Study Investigates Drivers Responsible for Madagascar Megafaunal Extinction - AZoCleantech
In the past thousand years, there was complete destruction of the endemic megafauna of Madagascar and the Mascarene islands. An international research team analyzed the probable drivers of this extinction by developing an 8000-year record of the previous clim…
Written by AZoCleantechOct 19 2020 In the past thousand years, there was complete destruction of the endemic megafauna of Madagascar and the Mascarene Islands. An international research team analyzed the probable drivers of this extinction by developing an 8000-year record of the previous climate of the island. Investigating the drivers of extinction: By analyzing stalagmites from the La Vierge Cave located on Rodrigues, the scientists reconstructed 8000 years of the region’s past climate. Image Credit: Hanying Li. The findings of the study revealed that although the ecosystem was resistant to previous climate stress it crumbled with a rise in human activities. Christoph Spötl from the Innsbruck Quaternary Research Group was one of the members of the international research team. The findings have now been reported in the Science Advances journal. Almost all of the Madagascan megafauna— which includes the well-known Dodo bird, giant tortoises, the Elephant Bird which stood 3 m tall and weighed around half a ton, and the gorilla-sized lemurs—disappeared between 1500 and 500 years ago. Did humans overhunt these animals to extinction? Or did they vanish due to climate change? There are various hypotheses, but the actual reason for the megafauna collapse continues to be mysterious, and a topic of intense debate. The Mascarene islands located to the east of Madagascar are of unique interest as they are the last islands on the planet to be colonized by humans. Interestingly, the islands’ megafauna collapsed within just 200 years after human settlement. In a study published recently in the Science Advances journal, an international research team discovered that it was possibly a “double whammy” of increased human activities together with a specifically acute spell of region-wide aridity, which may have led to the elimination of the megafauna. The team rejects climate change as the only reason, and instead proposes that the effect of human colonization was an essential contributor to the megafaunal collapse. Hanying Li, a postdoctoral scholar at the Xi’an Jiaotong University in China and the lead author of this study, compiled an elaborate history of the regional climate changes. The new paleoclimate record’s main source was derived from the small Mascarene island of Rodrigues in the southwest Indian Ocean, around 1600 km to the east of Madagascar. An island so remote and small that one will not find it on most schoolbook atlases.” Gayatri Kathayat, Study Co-Author and Associate Professor of Climate Science, Xi’an Jiaotong University Analysis of Cave Deposits Li and his collaborators developed their climate records by investigating the trace elements as well as oxygen and carbon isotopes from every incremental growth layer of stalagmites, which was collected from one of several caves present on this island. Many such analyses were performed at the Quaternary Research Group at the Institute of Geology. Variations in the geochemical signatures provided the information needed to reconstruct the region’s rainfall patterns over the last 8000 years. To analyze the stalagmites we used the stable isotope method in our lab in Innsbruck.” Christoph Spötl, Professor, University of Innsbruck Regardless of the distance present between the two islands, at Rodrigues and Madagascar, the summer rainfall is affected by the same global-wide tropical rain belt that fluctuates north and south with the seasons. “And when this belt falters and stays further north of Rodrigues, droughts can strike the whole region from Madagascar to Rodrigues,” explained Hai Cheng, senior co-author of the study. “Li’s work from Rodrigues demonstrates that the hydroclimate of the region experienced a series of drying trends throughout the last 8 millennia, which were frequently punctuated by ‘megadroughts’ that lasted for decades,” noted Hubert Vonhof, who is a co-author of the study and scientist at Max Planck Institute of Chemistry in Mainz, Germany. Resilient to Climate Stress The latest drying trends in the region began approximately 1500 years ago when the archaeological and proxy records started to exhibit definitive signs of higher human presence on the island. While we cannot say with 100 percent certainty whether human activity, such as overhunting or habitat destruction, was the proverbial last straw that broke the camel’s back, our paleoclimate records make a strong case that the megafauna had survived through all the previous episodes of even greater aridity. This resilience to past climate swings suggests that an additional stressor contributed to the elimination of the region’s megafauna.” Ashish Sinha, Professor of Earth Science, California State University “There are still many pieces missing to fully solve the riddle of megafauna collapse. This study now provides an important multi-millennial climatic context to megafaunal extinction,” stated Ny Rivao Voarintsoa from KU Leuven in Belgium, a native of Madagascar, who also contributed to this study. The study highlights the decimation of flora and fauna of Mauritius and Rodrigues: “Both islands were rapidly stripped of endemic species of vertebrates within two centuries of the initial human colonization, including the well-known flightless ‘Dodo’ bird from Mauritius and the saddle-backed ‘Rodrigues giant tortoise’ endemic to Rodrigues,” added Aurele Anquetil André, who is a reserve manager and chief conservator at the Francois Leguat Giant Tortoise and Cave Reserve at Rodrigues. “The story our data tells is one of resilience and adaptability of the islands’ ecosystems and fauna in enduring past episodes of severe climate swings for eons—until they were hit by human activities and climate change,” concluded the researchers. Journal Reference: Li, H., et al. (2020) A multimillennial climatic context for the megafaunal extinctions in Madagascar and Mascarene Islands. Science Advances. https://doi.org/10.1126/sciadv.abb2459. Source: https://www.uibk.ac.at/
New Molecular Photoswitch can Store Solar Energy for Later Consumption - AZoCleantech
Linköping University scientists have created a new molecule that is capable of absorbing solar energy and storing it in chemical bonds.
