For billions of years, life on Earth remained relatively simple. Only single-celled organisms that could live with little or no oxygen were able to survive in the seas.

Eventually, the rise of oxygen led to a proliferation of diverse, multicellular life. However the oceans have not remained unchanged since that chemical and biological revolution.

At several times in geological history, they have partially reverted back to their original bacterially-dominated, oxygen-free state – and they could do so again.

Today rising CO₂ levels are making the oceans warmer and more acidic. Deforestation and intensive farming are causing soils and nutrients to be flushed into the sea.

And increasingly, the oceans are being stripped of oxygen, leaving large ‘dead zones‘ in the Gulf of Mexico, the Baltic Sea and the Atlantic off West Africa.

These dead zones, smaller-scale revivals of the primeval oceans that existed before complex life, appear to be caused by poor land management, such as fertilisers draining from farms into the sea. It is a process that could be exacerbated by climate change – as has happened in the past.

How oceans become ‘dead’

Oceans lose their oxygen when animals and bacteria consume it faster than it can be replenished. This usually comes about in stagnant or algae-rich waters. In severe cases, all oxygen can be consumed rendering the waters ‘anoxic’ and inhospitable to animal life.

This happens today in isolated fjords and basins. And it has happened on a larger scale throughout Earth’s history, especially during the Cretaceous, towards the end of the dinosaur era 145-66m years ago. Then, large parts of the ancient oceans became anoxic, allowing vast amounts of organic matter to escape degradation, and in many cases forming deposits of oil and gas.

We can examine the extent of anoxia by looking for a certain type of ‘green sulfur bacteria‘ which require both sunlight and oxygen-depleted waters in order to conduct their rather exotic form of photosynthesis. Evidence of their presence can be found in ancient rocks – molecular proof that anoxia once extended from the seafloor almost all the way to the ocean’s surface.

These oceans thrived with microbial life. But animals need oxygen, and vast portions of these ancient oceans would have become ‘dead’ to them.

Life in the deep sea

Unlike almost every other ecosystem on our planet, the deep sea is bereft of light and plants. Animals down there largely live off marine snow, the scraps of organic matter that somehow escape from the surface world and sink to the twilight realm below. In this energy-starved world, creatures live solitary lives in emptiness, darkness and mystery.

And yet life is there. Krill thrive on the slowly-sinking snow. Sperm whales dive deep to consume the krill and emerge with scars from giant squid. And when a whale dies and its carcass plummets to the seafloor, it is set upon by sharks and fish who emerge from the darkness for the unexpected feast.

Within days the carcass is stripped to the bones – but even then, massive colonies of tube worms spring to life. All of these animals, the fish, whales and worms, depend on oxygen. Our oxygen-rich seas are an incredible contrast to the North Atlantic during some anoxic events.

Then, plesiosaurs (see photo, above right) and ichthyosaurs, feeding on magnificent ammonites, would have been confined to the sunlit, oxygen-rich realm near the surface, their maximum depth of descent marked by a layer of pink and then green water, pigmented by bacteria.

And below it, where the deeper waters were anoxic, only single-celled organisms adapted to life without oxygen were able to survive.

Could this happen again?

Conventional wisdom has been that such extreme anoxia in the future is unlikely, that Cretaceous ‘dead zones’ were a consequence of a markedly different geography. The ancient Atlantic Ocean was smaller and more restricted, lending itself to these extreme conditions.

This is a bit like the modern Black Sea, a restricted basin where fresh river water sits stably above salty and dense marine deep water. But the Black Sea doesn’t quite match up with what we know about ancient anoxic oceans.

For a start, if driven solely by geographical shape, why were the oceans not anoxic as the norm rather than only at certain times? Sometimes much larger oceans became dead zones, or the anoxia was restricted to coastal areas. And although ocean circulation was slower during warm climates, it did not stop – unlike in the Black Sea.

This suggests geography was important but not exclusively so. Algal blooms are a more likely trigger. These algae would have flourished after dramatic increases in nutrients caused by erosion and chemical weathering, driven by higher carbon dioxide concentrations, global warming and/or changes in the hydrological cycle – all of which we now know occurred prior to several anoxic events.

It is likely that today’s coastal dead zones are due not to climate change but to our excessive use of fertilisers. And it is unlikely that our future will revisit the widespread ocean anoxia of the past.

But the lessons of the past do suggest global warming could exacerbate the impacts of our poor land management, adding yet another pressure to already stressed ecosystems.

Richard Pancost is Professor of Biogeochemistry and Director of the Cabot Institute, University of Bristol.

This article was originally published on The Conversation. Read the original article.

Ten new power reactors began supplying electricity last year (eight of them in China), and eight reactors were permanently shut down.

Nuclear power’s 20-year pattern of stagnation continues. In 1995 there were 434 ‘operable’ reactors – operating plus temporarily shut down reactors. In 2005 there were 441, and now there are 439.

Thus there are fewer reactors today than there were a decade ago. Moreover the 439 figure includes 41 reactors in Japan that have been shut down for several years, and not all of them will be restarted.

The nuclear power industry’s malaise was all too evident at the COP21 UN climate change conference in Paris in December. Former World Nuclear Association executive Steve Kidd noted:

“It was entirely predictable that the nuclear industry achieved precisely nothing at the recent Paris COP21 talks and in the subsequent international agreement. …

“Analysis of the submissions of the 196 governments that signed up to the Paris agreement, demonstrating their own individual schemes on how to reduce national carbon emissions, show that nearly all of them exclude nuclear power.

“The future is likely to repeat the experience of 2015 when 10 new reactors came into operation worldwide but 8 shut down. So as things stand, the industry is essentially running to stand still.”

According to the International Atomic Energy Agency, only seven out of 196 countries mentioned nuclear power in their climate change mitigation plans prepared for the COP21 conference: China, India, Japan, Argentina, Turkey, Jordan and Niger.

Now it’s getting nasty

A striking feature of the debates around the COP21 conference was the vitriol directed at the anti-nuclear and environmental movements. Tim Judson from the Nuclear Information and Resource Service noted:

“The industry’s rhetoric is getting increasingly desperate and personal. The industry rolled out a new front group called ‘Nuclear for Climate’, which handed out thousands of copies of a book attacking anti-nuclear activists and blaming us for the climate crisis.

“Needless to say, their efforts to intimidate activists are backfiring. In fact, they have given us a clear sign of how close we are to winning.

