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Limiting global warming

December 4, 2024 By EarthWise Leave a Comment

A pressing question from the recently concluded 29th annual United Nations Climate Change Conference in Azerbaijan is how to transition away from fossil fuels and speed up climate mitigation in line with the 1.5 °C global warming target.

Keeping global average temperatures below 1.5 °C above pre-industrial levels is crucial to avoid the most severe impacts of climate change, including extreme weather, rising seas, biodiversity loss, and disruptions to food and water security.

According to a new study by researchers from Stockholm University, Chalmers University of Technology, and Uppsala University in Sweden, it is still possible to limit global warming to 1.5 °C. But the study found that the United States, the European Union, and 16 other countries will have to exceed their own current targets in order to achieve this global goal.

The study, which was recently published in the journal Nature Communications, introduced an “additional carbon accountability” indicator, which quantifies countries’ responsibility for mitigation and carbon dioxide removal in addition to achieving their own targets.

The study identified 18 countries that should be accountable for increasing their ambitions to stay within their equal per capita share of the global carbon budget for 1.5 °C. Additional carbon accountability is highest for the United States and China, and highest per capita for the United Arab Emirates, Russia, Saudi Arabia, and the U.S.

Failure to limit global warming risks catastrophic impacts of climate change.

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COP29: Possible to limit climate change to 1.5°C – if EU and 17 other countries go beyond their own targets

Photo, posted December 27, 2015, courtesy of Gerry Machen via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A structural battery

October 25, 2024 By EarthWise Leave a Comment

The size and especially the weight of batteries is a critical factor for most things that use them. Battery weight is a key limitation for computers and cell phones. It is even more of a limitation for electric cars, ships, or planes.

If the battery of a device or vehicle can also function as a load-bearing structure, its weight and energy consumption can be dramatically reduced. This concept of a structural battery is sometimes called massless energy storage. It has the potential to halve the weight of a laptop computer, make cell phones as thin as a credit card, and increase the range of an electric car by as much as 70%.

Researchers at Chalmers University in Sweden have been working on structural battery technology for many years. Their first published results in 2018 showed how stiff, strong carbon fibers could be used for chemical storage of electrical energy.

Since then, they have been creating batteries with increasing energy density. Their latest versions still have only a quarter of the capacity of today’s lithium-ion batteries. But if batteries can be part of the structure of a vehicle, for example, and can be made of lightweight materials like carbon fiber, then the overall weight of the vehicle can be greatly reduced and not nearly as much energy will be needed to power it.

The goal of the Chalmers research is to achieve battery performance that makes it possible to commercialize the technology. There is a lot of engineering work to be done before these structural batteries can go from laboratory proofs of concept to real world use. But the potential is quite promising.

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World’s strongest battery paves way for light, energy-efficient vehicles

Photo, posted August 8, 2024, courtesy of NOI Techpark via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Making wind turbines safer for birds

September 18, 2024 By EarthWise Leave a Comment

There are people who oppose the installation of wind turbines for a variety of reasons. It is true that wind turbines can be dangerous to birds. Estimates are that about 250,000 birds are killed flying into wind turbines each year in the U.S.

However, this data needs to be looked at in comparison to bird deaths from flying into electrical lines (25 million), vehicles (214 million), and building glass (at least 600 million). And even these figures pale in comparison to the more than 2 billion birds killed by domestic cats each year.

Despite these facts, it would still be great if fewer birds died from flying into wind turbines. Researchers at Oregon State University are part of a team looking at reducing bird collision risks from wind turbines by painting a single blade of the turbine black.

Recent research in Norway found that painting a single turbine blade black reduced the number of bird collisions by nearly 72%. Why should this work? The hypothesis is that the black-painted blades disrupt the visual uniformity of the airspace around the turbines and makes them more noticeable to birds, which prompts avoidance behavior.

The Norwegian data is based on a relatively small sample size and the Oregon State researchers as well as others in Spain, Sweden, and South Africa are working on more rigorous and comprehensive studies.

The hope is that this rather simple strategy could make windfarms safer for birds. Unfortunately, this approach is not likely to be very effective with bats, which rely more on auditory cues rather than visual cues.

