【揽瓜阁4.0】Day9 2021.01.26【自然科学-气候、地质、环境】

妥妥

  揽瓜阁俱乐部第四期

  Day9 2021.01.26

【自然科学-气候】

Using satellites to spot industry’s methane leaks：To help combat climate change

(The Economist - 884 字 长精读)

When scanning for emissions from a mud volcano in western Turkmenistan in January 2019, a satellite called Claire came across a large plume of methane drifting across the landscape. The discharge appeared to originate from a gas pipeline at the nearby Korpezhe oil and gasfield. Two more large plumes were also spotted in the area, including one from a compressor station. The company operating the satellite, ghgsat, based in Montreal, passed details via diplomats to officials in Turkmenistan, and after a few months the leaks stopped. This largely unknown incident illustrates two things: that satellites can play an important role in spotting leaks of greenhouse gases and, rather worryingly, that the extent of such leaks is often greatly underestimated.

The reason for concern is that although methane, the main constituent of natural gas, does not linger in the atmosphere for anywhere near as long as carbon dioxide does, it is a far more potent heat-trapping agent. About a quarter of man-made global warming is thought to be caused by methane. And between a fifth and a third of the methane involved is contributed by the oil and gas industry.

The data from Claire suggested the leak in Turkmenistan had been a big one. To establish just how big, Daniel Jacob of Harvard University and his colleagues studied the images obtained by this satellite along with observations made of the area at the time by the Tropospheric Monitoring Instrument (tropomi), which is carried by an atmospheric research satellite operated by the European Space Agency. The results, published in Geophysical Research Letters in November 2019, concluded that between February 2018 and January 2019 the three leaks would have released, between them, 142,000 tonnes of methane. This made the Turkmenistani leak far bigger than the 97,000 tonnes of methane discharged over four months by a notorious blowout at a natural-gas storage facility in Aliso Canyon, California, in 2015, which is reckoned to have been the worst natural-gas leak yet recorded in America.

There have been other big leaks, too. Last year a group of researchers led by Ilse Aben of the Netherlands Institute for Space Research studied tropomi images of a blowout at a natural-gas well in Belmont county, Ohio. This began on February 15th 2018 and took three weeks to control. In a paper published in the Proceedings of the National Academy of Sciences in December 2019, Dr Aben and her colleagues calculated from the images that the blowout was responsible for the equivalent of a quarter of the annual oil and gas industry’s methane emissions in the entire state of Ohio.

Methane can be detected spectroscopically. Like other gases, it absorbs light at characteristic frequencies. With a spectrometer mounted on a satellite it is possible to analyse light reflected from Earth for signs of the gas. As with the satellites that carry them, spectrometers come in many shapes and sizes. tropomi can also detect the spectral signs of other polluting gases, such as nitrogen dioxide, sulphur dioxide and carbon monoxide. It rides in a large bird, the Copernicus Sentinel-5P satellite, launched in October 2017, and in all weighing 980kg. The detector has an extensive view, looking at a strip of Earth 2,600km wide with a resolution that means a single pixel in the image represents an area 7km by 3.5km.

Observing things more closely is the speciality of Claire. This 15kg “nanosat”, about the size of a microwave oven, was launched in June 2016 to measure carbon dioxide and methane emissions. With a field of view 12km wide and a resolution better than 50 metres by 50 metres, Claire can spot leaks from individual industrial plants. ghgsat aims to launch two more methane-hunting nanosats later this year.

Claire surveys industrial facilities on behalf of firms that want to monitor their emissions. ghgsat’s chief executive, Stephane Germain, says employing satellites to do this is more reliable than using terrestrial methods. In November he plans to roll out a new service. This will provide a digital image of Earth which users will be able to zoom in on to explore continually updated patterns and hotspots of methane emissions. The map will have an average resolution of 2km by 2km and be free to use—although if companies want to look at things more closely they will need to pay.

Other methane-hunting satellites are coming. These include one due for launch in 2022 by Methanesat, an affiliate of the Environmental Defence Fund, an American non-profit organisation. The 350kg satellite will cost $88m to build and put into orbit. It will scan an area of land 200km wide with a resolution of 1km by 1km. According to Methanesat, it will be the most sensitive to emission levels yet, being able to detect methane concentrations as low as two parts-per-billion. Data collected by the satellite will be publicly available.

Having a number of complementary eyes-in-the sky will be an important way to help reduce methane emissions. Although Donald Trump has proposed rolling back Obama-era requirements for oil and gas companies to detect and fix methane leaks, the gas has commercial value so it does not make business sense to waste it. On top of that, for firms seeking to burnish their green credentials, plugging leaks is one of the most effective things they can do to help combat climate change.

Source: The Economist

【自然科学-地质】

Radiocarbon Dating by Accelerator MassSpectrometry

(WSY - 547字 短精读)

In general, conventional radiocarbon dating has effectively mapped out  the past 30,000 years in areas where  organic preservation has been favorable. Yet beyond a threshold of about  20,000 years the number of objects whose age can be determined with certainty diminishes rapidly. Accelerator mass spectrometry can push the threshold further back in time, however.