“Greenpeace International’s Kumi Naidoo reminded activists in a speech in December – in which he broadened the call for divestment to include nuclear, as well as fossil fuels – of the famous adage attributed to Gandhi about the path to victory: ‘First they ignore you. Then they laugh at you. Then they fight you. And then you win.'”

Perhaps the five stages of grief are relevant as nuclear lobbyists confront the reality that the nuclear renaissance didn’t eventuate and isn’t likely to. Denial and anger are very much in evidence, along with some bargaining (‘we need all low carbon power sources’), depression and, in time, acceptance.

China’s great leap forward

With 30 operable reactors, 24 under construction, and many more in the pipeline, China remains the only country with significant nuclear expansion plans. China is unlikely to meet any of its targets – 58 GW by 2020, 110 GW by 2030 and up to 250 GW by 2050 – but growth will be significant nonetheless.

Growth could however be derailed by a serious accident, which is all the more likely because of China’s inadequate nuclear safety standards, inadequate regulation, lack of transparency, repression of whistleblowers, world’s worst insurance and liability arrangements, security risks, and widespread corruption.

There are fears, for example, that China may press ahead with its twin-EPR project at Taishan despite fears over the metallurgy of its reactor vessels and heads. Similar components supplied to the EPR at Flamanville in France have been found to have areas of excessive carbon leading to brittleness and possible failure in use. The French project is now on hold and may never be completed.

Over the next 10-20 years, global nuclear capacity may increase marginally, with strong growth in China more than masking patterns of stagnation and decline elsewhere. Beyond that, the aging of the global fleet of power reactors will be sharply felt: the International Energy Agency anticipates almost 200 permanent shut-downs by 2040.

Steve Kidd notes that the industry is running to stand still, and it will have to run faster to stand still as the annual number of shut-downs increases.

Growth elsewhere?

India is the only other country where there is a possibility of significant nuclear growth in the nearish-future. But nuclear growth in India has been modest – six reactor start-ups over the past decade – and may remain so.

In early 2015, India claimed to have resolved one of the major obstacles to foreign investment by announcing measures to circumvent a liability law which does not completely absolve suppliers of responsibility for accidents.

But those claims were met with scepticism and a capital strike by most foreign suppliers is still in effect. Strong public opposition – and the Indian state’s brutal response to that opposition – will also continue to slow nuclear expansion.

India has just signed an ‘preliminary agreement’ with EDF to build a massive six-reactor EPR project at Jaitapur, 360km south of Mumbai. But given the still-unresolved liability issues and the EPR’s disastrous construction record to date, it’s hard imagine any but the most cautious of progress taking place.

Meanwhile renewables are surging ahead. One part of the Jaitapur deal that is likely to move ahead fast is 142MW of wind power in Gujarat that EDF is to develop with its Indian partner, SITAC.

And in mid-January 2016, the latest auction of solar energy capacity in India achieved a new record low price of 4.34 rupees / kWh (US$0.064; €0.059). Energy minister Piyush Goyal said: “Through transparent auctions with a ready provision of land, transmission and the like, solar tariffs have come down below thermal power cost.”

Russia has 35 operating reactors and eight under construction (including two very low power floating reactors). Only six reactors have started up over the past 20 years, and only four over the past decade. The pattern of slow growth will continue.

As for Russia’s ambitious nuclear export program, Steve Kidd noted in October 2014 that it “is reasonable to suggest that it is highly unlikely that Russia will succeed in carrying out even half of the projects in which it claims to be closely involved”.

South Korea has 25 operable reactors and three under construction. Six reactors have started up over the past decade. Along with China, India and Russia, South Korea is supposedly one of the four countries driving the ‘nuclear renaissance’. But the best the industry can hope for in South Korea is slow growth.

South Africa plans 9.6 GW of new nuclear capacity to add to the two Koeberg reactors. But the nuclear program is more theatre than reality. Pro-nuclear commentator Dan Yurman states:

“South Africa’s plans to build 9.6 GW of nuclear power will continue to be embroiled in political controversy and be hobbled by a lack of realistic financial plans to pay for the reactors.

“Claims by both Rosatom and Chinese state nuclear firms that they have won the business are not credible. Even if written down on paper, these claims of contracts cannot be guaranteed in the long term due to the political twists and turns by South African President Jacob Zuma.

“Most recently, he burned through three finance ministers over differences about whether the country could afford the cost of the reactors said to be at as much as US$100 billion including upgrades to the electrical grid. Additionally, Zuma is distracted by political and personal scandals.”

Brazil’s nuclear industry provided some theatre in 2015 with the arrest of Othon Luiz Pinheiro da Silva, the former CEO of Brazil’s nuclear power utility Eletronuclear, for allegedly accepting bribes to fix the bidding process for the Angra 3 reactor under construction 100 km from Rio de Janeiro. Fourteen other people were also charged as a result of the federal police’s ‘Operation Radioactivity’.

“The arrest is a tragedy for the industry,” said former Eletrobras’ chief executive Luiz Pinguelli Rosa. “The industry was already in crisis, but now the corruption concerns are bound to delay Angra 3 further and cause costs to rise even more.”

Newcomer countries: The World Nuclear Association claims that “over 45 countries are actively considering embarking upon nuclear power programmes.” Balderdash. Only two ‘newcomer’ countries are actually building reactors – Belarus and the United Arab Emirates. Other countries might join the nuclear club but newcomers will be few and far between.

Moreover, some countries are phasing out nuclear power. Countries with nuclear phase-out policies include Germany, Belgium, Taiwan, and Switzerland. Other countries – e.g. Sweden – may phase out nuclear power partly as a result of deliberate government policy and partly because of natural attrition: aging reactors are being shut down without replacement.

Stagnation and decline

Patterns of stagnation or slow decline in North America and western Europe can safely be predicted. In 2014, the European Commission forecast that EU nuclear generating capacity of 131 GW in 2010 will decline to 97 GW in 2025.

The European Commission forecasts that nuclear’s share of EU electricity generation will decline from 27% in 2010 to 21% in 2050, while the share from renewables will increase from 21% to 51.6%, and fossil fuels’ share will decline from 52% to 27%.

The most important nuclear power story of 2015 was legislation enacted in the French Parliament in July that will reduce nuclear’s share of electricity generation from 75% to 50% by ‘around’ 2025, and caps nuclear capacity at the current level of 63.2 GW.

