内容：Alice Ge 编辑：Alvin Wei
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Part I: Speaker
Bird Egg Colors Influenced By Local Climate
By Christopher Intagliata on October 29, 2019
Source: Scientific American
https://www.scientificamerican.com/podcast/episode/bird-egg-colors-influenced-by-local-climate/
[Rephrase 1, 01:50]
Part II: Speed
A new estimate triples the number of people in the path of rising seas
BY Sofie Bates | OCTOBER 29, 2019 AT 1:52 PM
[Time 2]
Sea level rise this century could flood coastal areas that are now home to 340 million to 480 million people, researchers from Climate Central, a research and advocacy group, report. That’s roughly triple the number of people estimated to be at risk using previous coastal elevation data.
The new estimate, published October 29 in Nature Communications, comes from efforts to refine NASA satellite elevation data, and it illustrates the implications of elevation data having been overestimated in some places by up to 5 to 10 meters. The results are presented in terms of how many people, by today’s population numbers, could be affected, but don’t predict how many people will actually be living in those coastal areas in 2100.
“The global threat from sea level rise and coastal flooding is far greater than what we thought it was,” says Benjamin Strauss, who heads Climate Central in Princeton, N.J.
While the research highlights an increased threat to people currently living in coastal areas, it does not estimate how much more land area will fall below flood projection lines, and whether that area includes a handful of coastal megacities or mostly large swaths of less populated land. So it’s unclear how many people in future cities might be at risk of inundation, which could limit the usefulness of the findings to city managers. The researchers say those details fell outside the scope of this study.
[234 words]
[Time 3]
Still, the new estimate attempts to correct a large margin of error found in previous estimates of global coastal elevations. Those estimates are based on NASA’s Shuttle Radar Topography Mission, or SRTM, which created a global topographic map from satellite images and radar data. SRTM measures elevation by bouncing radar signals off Earth’s surface — whether that’s a tree, a building or the land itself. So the method can overestimate elevation levels, especially in forests and cities.
“If we’re overestimating elevations [in coastal cities], we’re getting a very over-optimistic view of the impact of flooding,” says Ashton Shortridge, a geographer at Michigan State University in East Lansing who was not involved in the study.
In the new work, Strauss and computational scientist Scott Kulp fine-tuned SRTM’s elevation estimates using an artificial neural network, a computer algorithm meant to mimic how the brain processes information. The algorithm was programed to account for trees, bridges and buildings to recalculate land elevations as if Earth were naked to produce more accurate elevation estimates.
Using the new elevation estimates, the researchers used 2010 population data to calculate how many people live on land that could be affected by sea level rise driven by climate change. If global warming can be kept to 2 degrees Celsius above preindustrial levels (SN: 7/10/18), rising sea levels, projected by the Intergovernmental Panel on Climate Change in 2013, would swamp areas that are currently home to 360 million people, the researchers conclude.
In the worst-case scenario — emissions left unchecked and rapidly crumbling Antarctic ice cliffs dramatically increasing estimates of sea level rise (SN: 2/6/19) — 480 million people by today’s demographics could be living on land at risk from sea rise by 2100, the study says. No matter what the scenario, over 70 percent of the people newly estimated to be vulnerable live in eight Asian countries, with the biggest chunk in China.
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[The Rest]
That’s not to say coastal population trends won’t change. Humans may migrate in the face of flood risk (SN: 8/15/18), or cities could redesign infrastructure to better handle higher tides and frequent floods (SN: 8/6/19).
Still, the new projections for affected population by 2100 represent a considerable jump from estimates using SRTM data, Kulp says. Those ranged from 95 million to 170 million people.
“We knew it was going to be big, but the fact that there are — when we look at a global scale — three times as many people potentially vulnerable … it’s still quite shocking,” Kulp says.
[100 words]
Source: Science News
https://www.sciencenews.org/article/new-climate-change-estimate-triples-number-people-path-rising-sea-levels
Bird eggs laid in cold climates are darker, which may keep eggs warm
By Jonathan Lambert | OCTOBER 28, 2019 AT 12:00 PM
[Time 4]
Bird eggs come in a dizzying array of colors. But from a global perspective, that diversity follows a simple pattern — the colder the climate, the darker the egg, new research shows.
Darker eggs absorb more heat than lighter ones, which could help developing chicks stay warm while their parents forage for food, according to the study published online October 28 in Nature Ecology and Evolution.
Biologists have long tried to suss out the selective forces that shape and color a specific species’ eggs. Those forces include keeping eggs hidden from predators, protecting them from bacteria, signaling egg quality and maintaining egg warmth. “All of these hypotheses have some level of [evidential] support,” says Phillip Wisocki, who worked on the research while studying biology at Long Island University Post in Brookville, New York.
