Rising ocean waters from global warming could cost trillions of dollars

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Ocean waters are rising because of global warming. They are rising for two reasons. First, and perhaps most obvious, ice is melting. There is a tremendous amount of ice locked away in Greenland, Antarctica, and in glaciers. As the world warms, that ice melts and the liquid water flows to the oceans.

The other reason why water is rising is that warmer water is less dense – it expands. This expansion causes the surface of the water to rise.

Rising oceans are a big deal. About 150 million people live within 1 meter (3 feet) of sea level. About 600 million live within 10 meters (33 feet) of sea level. As waters rise, these people will have to go somewhere. It is inevitable that climate refugees will have to move their homes and workplaces because of rising waters.

In some places, humans will be able to build sea walls to block off the water’s rise. But, in many places, that won’t be possible. For instance, Miami, Florida has a porous base rock that allows sea water to permeate through the soils. You cannot wall that off. In other places, any sea walls would be prohibitively expensive.

It isn’t just the inevitable march of sea level that is an issue. Rising waters make storm surges worse. A great example is Superstorm Sandy, which hit the US East Coast in 2012. It cost approximately $65 bn of damage. The cost was higher because of sea level rise caused by global warming.

Climate scientists do their best to project how much and how fast oceans will rise in the future. These projections help city planners prepare future infrastructure. My estimation is that oceans will be approximately 1 meter higher in the year 2100, that is what our infrastructure should be prepared for. What I don’t know is how much this will cost us as a society.

A very recent paper was published that looked into this issue. The authors analyzed the cost of sea level if we limit the Earth to 1.5°C or 2°C warming. They also considered the future cost using “business as usual” scenarios.

What the authors found was fascinating. If humans take action to limit warming to 1.5°C, they estimate sea level will rise 52 cm by the year 2100. If humans hold global warming to 2°C, sea levels will rise by perhaps 63 cm by 2100.

The difference (11 cm) could cost $1.4 tn per year if no other societal adaptation is made. This is a staggering number and in itself, should motivate us to take action.

But the authors went further, they considered an even higher future temperature scenario (one that is essentially business as usual). With that future, global annual flood costs would increase to a whopping $14 tn per year.

In the study, the authors considered which countries and regions would suffer most. It turns out upper middle income countries will be worse off, particularly China. Higher-income countries have a slightly better prognosis because of their present flood protection standards. But make no mistake about it, we will all suffer and the suffering will be very costly.

There are four important takeaways from this study. First, while the economic costs are large, there is some range of projections. The actual costs may be lower or higher than the median predicted in the study. This is largely due to the fact that we don’t know how fast Greenland and Antarctica will melt. If they melt faster than projected, things will be worse than what I’ve described here.

Second, adaptation will help. By adaptation I mean making our societies less susceptible to sea level rise. For example, building sea walls when possible, building new infrastructure away from coasts, putting in natural breaks to limit storm surge during large storms, and making infrastructure more water-resistant.

Third, what we do now matters. If we can get off the high-emissions business as usual scenarios – if we can increase investment in clean and renewable energy – we can reduce the future costs.

Finally, while scientists often use 2100 as a benchmark year, it isn’t like oceans will stop rising then. In fact, we are committing ourselves to hundreds of years of rising oceans. The ocean has a lot of climate inertia. Once it starts rising, you cannot stop it. So, by focusing only on the year 2100, we are deluding ourselves into underestimating the long term costs.

This research shows it’s important to connect climate science with economic science. Too often, social scientists and economists with very little climate science understanding have tried to tell us that climate change is not a problem. Whenever you hear an economist or a social scientist give you a rosy future prediction, take it with a grain of salt. Their opinion is worthless without being backed by physical understanding. And the loudest economists and social scientists often have very little of this physical understanding.

Source: theguardian.com

(Dipla Aikaterini)

Baltic Sea oxygen levels at ‘1,500-year low due to human activity’

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The coastal waters of the Baltic have been starved of oxygen to a level unseen in at least 1,500 years largely as a result of modern human activity, scientists say. Nutrient run-off from agriculture and urban sewage are thought to be to blame.

“Dead zones” – areas of sea, typically near the bottom, with a dearth of oxygen – are caused by a rise in nutrients in the water that boosts the growth of algae. When these organisms die and sink to the seafloor, bacteria set to work decomposing them, using up oxygen in the process.