The legislation also establishes a target of 32% of electricity generation from renewables by 2030, a 40% reduction in greenhouse gas emissions and a 20% reduction in overall energy consumption by 2030.

In April 2015, a report by ADEME, a French government agency under the Ministries of Ecology and Research, shows that 100% renewable electricity supply by 2050 in France is feasible and affordable.

French EPR reactor projects in France and Finland are three times over budget and many years behind schedule. As already noted, in April 2015 it was revealed that EDF’s Flamanville EPR under construction in France has a weak pressure vessel and head, and that the same problem may afflict China’s twin-EPR project with EDF at Taishan.

A January 2016 update to the World Nuclear Industry Status Report discusses the miserable state of the French nuclear industry:

“The French state-controlled AREVA, having announced an outlook of a further ‘heavy loss’ in 2015, was downgraded by credit-rating agency Standard & Poor’s to B+ (“highly speculative”). On 29 December 2015, the company plunged to a new historic low on the stock market (€5.30 compared to €72.50 eight years ago).

“On 7 December 2015, Euronext ejected the French heavy weight Électricité de France (EDF), largest nuclear utility in the world and “pillar of the Paris Stock Exchange”, from France’s key stock market index, known as CAC40. One day later, EDF shares lost another four percent of their value, which led to a new low, a drop of over 85 percent from its 2007 level. …

“The French nuclear industry’s international competitors are not doing much better. AREVA’s Russian counterpart Atomenergoprom as well as the Japanese controlled Toshiba-Westinghouse were both downgraded to ‘junk’ (‘speculative’) by credit-rating agencies during the year.”

Next door in Belgium, ageing reactors at Doel and Tihange – shut down a year ago because of serious safety concerns over numerous leaks and, at Tihange, 16,000 reactor vessel cracks – are scheduled to start up shortly, triggering serious concern across Europe. An Avaaz petition to be delivered to Belgium by German Environment Minister Barbara Hendricks on Monday has already attracted almost 500,000 signatures.

In the United States, utilities announced two more reactor shut-downs in 2015: the FitzPatrick reactor in New York will be shut down in 2016, and the Pilgrim reactor in Massachusetts will be closed between 2017 and 2019.

Five reactors are under construction but a greater number have been shut down recently or will be shut down in the next few years. The last reactor start-up was in 1996. In August 2015 the Environmental Protection Agency released its final Clean Power Plan, which failed to give the nuclear industry the subsidies and handouts it was seeking.

A decade ago, the US Nuclear Regulatory Commission was flooded with applications for US$127 billion (€117b) worth of reactor projects. Now, obituaries for the US nuclear power renaissance are increasingly common.

The situation is broadly similar in the United Kingdom – the nuclear power industry there is scrambling just to stand still. It should be clear by the end of this year whether the extraordinarily expensive Hinkley C EPR project will go ahead. But the signs are not good for the project’s backers: EDF was due to make its ‘final investment decision’ this week, but flunked out owing to its inability to raise the necessary £18 billion.

According to the World Nuclear Association, most of the UK’s reactors are to be retired by 2023. If other projects prove to be as expensive and difficult as Hinkley C, it’s unlikely that new nuclear capacity will match retirements.

In Japan, only two of the country’s 43 operable reactors are actually operating. Perhaps half to two-thirds of the reactors will eventually restart. Five reactors were permanently shut down in 2015, and the six reactors at Fukushima Daiichi have been written off.

Before the Fukushima disaster, Tokyo planned to add another 15-20 reactors to the fleet of 55, giving a total of 70-75 reactors. Thus, Japan’s nuclear power industry will be at most half the size it might have been if not for the Fukushima disaster.

Generation IV reactors to the rescue?

Rhetoric about ‘super safe’, ‘best thing since sliced bread’ Generation IV reactors will likely continue unabated. That said, critical reports released by the US and French governments last year may signal a slow shift away from Generation IV reactor rhetoric.

The report by the French Institute for Radiological Protection and Nuclear Safety (IRSN) – a government authority under the Ministries of Defense, the Environment, Industry, Research, and Health – states: “There is still much R&D to be done to develop the Generation IV nuclear reactors, as well as for the fuel cycle and the associated waste management which depends on the system chosen.”

IRSN is also sceptical about safety claims: “At the present stage of development, IRSN does not notice evidence that leads to conclude that the systems under review are likely to offer a significantly improved level of safety compared with Generation III reactors … “

The US Government Accountability Office released a report in July 2015 on the status of small modular reactors (SMRs) and other ‘advanced’ reactor concepts in the US. The report concluded:

“While light water SMRs and advanced reactors may provide some benefits, their development and deployment face a number of challenges … Depending on how they are resolved, these technical challenges may result in higher-cost reactors than anticipated, making them less competitive with large LWRs [light water reactors] or power plants using other fuels …

“Both light water SMRs and advanced reactors face additional challenges related to the time, cost, and uncertainty associated with developing, certifying or licensing, and deploying new reactor technology, with advanced reactor designs generally facing greater challenges than light water SMR designs.

“It is a multi-decade process, with costs up to $1 billion to $2 billion, to design and certify or license the reactor design, and there is an additional construction cost of several billion dollars more per power plant.”

Even SMR boosters are struggling to put a positive spin on the situation. Launching a Nuclear Energy Insider report on SMRs, lead author Kerr Jeferies said: “From the outside it will seem that SMR development has hit a brick wall, but to lump the sector’s difficulties together with the death of the so-called nuclear renaissance would be missing the point.”

According to a US think tank, 48 companies in north America, backed by more than US$1.6 billion (€1.5b) in private capital, are developing plans for advanced nuclear reactors. But even if all that capital was invested in a single R&D project, it would not suffice to commercialise a new reactor type.

The UK government also sees a big future for SMRs and has even promised to spend £250 million on “nuclear innovation and Small Modular Reactors”. But it will face two big problems. First, the money won’t go far. And second, nuclear power is already being outcompeted by wind and solar, which are getting cheaper all the time.

Dan Yurman notes in his review of nuclear developments in 2015: “Efforts by start-up type firms to build advanced reactors will continue to generate a lot of media hype, but questions are abundant as to whether this activity will result in prototypes.

“For venture capital firms that have invested in advanced designs, cashing out may mean licensing a design to an established reactor vendor rather than building a first-of-a-kind unit.”

