaders at the UN summit need to set ambitious targets and timetables to achieve the switch to renewables.

Technologies exist

Using case histories − from small islands in the Canaries to great commercial cities such as Frankfurt in Germany and Sydney in Australia − the report makes clear that the technologies to go 100% renewable exist already.

In many cases, the switch has the combined effect of saving money for the community concerned and creating jobs, making everyone more prosperous. In all cases, improvements in energy efficiency are essential to meeting targets.

Where the100% renewable target is adopted, it gives the clearest signal to business that investments in clean technologies will be secure. The report says: “The benefits range from savings on fossil fuel imports, improved energy, and economic security, as well as reduced energy and electricity costs for governments, local residents and businesses.”

There is no case made for nuclear power. Indeed, the report says that the uranium needed for nuclear fuel is − like coal, oil and gas − a finite resource that will soon be running out.

One of the case histories in the report is the Fukushima Prefecture in Japan. In March 2011,  it sustained the world’s worst nuclear accident since the 1986 Chernobyl disaster in Ukraine, and has now opted to go for 100% electricity from renewables by 2040.

Some of the 100% renewable targets detailed in the report are just for electricity production. The authors − Toby Couture, founder of the Berlin-based energy consultancy E3 Analytics, and Anna Leidreiter, climate and energy policy officer at the World Future Council − point out that heating and cooling, and particularly transport, without fossil fuels is far more challenging, but still equally possible. Some countries are already committed to it.

Denmark, a pioneer in the field, has a target of achieving all its electricity and heating needs from renewables by 2035, and all energy sectors − including transport − by 2050. This includes an expansion of wind and solar power, biogas, ground source heat pumps, and wood-based biomass. Because of its investments, the country expects to have saved €920 million on energy costs by 2020.

At the opposite end of the scale, El Hierro, a small island in the Canaries, has a 100% energy strategy, using a wind farm and a volcanic crater. When excess electricity is produced by the wind farm, water is pumped into the volcanic crater, which acts as a storage lake for a hydroelectric plant. This supplements the island’s electricity supply when the wind drops or when demand is very high.

A future component of El Hierro’s strategy is to replace the island’s entire stock of 4,500 cars with electric vehicles, so cutting the need to import fuel.

Surplus electricity

Some places have already exceeded 100% electricity from renewables. The Rhein-Hunsruck district west of Frankfurt, Germany, managed this in 2012, and expects by the end of this year to be producing 230% of its needs, exporting the surplus to neighbouring areas through the national grid. It hopes to use the surplus in future for local transportation, hydrogen or methane production.

There are many other examples in the report, including from San Francisco in the US, Cape Verde island in West Africa, Bangladesh, Costa Rica, and Tuvalu island in the Pacific. These show that both rich and poor communities can share the benefits of the renewable revolution – and, in the case of the 3 billion people still without electric power in the world, bypass the need for fossil fuels altogether.

Jeremy Leggett, a pioneer of solar power and author of a foreword to the report, says: “We are on the verge of a profound and urgently necessary shift in the way we produce and use energy.

“This shift will move the world away from the consumption of fossil resources towards cleaner, renewable forms of power. Renewable energy technologies are blowing the whistle on oil dependency and will spark an economic and social renaissance.

“The question is: Do we make this transition from fossil resources to renewables on our own terms, in ways that maximise the benefits to us today and to future generations, or do we turn our heads away and suffer the economic and social shocks that rising prices and market volatility will create?” – Climate News Network

Climate action and economies can grow together

Investing in renewables such as solar energy can spur economic activity Image: Alex Snyder/Wayne National Forest via Wikimedia Commons
Working together: investing in renewables such as solar energy can spur economic activity
Image: Alex Snyder/Wayne National Forest via Wikimedia Commons

By Kieran Cooke

A new global commission report by major political and business figures refutes the claim that economic expansion and tackling climate change can’t both be achieved at the same time.

LONDON, 17 September, 2014 − We can have our cake and eat it. That’s the main message of a new study that says the idea that we have to choose between battling against climate change or promoting growth in the world’s economy is a “false dilemma”.