The resulting lack of oxygen not only curtails habitats for creatures that live on the seafloor, but also affects fish stocks and can lead to blooms of toxic cyanobacteria.

But it is not a problem confined to the Baltic. Earlier this year a study revealed that ocean dead zones have quadrupled in size since the 1950s, and are found the world over in coastal regions of high population, from Europe to North America and China.

Researchers behind the latest study say that while nations are taking action to help waters rebound, individuals can help.

“In terms of the general public, one of the main things to do in the future may be to reduce the proportion of meat in the diet. Livestock agriculture generates higher nutrient losses per kilogram of food produced,” said Sami Jokinen, a PhD student at the University of Turku, and Tom Jilbert, an assistant professor of the University of Helsinki, who are co-authors of the research.

At present, the Baltic Sea dead zone extends across 70,000 km2 – an area almost twice the size of Denmark, Jokinen says. The team say the lack of oxygen in the waters at the bottom is seasonal, related to layering of the water resulting from summer heating of the surface.

While previous studies have revealed that oxygen depletion has occurred in the central Baltic at various points in time in the past several thousand years, the latest study looks at how oxygen levels have changed in coastal waters.

Writing in the journal Biogeosciences, the team, from Finland and Germany, describe how they probed the issue by removing two four-metre-long cores from a site between the coasts of Sweden and Finland.

The team used a host of measures to analyse one of the cores, including looking at the grain sizes of the sediment layers and ratios of different types of elements. They also used both cores to hunt for trace fossil burrows from organisms that lived in the sediment.

Among the findings, they found clear layers of sediment dating back to just over 100 years, suggesting that animals including bivalves and annelids disappeared from the bottom of the sea from this point.

The upshot was that the researchers were able to reconstruct how oxygen levels at the seafloor have changed over the past 1,500 years, revealing that while the degree of oxygen depletion in coastal areas has varied over the period – largely due to changes in the climate – there has been a marked depletion in the past 100 years or so.

The researchers say they were surprised to find that the steep drop in oxygen levels began before the postwar peak in urbanisation and intensive agriculture in the region in the 1950s. They say a combination of factors is likely to blame, including an uplift of the Baltic area as well as human activity – the latter a factor that appears to have become increasingly important.

“Our evidence of deoxygenation at the beginning of the 20th century suggests that the human influence was felt earlier – in other words, that the system is more sensitive than we thought previously,” Jokinen and Jilbert told the Guardian.

The pair note that since 2007, coastal nations around the Baltic Sea have attempted to improve the situation with an action plan to reduce nutrients flowing into the waters, and that oxygen levels are on the rise in waters off Stockholm. But, they add, global warming might be hindering progress, with no evidence of recovery seen in the regions examined.

“It is likely delaying the recovery process, because oxygen dissolves less easily in warm water,” they said.

Callum Roberts, professor of marine conservation at the University of York, who was not involved in the research, welcomed the study.

“Its great strengths are the fine-scale resolution of the timing of changes in conditions, and its ability to take us back all the way to Europe in the dark ages, long before the industrial revolution and modern population growth,” he said. “By doing so, the researchers can separate human from environmental forces shaping the Baltic, to show that Baltic dead zones are the responsibility of those who live along its shores.”

But, he said, the study also raised concerns.

“One troubling finding is that recent efforts to reduce pollution have not yet led to recovery,” said Roberts. “The Baltic is stuck in a vicious cycle in which low oxygen at the seabed releases nutrients trapped in bottom sediments to fuel yet more plankton bloom and bust that causes the dead zones to get bigger.”

Source: theguardian.com

(Dipla Aikaterini)

Most of Europe’s rivers and lakes fail water quality tests – report

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The vast majority of Europe’s rivers, lakes and estuaries have failed to meet minimum ecological standards for habitat degradation and pollution, according to a damning new report.

Only 40% of surface water bodies surveyed by the European Environmental Agency (EEA) were found to be in a good ecological state, despite EU laws and biodiversity protocols.

England was one of the poorer performers to emerge from the State of Our Waters report, which studied 130,000 waterways.

The EU’s environment commissioner, Karmenu Vella, said there had been a slight improvement in freshwater quality since 2010. “But much more needs to be done before all lakes, rivers, coastal waters and groundwater bodies are in good status,” he added. “Tackling pollution from agriculture, industry and households requires joint efforts from all water users throughout Europe.”