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Scientists studying impact of painting wind turbine blade black to reduce bird collisions

Photo, posted May 21, 2024, courtesy of Roy Harryman via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Sodium-ion batteries

January 31, 2024 By EarthWise Leave a Comment

The transition away from fossil fuels is driving a rapidly increasing need for batteries. Both electric vehicles and energy storage for the electric grid are enormous consumers of batteries. At present, lithium-ion batteries are almost universally used for these purposes. They have been getting better all the time and cheaper all the time and are likely to be the answer for the foreseeable future. But they are not perfect.

Lithium is only found in a relatively small number of places and mining and extracting it is fairly expensive and environmentally unfriendly. Lithium-ion batteries also frequently contain cobalt, which has its own set of problems. There are also safety issues related to the flammability of lithium-ion batteries.

As a result, there continue to be numerous efforts to identify and develop alternative battery technologies. One of these is sodium-ion batteries, which are similar in many ways to lithium-ion batteries but in which sodium replaces lithium as the cathode material.

Sodium is extremely common – it’s found in ordinary salt – and sodium-ion batteries have a high energy density and are easy to produce. They should have a long lifetime and have a more benign environmental impact than lithium-ion. Many companies and researchers are working on sodium-ion batteries and are making good progress.

A study by Chalmers University in Sweden looked at the potential for sodium-ion batteries and found that the batteries are particularly promising for use in energy storage even in their current state of development and could eventually be used in cars. Whether sodium-ion batteries can be good enough and cheap enough quickly enough to give lithium-ion a run for its money remains to be seen.

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Resource-efficient and climate-friendly with sodium-ion batteries

Photo, posted March 12, 2013, courtesy of Chris Hunkeler via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A Better Way To Recycle Plastic | Earth Wise

July 25, 2022 By EarthWise Leave a Comment

The current state of plastic recycling is not very effective. Plastic recycling is only able to replace 15-20% of the fossil-fuel-derived raw material needed to produce society’s demand for plastic.

Researchers at Chalmers University in Sweden have now demonstrated how the carbon content in mixed waste could be used to replace all of the fossil raw materials in the production of new plastic. In principle, their technology could completely eliminate the climate impact of plastic materials.

According to the researchers, there are enough carbon atoms in waste to meet the needs of all global plastic production.

The Chalmers process is based on thermochemical technology and involves heating waste to 1100-1500 degrees Fahrenheit. The waste is thereby vaporized and when hydrogen is added, becomes a carbon-based substance that can replace the fossil-fuel building blocks of plastic. The method does not require sorting the waste materials. Different types of waste, such as old plastic products and even paper cups, with or without food residues, can be fed into the recycling reactors. The researchers are now developing the techniques required to utilize their recycling technology in the same factories in which plastic products are currently being made from fossil oil or gas.

The principle of the process is inspired by the natural carbon cycle in which plants break down into carbon dioxide when they wither and die, and then photosynthesis uses carbon dioxide and solar energy to grow new plants.

Producing new plastics would no longer require petroleum or other fossil fuels as raw materials. If the energy needed to drive the recycling reactors is taken from renewable sources, plastics could become the basis of a sustainable and circular economy.

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Pioneering recycling turns mixed waste into premium plastics with no climate impact

Photo, posted August 10, 2013, courtesy of Lisa Risager via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Climate Resilient Microalgae | Earth Wise

July 21, 2022 By EarthWise Leave a Comment

The plight of the world’s coral reefs has been a growing environmental crisis for many years. Coral reefs provide sustenance and income to half a billion people, are major tourist attractions, protect coastlines, and are important centers of biodiversity. And because of the warming climate as well as other effects of human activity, more than half of the world’s coral reefs are under stress.

The primary threat is coral bleaching, which is the disruption of the symbiotic relationship between coral polyps (which are tiny animals) and the heavily pigmented microalgae that live within the coral structures and provide most of the energy for the polyps. When corals are stressed, often because water temperatures are too high, they expel the microalgae within them. The structures then become transparent, leaving only the white skeletal corals. Bleached corals aren’t dead, but they are at great risk of starvation and disease until and unless new symbiont algae are acquired.

A new study by scientists at Uppsala University in Sweden investigated how different species of coral symbiont algae react to temperature stress. They discovered differences among symbiont cells that enable the prediction of how temperature stress tolerant the cells are. Such predictive ability could provide the means to identify and select more temperature-tolerant coral symbionts that could conceivably be introduced into coral host larvae in order to make corals more robust against climate change.