The report, The New Climate Economy, was produced by the Global Commission on the Economy and Climate, chaired by Felipe Calderón, the former president of Mexico, and including eminent economist Lord [Nicholas] Stern.

Calderon, addressing what he describes as a “false dilemma”, says: “The message to leaders is clear. We don’t have to choose between economic growth and a safe climate. We can have both.”

Lord Stern, author of the 2006 Stern Review, which comprehensively detailed, for the first time, the economic consequences of not taking action on climate change, says decisions being made now will determine the future of both the economy and the climate.

High-quality growth

“If we choose low-carbon investment, we can generate strong, high-quality growth – not just in the future, but now,” he says. “But if we continue down the high-carbon route, climate change will bring severe risks to long-term prosperity.”

The commission’s report, released at the United Nations in New York shortly before a major UN climate summit, says there are now big opportunities for achieving strong economic growth and, at the same time, lowering emissions across three sectors:

  • Building more compact, better connected cities will improve the quality of life of urban dwellers, improve economic performance, and lower emissions.
  • Improved land use can cut emissions resulting from deforestation. Restoring 12% of the world’s degraded land would dramatically raise farmers’ incomes.
  • More and more of the world’s energy is likely to be generated by renewables, cutting dependence on highly-polluting coal. Renewables is now a big growth industry, spurring on various economic activities.

The report says that about US$90 trillion is likely to be invested in infrastructure in the world’s cities, agriculture and energy systems over the next 15 years, and spending should be directed towards low-carbon growth that would not only benefit the climate but also business productivity.

The study calls for the phasing out of huge amounts spent worldwide on subsidies for fossil fuels – currently US$600 billion, compared with US$100bn for renewable, the report says. Competitive energy markets, consistent government policy, a strong price for carbon, and greatly expanded research in low carbon technologies are also needed.

If fully implemented, the report’s authors calculate, a reduction of up to 90% in emissions could be achieved by 2030, and dangerous climate change would be averted.

Meaningful action

Although the report’s findings have been endorsed by a wide range of leading politicians, business figures and economists, there are those who would argue against the idea that economic growth can be achieved alongside meaningful action on climate change.

For example, the New Economics Foundation (NEF), a UK thinktank, contends that indefinite global economic growth is unsustainable.

In a 2010 report, Growth Isn’t Possible, the NEF said economic growth is constrained by the finite nature of the planet’s natural resources. “Growth forever, as conventionally defined, within fixed though flexible limits, is not possible,” it said. “Sooner or later, we will hit the biosphere’s buffers.”

Others would point out that although a carbon market has been in operation for several years, the price of carbon has failed to rise. The introduction of market forces and competition in the energy sector in many countries has done little to lessen greenhouse gas emissions.

In many countries, including India, China, Australia and some states in Europe, a central role in driving economic growth is still played by coal, the most polluting of all energy sources. – Climate News Network

Warming will leave drought-hit California reeling

 

The treeline below Tells Peak in California’s Sierra Nevada mountains Image: Nick Ares via Wikimedia Commons
The treeline below Tells Peak in California’s Sierra Nevada mountains
Image: Nick Ares via Wikimedia Commons

By Tim Radford

Researchers in the US warn that climate change could worsen California droughts by drastically reducing water flow from the Sierra Nevada mountains − and also threatens the extinction of a rare species of fish.

LONDON, 16 September, 2014 − Things could soon get worse for drought-hit California. New research predicts that, by the close of the century, global warming could have reduced the flow of water from the Sierra Nevada mountains by at least a quarter.

Michael Goulden, associate professor of earth system science at the University of California Irvine, and Roger Bales, director of the Sierra Nevada Research Institute at the University of California Merced, publish their alarming findings in the Proceedings of the National Academy of Sciences.

Plant growth

Their research looked not at the long-term projections for precipitation in the US south-west, but simply at the effect of higher average temperatures on plant growth.

Mountains in many ways mimic hemispheres: just as trees become more stunted at higher latitudes, so they get smaller and less frequent at higher altitudes. Temperature ultimately controls plant growth.

But a projected warming of 4.1°C by 2100 would make a big difference to plant growth in the Arctic tundra and around the present alpine treeline everywhere in the world.