Petition: ‘Belgium: Stop the next Chernobyl‘ by Avaaz.

Dr Jim Green is the national nuclear campaigner with Friends of the Earth Australia and editor of the Nuclear Monitor newsletter, where this article was originally published. Nuclear Monitor is published 20 times a year. It has been publishing deeply researched, often strongly critical articles on all aspects of the nuclear cycle since 1978. A must-read for all those who work on this issue!

The unusually hot summers in Europe over the last three decades are further evidence that human activities are largely responsible for recent global warming, according to new research.

The scientists say they have found no 30-year periods in the last 2,000 years that have exceeded the mean average European summer temperature of the years from 1986 to 2015.

The new research says that already most of Europe has experienced strong summer warming in the past few decades, with severe heatwaves in 2003, as well as in 2010 and in 2015.

This new data adds to the fears expressed by scientists this week that parts of the Mediterranean and Arctic regions will heat up by 3.4C and 6C respectively above pre-industrial levels.

Sonia Seneviratne, head of the land-climate dynamics group at Switzerland’s Institute for Atmospheric and Climate Science (ETH Zurich), and colleagues reported in Nature on the meaning of a 2C global average warming. She says:

“We even see starkly different rates of extreme warming over land when global average temperatures reach just 1.5C, which is the limit to the rate of warming agreed to at the Paris climate talks. At 1.5C, we would still see temperature extremes in the Arctic rise by 4.4C, and a 2.2C warming of extremes around the Mediterranean basin.”

Historical evidence

According to the new report, published in Environmental Research Letters “reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE …

“Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 year periods in either reconstruction that exceed the mean average European summer temperature of the last three decades (1986-2015 CE).”

The 45 scientists, from 13 countries, say their research now puts the current warmth in the context of the last 2,100 years, using tree-ring information and historical documentary evidence. Their interdisciplinary study involved the collaboration of researchers from Past Global Changes (PAGES), a core project of the global sustainability science programme, Future Earth.

During Roman times, up until the 3rd century, there were warm summers, followed by generally cooler conditions from the 4th to the 7th centuries. A generally warm medieval period was followed by a mostly cold Little Ice Age from the 14th to the 19th centuries.

The scientists say the pronounced warming early in the 20th century and in recent decades is well represented by the tree-ring data and historical evidence on which their reconstruction is based.

Time to prepare for future extreme climate events

They also say the evidence suggests that past natural changes in summer temperature are greater than previously thought, suggesting that climate models may underestimate the full range of future extreme events, including heatwaves.

This past variability has been associated with large volcanic eruptions and changes in the amount of energy received from the sun.

The scientists say their finding that temperatures over the last 30 years lie outside the range of these natural variations supports the conclusion reached by the Intergovernmental Panel on Climate Change that recent warming is mainly caused by human activity.

“We now have a detailed picture of how summer temperatures have changed over Europe for more than 2,000 years and we can use that to test the climate models that are used to predict the impacts of future global warming“, says the co-ordinator of the study, Professor Jürg Luterbacher, director of the department of geography at the Justus Liebig University of Giessen, Germany.

Professor Luterbacher co-authored a 2014 report titled ‘The year-long unprecedented European heat and drought of 1540 – a worst case‘, published in Climate Change. The report drew on more than 300 first-hand documentary weather report sources.

He and his colleagues wrote then that Europe was affected in 1540 by “an unprecedented 11-month-long megadrought … We found that an event of this severity cannot be simulated by state-of-the-art climate models.”

They concluded: “Given the large spatial extent, the long duration and the intensity of the 1540 heat and drought, the return of such an event in the course of intensified global warming involves staggering losses.”

Alex Kirby writes for Climate News Network.

For billions of years, life on Earth remained relatively simple. Only single-celled organisms that could live with little or no oxygen were able to survive in the seas.

Eventually, the rise of oxygen led to a proliferation of diverse, multicellular life. However the oceans have not remained unchanged since that chemical and biological revolution.

At several times in geological history, they have partially reverted back to their original bacterially-dominated, oxygen-free state – and they could do so again.

Today rising CO₂ levels are making the oceans warmer and more acidic. Deforestation and intensive farming are causing soils and nutrients to be flushed into the sea.

And increasingly, the oceans are being stripped of oxygen, leaving large ‘dead zones‘ in the Gulf of Mexico, the Baltic Sea and the Atlantic off West Africa.

These dead zones, smaller-scale revivals of the primeval oceans that existed before complex life, appear to be caused by poor land management, such as fertilisers draining from farms into the sea. It is a process that could be exacerbated by climate change – as has happened in the past.

How oceans become ‘dead’

Oceans lose their oxygen when animals and bacteria consume it faster than it can be replenished. This usually comes about in stagnant or algae-rich waters. In severe cases, all oxygen can be consumed rendering the waters ‘anoxic’ and inhospitable to animal life.

This happens today in isolated fjords and basins. And it has happened on a larger scale throughout Earth’s history, especially during the Cretaceous, towards the end of the dinosaur era 145-66m years ago. Then, large parts of the ancient oceans became anoxic, allowing vast amounts of organic matter to escape degradation, and in many cases forming deposits of oil and gas.

We can examine the extent of anoxia by looking for a certain type of ‘green sulfur bacteria‘ which require both sunlight and oxygen-depleted waters in order to conduct their rather exotic form of photosynthesis. Evidence of their presence can be found in ancient rocks – molecular proof that anoxia once extended from the seafloor almost all the way to the ocean’s surface.

These oceans thrived with microbial life. But animals need oxygen, and vast portions of these ancient oceans would have become ‘dead’ to them.

Life in the deep sea

Unlike almost every other ecosystem on our planet, the deep sea is bereft of light and plants. Animals down there largely live off marine snow, the scraps of organic matter that somehow escape from the surface world and sink to the twilight realm below. In this energy-starved world, creatures live solitary lives in emptiness, darkness and mystery.

And yet life is there. Krill thrive on the slowly-sinking snow. Sperm whales dive deep to consume the krill and emerge with scars from giant squid. And when a whale dies and its carcass plummets to the seafloor, it is set upon by sharks and fish who emerge from the darkness for the unexpected feast.

Within days the carcass is stripped to the bones – but even then, massive colonies of tube worms spring to life. All of these animals, the fish, whales and worms, depend on oxygen. Our oxygen-rich seas are an incredible contrast to the North Atlantic during some anoxic events.

