Streams may emit more carbon dioxide in a warmer climate

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Streams and rivers could pump carbon dioxide into the air at increasing rates if they continue to warm, potentially compounding the effects of global warming, a new worldwide analysis has shown.

To reach that conclusion, an international research team conducted the first continental-scale study of flows into and out of streams across six major climatic zones. They collected data in watersheds from Puerto Rico and Oregon to Australia and Alaska. In each one, scientists analyzed the balance between photosynthesis—which uses atmospheric CO2 to generate plant material such as roots and leaves—and respiration, which pumps CO2 back into the air.

The scientists published their results this week in the journal Nature Geoscience.

The issue is important because the world’s rivers and streams exchange carbon with the atmosphere at rates that are comparable with land-based ecosystems and the oceans. If continues, an increase in stream-based carbon emissions could add to the concentration of heat-trapping CO2 in the atmosphere.

“This paper is the first to look at the effects of climate change on stream metabolism at the continental scale using field observations,” said Alba Argerich, co-author who monitored McRae Creek and Lookout Creek in the H. J. Andrews Experimental Forest east of Eugene, Oregon. “This approach takes into consideration the complexity of an ecosystem, as opposed to controlled experiments where you recreate simplified versions of an ecosystem.”

Argerich and other scientists monitored streams for water temperature, dissolved oxygen and sunlight at the water surface. The researchers also simulated the balance between net primary production (the product of photosynthesis by all organisms in the stream) and respiration under a 1-degree Celsius rise in stream temperature.

The net result of the simulations, they reported, was a 24 percent shift toward more respiration and CO2 emissions. However, not all streams are projected to respond in the same manner. The shift toward more CO2 emissions appears to be more pronounced in warmer streams, the scientists found, while colder streams might actually see an increase in net primary production. Carbon cycling in streams can also be affected by other factors such as the plants and microbes in the stream ecosystem and nutrients flowing into the water from surrounding lands.

Argerich conducted her work as a researcher in the College of Forestry at Oregon State University. She is now an assistant professor in the School of Natural Resources at the University of Missouri.

In previous work at the H.J. Andrews Forest, Argerich showed that small streams can export surprising amounts of carbon both downstream and to the atmosphere. “This paper confirms the role of streams as an active source of CO2 to the atmosphere, which can be even become more important as global temperatures increase,” she said.

Source: phys.org

(Dipla Aikaterini)

New research reveals ocean waves play greater role in trapping carbon dioxide

For decades scientists have investigated the influence of the world’s oceans in trapping greenhouse gasses. But a groundbreaking new study involving an academic from Heriot-Watt University has found waves play a greater role in this process than previously understood.

The research, published in Scientific Reports, shows that when waves break on the surface, such as in high winds, a substantial number of bubbles are injected to depths of at least one metre. These bubbles tend to partially dissolve, releasing into the water. The discovery means an increase in the current global estimates of the oceanic sink of carbon dioxide and rates of ocean acidification.

Led by the University of Southampton, the study was published in collaboration with UK-based scientists including Dr. David Woolf at Heriot-Watt’s Orkney Campus. He applied his expertise in modelling the processes of air-sea gas exchange for the project and said: “The role of bubbles in the air-sea exchange of gases has been of interest for decades, but firm conclusions have been prevented by a lack of adequate data. Participation in this project has been very rewarding since measurements are finally giving us the information we need.”

The results of the study, titled ‘Asymmetric transfer of CO2 across a broken sea surface’, indicate a much larger imbalance of carbon dioxide than previously suggested, contradicting an assumption inherent in most existing estimates of ocean atmosphere gas transfer.

The research could help the science community gain a stronger understanding of the influence of the ocean in contributing to global climate control.

Professor Tim Leighton, Principal Investigator for the study from the University of Southampton, said: “If the amount of carbon dioxide dissolving into the seas from the atmosphere exactly balanced the amount leaving the seas and entering the atmosphere, we would have a steady state situation.

“However, our data suggests that in stormy seas the bubble-induced asymmetry in dissolving into the oceans, as compared to previously dissolved carbon dioxide being released back into the atmosphere, is many times greater than scientists currently estimate.