The scientists contemplated snow and rain conditions in the King’s River Basin in the Sierra Nevada range. They looked at how much flows downstream to local communities, and how much goes back into the atmosphere as water vapour. Then they did their sums.

They calculated that the 4.1°C temperature rise in the region would increase the density of vegetation at high elevations, with a 28% increase in evapotranspiration − the process that draws water up through the roots to the leaves, and then releases it as vapour through the pores. And what was true for one river basin, they thought, should be true for the whole area. River run-off could drop by 26%.

“Scientists have recognised for a while that something like this was possible, but no one has been able to quantify whether it could be a big effect,” said Professor Goulden. “It’s clear that this could be a big effect of climate warming and that managers need to recognise and plan for the possibility of increased water losses from forest evaporation.”

Endangered fish

MEANWHILE, climate change threatens to wipe out an endangered species of fish in a remote area of Nevada.

The Devils Hole pupfish (Cyprinodon diabolis) is not just rare, it is very rare: the population has fallen as low as 35 individuals. It lives in the geothermally-warmed waters of a limestone cavern in the Devils Hole in the Mojave desert, and its existence was probably always precarious. The fish are little more than 2cms long, iridescent blue, and they have made their home in the upper 25 metres of the cavern’s waters for at least 10,000 years.

Devils Hole pupfish are only 2cms long Image: Nevada Fish & Wildlife Office
Devils Hole pupfish are only 2cms long
Image: Nevada Fish & Wildlife Office via Wikimedia Commons

But Mark Hausner, a hydrogeologist at the Desert Research Institute in Las Vegas, Nevada, and colleagues report in the journal Water Resources Research that there is only a 10-week window in which the water temperatures are optimal, and there is enough food available, for new larvae to hatch.

Climate change is bringing the already-warm water to dangerous temperature levels, and this has already shortened by at least one week the brief opportunity to restore the population. When counts began in 1972, there were more than 500 of the fish. A decade ago there were 171, and at the last count there were only 92.

“This is a fish that does live in a fishbowl, an incredibly hostile fishbowl, and you can’t move the fishbowl,” said one of the report’s authors, Scott Tyler, professor in the Department of Geological Sciences and Engineering at the University of Nevada, Reno. “This is a species that can’t adapt or change or leave to go to a better environment.” − Climate News Network

Drowned tropical forests add to climate change

Dead trees poke out of the Nam Theun 2 dam reservoir, Laos. Image: Dominique Serça/CNRS
Dead trees poke eerily out of the Nam Theun 2 dam reservoir in Laos
Image: Dominique Serça/CNRS

By Paul Brown

New scientific data supports the belief that methane emissions from big hydroelectric dams in the tropics outweigh the benefits that this form of renewable energy provides.

LONDON, 11 September, 2014 − Big dams built in the tropics to produce hydroelectricity have long been highly controversial − and data gathered in Laos by a French team studying methane emissions confirms that dams can add to global warming, not reduce it.

In many rocky regions low on vegetation and population, such as in Iceland and other northern mountainous regions, the production of electricity from hydropower is clearly a net gain in the battle against climate change.

In Asia, Africa and South America, however, masses of methane are produced from dams by the drowning of tropical forests in them. As long ago as 2007, researchers at Brazil’s National Institute for Space Research calculated that the world’s largest dams emitted 104 million tonnes of methane annually and were responsible for 4% of the human contribution to climate change.

Short-term threat

Since methane has an impact 84 times higher over 20 years than the same quantity of carbon dioxide, this is a serious short-term threat to pushing the planet towards the danger threshold of increasing temperatures by 2˚C .

Despite the warnings that big dams in the tropics might be adding to climate change, governments go on building them − while often claiming that large dams equal clean energy.

The new research shows that the methane discharges are probably even worse than current calculations.

In an attempt to find out exactly what the perils and benefits of big dams in the tropics can be, a French team from the National Centre for Scientific Research (CNRS) has been studying the Nam Theun 2 reservoir in Laos − the largest in Southeast Asia − prior to its filling, in May 2008, right up to the present to calculate the total methane emissions.

Methane is produced by bacteria feeding on the plant material drowned when the dam is filled. This is added to by more organic matter that is washed into it by rivers and rains.