Then, plesiosaurs (see photo, above right) and ichthyosaurs, feeding on magnificent ammonites, would have been confined to the sunlit, oxygen-rich realm near the surface, their maximum depth of descent marked by a layer of pink and then green water, pigmented by bacteria.

And below it, where the deeper waters were anoxic, only single-celled organisms adapted to life without oxygen were able to survive.

Could this happen again?

Conventional wisdom has been that such extreme anoxia in the future is unlikely, that Cretaceous ‘dead zones’ were a consequence of a markedly different geography. The ancient Atlantic Ocean was smaller and more restricted, lending itself to these extreme conditions.

This is a bit like the modern Black Sea, a restricted basin where fresh river water sits stably above salty and dense marine deep water. But the Black Sea doesn’t quite match up with what we know about ancient anoxic oceans.

For a start, if driven solely by geographical shape, why were the oceans not anoxic as the norm rather than only at certain times? Sometimes much larger oceans became dead zones, or the anoxia was restricted to coastal areas. And although ocean circulation was slower during warm climates, it did not stop – unlike in the Black Sea.

This suggests geography was important but not exclusively so. Algal blooms are a more likely trigger. These algae would have flourished after dramatic increases in nutrients caused by erosion and chemical weathering, driven by higher carbon dioxide concentrations, global warming and/or changes in the hydrological cycle – all of which we now know occurred prior to several anoxic events.

It is likely that today’s coastal dead zones are due not to climate change but to our excessive use of fertilisers. And it is unlikely that our future will revisit the widespread ocean anoxia of the past.

But the lessons of the past do suggest global warming could exacerbate the impacts of our poor land management, adding yet another pressure to already stressed ecosystems.

Richard Pancost is Professor of Biogeochemistry and Director of the Cabot Institute, University of Bristol.

This article was originally published on The Conversation. Read the original article.

The unusually hot summers in Europe over the last three decades are further evidence that human activities are largely responsible for recent global warming, according to new research.

The scientists say they have found no 30-year periods in the last 2,000 years that have exceeded the mean average European summer temperature of the years from 1986 to 2015.

The new research says that already most of Europe has experienced strong summer warming in the past few decades, with severe heatwaves in 2003, as well as in 2010 and in 2015.

This new data adds to the fears expressed by scientists this week that parts of the Mediterranean and Arctic regions will heat up by 3.4C and 6C respectively above pre-industrial levels.

Sonia Seneviratne, head of the land-climate dynamics group at Switzerland’s Institute for Atmospheric and Climate Science (ETH Zurich), and colleagues reported in Nature on the meaning of a 2C global average warming. She says:

“We even see starkly different rates of extreme warming over land when global average temperatures reach just 1.5C, which is the limit to the rate of warming agreed to at the Paris climate talks. At 1.5C, we would still see temperature extremes in the Arctic rise by 4.4C, and a 2.2C warming of extremes around the Mediterranean basin.”

Historical evidence

According to the new report, published in Environmental Research Letters “reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE …

“Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 year periods in either reconstruction that exceed the mean average European summer temperature of the last three decades (1986-2015 CE).”

The 45 scientists, from 13 countries, say their research now puts the current warmth in the context of the last 2,100 years, using tree-ring information and historical documentary evidence. Their interdisciplinary study involved the collaboration of researchers from Past Global Changes (PAGES), a core project of the global sustainability science programme, Future Earth.

During Roman times, up until the 3rd century, there were warm summers, followed by generally cooler conditions from the 4th to the 7th centuries. A generally warm medieval period was followed by a mostly cold Little Ice Age from the 14th to the 19th centuries.

The scientists say the pronounced warming early in the 20th century and in recent decades is well represented by the tree-ring data and historical evidence on which their reconstruction is based.

Time to prepare for future extreme climate events

They also say the evidence suggests that past natural changes in summer temperature are greater than previously thought, suggesting that climate models may underestimate the full range of future extreme events, including heatwaves.

This past variability has been associated with large volcanic eruptions and changes in the amount of energy received from the sun.

The scientists say their finding that temperatures over the last 30 years lie outside the range of these natural variations supports the conclusion reached by the Intergovernmental Panel on Climate Change that recent warming is mainly caused by human activity.

“We now have a detailed picture of how summer temperatures have changed over Europe for more than 2,000 years and we can use that to test the climate models that are used to predict the impacts of future global warming“, says the co-ordinator of the study, Professor Jürg Luterbacher, director of the department of geography at the Justus Liebig University of Giessen, Germany.

Professor Luterbacher co-authored a 2014 report titled ‘The year-long unprecedented European heat and drought of 1540 – a worst case‘, published in Climate Change. The report drew on more than 300 first-hand documentary weather report sources.

He and his colleagues wrote then that Europe was affected in 1540 by “an unprecedented 11-month-long megadrought … We found that an event of this severity cannot be simulated by state-of-the-art climate models.”

They concluded: “Given the large spatial extent, the long duration and the intensity of the 1540 heat and drought, the return of such an event in the course of intensified global warming involves staggering losses.”

Alex Kirby writes for Climate News Network.

For billions of years, life on Earth remained relatively simple. Only single-celled organisms that could live with little or no oxygen were able to survive in the seas.

Eventually, the rise of oxygen led to a proliferation of diverse, multicellular life. However the oceans have not remained unchanged since that chemical and biological revolution.

At several times in geological history, they have partially reverted back to their original bacterially-dominated, oxygen-free state – and they could do so again.

Today rising CO₂ levels are making the oceans warmer and more acidic. Deforestation and intensive farming are causing soils and nutrients to be flushed into the sea.

And increasingly, the oceans are being stripped of oxygen, leaving large ‘dead zones‘ in the Gulf of Mexico, the Baltic Sea and the Atlantic off West Africa.

These dead zones, smaller-scale revivals of the primeval oceans that existed before complex life, appear to be caused by poor land management, such as fertilisers draining from farms into the sea. It is a process that could be exacerbated by climate change – as has happened in the past.

How oceans become ‘dead’

Oceans lose their oxygen when animals and bacteria consume it faster than it can be replenished. This usually comes about in stagnant or algae-rich waters. In severe cases, all oxygen can be consumed rendering the waters ‘anoxic’ and inhospitable to animal life.