“The excess Co2, which gas dissolves into stormy seas through bubbles, will increase as the proportion of CO2 in the atmosphere increases.

The study was published in collaboration between Professor Tim Leighton, his Ph.D. student Dr. David Coles, Professor Paul White at the University of Southampton’s Institute of Sound and Vibration Research, Professor Meric Srokosz from the National Oceanography Centre and Dr. David Woolf.

The research team have passed on all of their methods, equipment, computer codes and findings to other groups around the UK for further investigation.

Source: phys.org

(Dipla Aikaterini)

Another extreme heat wave strikes the North Pole

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In four of the past five winters, the North Pole has witnessed dramatic temperatures spikes, which previously were rare. Now, in the lead up to summer, the temperature has again shot up to unusually high levels at the tip of the planet.

Scientists say this warming could hasten the melt of Arctic sea ice, which is already near record low levels.

In just the past few days, the temperature at the North Pole has soared to the melting point of 32 degrees, which is about 30-35 degrees (17-19 Celsius) above normal.

Much of the entire Arctic north of 80 degrees latitude is abnormally warm. The temperature averaged over the whole region appears to be the warmest on record for the time of year, dating back to at least 1958. It is about 18 degrees (10 Celsius) above the normal of 4 degrees (minus 16 Celsius).

As the warm air intruded the Arctic, sea ice melted suddenly. The Norway Ice Service tweeted the sea ice area near Svalbard, the small island chain between Norway and the North Pole, fell by about 32,000 square miles (82,000 square kilometers) to the second lowest area on record. The amount of ice lost is enough to cover the entire state of South Carolina.

Zachary Labe, a climate scientist at University of California in Irvine, said that such a pulse of warm, moist air into the Arctic can “have a long-lasting fingerprint” that preconditions the ice to melt more rapidly in the summer.

Indeed, a study published last year in the Journal of Geophysical Research found that these spring intrusions of warm, moist air can “can initiate sea ice melt that extends to a large area” through the summer and fall.

Already, Arctic sea ice is near its lowest extent on record. The Bering and Chukchi seas have never had so little ice in recorded history.

Interestingly, while much of the Arctic has turned abnormally warm, the cold air normally entrenched over the region has had to move somewhere. In recent days, it has parked over south central Greenland where temperatures are 30 to 35 degrees colder than normal.

Jesper Eriksen, a meteorologist with the Danish Meteorological Institute, tweeted that the temperature at Summit Station, near the top of the Greenland ice sheet, plummeted to minus 47 degrees (minus 44 Celsius), very close to the coldest temperature on record for the month of May of minus 50 (minus 45.6 Celsius).

The contrast between frigid air over interior Greenland and unusually mild air over the Arctic is leading to very stormy conditions over the Canadian Arctic Archipelago.

The warming of the Arctic and loss of ice are likely strongly connected to the buildup of greenhouse gases in the atmosphere from human activities. On Friday, a NOAA study was published that found that the “extraordinary heat” that affected the Arctic in 2016 “could not have happened without the steep increases in greenhouse gas concentrations.”

Source: washingtonpost.com

(Dipla Aikaterini)

The Sahara Desert Is Growing. Here’s What That Means

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The Sahara — the world’s biggest hot desert — is getting even bigger. In fact, it is currently about 10 percent larger than it was nearly a century ago, and scientists suggest that climate change is partly responsible.

In a new study, researchers examined rainfall data gathered across Africa, consulting records dating back to 1920 and noting how changing conditions affected regions around the boundaries of the great desert.

They discovered that while some natural climate cycles could partly explain reduced rainfall and desert expansion southward, human-driven climate change is also playing a part. And if climate change continues unchecked, the Sahara’s slow growth will likely continue, the study authors reported. [The Sahara: Facts, Climate and Animals of the Desert].

Previously, scientists had explored the Sahara’s expansion by examining satellite data dating back to the 1980s. This study, which was supported by the U.S. National Science Foundation, is the first to analyze long-term trends in rainfall and surface air temperature over a timescale of nearly an entire century, the study’s lead author, Natalie Thomas, a doctoral candidate in atmospheric and oceanic science at the University of Maryland, told Live Science.