Measuring the methane produced is the tricky bit as it reaches the atmosphere in three ways. Some is dissolved in the water and reaches the atmosphere by diffusion, some goes through the turbines and is released downstream, and the third way is called ebullition – which means bubbles of methane coming directly to the surface and going straight into the atmosphere.

It is these last gas emissions that have been so hard to measure, but the team has developed automatic measuring devices that work 24 hours a day.

The measurements carried out on the Nam Theun 2 reservoir enabled the scientists to show that ebullition accounted for between 60% and 80% of total emissions from the reservoir in the first years following filling.

Maximum emissions

In addition, ebullition intensity varies at night and seasonally. During the four months of the hot dry season (mid-February to mid-June), emissions reach their maximum because water levels are low. Daily variations are controlled by atmospheric pressure: during the two daily pressure drops (in the middle of the day and the middle of the night), methane (CH4) ebullition increases.

With the help of a statistical model, day-to-day data related to atmospheric pressure and water level was used by the researchers to reconstruct emissions by ebullition over a continuous four-year period (2009-2013).

The results obtained highlight the importance of very frequent measurements of methane fluxes. They also show that the ebullition process − and therefore the amount of methane emitted from tropical reservoirs during their first years of operation − has most certainly been underestimated until now.

For the researchers, the next stage will be to quantify diffusion at the surface of the reservoir and emissions downstream from the dam to the same level of accuracy. This will enable them to complete the assessment of methane emissions from this reservoir, and better assess the contribution they make to the global greenhouse effect. – Climate News Network

Weather patterns show climate is changing US

Streams feeding the Verde River in Arizona may be drying up Image: Jennifer Horn via Wikimedia Commons
Streams feeding the Verde River in Arizona may be drying up
Image: Jennifer Horn via Wikimedia Commons

By Tim Radford

Fiercer tornadoes, more prolonged periods of drought and loss of native fish species are some of the damaging impacts predicted for the US as greenhouse gas emissions continue to rise.

LONDON, 10 September, 2014 − The climate is changing . . . and America’s heartland and southwest are changing with it.

In the southwestern state of Arizona, the streams may be drying up − and that could mean that native fish species will die out.

In the midwest states that citizens call Tornado Alley, the evidence is that there are fewer tornado days per year, but the density and strength of those tornadoes that do form is growing as greenhouse gas emissions continue to rise.

And in the west, which is in the grip of a prolonged drought, things are looking up − but not in a good way. Relieved of the weight of water they normally bear – the 240 billion tonnes of snow and rain that have not fallen since the drought began – the land is starting to rise, with mountains as much as 15 millimetres higher.

More arid

The current drought may not be evidence of climate change – there is a long history of periodic drought in the region – but in general the US southwest is expected to become steadily more arid as planetary temperatures soar.

Kristin Jaeger, assistant professor at Ohio State University’s School of Environment and Natural Resources, reports in the Proceedings of the National Academy of Sciences of the USA that she and colleagues decided to model the surface flow of the Verde River Basin in Arizona by 2050.

Fish that live in these waters are already threatened or endangered, their survival depending on being able to move around the watershed to eat, to spawn and to raise offspring. But the computer simulations for the future suggest that there will be a 17% increase in dried-up streams and a 27% increase in days when there will be no flow of water at all.

What this will do is sever connections between streams, and the deeper pools will become isolated. Native species, such as the speckled dace, the roundtail chub and the Sonora sucker, will increasingly have nowhere to go.

Dr Jaeger calls the estimates conservative. She and her fellow researchers did not take account of the groundwater that will be removed to support the expected 50% increase in human population in Arizona by 2050.

In the US, tornadoes are a fact of life – and death. In 2011, for example, it experienced 1,700 storms during the tornado season, and 550 people died. But scientists have begun to detect a pattern of change. In 1971, there were only 187 days with tornadoes, and in 2013, there were only 79 days, according to James Eisner, a geographer at Florida State University, and colleagues in a report in the journal Climate Dynamics.

But the tornadoes that do form are distinguished by what the scientists call “increasing efficiency”. They are more severe, and there are more of them on a given day.