This happens today in isolated fjords and basins. And it has happened on a larger scale throughout Earth’s history, especially during the Cretaceous, towards the end of the dinosaur era 145-66m years ago. Then, large parts of the ancient oceans became anoxic, allowing vast amounts of organic matter to escape degradation, and in many cases forming deposits of oil and gas.

We can examine the extent of anoxia by looking for a certain type of ‘green sulfur bacteria‘ which require both sunlight and oxygen-depleted waters in order to conduct their rather exotic form of photosynthesis. Evidence of their presence can be found in ancient rocks – molecular proof that anoxia once extended from the seafloor almost all the way to the ocean’s surface.

These oceans thrived with microbial life. But animals need oxygen, and vast portions of these ancient oceans would have become ‘dead’ to them.

Life in the deep sea

Unlike almost every other ecosystem on our planet, the deep sea is bereft of light and plants. Animals down there largely live off marine snow, the scraps of organic matter that somehow escape from the surface world and sink to the twilight realm below. In this energy-starved world, creatures live solitary lives in emptiness, darkness and mystery.

And yet life is there. Krill thrive on the slowly-sinking snow. Sperm whales dive deep to consume the krill and emerge with scars from giant squid. And when a whale dies and its carcass plummets to the seafloor, it is set upon by sharks and fish who emerge from the darkness for the unexpected feast.

Within days the carcass is stripped to the bones – but even then, massive colonies of tube worms spring to life. All of these animals, the fish, whales and worms, depend on oxygen. Our oxygen-rich seas are an incredible contrast to the North Atlantic during some anoxic events.

Then, plesiosaurs (see photo, above right) and ichthyosaurs, feeding on magnificent ammonites, would have been confined to the sunlit, oxygen-rich realm near the surface, their maximum depth of descent marked by a layer of pink and then green water, pigmented by bacteria.

And below it, where the deeper waters were anoxic, only single-celled organisms adapted to life without oxygen were able to survive.

Could this happen again?

Conventional wisdom has been that such extreme anoxia in the future is unlikely, that Cretaceous ‘dead zones’ were a consequence of a markedly different geography. The ancient Atlantic Ocean was smaller and more restricted, lending itself to these extreme conditions.

This is a bit like the modern Black Sea, a restricted basin where fresh river water sits stably above salty and dense marine deep water. But the Black Sea doesn’t quite match up with what we know about ancient anoxic oceans.

For a start, if driven solely by geographical shape, why were the oceans not anoxic as the norm rather than only at certain times? Sometimes much larger oceans became dead zones, or the anoxia was restricted to coastal areas. And although ocean circulation was slower during warm climates, it did not stop – unlike in the Black Sea.

This suggests geography was important but not exclusively so. Algal blooms are a more likely trigger. These algae would have flourished after dramatic increases in nutrients caused by erosion and chemical weathering, driven by higher carbon dioxide concentrations, global warming and/or changes in the hydrological cycle – all of which we now know occurred prior to several anoxic events.

It is likely that today’s coastal dead zones are due not to climate change but to our excessive use of fertilisers. And it is unlikely that our future will revisit the widespread ocean anoxia of the past.

But the lessons of the past do suggest global warming could exacerbate the impacts of our poor land management, adding yet another pressure to already stressed ecosystems.

Richard Pancost is Professor of Biogeochemistry and Director of the Cabot Institute, University of Bristol.

This article was originally published on The Conversation. Read the original article.

The unusually hot summers in Europe over the last three decades are further evidence that human activities are largely responsible for recent global warming, according to new research.

The scientists say they have found no 30-year periods in the last 2,000 years that have exceeded the mean average European summer temperature of the years from 1986 to 2015.

The new research says that already most of Europe has experienced strong summer warming in the past few decades, with severe heatwaves in 2003, as well as in 2010 and in 2015.

This new data adds to the fears expressed by scientists this week that parts of the Mediterranean and Arctic regions will heat up by 3.4C and 6C respectively above pre-industrial levels.

Sonia Seneviratne, head of the land-climate dynamics group at Switzerland’s Institute for Atmospheric and Climate Science (ETH Zurich), and colleagues reported in Nature on the meaning of a 2C global average warming. She says:

“We even see starkly different rates of extreme warming over land when global average temperatures reach just 1.5C, which is the limit to the rate of warming agreed to at the Paris climate talks. At 1.5C, we would still see temperature extremes in the Arctic rise by 4.4C, and a 2.2C warming of extremes around the Mediterranean basin.”

Historical evidence

According to the new report, published in Environmental Research Letters “reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE …

“Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 year periods in either reconstruction that exceed the mean average European summer temperature of the last three decades (1986-2015 CE).”

The 45 scientists, from 13 countries, say their research now puts the current warmth in the context of the last 2,100 years, using tree-ring information and historical documentary evidence. Their interdisciplinary study involved the collaboration of researchers from Past Global Changes (PAGES), a core project of the global sustainability science programme, Future Earth.

During Roman times, up until the 3rd century, there were warm summers, followed by generally cooler conditions from the 4th to the 7th centuries. A generally warm medieval period was followed by a mostly cold Little Ice Age from the 14th to the 19th centuries.

The scientists say the pronounced warming early in the 20th century and in recent decades is well represented by the tree-ring data and historical evidence on which their reconstruction is based.

Time to prepare for future extreme climate events

They also say the evidence suggests that past natural changes in summer temperature are greater than previously thought, suggesting that climate models may underestimate the full range of future extreme events, including heatwaves.

This past variability has been associated with large volcanic eruptions and changes in the amount of energy received from the sun.

The scientists say their finding that temperatures over the last 30 years lie outside the range of these natural variations supports the conclusion reached by the Intergovernmental Panel on Climate Change that recent warming is mainly caused by human activity.

“We now have a detailed picture of how summer temperatures have changed over Europe for more than 2,000 years and we can use that to test the climate models that are used to predict the impacts of future global warming“, says the co-ordinator of the study, Professor Jürg Luterbacher, director of the department of geography at the Justus Liebig University of Giessen, Germany.

Professor Luterbacher co-authored a 2014 report titled ‘The year-long unprecedented European heat and drought of 1540 – a worst case‘, published in Climate Change. The report drew on more than 300 first-hand documentary weather report sources.

He and his colleagues wrote then that Europe was affected in 1540 by “an unprecedented 11-month-long megadrought … We found that an event of this severity cannot be simulated by state-of-the-art climate models.”