Deserts are defined as places on Earth that receive less than 10 inches (25 centimeters) of rainfall per year, according to the U.S. Geological Survey (USGS). With a surface area of about 3.6 million square miles (9.4 million square kilometers), the Sahara is the third-largest desert in the world. Only the cold deserts are bigger: icy Antarctica’s frozen desert spans about 5.5 million square miles (14.2 million square km), and the Arctic desert covers around 5.4 million square miles (13.98 million square km), USGS reported.

“A strong expansion”

The study authors originally set out to examine seasonal cycles of temperature and rainfall across Africa, consulting data spanning 1920 to 2013. But their attention was quickly drawn to trends of decreasing precipitation in the Sahel, a semiarid region linking the Sahara to the savannas of Sudan. By looking at this more closely, they hoped to discover how rainfall trends might be linked to the Sahara’s growth over time, according to Thomas.

To a certain extent, many deserts’ boundaries expand and contract seasonally, as conditions fluctuate between wetter or drier. But the researchers found that there has been “a strong expansion” of the Sahara within the 20th century, Thomas said.

Depending on the season, the Sahara experienced growth of at least 11 percent, and it grew by as much as 18 percent during the driest summer months, according to data collected over roughly 100 years. Over the course of a century, it steadily expanded to become about 10 percent bigger than it was in 1920, the study authors reported.

Much of the Sahara’s overall size increase can be explained by climate cycles driven by anomalies in sea-surface temperatures. These cyclical changes in turn affect surface temperatures and precipitation on land, and their impact can last for decades, according to the study.

“Decades of drought”

One such cycle, the Atlantic Multidecadal Oscillation (AMO), entered what is known as a “negative phase” — with cooler-than-average sea-surface temperatures — in the 1950s, bringing heat and dry conditions to the Sahel region and fueling a drought that lasted until the 1980s, Thomas said.

Using statistical methods, the scientists compensated for the effects of the AMO on average rainfall, and thereby calculated how much of the Sahara’s growth could be explained by the dryness that the cycle’s negative phase produces. They estimated that the AMO accounted for about two-thirds of the desert’s expansion — but one-third of the Sahara’s remaining growth was likely the result of climate change.

The researchers’ findings point to changes that occur over decades rather than in a single year, and that makes it hard to predict exactly how the Sahara’s continued growth could affect the wildlife and people near its changing borders. But as the places where humans grow food become increasingly drier, some areas could become more vulnerable to drought, bringing a greater risk of famine to the people who live there, Thomas said.

The findings were published online (March 29) in the Journal of Climate.

Source: livescience.com

(Dipla Aikaterini)

In Energy Breakthrough, India Added More Renewable Than Fossil Fuel Capacity for the First Time Last Year

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India added more energy capacity from renewable energy sources last year than from conventional sources like coal for the first time, an important breakthrough for a country that struggles with high greenhouse gas emissions and deadly air pollution.

Not only did renewables exceed conventional sources, they exceeded them by more than two times. Between April 2017 and March 2018, the subcontinent added about 11,788 megawatts of renewable energy capacity and only 5,400 megawatts of capacity from fossil fuels or large hydropower projects, Quartz India reported Thursday.

The vast majority of that that added capacity—9,009 megawatts—came from ground solar power. A total of 1,766 megawatts came from wind power, 352 came from rooftop solar and 657 megawatts came from biomass, small-scale hydropower and waste-to-energy.

The added capacity reflects an increased commitment by India’s government to add 175,000 megawatts of renewable energy capacity by 2022. However, while last year’s progress was impressive, it actually fell behind government targets for wind and rooftop solar. The government had set an added wind power capacity target of 4,000 megawatts and a rooftop solar capacity target of 1,000 megawatts.

Still, pushing past fossil fuels, which currently supply more than 70 percent of India’s power, is a good sign for the global fight against climate change. In 2016, India’s greenhouse gas emissions rose by 4.7 percent, more than any other major emitter’s, The Hindustan Times reported in September 2017.

It is also a positive move for a country with two of the world’s most polluted mega-cities, according to the latest World Health Organization (WHO) data released Tuesday. Delhi is the most polluted mega-city in the world, with pollution levels 10 times worse than WHO guidelines.