“We may be less threatened by tornadoes on a day-to-day basis, but when they do come, they come like there’s no tomorrow,” said Professor Eisner.

Meanwhile, Adrian Borsa  and other researchers at Scripps Institution of Oceanography in San Diego report in the journal Science that they have been looking at data from GPS satellite ground stations, to discover that – thanks to the current drought – all of them are on the move.

Highest uplift

Overall, the surface of the arid west has gained 4mm in altitude since the drought began, and the highest uplift, 15mm, has been measured in the mountains.

They put it down to the water that has not fallen and which would normally have covered the mountains as heavy snow. Altogether, the water deficit is 240 gigatonnes, or 62 trillion gallons − the equivalent of a 10cm layer of water across the entire west of the US.

This is roughly the equivalent of the mass of ice lost each year from the Greenland ice sheet.

The crustal movement is not expected to have any impact on the likelihood of earthquakes in, for example, California, but the study could offer researchers a new way of measuring fresh water resources over very large regions.

It could be a case of don’t worry about all those rainfall gauges, just watch how the earth moves. Or, in the researchers technical language, such observations “have the potential to expand dramatically the capabilities of the current hydrological observing network”. – Climate News Network

Ocean acidification and GHGs hit record levels

Reef grief: corals, fisheries and tourism will all be damaged by  ocean acidification Image: Ritiks via Wikimedia Commons
Reef stricken: corals, fisheries and tourism will all be damaged by ocean acidification
Image: Ritiks via Wikimedia Commons

By Alex Kirby

New scientific evidence of the highest greenhouse gas concentrations on record is compounded by the revelation that oceans are acidifying faster than at any time in the last 300 million years.

LONDON, 9 September, 2014 – The World Meteorological Organisation (WMO) reports that the amounts of atmospheric greenhouse gases reached a new high in 2013, driven by rapidly rising levels of carbon dioxide.

The news is consistent with trends in fossil fuel consumption. But what comes as more of a surprise is the WMO’s revelation that the current rate of ocean acidification, which greenhouse gases (GHGs) help to cause, appears unprecedented in at least the last 300 million years.

The details of growing GHG levels are in the annual Greenhouse Gas Bulletin, published by the WMO – the United Nations specialist agency that plays a leading role in international efforts to monitor and protect the environment.

They show that between 1990 and 2013 there was a 34% increase in radiative forcing – the warming effect on our climate – because of long-lived greenhouse gases such as carbon dioxide (CO2), methane and nitrous oxide.

Complex interactions

The Bulletin reports on atmospheric concentrations – not emissions − of greenhouse gases. Emissions are what go into the atmosphere, while concentrations are what stay there after the complex system of interactions between the atmosphere, biosphere (the entire global ecological system) and the oceans.

About a quarter of total emissions are taken up by the oceans and another quarter by the biosphere, cutting levels of atmospheric CO2.

In 2013, the atmospheric concentration of CO2 was 142% higher than before the Industrial Revolution started, in about 1750. Concentrations of methane and nitrous oxide had risen by 253% and 121% respectively.

The observations from WMO’s Global Atmosphere Watch network showed that CO2 levels increased more from 2012 to 2013 than during any other year since 1984. Scientists think this may be related to reduced CO2 absorption by the Earth’s biosphere, as well as by the steady increase in emissions.

Although the oceans lessen the increase in CO2 that would otherwise happen in the atmosphere, they do so at a price to marine life and to fishing communities − and also to tourism. The Bulletin says the oceans appear to be acidifying faster than at any time in at least the last 300 million years.

“We know without any doubt that our climate is changing and our weather is becoming more extreme due to human activities such as the burning of fossil fuels,” said the WMO’s secretary-general, Michel Jarraud.

“We are running out of time. The laws
of physics are non-negotiable.”

“The Greenhouse Gas Bulletin shows that, far from falling, the concentration of carbon dioxide in the atmosphere actually increased last year at the fastest rate for nearly 30 years. We are running out of time. The laws of physics are non-negotiable.

“The Bulletin provides a scientific base for decision-making. We have the knowledge and we have the tools for action to try to keep temperature increases within 2°C to give our planet a chance and to give our children and grandchildren a future. Pleading ignorance can no longer be an excuse for not acting.”