The research has a ways to go, but the new tools may help coral reef monitoring and increase the speed at which reef restoring efforts can create stocks of climate-resistant symbionts.

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Climate resilient microalgae could help restore coral reefs

Photo, posted September 28, 2009, courtesy of Matt Kieffer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Methane From Thawing Permafrost | Earth Wise

June 29, 2022 By EarthWise Leave a Comment

The Arctic permafrost contains a massive amount of carbon in the form of frozen soil, which contains remnants of plants and animals that died millennia ago. Estimates are that there is 2 ½ times as much carbon trapped in this Arctic soil than there is in total in the atmosphere today.

As the Arctic warms, the permafrost is starting to thaw. Once that happens, microbes begin to consume the previously frozen organic matter trapped in the soil. As part of this process, the microbes produce large amounts of methane, which is an extremely potent greenhouse gas. Thus, there continues to be great concern that wide-scale thawing of the permafrost would result in massive amounts of methane being released into the atmosphere.

A recent study in northern Sweden revealed a glimmer of hope. The study gauged methane emissions from a swath of permafrost that thawed in the 1980s and another that thawed 10 or 15 years later.

In the first area, as ice melted underground, water on the surface sank down into the soil. As the surface dried out, new plants emerged that helped to keep methane emissions buried underground.

Grasses found in wet areas have straw-like structures that convey oxygen to their roots. The straws also allow methane in the soil to escape into the atmosphere. As the areas dry out, other plants lacking the straws can sometimes replace the grasses. When methane can’t escape, soil bacteria break it down into carbon dioxide.

The result is that the permafrost releases only a tenth of the methane as expected. The hope is that changes in plant cover driven by climate change may limit methane emissions from thawing permafrost.

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Thawing Permafrost In Sweden Releases Less Methane Than Feared, Study Finds

Photo, posted July 7, 2014, courtesy of NPS Climate Change Response via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Importance Of City Trees | Earth Wise

January 28, 2022 By EarthWise Leave a Comment

It is well known that green spaces can improve the quality of life and create a better climate in cities. City trees and vegetation can help reduce urban heat island effects by shading buildings and roads, deflecting radiation from the sun, and releasing moisture into the atmosphere. City trees and green spaces have also been proven to increase property values, promote wildlife and plant diversity, reduce noise pollution, and improve human health. But how important are trees and vegetation for producing cleaner air in cities?

According to a new study led by researchers at the University of Gothenburg in Sweden, trees do contribute to cleaner air in cities, but the degree to which they do so varies greatly between different locations.

The research team measured air pollutants across seven urban settings in the city of Gothenburg, and compared them with pollutants on the leaves of deciduous trees. The researchers chose to focus on polycyclic aromatic hydrocarbons (PAHs), which are pollutants generated primarily during the incomplete combustion of organic materials, like coal, oil, and wood.

The results revealed that the pollutants in leaves did increase over time. The researchers were able to show a clear correlation between the level of air pollutants and the concentration of pollutants in leaves.

But at the same time, the researchers discovered that pollution levels varied greatly between measurement sites. For example, the levels of PAHs were seven times higher at the most polluted site (the city’s main bus station) than they were at a location on the periphery of the city.

The research team hopes its findings will be used to help guide the planning of future urban landscapes.

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Trees are important for cleaner air in cities

Photo, posted November 5, 2021, courtesy of Maria Eklind via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Batteries On Wheels | Earth Wise

December 24, 2021 By EarthWise Leave a Comment

Transportation accounts for nearly a quarter of the direct carbon dioxide emissions coming from burning fuel. As a result, electrification of transport is one of the major ways we can reduce emissions. Increasing the number of electric vehicles over time is essential for meeting emissions targets.

But electric vehicles have the potential to do more than deliver emissions reduction; they can also provide other energy services.

More and more electric cars provide over 200 miles of driving range, but most cars are actually driven no more than 30 miles a day. As a result, the fleet of electric cars represents a huge bank of energy stored in battery packs and mostly sitting around unused. This presents an opportunity to leverage this resource.

Car battery packs could be used to absorb excess renewable energy generated in the middle of the day (for example from solar installations) or at night (from wind farms) and potentially then to export stored energy to power homes and support the grid. This energy system is known as V2G, or vehicle-to-grid technology.