Pollution levels have gotten so bad that they are impacting one of the country’s most famous landmarks. The Indian Supreme Court warned on Tuesday that the Taj Mahal is turning brown and green due to air pollution and to excrement from insects attracted to the polluted Yamuna river nearby, The Independent reported Wednesday.

“It is very serious. It seems you are helpless. It has to be saved. You can get help from experts from outside to assess the damage done and restore it,” Supreme Court judges Madan Lokur and Deepak Gupta said, ordering the state government to fix the problem.

Source: ecowatch.com

(Dipla Katerina)

How valuable are trees?

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Megacities are on the rise. There are currently 47 such areas around the globe, each housing more than 10 million residents.

More than half the global population now lives in urban areas, comprising about 3 percent of the Earth. The ecological footprint of this growth is vast and there’s far more that can be done to improve life for urban residents around the world.

When it comes to natural spaces, trees are keystone species in the urban ecosystem, providing a number of services that benefit people. My research team has calculated just how much a tree matters for many urban areas, particularly megacities. Trees clean the air and water, reduce stormwater floods, improve building energy use and mitigate climate change, among other things.

For every dollar invested in planting, cities see an average of $2.25 return on their investment each year.

Measuring trees

Our team, led by Dr. David Nowak of the USDA Forest Service and Scott Maco of Davey Institute, develops the tree benefits software i-Tree Tools.

These tools simulate the relationship between trees and ecosystem services they provide. These services can include food, clean air and water, climate and flood control, pollination, recreation and noise damping. We currently don’t simulate many services, so our calculations actually underestimate the value of urban trees.

Volunteers Dalia Elbihi and her father, Faycal Elbihi, dig holes for new trees at Milby Park in Houston. Photo: Leslie Plaza Johnson, Freelancer / For The Chronicle / Freelance

Our software can simulate how a tree’s structure – such as height, canopy size and leaf area – affects the services it provides. It can estimate how trees will reduce water flooding or explore how trees will affect air quality, building energy use and air pollution levels in their community. It can also allow users to inventory trees in their own area.

Our systematic aerial surveys of 35 megacities suggest that 20 percent of the average megacity’s urban core is covered by forest canopy. But this can vary greatly. Trees cover just 1 percent of Lima, Peru, versus 36 percent in New York City.

We wanted to determine how much trees contribute to human well-being in the places where humans are most concentrated, and nature perhaps most distant. In addition, we wanted to calculate how many additional trees could be planted in each megacity to improve the quality of life.

How tree density affects a city

We looked in detail at 10 megacities around the world, including Beijing, Cairo, Mexico City, Los Angeles and London. These megacities are distributed across five continents and represent different natural habitats. Cairo was the smallest, at 1173 square kilometers, while Tokyo measured in at a whopping 18,720.

For most cities, we looked at Google Maps aerial imagery, randomly selecting 500 points and classifying each as tree canopy, grass, shrub and so on. We calculated that tree cover was linked to significant cost savings. Each square kilometer saved about $0.93 million in air pollution health care costs, $20,000 by capturing water runoff and $478,000 in building energy heating and cooling savings.

What’s more, the median annual value of carbon dioxide sequestered by megacity tree cover was $7.9 million. That comes out to about $17,000 per square kilometer. The total CO2 stored was valued at $242 million, using a measure called the social cost of carbon.

The sum of all annual services provided by the megacity trees had a median annual value of $505 million. That provides a median value of $967,000 per square kilometer of tree cover.

Trees in your city

An entire urban forest can provide services for a good life.

All the cities we studied had the potential to add additional trees, with about 18 percent of the metropolitan area on average available. Potential spots included areas with sidewalks, parking lots and plaza areas. The tree’s canopy could extend above the human-occupied area, with the trunk positioned to allow for pedestrian passage or parking.

New trees are planted in the Eastern Glades of Memorial Park in April 2018. Photo: Michael Ciaglo, Houston Chronicle / Houston Chronicle / Michael Ciaglo

Want to conserve forests and plant more trees in your area? Everyone can take action. City and regional planners can continue to incorporate the planning for urban forests. Those who are elected to office can continue to share a vision that the urban forest is an important part of the community, and they can advocate and support groups that are looking to increase it.