But scientists weren’t sure whether any of these factors were important in determining egg diversity globally. “If your focus is too narrow, you can miss a lot of what’s going on,” says Wisocki’s adviser, biologist Daniel Hanley.
Using museum collections of bird eggs, Hanley, Wisocki and their colleagues compiled data on eggs from 634 bird species from 36 of the 40 living orders of birds. They then analyzed the data against a global map, and found that the brightness and color of eggshells closely correlated with temperature, even after correcting for color similarities between closely related species.
Birds in “the far north, which tends to be colder, had darker, browner eggs,” Hanley says. Eggs became lighter and slightly bluer for birds living closer to the equator, though egg colors were generally more variable in the tropics.
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[Time 5]
The researchers suggest the trend may reflect adaptation to the cold: A dark egg, like a dark car parked in the sun, absorbs more thermal radiation from the sun than lighter eggs. Testing the theory, the researchers exposed white, brown and blue chicken eggs to direct sunlight and tracked heat retention. Sure enough, brown eggs warmed up faster and cooled down more slowly than the lighter eggs.
“In the Arctic, parents have to go out to forage and get back to their eggs quickly,” Hanley says. “If you can buy them five extra minutes, that can actually be really beneficial for them.”
Biologist Mary Caswell Stoddard welcomed the study’s attention to the role of egg color in thermoregulation. “That’s part of what makes this study, and the discovery that birds living in colder habitats tend to lay darker eggs, so exciting,” though undoubtedly there are other selective factors at play, says Stoddard, of Princeton University.
Still, Wisocki says the study shows climate to be a major driver of egg color variation, while also expanding the notion of what color is for (SN: 10/31/18). “We usually think about color through the lens of perception — mating displays, camouflage, signaling,” he says. “In this study we show that color matters, but the observer isn’t important.”
[213 words]
Source: Science News
https://www.sciencenews.org/article/bird-eggs-laid-cold-climates-are-darker-may-keep-eggs-warm
This device harnesses the cold night sky to generate electricity in the dark
By Maria Temming | SEPTEMBER 12, 2019 AT 11:00 AM
[Time 6]
A new device is an anti-solar panel, harvesting energy from the cold night sky.
By harnessing the temperature difference between Earth and outer space, a prototype of the device produced enough electricity at night to power a small LED light. A bigger version of this nighttime generator could someday light rooms, charge phones or power other electronics in remote or low-resource areas that lack electricity at night when solar panels don’t work, researchers report online September 12 in Joule.
The core of the new night-light is a thermoelectric generator, which produces electricity when one side of the generator is cooler than the other (SN: 6/1/18). The sky-facing side of the generator is attached to an aluminum plate sealed beneath a transparent cover and surrounded with insulation to keep heat out. This plate stays cooler than the ambient air by shedding any heat it absorbs as infrared radiation (SN: 9/28/18). That radiation can zip up through the transparent cover and the atmosphere toward the cold sink of outer space.
Meanwhile, the bottom of the generator is attached to an exposed aluminum plate that is continually warmed by ambient air. At night, when not baking under the sun, the top plate can get a couple of degrees Celsius cooler than the bottom of the generator.
Engineer Wei Li of Stanford University and colleagues tested a 20-centimeter prototype of the device on a clear December night in Stanford, Calif. The generator produced up to about 25 milliwatts of power per square meter of device — enough to light a small light-emitting diode, or LED, bulb. The team estimates that further design improvements, like better insulation around the cool top plate, could boost production up to at least 0.5 watts per square meter.
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[The Rest]
“It’s a very clever idea,” says Yuan Yang, a materials scientist at Columbia University not involved in the work. “The power generation is much less than solar panels,” which generally produce at least 100 watts per square meter. But this nighttime generator may be useful for emergency backup power, or energy for people living off the grid, Yang says.
A typical lamp bulb might consume a few watts of electricity, says Shanhui Fan, an electrical engineer at Stanford University who worked on the device. So a device that took up a few square meters of roof space could light up a room with energy from the night sky.
Aaswath Raman, a materials scientist and engineer at UCLA, also envisions using their team’s generator to help power remote weather stations or other environmental sensors. This may be especially useful in polar regions that don’t see sunlight for months at a time, Raman says. “If you have some low-power load and you need to power it through three months of darkness, this might be a way.”
[175 words]
Source: Science News
https://www.sciencenews.org/article/device-harnesses-cold-night-sky-generate-electricity-dark
Part III: Obstacle
Engineers develop a new way to remove carbon dioxide from air
October 25, 2019 | Massachusetts Institute of Technology
[Paraphrase 7]
A new way of removing carbon dioxide from a stream of air could provide a significant tool in the battle against climate change. The new system can work on the gas at virtually any concentration level, even down to the roughly 400 parts per million currently found in the atmosphere.