The University of Queensland in Australia has launched a unique international trial to see if the spare battery capacity in vehicles could be used for these purposes. The university has partnered with Teslascope, which is an online analytics platform used by Tesla owners to track the performance of their cars. Tesla owners wishing to be part of the study authorize the collection of their data and, in turn, receive a free 12-month subscription to the Teslascope service. The study will collect data from Tesla owners in Australia, the US, Canada, Norway, Sweden, Germany, and the UK.

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Can EV spare battery capacity support the grid?

Photo, posted February 8, 2009, courtesy of City of St Pete via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Transparent Wood | Earth Wise

June 14, 2021 By EarthWise Leave a Comment

In recent years, there have been efforts to change the nature of wood to give it new properties. People have demonstrated so-called augmented wood with integrated electronics, energy storage capabilities, and other properties. Several different groups of researchers have developed wood that is actually transparent.

In 2016, researchers at KTH Royal Institute of Technology in Stockholm demonstrated transparent wood made by selectively extracting lignin – the substance that makes up the cell walls of wood -and replacing it with a polymer. The result is a new material that is weatherproof, fairly fire resistant, stronger than wood, lighter than wood, and transparent.

When the lignin is removed from wood, the empty pores left behind need to be filled with something that restores the wood’s strength. The early versions of transparent wood used polymethyl methacrylate – essentially acrylic plastic – for this purpose. But that material is made from petroleum, so it is not an environmentally desirable approach.

Recently, the KTH researchers have successfully tested an eco-friendly alternative: limonene acrylate, which is a monomer made from renewable citrus, such as peel waste that can be recycled from the orange juice industry.

There are many potential applications for transparent wood as a structural material. These include load-bearing windows, skylights, and semi-transparent facades that are strong and thermally insulating and yet permit light to enter.

Transparent wood would be a very attractive material for many applications in that it comes from renewable sources and offers excellent mechanical properties including strength, toughness, low density, and low thermal conductivity.

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Citrus derivative makes transparent wood 100 percent renewable

Photo, posted October 12, 2018, courtesy of Mussi Katz via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Red Hot Chili Solar Panels | Earth Wise

April 9, 2021 By EarthWise Leave a Comment

The majority of solar panels in use today are made from either single-crystal or polycrystalline silicon, the same stuff used to make the ubiquitous chips in computers, cell phones, and countless other devices. In addition, a growing fraction of solar panels utilize thin-film technology, which offers cost and flexibility advantages.

Monocrystal silicon still provides the highest efficiency and longest lifespan in commercially available panels, but the lower costs and some other features of thin-film solar panels are growing that market over time.

More recently, perovskite solar cell technology has been a source of great interest in the research community. Perovskites are a class of minerals with a specific crystalline structure that already have uses in various applications. As a solar cell material, perovskites offer the potential for converting more sunlight to electricity, being manufactured far more cheaply using no exotic or expensive materials, being more defect-tolerant, as well as a having number of other advantages. They also have the potential for having very high efficiency.

Recently, a group of researchers in China and Sweden published results of studies demonstrating that the addition of a novel ingredient has increased the efficiency of perovskite solar cells to nearly 22%, which is better than most commercial silicon solar cells. The ingredient is capsaicin, the chemical that gives chili peppers their spicy sting. Adding capsaicin expands the grains that make up the active material of the solar cell, allowing the more effective transport of electricity.

Why did the researchers think of adding the active ingredient of hot peppers to a solar cell in the first place? So far, they aren’t saying.

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Solar panels capture more sunlight with capsaicin – the chemical that makes chili peppers spicy

Photo, posted August 16, 2019, courtesy of Pedro via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Electric Cars And The Environment | Earth Wise

April 20, 2020 By EarthWise Leave a Comment

There are articles in the media all the time questioning whether electric cars are really better for the environment than those powered by fossil fuels. The usual argument is that once emissions from vehicle production and electricity generation are taken into account, electric cars are no greener than gas cars, or even worse for the environment. Of course, these arguments tend to be made by oil companies and their supporters.

A new study by three European universities looked at this very issue in detail. They carried out a life-cycle assessment in which they not only calculated greenhouse gas emissions generated when using cars, but also in the production chain and waste processing.