The ConversationIndividuals who cannot plant a tree might add a potted shrub, which is smaller than a tree but has a leafy canopy that can contribute similar benefits. For the property owner wanting to take charge, our i-Tree software can assist with selecting a tree type and location. A local arborist or urban forester could also help.

Theodore Endreny is Professor of Water Resources & Ecological Engineering at the State University of New York College of Environmental Science and Forestry

Source: houstonchronicle.com

(Dipla Katerina)

More than 95% of world’s population breathe dangerous air, major study finds

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More than 95% of the world’s population breathe unsafe air and the burden is falling hardest on the poorest communities, with the gap between the most polluted and least polluted countries rising rapidly, a comprehensive study of global air pollution has found.

Cities are home to an increasing majority of the world’s people, exposing billions to unsafe air, particularly in developing countries, but in rural areas the risk of indoor air pollution is often caused by burning solid fuels. One in three people worldwide faces the double whammy of unsafe air both indoors and out.

The report by the Health Effects Institute used new findings such as satellite data and better monitoring to estimate the numbers of people exposed to air polluted above the levels deemed safe by the World Health Organisation. This exposure has made air pollution the fourth highest cause of death globally, after high blood pressure, diet and smoking, and the greatest environmental health risk.

Experts estimate that exposure to air pollution contributed to more than 6m deaths worldwide last year, playing a role in increasing the risk of stroke, heart attack, lung cancer and chronic lung disease. China and India accounted for more than half of the death toll.

Burning solid fuel such as coal or biomass in their homes for cooking or heating exposed 2.6 billion people to indoor air pollution in 2016, the report found. Indoor air pollution can also affect air quality in the surrounding area, with this effect contributing to one in four pollution deaths in India and nearly one in five in China.

Bob O’Keefe, vice-president of the institute, said the gap between the most polluted air on the planet and the least polluted was striking. While developed countries have made moves to clean up, many developing countries have fallen further behind while seeking economic growth.

He said there was now an 11-fold gap between the most polluted and least polluted areas, compared with a six-fold gap in 1990. “Air pollution control systems still lag behind economic development [in poorer nations],” he said.

But he added: “There are reasons for optimism, though there is a long way to go. China seems to be now moving pretty aggressively, for instance in cutting coal and on stronger controls. India has really begun to step up on indoor air pollution, for instance through the provision of LPG [liquefied petroleum gas] as a cooking fuel, and through electrification.”

The number of people exposed to indoor air pollution from burning solid fuels has fallen from an estimated 3.6 billion around the world in 1990 to about 2.4 billion today, despite a rising population.

Emissions from transport are a growing concern, however, as road traffic increases. Diesel fuel is a leading cause of air pollution in some rich countries, including the UK, but in poorer countries the often decrepit state of many vehicles means petrol-driven engines can be just as bad in their outputs, especially of the fine particulate matter blamed for millions of deaths a year.

O’Keefe said governments were under increasing pressure to deal with the problems through regulation and controls, and hailed internet access as having a significant impact.

Social media has been very important, as a growing number of people have access to it and to data and discussions [on air pollution]. People now have the ability to worry about not just the food they eat and a roof over the head, but they have the means to discuss [issues] in public,” he said.

Tuesday’s report reinforces an increasing volume of data in recent years that has shown how air pollution is increasing and causing deaths. More data has become available in the past decade from satellites and on-the-ground monitoring, while large-scale studies have revealed more of the health risks arising from breathing dirty air, which rarely kills people directly but is now known to contribute to other causes of death.

Source: theguardian.com

(Dipla Katerina)

Mountain erosion may add CO2 to the atmosphere

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Scientists have long known that steep mountain ranges can draw carbon dioxide (CO2) out of the atmosphere—as erosion exposes new rock, it also starts a chemical reaction between minerals on hill slopes and CO2 in the air, “weathering” the rock and using CO2 to produce carbonate minerals like calcite.

A new study led by researchers from the Woods Hole Oceanographic Institution (WHOI), however, has turned this idea on its head. In paper released on April 12th in the journal Science, the scientists announced that the erosion process can also be a source of new CO2 gas, and can release it back into the atmosphere far faster than it’s being absorbed into newly-exposed rock.