They concluded: “Given the large spatial extent, the long duration and the intensity of the 1540 heat and drought, the return of such an event in the course of intensified global warming involves staggering losses.”

Alex Kirby writes for Climate News Network.

For billions of years, life on Earth remained relatively simple. Only single-celled organisms that could live with little or no oxygen were able to survive in the seas.

Eventually, the rise of oxygen led to a proliferation of diverse, multicellular life. However the oceans have not remained unchanged since that chemical and biological revolution.

At several times in geological history, they have partially reverted back to their original bacterially-dominated, oxygen-free state – and they could do so again.

Today rising CO₂ levels are making the oceans warmer and more acidic. Deforestation and intensive farming are causing soils and nutrients to be flushed into the sea.

And increasingly, the oceans are being stripped of oxygen, leaving large ‘dead zones‘ in the Gulf of Mexico, the Baltic Sea and the Atlantic off West Africa.

These dead zones, smaller-scale revivals of the primeval oceans that existed before complex life, appear to be caused by poor land management, such as fertilisers draining from farms into the sea. It is a process that could be exacerbated by climate change – as has happened in the past.

How oceans become ‘dead’

Oceans lose their oxygen when animals and bacteria consume it faster than it can be replenished. This usually comes about in stagnant or algae-rich waters. In severe cases, all oxygen can be consumed rendering the waters ‘anoxic’ and inhospitable to animal life.

This happens today in isolated fjords and basins. And it has happened on a larger scale throughout Earth’s history, especially during the Cretaceous, towards the end of the dinosaur era 145-66m years ago. Then, large parts of the ancient oceans became anoxic, allowing vast amounts of organic matter to escape degradation, and in many cases forming deposits of oil and gas.

We can examine the extent of anoxia by looking for a certain type of ‘green sulfur bacteria‘ which require both sunlight and oxygen-depleted waters in order to conduct their rather exotic form of photosynthesis. Evidence of their presence can be found in ancient rocks – molecular proof that anoxia once extended from the seafloor almost all the way to the ocean’s surface.

These oceans thrived with microbial life. But animals need oxygen, and vast portions of these ancient oceans would have become ‘dead’ to them.

Life in the deep sea

Unlike almost every other ecosystem on our planet, the deep sea is bereft of light and plants. Animals down there largely live off marine snow, the scraps of organic matter that somehow escape from the surface world and sink to the twilight realm below. In this energy-starved world, creatures live solitary lives in emptiness, darkness and mystery.

And yet life is there. Krill thrive on the slowly-sinking snow. Sperm whales dive deep to consume the krill and emerge with scars from giant squid. And when a whale dies and its carcass plummets to the seafloor, it is set upon by sharks and fish who emerge from the darkness for the unexpected feast.

Within days the carcass is stripped to the bones – but even then, massive colonies of tube worms spring to life. All of these animals, the fish, whales and worms, depend on oxygen. Our oxygen-rich seas are an incredible contrast to the North Atlantic during some anoxic events.

Then, plesiosaurs (see photo, above right) and ichthyosaurs, feeding on magnificent ammonites, would have been confined to the sunlit, oxygen-rich realm near the surface, their maximum depth of descent marked by a layer of pink and then green water, pigmented by bacteria.

And below it, where the deeper waters were anoxic, only single-celled organisms adapted to life without oxygen were able to survive.

Could this happen again?

Conventional wisdom has been that such extreme anoxia in the future is unlikely, that Cretaceous ‘dead zones’ were a consequence of a markedly different geography. The ancient Atlantic Ocean was smaller and more restricted, lending itself to these extreme conditions.

This is a bit like the modern Black Sea, a restricted basin where fresh river water sits stably above salty and dense marine deep water. But the Black Sea doesn’t quite match up with what we know about ancient anoxic oceans.

For a start, if driven solely by geographical shape, why were the oceans not anoxic as the norm rather than only at certain times? Sometimes much larger oceans became dead zones, or the anoxia was restricted to coastal areas. And although ocean circulation was slower during warm climates, it did not stop – unlike in the Black Sea.

This suggests geography was important but not exclusively so. Algal blooms are a more likely trigger. These algae would have flourished after dramatic increases in nutrients caused by erosion and chemical weathering, driven by higher carbon dioxide concentrations, global warming and/or changes in the hydrological cycle – all of which we now know occurred prior to several anoxic events.

It is likely that today’s coastal dead zones are due not to climate change but to our excessive use of fertilisers. And it is unlikely that our future will revisit the widespread ocean anoxia of the past.

But the lessons of the past do suggest global warming could exacerbate the impacts of our poor land management, adding yet another pressure to already stressed ecosystems.

Richard Pancost is Professor of Biogeochemistry and Director of the Cabot Institute, University of Bristol.

This article was originally published on The Conversation. Read the original article.

The unusually hot summers in Europe over the last three decades are further evidence that human activities are largely responsible for recent global warming, according to new research.

The scientists say they have found no 30-year periods in the last 2,000 years that have exceeded the mean average European summer temperature of the years from 1986 to 2015.

The new research says that already most of Europe has experienced strong summer warming in the past few decades, with severe heatwaves in 2003, as well as in 2010 and in 2015.

This new data adds to the fears expressed by scientists this week that parts of the Mediterranean and Arctic regions will heat up by 3.4C and 6C respectively above pre-industrial levels.

Sonia Seneviratne, head of the land-climate dynamics group at Switzerland’s Institute for Atmospheric and Climate Science (ETH Zurich), and colleagues reported in Nature on the meaning of a 2C global average warming. She says:

“We even see starkly different rates of extreme warming over land when global average temperatures reach just 1.5C, which is the limit to the rate of warming agreed to at the Paris climate talks. At 1.5C, we would still see temperature extremes in the Arctic rise by 4.4C, and a 2.2C warming of extremes around the Mediterranean basin.”

Historical evidence

According to the new report, published in Environmental Research Letters “reconstructions indicate that the mean 20th century European summer temperature was not significantly different from some earlier centuries, including the 1st, 2nd, 8th and 10th centuries CE …

“Recent summers, however, have been unusually warm in the context of the last two millennia and there are no 30 year periods in either reconstruction that exceed the mean average European summer temperature of the last three decades (1986-2015 CE).”

The 45 scientists, from 13 countries, say their research now puts the current warmth in the context of the last 2,100 years, using tree-ring information and historical documentary evidence. Their interdisciplinary study involved the collaboration of researchers from Past Global Changes (PAGES), a core project of the global sustainability science programme, Future Earth.