Their conclusions are that under current conditions, driving an electric car is better for the climate than conventional gasoline cars in 95% of the world. The only exceptions are places like Poland, where almost all electricity comes from coal-fired plants.

Average lifetime emissions associated with electric cars are up to 70% lower than gas cars in countries like Sweden and France and about 30% lower in England.

It is important to note than in a few years, even inefficient electric cars will be less emission-intensive than gas cars because electricity generation is becoming less carbon-intensive all the time. The study projects that by 2050, half of the world’s cars will be electric resulting in carbon dioxide emission reductions of 1.5 billion tons.

The study states that the idea that electric cars could increase emissions is a myth. The detailed study has run the numbers for all around the world and even in the worst-case scenario, there would be a reduction in emissions in almost all cases.

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Electric cars better for climate in 95% of the world

Photo, posted February 13, 2019, courtesy of Guillaume Vachey via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Scandinavian Wine

December 20, 2019 By EarthWise Leave a Comment

The warming climate is creating some unexpected entrepreneurial opportunities. Many places that have traditionally dominated the wine industry are starting to be worried that the local climates that made them ideal for vineyards are changing and becoming much less ideal. On the other hand, places where wine-making was regarded as a losing proposition are becoming much more hospitable. A prime example is Scandinavia.

Nordic vintners are increasingly convinced that they can develop thriving commercial operations in what used to be places that are too cold for successful wine-making.

Denmark now has 90 commercial vineyards, up from just two 15 years ago. Forty vineyards have sprung up in Sweden. About a dozen vineyards are now operating as far north as Norway.

Many of these Nordic vineyards are in the startup stage and are tiny compared with the established wineries of Europe. Europe has 10 million acres of vineyards, which is enough to cover almost the entire country of Denmark. At the moment, there are only about 1,000 acres of vineyards in Denmark and Sweden.

But, looking forward, Scandinavia’s climate is forecast to be more like northern France, as regional temperatures climb as much as 10 degrees Fahrenheit. Over the past decade, warming has produced milder winters, a longer growing season, and even a small but rising number of award-winning Scandinavian wines.

Meanwhile, traditional wine-growing regions are also dealing with climate change. Winemakers in France, for example, are experimenting with grapes from warmer countries like Tunisia to see if they can retain the tastes and yields that are the basis of a multibillion-dollar wine industry. Spanish and Italian winemakers are planting grapes higher up on mountainsides or on shaded north-facing slopes to preserve the quality of their wine.

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Scandinavian Wine? A Warming Climate Tempts Entrepreneurs

Photo, posted August 24, 2019, courtesy of Ron Reiring via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Beavers And Biodiversity

October 10, 2019 By EarthWise Leave a Comment

Beavers are large, semi-aquatic rodents known best for their ability to construct dams, canals, and lodges (their homes). They are among the largest rodents in the world. With powerful jaws and strong teeth, beavers fell trees to use as building materials, often changing their environment in ways few other animals can. But in a good way. As it turns out, beavers are important for biodiversity.

According to new research from the Faculty of Natural Sciences at the University of Stirling in Scotland, reintroducing beavers to their native habitats is an important step towards solving the freshwater biodiversity crisis.

Researchers surveyed water plants and beetles in 20 wetlands in Sweden – 10 created by beavers and 10 that were not – in order to understand what impact beavers might have on the variety of plant and animal life around them.

The research team’s findings build on previous work that has shown that beavers have an important impact on biodiversity. This latest study discovered that the number of species found only in beaver-built ponds was 50% higher than in other non beaver-built wetlands in the same region.

Beavers are known to be profound engineers of the environment. They use wood to build dams across rivers in order to form ponds behind them. They do this to raise the water level in order to avoid predators, like bears and wolves. But it turns out many other plants and animals, like water plants and beetles, also benefit from their work.

According to the research team, reintroducing beavers to their native habitats should benefit the wider biodiversity and be seen as an important step towards solving the freshwater biodiversity crisis.

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Beaver reintroduction key to solving freshwater biodiversity crisis

Photo, posted October 2, 2014, courtesy of USFWS Midwest Region via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Wildfires And Carbon

September 17, 2019 By EarthWise Leave a Comment

This summer has been an unprecedented year for fires in the Arctic. Major fires have burned throughout the Arctic in Russia, Canada, and Greenland. In total these fires released 50 million tons of carbon dioxide in June alone, which is as much as Sweden emits in an entire year.