“This goes against a long-standing hypothesis that more mountains mean more erosion and weathering, which means an added reduction of CO2. It turns out it’s much more complicated than that,” says Jordon Hemingway, a postdoctoral fellow at Harvard University and lead author on the paper.

The source of this extra CO2 isn’t entirely geological. Instead, it’s the byproduct of tiny microbes in mountain soils that “eat” ancient sources of organic that are trapped in the rock. As the microbes metabolize these minerals, they spew out .

The researchers came to this realization after studying one of the most erosion-prone mountain chains in the world—the central range of Taiwan. This steep-sided range is pummeled by more than three major typhoons each year, each of which mechanically erode the and rock through heavy rains and winds.

Hemingway and his colleagues examined samples of soil, bedrock, and river sediments from the central range, looking for telltale signs of organic carbon in the rock. What they found there surprised them.

“At the very bottom of the soil profile, you have basically unweathered rock. As soon as you hit the base of the soil, layer, though, you see that’s loose but not yet fully broken down, and at this point the present in the bedrock seems to disappear entirely,” notes Hemingway. At that point in the soil, the team also noticed an increase in lipids that are known to come from bacteria, he adds.

“We don’t yet know exactly which bacteria are doing this—that would require genomics, metagenomics, and other microbiological tools that we didn’t use in this study. But that’s the next step for this research,” says WHOI marine geochemist Valier Galy, senior author and Hemingway’s advisor in the MIT/WHOI Joint Program.

The group is quick to note that the total level of CO2 released by these microbes isn’t severe enough to have any immediate impact on climate change—instead, these processes take place on geologic timescales. The WHOI team’s research may lead to a better understanding of how mountain-based (or “lithospheric”) carbon cycles actually work, which could help generate clues to how CO2 has been regulated since the Earth itself formed.

“Looking backwards, we’re most interested in how these processes managed to keep the levels of CO2 in the atmosphere more or less stable over millions of years. It allowed Earth to have the climate and conditions it’s had—one that has promoted the development of complex life forms,” says Hemingway. “Throughout our Earth’s history, CO2 has wobbled over time, but has remained in that stable zone. This is just an update of the mechanism of geological processes that allows that to happen,” he adds.

Source: phys.org

(Dipla Katerina)

New Solar Capacity Exceeded All Other Fuel Sources Combined in 2017, Study Finds

In 2017, the world invested more in solar power than it did in any other energy technology and installed more new solar capacity than all other energy sources combined, including fossil fuels.

Those are the bright findings of a UN-backed report Global Trends in Renewable Energy Investment 2018, published Thursday.

The report, a collaboration between the United Nations Environment Programme, Bloomberg New Energy Finance, and the Frankfurt School of Finance and Management, found that investors committed $279.8 billion to renewable energy overall, excluding large dams, and $160.8 billion to solar specifically.

“The extraordinary surge in solar investment shows how the global energy map is changing and, more importantly, what the economic benefits are of such a shift,” UNEP head Erik Solheim said in a UN press release about the report.

Solheim added that those benefits included the creation of more better paying, higher quality jobs.

China was the decided leader in solar and renewable investment. It was responsible for more than half of the 98 gigawatts of solar capacity added last year and 45 percent of the dollars invested in renewables over all.

The U.S. followed China as No. 2 in the top 10 list of renewable-investing countries, but it lagged far behind. It invested $40.5 billion in renewable energy, down six percent from 2016. China, on the other hand, upped its investments by 30 percent to $126.1 billion.

Overall, 2017 continued a trend begun in 2015 of developing countries investing more in renewable energy than developed countries. Developing countries increased their investments by 20 percent to $177 billion, accounting for 63 percent of total investments, while developed countries decreased their investments by 19 percent to $103 billion.

Renewable energy investment in the UK, Germany and Japan all took major hits, falling by 65 percent, 35 percent and 28 percent, respectively. The countries still ranked seventh, fifth and third for overall investments.

Mexico, Australia and Sweden, meanwhile, increased their commitments by substantial amounts: 810 percent, 147 percent and 127 percent, in order. They were ranked ninth, tenth and sixth overall.