Wendy Watson-Wright, executive secretary of the Intergovernmental Oceanographic Commission of UNESCO, said: “It is high time the ocean, as the primary driver of the planet’s climate and attenuator of climate change, becomes a central part of climate change discussions.

“If global warming is not a strong enough reason to cut CO2 emissions, ocean acidification should be, since its effects are already being felt and will increase for many decades to come.”

The amount of CO2 in the atmosphere reached 396.0 parts per million (ppm) in 2013. At the current rate of increase, the global annual average concentration is set to cross the symbolic 400 ppm threshold within the next two years.

More potent

Methane, in the short term, is a far more powerful greenhouse gas than CO2 − 34 times more potent over a century, but 84 times more over 20 years.

Atmospheric methane reached a new high of about 1,824 parts per billion (ppb) in 2013, because of increased emissions from human sources. Since 2007, it has started increasing again, after a temporary period of levelling-off.

Nitrous oxide’s atmospheric concentration in 2013 was about 325.9 ppb. Its impact on climate, over a century, is 298 times greater than equal emissions of CO2. It also plays an important role in the destruction of the ozone layer that protects the Earth from harmful ultraviolet solar radiation.

The oceans currently absorb a quarter of anthropogenic CO2 emissions − about 4kg of CO2 per day per person. Acidification will continue to accelerate at least until mid-century, according to projections from Earth system models. − Climate News Network

Bluefin tuna follow prey to warming high Arctic

Large bluefin tuna that were caught among mackerel near Greenland Image: Greenland Fisheries License Control Authority
Large bluefin tuna that were caught among mackerel near Greenland
Image: Greenland Fisheries License Control Authority

By Alex Kirby

A research ship’s surprise catch of bluefin tuna further north than ever recorded indicates that climate change is restructuring the food web as the waters of east Greenland get warmer.

LONDON, 8 September, 2014 − Biologists and fishermen aboard a scientific cruise in the Arctic while they investigated mackerel stocks caught more than they bargained for − three large bluefin tuna, each weighing about 100 kilograms.

The research ship was sailing through the Denmark Strait, which separates Greenland from Iceland. Bluefin tuna are very seldom found near Greenland, and there are no other scientific reports of them venturing that far north. The most recent report of a tuna anywhere near was a stranding in 1900, a long way south at Qaqortoq, on the south-western tip of Greenland.

Details of the find, during a cruise in August 2012 organised by the Center for Macroecology, Evolution and Climate at the University of Copenhagen, have now been published in the journal Global Change Biology.

Expanded range

The lead author, Professor Brian MacKenzie, said bluefin tuna usually search for prey in areas where surface temperatures are warmer than 11°C.

At the time of the catch, the Denmark Strait was unusually warm, and one of tuna’s preferred prey species, mackerel, had already expanded their range into the region.

Professor MacKenzie and his colleagues write: “Regional temperatures in August 2012 were historically high and contributed to a warming trend since 1985, when temperatures began to rise.

“The presence of bluefin tuna in this region is likely due to a combination of warm temperatures . . . and immigration of an important prey species to the region. We conclude that a cascade of climate change impacts is restructuring the food web in east Greenland waters.”

They say their data was too limited to estimate how many tuna came so far north, but because bluefins are a schooling species − with schools having from 10 to 100 individuals − and because the three tuna were caught in the same haul, it is likely there were many more present.

The report says: “Satellite imagery showing the spread of warm water from the south-east towards east Greenland suggests that recent warming and climate change may have opened a migration pathway from the European shelf towards Greenland for migratory species.”

It acknowledges that the fish may have swum to the Denmark Strait from the north-west Atlantic, and concludes: “Our results show that rising temperatures have been progressively leading a . . . trophic [high in the food chain] cascade into east Greenland waters via improved thermal conditions for migratory prey and predator species.”

New fishing quotas

Nobody knows why bluefin tuna disappeared from the waters near Denmark and in the Norwegian Sea during the 1960s, nor when they might return. But Iceland and Norway have been allocated new fishing quotas of 30 tonnes each for the species in 2014.