In an average year, wildfires around the world burn an area equivalent to the size of India and emit more carbon dioxide to the atmosphere than global road, rail, shipping and air transport combined.

Ordinarily, this is part of a natural cycle. As vegetation in burned areas regrows, it draws CO2 back out of the atmosphere through photosynthesis. This is part of the fire-recovery cycle, which can take less than a year in grasslands, but decades in forests. But in Arctic or tropical peatlands, full recovery may not occur for centuries.

A recent study looked at and quantified the important role that charcoal plays in helping to compensate for carbon emissions from fires. In wildfires, some of the vegetation is not consumed by burning, but instead is transformed to charcoal – referred to as pyrogenic carbon. This carbon-rich material can be stored in soils and oceans over very long time periods.

Researchers have combined field studies, satellite data, and modelling to quantify the amount of carbon that is placed in storage in the form of charcoal. Their results are that the production of pyrogenic carbon amounts to about 12% of the CO2 emissions from fires and can be considered a significant buffer for landscape fire emissions.

Charcoal does not represent a solution to the problem of increasingly intense wildfires, but it is important to take it into account in understanding what is happening.

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How wildfires trap carbon for centuries to millennia

Photo, posted August 17, 2018, courtesy of the Bureau of Land Management Oregon and Washington via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Climate Change And Economic Inequality

June 3, 2019 By EarthWise 1 Comment

A new study by Stanford University looked at the effects of climate change on global economic inequality. The study found that the gap between the economic output of the world’s richest and poorest countries is larger today than it would have been without global warming.

The warming climate has enriched cooler countries like Norway and Sweden while dragging down economic growth in warm countries such as India and Nigeria. The results of the study showed that most of the poorest countries on Earth are considerably poorer than they would have been in the absence of rising temperatures. At the same time, the majority of rich countries are richer than they would have otherwise been.

Detailed analysis of 50 years of annual temperature and GDP measurements for 165 countries demonstrated that growth during warmer than average years has accelerated in cool nations and slowed in warm nations. Historical data clearly show that crops are more productive, people are healthier, and they are more productive at work when temperatures are neither too hot nor too cold. That means that in cold countries, a little bit of warming can help but the opposite is true in places that are already hot.

For most counties, whether global warming has helped or hurt economic growth is pretty certain. Tropical countries in particular tend to have temperatures far outside the ideal for economic growth and they are already among the poorest countries. It is less clear how warming has influenced growth in countries in the middle latitudes, such as here in the United States. Some of the largest economies are near the perfect temperature for economic output but continued warming in the future is likely to push them away from the temperature optimum.

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Climate change has worsened global economic inequality

Photo, posted November 1, 2011, courtesy of CIAT via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Liquid Fuel From The Sun

February 21, 2019 By EarthWise Leave a Comment

Most forms of energy we use ultimately come from the sun in one way or another. Even fossil fuels are the end product of millions of years of plant life that captured solar energy. The advantage fossil fuels have over direct solar power is that they are, in fact, fuels and therefore can be stored for use when needed.

Scientists in Sweden have now developed a specialized fluid that absorbs some of the sun’s energy, holds it for months or even years, and then releases it when needed. This solar thermal fuel is like a rechargeable battery for heat rather than electricity.

The special fluid is pumped through transparent tubes where ultraviolet light from the sun excites its molecules into an energized state. A compound called norbornadiene is converted into quadricyclane. The quadricyclane is a quite stable substance until it is passed over a cobalt-based catalyst, which causes it to turn back into norbornadiene and release copious amounts of heat.

Such a solar thermal fuel could be stored in uninsulated tanks in homes or factories or piped or trucked to where it was needed. It could then be used for water heaters, dishwashers, or clothes driers. The room temperature fluid quickly warms to about 183 degrees when passed over the catalyst, plenty warm enough for heating a home or office. Both the fuel and the catalyst are damaged very little by the reactions, so the process can be recycled many times.

There is much development work needed to optimize shelf life, energy density, good recyclability and other properties before this technology can be commercialized but there are at least 15 groups around the world now studying this intriguing way to get liquid fuel from the sun.

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