Scotland dramatically outperformed England in the clean water stocktake which covers the 2010-15 period, with water standards similar to much of Scandinavia.

Precise comparisons are difficult as reporting methodologies vary across Europe but water quality in England was in the bottom half of the European table, and had deteriorated since the last stocktake in 2010.

Peter Kristensen, the report’s lead author told the Guardian that higher population densities, more intensive agricultural practices, and better monitoring of waterways had all contributed to the result.

England is comparable to countries in central Europe with a high proportion of water bodies failing to reach good status,” he said. “The situation is much better in Scotland, where only around 45% of sites failed [to meet minimum standards].”

“It would be advisable for England to continue with legislation similar to the water framework directive after Brexit,” he added.

The directive aims to protect human health, water supply, ecosystems and biodiversity and was supposed to oblige EU countries to achieve a good ecological status for their waterways by 2015.

But they have not, and their failure to do so threatens the bloc’s 2020 biodiversity goals, according to Andreas Baumueller, WWF Europe’s head of natural resources.

“This report shows that we are nowhere [near] halting biodiversity loss by 2020,” he said. “It is just another symptom that we will miss the targets set by heads of states. The legislation is there in the form of the EU’s Water Framework Directive, but the political will is clearly lacking to make it work on the ground.”

The EEA survey revealed a divide between chemical pollution in ground and surface water sites. Three-quarters of groundwater samples were of good quality; 62% of rivers, estuaries and lakes were not.

Mercury contamination was one of the most common problems, with overuse of pesticides, inadequate waste treatment plants and tainted rainfall all contributing to the results.

Hans Bruyninckx, the EEA’s executive director said: “We must increase efforts to ensure our waters are as clean and resilient as they should be – our own wellbeing and the health of our vital water and marine ecosystems depend on it.”

Source: theguardian.com

(Dipla Aikaterini)

Global temperature rises could be double those predicted by climate modelling

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Temperature rises as a result of global warming could eventually be double what has been projected by climate models, according to an international team of researchers from 17 countries.

Sea levels could also rise by six metres or more even if the world does meet the 2 degree target of the Paris accord.

The findings, published last week in Nature Geoscience, were based on observations of evidence from three warm periods in the past 3.5m years in which global temperatures were 0.5-2 degrees above the pre-industrial temperatures of the 19th century.

The researchers say they increase the urgency with which countries need to address their emissions.

The scientists used a range of measurements to piece together the impacts of past climatic changes to examine how a warmer earth would appear once the climate has stabilised.

They found sustained warming of one to two degrees had been accompanied by substantial reductions of the Greenland and Antarctic ice sheets and sea level rises of at least six metres – several metres higher than what current climate models predict could occur by 2100.

“During that time, the temperatures were much warmer than what our models are predicting and the sea levels were much higher,” said Katrin Meissner from the University of New South Wales’s Climate Change Research Centre and one of the study’s lead authors.

She said the effects today would mean populous urban areas around the world and entire countries in the Pacific would be underwater.

Two degrees can seem very benign when you see it on paper but the consequences are quite bad and ecosystems change dramatically.”

Meissner said potential changes even at two degrees of warming were underestimated in climate models that focused on the near term.

“Climate models appear to be trustworthy for small changes, such as for low-emission scenarios over short periods, say over the next few decades out to 2100,” she said. “But as the change gets larger or more persistent … it appears they underestimate climate change.”

The researchers looked at three documented warm periods, the Holocene thermal maximum, which occurred 5,000 to 9,000 years ago, the last interglacial, which occurred 116,000 to 129,000 years ago, and the mid-Pliocene warm period, which occurred 3m to 3.3 m years ago.

In the case of the first two periods examined, the climate changes were caused by changes in the earth’s orbit. The mid-Pliocene event was the result of atmospheric carbon dioxide concentrations that were at similar levels to what they are today.

In each case, the planet had warmed at a much slower rate than it is warming at today as a result of rising greenhouse gas emissions caused by humans.

“Observations of past warming periods suggest that a number of amplifying mechanisms, which are poorly represented in climate models, increase long-term warming beyond climate model projections,” Prof Hubertus Fischer of the University of Bern, one of the study’s lead authors.