An adult bluefin tuna is typically 1.5m-2m long, but some have been as big as 4.5m and weighed 650 kg. The fish are highly prized for sushi, especially in Japan.

Further climate-related changes in distributions of commercial fish such as mackerel and herring will mean new fishery and ecosystem management plans are going to be needed, says the report’s co-author, Helle Siegstad, head of the Department for Fish and Shellfish at the Greenland Institute of Natural Resources.

The Denmark Strait tuna will be discussed at the annual science conference of the International Council for the Exploration of the Sea (ICES), which starts on 15 September in the Spanish coastal city of A Coruña. – Climate News Network

Fresh water causes Antarctic seas to rise faster

Meltwater from Antarctic glaciers is causing sea levels to rise Image Jason Auch via Wikimedia Commons
Glacial meltwater is a key factor in the sea level rise in Antarctica
Image Jason Auch via Wikimedia Commons

By Tim Radford

Researchers in the UK have established that billions of tonnes of fresh water from melting glaciers are causing Antarctic sea levels to rise much higher and faster than the global average.

LONDON, 7 September, 2014 − Sea levels around Antarctica are rising faster than anywhere else in the southern ocean. The global average rise in ocean heights in the last 19 years has been 6cms, but the rise in seas around Antarctica is 2cms higher.

This seemingly counter-intuitive finding is certainly a consequence of melting ice in the Southern Ocean, but the connection with global warming is, for the moment, tenuous. The agency that is behind the rising sea levels is simply an excess of fresh water from melting glaciers − about 350 billion tonnes of it.

“Fresh water is less dense than salt water, and so in regions where an excess of fresh water has accumulated we expect a localised rise in sea level,” says Craig Rye, an oceanography researcher at of the University of Southampton in the UK, who, with colleagues, has published the findings in Nature Geoscience.

Partly because the oceans are warmer and are therefore expanding, and partly because the terrestrial glaciers are in retreat, global sea levels on average have crept up by about 3 millimetres a year. Waters off the Antarctic shelf seem to be gaining an additional 2mm a year.

Less saline

The scientists studied satellite scans of a region of more than a million square kilometres to make their finding, and used ship-based studies of the Antarctic sea water to confirm that is has become less saline.

The melting of the Antarctic ice sheet – German scientists recently calculated that around 125 cubic kilometres of meltwater is running off the continent each year − and the thinning of the floating ice shelves is enough to explain the unexpected rise.

Computer model studies confirm the interpretation that the rise is happening because the southern seas have just got fresher. The consequences in the longer term are uncertain.

Rye, a postgraduate researcher, said: “The interaction between air, sea and ice in these seas is central to the stability of the Antarctic ice sheet and global sea levels, as well as other environmental processes, such as the generation of Antarctic bottom water, which cools and ventilates much of the global ocean abyss.” – Climate News Network

Less snow won’t end blizzard hazard

Clearing a station platform in Brookly, New York, during the snowstorms in January this year Image: Patrick Cashin/MTA via Wikimedia Commons
Clearing a train station in New York during snowstorms in January this year
Image: Patrick Cashin/MTA via Wikimedia Commons

By Tim Radford

New research predicts that while there will be less snow in a warming world, the sort of severe snowstorms that caused chaos in the US this year will remain a serious hazard.

LONDON, 6 September, 2014 − There’s still a chance that some people who dream of a white Christmas will get their wish. While there may be less snow falling overall in a warming world, there will still be blizzards.

Paul O’Gorman, an atmospheric scientist at the Massachusetts Institute of Technology in the US, reports in Nature that he studied daily snowfall in the northern hemisphere through the prism of 20 different climate models. Each of these projected climate change over a century, according to various emissions of greenhouse gases.

He also looked at seasonal average and extreme snowfall events, both under current conditions and as the planet warms. And the conclusion is that the kind of snowstorms that hit the US in 2014 will remain a hazard, even though there may be fewer of them.

Climate models

“Many studies have looked at average snowfall over a season in climate models, but there’s less known about these very heavy snowfalls,” Dr O’Gorman said. “In some regions, it is possible for average snowfall to decrease but the snowfall extremes actually increase.”