During Roman times, up until the 3rd century, there were warm summers, followed by generally cooler conditions from the 4th to the 7th centuries. A generally warm medieval period was followed by a mostly cold Little Ice Age from the 14th to the 19th centuries.

The scientists say the pronounced warming early in the 20th century and in recent decades is well represented by the tree-ring data and historical evidence on which their reconstruction is based.

Time to prepare for future extreme climate events

They also say the evidence suggests that past natural changes in summer temperature are greater than previously thought, suggesting that climate models may underestimate the full range of future extreme events, including heatwaves.

This past variability has been associated with large volcanic eruptions and changes in the amount of energy received from the sun.

The scientists say their finding that temperatures over the last 30 years lie outside the range of these natural variations supports the conclusion reached by the Intergovernmental Panel on Climate Change that recent warming is mainly caused by human activity.

“We now have a detailed picture of how summer temperatures have changed over Europe for more than 2,000 years and we can use that to test the climate models that are used to predict the impacts of future global warming“, says the co-ordinator of the study, Professor Jürg Luterbacher, director of the department of geography at the Justus Liebig University of Giessen, Germany.

Professor Luterbacher co-authored a 2014 report titled ‘The year-long unprecedented European heat and drought of 1540 – a worst case‘, published in Climate Change. The report drew on more than 300 first-hand documentary weather report sources.

He and his colleagues wrote then that Europe was affected in 1540 by “an unprecedented 11-month-long megadrought … We found that an event of this severity cannot be simulated by state-of-the-art climate models.”

They concluded: “Given the large spatial extent, the long duration and the intensity of the 1540 heat and drought, the return of such an event in the course of intensified global warming involves staggering losses.”

Alex Kirby writes for Climate News Network.

For billions of years, life on Earth remained relatively simple. Only single-celled organisms that could live with little or no oxygen were able to survive in the seas.

Eventually, the rise of oxygen led to a proliferation of diverse, multicellular life. However the oceans have not remained unchanged since that chemical and biological revolution.

At several times in geological history, they have partially reverted back to their original bacterially-dominated, oxygen-free state – and they could do so again.

Today rising CO₂ levels are making the oceans warmer and more acidic. Deforestation and intensive farming are causing soils and nutrients to be flushed into the sea.

And increasingly, the oceans are being stripped of oxygen, leaving large ‘dead zones‘ in the Gulf of Mexico, the Baltic Sea and the Atlantic off West Africa.

These dead zones, smaller-scale revivals of the primeval oceans that existed before complex life, appear to be caused by poor land management, such as fertilisers draining from farms into the sea. It is a process that could be exacerbated by climate change – as has happened in the past.

How oceans become ‘dead’

Oceans lose their oxygen when animals and bacteria consume it faster than it can be replenished. This usually comes about in stagnant or algae-rich waters. In severe cases, all oxygen can be consumed rendering the waters ‘anoxic’ and inhospitable to animal life.

This happens today in isolated fjords and basins. And it has happened on a larger scale throughout Earth’s history, especially during the Cretaceous, towards the end of the dinosaur era 145-66m years ago. Then, large parts of the ancient oceans became anoxic, allowing vast amounts of organic matter to escape degradation, and in many cases forming deposits of oil and gas.

We can examine the extent of anoxia by looking for a certain type of ‘green sulfur bacteria‘ which require both sunlight and oxygen-depleted waters in order to conduct their rather exotic form of photosynthesis. Evidence of their presence can be found in ancient rocks – molecular proof that anoxia once extended from the seafloor almost all the way to the ocean’s surface.

These oceans thrived with microbial life. But animals need oxygen, and vast portions of these ancient oceans would have become ‘dead’ to them.

Life in the deep sea

Unlike almost every other ecosystem on our planet, the deep sea is bereft of light and plants. Animals down there largely live off marine snow, the scraps of organic matter that somehow escape from the surface world and sink to the twilight realm below. In this energy-starved world, creatures live solitary lives in emptiness, darkness and mystery.

And yet life is there. Krill thrive on the slowly-sinking snow. Sperm whales dive deep to consume the krill and emerge with scars from giant squid. And when a whale dies and its carcass plummets to the seafloor, it is set upon by sharks and fish who emerge from the darkness for the unexpected feast.

Within days the carcass is stripped to the bones – but even then, massive colonies of tube worms spring to life. All of these animals, the fish, whales and worms, depend on oxygen. Our oxygen-rich seas are an incredible contrast to the North Atlantic during some anoxic events.

Then, plesiosaurs (see photo, above right) and ichthyosaurs, feeding on magnificent ammonites, would have been confined to the sunlit, oxygen-rich realm near the surface, their maximum depth of descent marked by a layer of pink and then green water, pigmented by bacteria.

And below it, where the deeper waters were anoxic, only single-celled organisms adapted to life without oxygen were able to survive.

Could this happen again?

Conventional wisdom has been that such extreme anoxia in the future is unlikely, that Cretaceous ‘dead zones’ were a consequence of a markedly different geography. The ancient Atlantic Ocean was smaller and more restricted, lending itself to these extreme conditions.

This is a bit like the modern Black Sea, a restricted basin where fresh river water sits stably above salty and dense marine deep water. But the Black Sea doesn’t quite match up with what we know about ancient anoxic oceans.

For a start, if driven solely by geographical shape, why were the oceans not anoxic as the norm rather than only at certain times? Sometimes much larger oceans became dead zones, or the anoxia was restricted to coastal areas. And although ocean circulation was slower during warm climates, it did not stop – unlike in the Black Sea.

This suggests geography was important but not exclusively so. Algal blooms are a more likely trigger. These algae would have flourished after dramatic increases in nutrients caused by erosion and chemical weathering, driven by higher carbon dioxide concentrations, global warming and/or changes in the hydrological cycle – all of which we now know occurred prior to several anoxic events.

It is likely that today’s coastal dead zones are due not to climate change but to our excessive use of fertilisers. And it is unlikely that our future will revisit the widespread ocean anoxia of the past.

But the lessons of the past do suggest global warming could exacerbate the impacts of our poor land management, adding yet another pressure to already stressed ecosystems.

Richard Pancost is Professor of Biogeochemistry and Director of the Cabot Institute, University of Bristol.

This article was originally published on The Conversation. Read the original article.