“This suggests the carbon budget to avoid 2°C of global warming may be far smaller than estimated, leaving very little margin for error to meet the Paris targets.”

Source: theguardian.com

(Dipla Aikaterini)

2017 Was a Really Bad Year for Tropical Forests

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Tropical forests suffered some of their worst losses in history last year, according to a new report from the monitoring group Global Forest Watch.

About 39 million acres, or 61,000 square miles, of forest cover disappeared in 2017—an area approximately the size of Bangladesh. That makes it the second-worst year on record, topped only by losses in 2016.

It’s discouraging news for global climate mitigation efforts. Healthy tropical forests store vast amounts of carbon, while deforestation can release that carbon back into the atmosphere.

And research suggests declines in tropical forest cover are taking their toll: Last year, a blockbuster study in Science concluded that tropical forests—because of their widespread destruction—are actually a net source of carbon to the atmosphere, rather than a carbon sink, as many experts had previously assumed.

The new data present “an alarming story of the situation for the world’s rainforests”, Andreas Dahl-Jørgensen, deputy director of Norway’s International Climate and Forest Initiative, said during a teleconference announcing the findings. “We simply won’t meet the climate targets that we agreed [to] in Paris without a drastic reduction in tropical deforestation and restoration of forests around the world.

The findings were released yesterday morning as representatives from around the world convened in Oslo, Norway, for an international forum on conserving tropical forests. A major focus of the conference includes the role of forests in global climate action.

Several recent estimates have underscored the significant contributions of deforestation to global carbon output—both the 2017 Science paper and a more recent estimate from the Global Carbon Project have suggested that forest losses and degradation may account for more than 10 percent of the world’s emissions.

But while the potential of forests to store or emit carbon remains their most substantial role in global climate efforts, some scientists note that forest losses may influence climate in other ways, as well. A new report from the World Resources Institute, also released this week to coincide with the Oslo forum, points out that deforestation can affect local temperatures and even alter the local water cycle. The report cites a range of recent studies on these effects.

Tree cover, for instance, has the potential to either warm or cool a local climate, depending on a combination of factors. On the one hand, trees tend to be darker in color than their surroundings, meaning they absorb more sunlight and more heat. On the other hand, they also release water into the air through their leaves, and they help to break up landscapes in ways that can disperse heat—both factors that may cool the local climate. Trees also release certain chemical compounds into the atmosphere that can have either cooling or warming effects.

But some recent research suggests that the cooling effect of trees may win out—meaning deforestation can drive local temperatures up and exacerbate the influence of ongoing climate change. A paper published in Nature Climate Change in April, for instance, links deforestation in the Northern Hemisphere to an increase in the intensity of hot days throughout the year.

Overall, the study suggests that deforestation probably accounted for more than half the warming that occurred over North America between 1920 and 1980. This effect has now been outstripped by the growing influence of human-caused climate change, but the researchers say deforestation may still account for nearly a third of the region’s warming (Climatewire, April 24).

2016 paper in Science had a similar message, suggesting forest losses around the world generally drive local temperatures higher. In fact, on a global average, it suggests the warming they produce may be the equivalent of about 18 percent of the influence from human-caused greenhouse gas emissions.

Other research suggests that deforestation could affect regional precipitation patterns. Trees lose water through their leaves, putting moisture back into the air—so tree cover losses can lead to drier local climates.

The effect may be particularly pronounced in tropical rainforests. One 2015 study found that deforestation in the Amazon basin reduces the region’s rainfall—and suggests that if the current deforestation rate continues, average rainfall throughout the Amazon basin could decline by more than 8 percent by 2050.

The point, the WRI report notes, is that “tropical forest loss is having a larger impact on the climate than has been commonly understood.”

Deforestation and degradation contribute substantially to global carbon emissions, thus helping fuel the progression of human-caused climate change. And at the same time, other non-carbon climate effects of deforestation may also be compounding the influence of global warming.

“When you add up these impacts of forest loss, one thing is clear: People living closest to deforested areas face a hotter, drier reality,” said Nancy Harris of WRI, who co-authored the report with Michael Wolosin of Forest Climate Analytics.

The new findings from the Global Forest Watch add renewed urgency to the global conversation on forest conservation and its role in international climate mitigation.

“A lot is hinging on our success in reversing these trends,” Dahl-Jørgensen said.

Source: scientificamerican.com

(Dipla Aikaterini)