Climate scientists have consistently warned that a rise in average planetary temperatures is likely to be accompanied by a rise in the frequency or intensity of extreme events.

By these, they usually mean windstorms, floods and heat waves. But ice storms remain part of the picture too. That is because even as temperatures on average creep up, there will be places and seasons where the rain could still turn to snow.

The study found that, under high warming scenarios, those low-lying regions with average winter temperatures normally just below freezing would see a 65% reduction in average winter snowfall. But in these places, the heaviest snowstorms on average became only 8% less intense. In the higher latitudes, extreme snowfall became more intense, with 10% more snow, even under scenarios of relatively high average warming.

Heaviest falls

There is a relatively narrow temperature range − just below freezing point − at which the heaviest snowfalls seem to occur.

“People may know the expression, ‘It’s too cold to snow,’” Dr O’Gorman said. “If it’s very cold, there is too little water vapour in the air to support a very heavy snowfall, and if it’s too warm, most of the precipitation will fall as rain.

“Snowfall extremes still occur in the same narrow temperature range with climate change, and so they respond differently to climate change compared to rainfall extremes or average snowfall.” – Climate News Network

Sun sheds light on Arctic carbon puzzle

Sun reflects through ice crystals on the Arctic Ocean Image: Mike Dunn/NOAA Climate Program via Wikimedia Commons
The sun reflects from ice crystals on the Arctic Ocean
Image: Mike Dunn/NOAA Climate Program via Wikimedia Commons

By Tim Radford

Scientists discover that, as the Arctic continues to warm, sunlight will be the major cause of CO2 escaping into the atmosphere from vegetation preserved in frozen soil.

LONDON, 4 September, 2014 − One of the puzzles of the permafrost has been solved by scientists in the US. The key to the carbon cycle in the Arctic north is not the microbe population − it’s the sunlight.

Such a discovery is not, strictly speaking, concerned with climate change, but with the more detailed question of how the world works – specifically, how the carbon that was once plant material gets back into the atmosphere.

However, since the Arctic permafrost is home to half of all the organic carbon trapped in the soils of the entire Earth, the finding is ominous.

The Arctic is one of the fastest warming regions on the planet. As it warms, more and more carbon dioxide is likely to escape from the half-decayed tundra vegetation preserved in the frozen soil and will find its way into the atmosphere, to accelerate still further warming.

For the moment, the study is another piece fitted into place in a wider understanding of the carbon cycle.

Organic carbon

Rose Cory, of the University of Michigan, US, reports with colleagues, in the journal Science, that they measured the speeds at which bacteria and sunlight converted dissolved organic carbon in the lakes and rivers of Alaska.

In the standard domestic garden compost heap, the hard work of turning such things as decaying cabbage stalks, potato peelings and grass cuttings back into carbon dioxide and methane is performed by microbes.

But visible and ultraviolet light beams also pack a punch. They too can oxidise organic carbon and turn it back into gas molecules.

In 2013, Dr Cory and colleagues established that levels of dissolved organic carbon in a region that was once permanently frozen were rising, giving microbes and other conversion processes a chance to get to work.

The researchers took samples of flowing and still water from 135 lakes and 73 rivers on Alaska’s North Slope over a three-year period, and then incubated them under differing conditions of light.

More efficient

They found that sunlight was 19 times more efficient than microbes at processing the carbon, and could account for between 70% and 95% of all the carbon released from Alaskan water.

“We’re likely to see more carbon dioxide released from thawing permafrost than people had previously believed,” Dr Cory said. “We are able to say that because we now know that sunlight plays a key role and that carbon released from thawing permafrost is readily converted to carbon dioxide once it is exposed to sunlight.”

Microbes are less efficient in low temperatures. And the sunlight works more efficiently because it can directly degrade the dissolved organic carbon, and can also convert it into a condition that makes it more accessible for the microbes.

“This is because most of the fresh water in the Arctic is shallow, meaning sunlight can reach the bottom of any river – and most lakes – so that no dissolved organic carbon is kept in the dark,” said Byron Crump, a microbial ecologist at Oregon State University, and a co-author of the report. “Also there is little shading of rivers and lakes in the Arctic because there are no trees.” – Climate News Network