Most methods of removing carbon dioxide from a stream of gas require higher concentrations, such as those found in the flue emissions from fossil fuel-based power plants. A few variations have been developed that can work with the low concentrations found in air, but the new method is significantly less energy-intensive and expensive, the researchers say.
The technique, based on passing air through a stack of charged electrochemical plates, is described in a new paper in the journal Energy and Environmental Science, by MIT postdoc Sahag Voskian, who developed the work during his PhD, and T. Alan Hatton, the Ralph Landau Professor of Chemical Engineering.
The device is essentially a large, specialized battery that absorbs carbon dioxide from the air (or other gas stream) passing over its electrodes as it is being charged up, and then releases the gas as it is being discharged. In operation, the device would simply alternate between charging and discharging, with fresh air or feed gas being blown through the system during the charging cycle, and then the pure, concentrated carbon dioxide being blown out during the discharging.
As the battery charges, an electrochemical reaction takes place at the surface of each of a stack of electrodes. These are coated with a compound called polyanthraquinone, which is composited with carbon nanotubes. The electrodes have a natural affinity for carbon dioxide and readily react with its molecules in the airstream or feed gas, even when it is present at very low concentrations. The reverse reaction takes place when the battery is discharged -- during which the device can provide part of the power needed for the whole system -- and in the process ejects a stream of pure carbon dioxide. The whole system operates at room temperature and normal air pressure.
"The greatest advantage of this technology over most other carbon capture or carbon absorbing technologies is the binary nature of the adsorbent's affinity to carbon dioxide," explains Voskian. In other words, the electrode material, by its nature, "has either a high affinity or no affinity whatsoever," depending on the battery's state of charging or discharging. Other reactions used for carbon capture require intermediate chemical processing steps or the input of significant energy such as heat, or pressure differences.
"This binary affinity allows capture of carbon dioxide from any concentration, including 400 parts per million, and allows its release into any carrier stream, including 100 percent CO2," Voskian says. That is, as any gas flows through the stack of these flat electrochemical cells, during the release step the captured carbon dioxide will be carried along with it. For example, if the desired end-product is pure carbon dioxide to be used in the carbonation of beverages, then a stream of the pure gas can be blown through the plates. The captured gas is then released from the plates and joins the stream.
In some soft-drink bottling plants, fossil fuel is burned to generate the carbon dioxide needed to give the drinks their fizz. Similarly, some farmers burn natural gas to produce carbon dioxide to feed their plants in greenhouses. The new system could eliminate that need for fossil fuels in these applications, and in the process actually be taking the greenhouse gas right out of the air, Voskian says. Alternatively, the pure carbon dioxide stream could be compressed and injected underground for long-term disposal, or even made into fuel through a series of chemical and electrochemical processes.
The process this system uses for capturing and releasing carbon dioxide "is revolutionary" he says. "All of this is at ambient conditions -- there's no need for thermal, pressure, or chemical input. It's just these very thin sheets, with both surfaces active, that can be stacked in a box and connected to a source of electricity."
"In my laboratories, we have been striving to develop new technologies to tackle a range of environmental issues that avoid the need for thermal energy sources, changes in system pressure, or addition of chemicals to complete the separation and release cycles," Hatton says. "This carbon dioxide capture technology is a clear demonstration of the power of electrochemical approaches that require only small swings in voltage to drive the separations."
In a working plant -- for example, in a power plant where exhaust gas is being produced continuously -- two sets of such stacks of the electrochemical cells could be set up side by side to operate in parallel, with flue gas being directed first at one set for carbon capture, then diverted to the second set while the first set goes into its discharge cycle. By alternating back and forth, the system could always be both capturing and discharging the gas. In the lab, the team has proven the system can withstand at least 7,000 charging-discharging cycles, with a 30 percent loss in efficiency over that time. The researchers estimate that they can readily improve that to 20,000 to 50,000 cycles.
The electrodes themselves can be manufactured by standard chemical processing methods. While today this is done in a laboratory setting, it can be adapted so that ultimately they could be made in large quantities through a roll-to-roll manufacturing process similar to a newspaper printing press, Voskian says. "We have developed very cost-effective techniques," he says, estimating that it could be produced for something like tens of dollars per square meter of electrode.
Compared to other existing carbon capture technologies, this system is quite energy efficient, using about one gigajoule of energy per ton of carbon dioxide captured, consistently. Other existing methods have energy consumption which vary between 1 to 10 gigajoules per ton, depending on the inlet carbon dioxide concentration, Voskian says.
The researchers have set up a company called Verdox to commercialize the process, and hope to develop a pilot-scale plant within the next few years, he says. And the system is very easy to scale up, he says: "If you want more capacity, you just need to make more electrodes."
Source: Science Daily
https://www.sciencedaily.com/releases/2019/10/191025170815.htm |
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发表于 2019-10-31 14:18:32
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