Rounding out the top 10 list were India at No. 4 and Brazil at No. 8. Together with China, the three emerging economies accounted for just over half of global renewable investments.

While they didn’t make it onto the top ten, Egypt and the United Arab Emirates made impressive strides, increasing their renewable investments by six times and 29 times, respectively.

As solar investments rose, costs fell. The cost per megawatt-hour for a solar installation dropped by 15 percent to $86.

However, while the reported investments bode good things for the future, the report found that present energy use shows we still have a ways to go. The proportion of energy generated by renewable sources in 2017 was 12.1 percent, up from 11 percent the year before.

Climate change is moving faster than we are,” Solheim, UN Framework Convention on Climate Change Executive Secretary Patricia Espinosa, and Frankfurt School President Nils Stieglitz wrote in the report’s foreword. “Last year was the second hottest on record and carbon dioxide levels continue to rise. In electricity generation, new renewables still have a long way to go. While renewable generating costs have declined, and governments are phasing-out fossil fuel subsidies — they amounted to a total US$260 billion in 2016 — the transition needs to accelerate and be complemented by strong private finance that can make sure this global momentum continues,” they wrote.

Source: desmogblog.com

(Dipla Katerina)

Underwater melting of Antarctic ice far greater than thought, study finds

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Hidden underwater melt-off in the Antarctic is doubling every 20 years and could soon overtake Greenland to become the biggest source of sea-level rise, according to the first complete underwater map of the world’s largest body of ice.

Warming waters have caused the base of ice near the ocean floor around the south pole to shrink by 1,463 square kilometres – an area the size of Greater London – between 2010 and 2016, according to the new study published in Nature Geoscience.

The research by the UK Centre for Polar Observation and Modelling at the University of Leeds suggests climate change is affecting the Antarctic more than previously believed and is likely to prompt global projections of sea-level rise to be revised upward.

Until recently, the Antarctic was seen as relatively stable. Viewed from above, the extent of land and sea ice in the far south has not changed as dramatically as in the far north.

But the new study found even a small increase in temperature has been enough to cause a loss of five metres every year from the bottom edge of the ice sheet, some of which is more than 2km underwater.

“What’s happening is that Antarctica is being melted away at its base. We can’t see it, because it’s happening below the sea surface,” said Professor Andrew Shepherd, one of the authors of the paper. “The changes mean that very soon the sea-level contribution from Antarctica could outstrip that from Greenland.”

The study measures the Antarctic’s “grounding line” – the bottommost edge of the ice sheet across 16,000km of coastline. This is done by using elevation data from the European Space Agency’s CryoSat-2 and applying Archimedes’s principle of buoyancy, which relates the thickness of floating ice to the height of its surface.

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The greatest declines were seen in west Antarctica. At eight of the ice sheet’s 65 biggest glaciers, the speed of retreat was more than five times the rate of deglaciation since the last ice age. Even in east Antarctica, where some scientists – and many climate deniers – had previously believed ice might be increasing based on surface area, glaciers were at best stable and at worst in retreat when underwater ice was taken into account.

“It should give people more cause for concern,” said Shepherd. “Now that we have mapped the whole edge of the ice sheet, it rules out any chance that parts of Antarctica are advancing. We see retreat in more places and stasis elsewhere. The net effect is that the ice sheet overall is retreating. People can’t say ‘you’ve left a stone unturned’. We’ve looked everywhere now.”

The results could prompt an upward revision of sea-level rise projections. 10 years ago, the main driver was Greenland. More recently, the Antarctic’s estimated contribution has been raised by the Intergovernmental Panel on Climate Change. But its forecasts were based on measurements from the two main west Antarctic glaciers – Thwaites and Pine Island – a sample that provides an overly narrow and conservative view of what is happening when compared with the new research.

The study’s lead author, Hannes Konrad, said there was now clear evidence that the underwater glacial retreat is happening across the ice sheet.

“This retreat has had a huge impact on inland glaciers,” he said, “because releasing them from the sea bed removes friction, causing them to speed up and contribute to global sea level rise.”

Source: theguardian.com

(Dipla Katerina)