At a horizon of 40,000 years the  amount of carbon 14 in a bone or a piece of charcoal can be truly mi nute: such a specimen may contain  only a few thousand C-14 atoms. Consequently equally small quantities of  modern carbon can severely skew the  measurements. Contamination of this  kind amounting to 1 percent of the  carbon in a sample 25,000 years old  would make it appear to be about  1,500 years younger than its actual  age. Such contamination would, however, reduce the apparent age of a  60,000-year-old object by almost 50  percent. Clearly proper sample-decontamination procedures are of particular importance in the dating of very  old artifacts. Unfortunately stringent  specimen handling and treatment procedures ultimately result in relatively small sample sizes, which conventional radiocarbon dating is poorly  equipped to handle. Moreover, conventional radiocarbon dating would  still face the insurmountable problem  of discriminating the radioactivity of  the sample from ambient background  radiation.

Neither sample size nor background radiation present problems to radiocarbon accelerator dating, and so rel atively minor improvements in sample chemistry can lead to sharper and  more extensive chronologies. For example, accelerator dating of purified amino acids from bones more than 25,000 years old showed that their age had previously been consistently underestimated by 1,000 or more years.  The earlier, conventional measurements had been based on whole collagen, which cannot be guaranteed to be free of modern carbon.

One controversy of long standing on which the new dating technique has already had a major impact concerns the  first human migrations to the New World. An accurate time scale for  the colonization of America is crucial in order to assess how quickly the first Paleo-Indian hunters and gatherers dispersed, settled and developed  their ethnic and linguistic diversity.  Most observers agree that the earliest  human inhabitants of America came from northeastern Asia probably between 25,000 and 12,000 years ago,  crossing over a land bridge that then  connected Siberia with Alaska. Nevertheless, human skeletons were found in  the New World at disparate locations, such as Canada and Peru, that seemed  to be considerably older than expected. Accelerator mass spectrometry has refuted these claims: no skeletal remains yet found in America appear to be more than 12,000 years old. If  other such finds are made in the future, accelerator mass spectrometry will quite probably be the dating technique called on to determine the skeleton's age directly.

Accelerator dating may also prove to be invaluable in establishing an uthoritative chronology of Neanderthal man. The archaeological evidence available indicates a rather abrupt disappearance of this human subspecies at the beginning of the Upper Paleolithic, about 35,000 years ago. Although it is too early to be sure, dating by accelerator mass spectrometry may reveal that the Upper Paleolithic and  the period preceding it, the Middle Paleolithic, were unduly compressed by  the limitations of conventional dating  methods. If this was the case, there would have been much more time for the Neanderthal's disappearance than has commonly been supposed.

Source: WSY

【自然科学-环境】

Ice Age Temperatures Help Predict Future Warming

(科学美国人 2分49秒 精听)

先做听力再核对原文哦~

How much colder was it at the peak of the last ice age? That’s a question scientists have been trying to answer for decades. And now they have a new best guess: 11 degrees Fahrenheit.

That’s a lot, especially considering it’s a global average. Parts of North America were much colder.

“First of all, large areas of the northeast were completely under ice. So that would have been pretty chilly; you wouldn’t be living there. But even here in the west, right, where we weren’t covered by an ice sheet, it would have been something like 20 degrees Fahrenheit lower.”

Jessica Tierney, a paleoclimatologist at the University of Arizona. Tierney and her colleagues spent years compiling information about Earth’s climate at the height of the last glacial period, about 20,000 years ago.

“We obviously don’t have thermometers in the glacial period, so we have to instead look for these kinds of stand-in indicators.”

One kind of stand-in is plankton that lived in the ocean and got preserved in marine sediments. Scientists use these fossils to infer past ocean temperatures by studying changes in the chemistry of their shells and in the kinds of fats and other compounds they produced.

Tierney and her team then combined these data with a climate model to give a full picture of glacial conditions.

“It’s actually a technique used every day in weather forecasting. What’s new is we’re using it for the past, not the future. We are actually hindcasting, if you will, rather than forecasting.”

The study is in the journal Nature. The findings suggest that the last ice age was significantly colder than scientists thought. And that matters today.

“The reason that we want to know how cold the last ice age is, beyond the fact that it’s just a cool thing to know, is that we can actually use it to understand a quantity called climate sensitivity.”

Climate sensitivity is a measure of how much the planet warms in response to rising greenhouse gases. In this long-ago case, we know how much carbon dioxide concentrations increased between the last ice age and preindustrial period from air bubbles trapped in ancient ice. And now we have Tierney’s new results on the temperature difference between glacial and interglacial conditions. Together, these data suggest that low-end estimates of climate sensitivity—in which greenhouse gases don’t cause much warming—are unlikely to be correct.

“If we had low climate sensitivity, then we would be less worried, you know, about what all the CO2 emissions are going to do. And so we can kind of rule that possibility out—that’s not great news.”

Source: Scientific American

【笔记格式要求】

同学们任选 2 篇文章精读/精听并进行笔记打卡

精读笔记格式要求：

1.总结文章中心大意

2.总结分论点或每段段落大意

3.摘抄印象深刻或者觉得优美的句子

4.总结文章中的生词

5.记录阅读时间、总结时间、总时间

精听笔记格式要求：

1.逐句听写整篇文章

2.对照原文修改听写稿，标记出错原因

3.总结文章中心大意

4.总结精听过程中的生词

5.记录听写时间、总结时间、总时间

这里也给大家三点学习小建议哦~

精读：如遇到读不懂的复杂句，建议找出句子主干，分析句子成分，也可以尝试翻译句子来帮助理解~

精听：建议每句不要反复纠结听，如果听 5 遍都没听出来，那就跳过，等完成后再回听总结原因，时间宝贵，不要过于执着哦~

再战请勿拦

第二篇没太看懂

咖喱团

还有一天了~~

LouisTan

阅读练习，328打卡