Written by AZoCleantechSep 1 2020 Linköping University (LiU)scientists have created a new molecule that is capable of absorbing solar energy and storing it in chemical bonds. Bo Durbeej and his group use advanced computer simulations of chemical reactions, which are performed at the National Supercomputer Centre, NSC, in Linköping. Image Credit: Thor Balkhed. A potential long-term application of the new molecule is to efficiently trap the energy from sunlight and preserve it for later usage. The Earth receives several times more energy from the Sun that exceeds human consumption. Solar energy facilities normally absorb this energy; however, one major difficulty regarding solar energy is its efficient storage, such that the energy is always available even when the Sun has set. This made the LiU researchers analyze the prospect of trapping and storing the Sun’s energy in a novel molecule. Our molecule can take on two different forms: a parent form that can absorb energy from sunlight, and an alternative form in which the structure of the parent form has been changed and become much more energy-rich, while remaining stable. This makes it possible to store the energy in sunlight in the molecule efficiently. Bo Durbeej, Study Lead and Professor of Computational Physics, Department of Physics, Chemistry, and Biology, Linköping University The new molecule is part of a group called “molecular photoswitches.” These molecular photoswitches invariably exist in two different forms—isomers—that vary in their chemical structures. Both forms have diverse characteristics, and with regard to the new molecule created by the LiU research group, this difference lies in the energy content. Light energy influences the chemical structures of all photoswitches. This implies that the structure and, therefore, the properties of a photoswitch can be altered by illuminating it. Molecular electronics is one potential area of application for photoswitches; the two versions of the molecule in molecular electronics have diverse electrical conductivities. Another domain is photopharmacology, wherein one version of the molecule is pharmacologically active and can attach to a particular target protein in the body, whereas the other version is pharmacologically inactive. In the research field, experiments are initially carried out and theoretical work verifies the experimental results at a later stage, but the process was reversed in this study. Bo Durbeej and his team work in theoretical chemistry, and perform simulations and calculations of chemical reactions. This includes sophisticated computer simulations, which are carried out on supercomputers at the National Supercomputer Centre, NSC, in Linköping. These calculations revealed that the newly developed molecule would go through the chemical reaction required by the team, and that it would happen very fast, all in less than 200 fs. The team’s associates from the Research Centre for Natural Sciences in Hungary were subsequently able to construct the molecule, and carried out experiments that validated the theoretical prediction. To enable the molecule to store large amounts of solar energy, the team had tried to make the energy variation between both isomers as large as possible. The parent form of the new molecule is highly stable, a trait that, in the field of organic chemistry, is indicated by stating that the molecule is “aromatic.” The standard molecule contains three rings, each of which is aromatic. But when this molecule captures light, the aromaticity vanishes, such that the molecule turns out to have more abundant energy. The research, performed by the LiU team, has been published in the Journal of the American Chemical Society. It shows that the idea of swapping between non-aromatic and aromatic states of a molecule has a huge potential in the domain of molecular photoswitches. Most chemical reactions start in a condition where a molecule has high energy and subsequently passes to one with a low energy. Here, we do the opposite—a molecule that has low energy becomes one with high energy. We would expect this to be difficult, but we have shown that it is possible for such a reaction to take place both rapidly and efficiently. Bo Durbeej, Study Lead and Professor of Computational Physics, Department of Physics, Chemistry, and Biology, Linköping University At present, the team will explore the ideal way to discharge the stored energy from the energy-rich form of the molecule. The study was financially supported by the Olle Engkvist Foundation, the Hungarian Academy of Sciences, the Swedish Research Council, and the National Research, Development, and Innovation Office in Hungary. The National Supercomputer Centre, NSC, generously offered computing time. Oruganti, B., et al. (2020) Photoinduced Changes in Aromaticity Facilitate Electrocyclization of Dithienylbenzene Switches. Journal of the American Chemical Society. doi.org/10.1021/jacs.0c06327. Source: https://liu.se
Research Reveals Sensitivity of Earth’s Climate to Carbon Dioxide - AZoCleantech
Researchers who performed the most detailed and advanced study of climate sensitivity have now reported more confidently about the sensitivity level of Earth’s climate to carbon dioxide.
Written by AZoCleantechJul 23 2020 Researchers who performed the most detailed and advanced study of climate sensitivity have now reported more confidently about the sensitivity level ofEarth’s climate to carbon dioxide. This is the first study of its kind to be performed, to date. Narrowing the range of climate sensitivity has been a major challenge since the seminal US National Research Council paper came up with a 1.5 °C–4.5 °C range in 1979. Image Credit: NOAA (Unsplash). For over four decades, the projected likely range of the ultimate worldwide temperature response to a doubling of carbon dioxide in the air when compared to pre-industrial levels has continued to remain at 1.5 °C–4.5 °C. The latest study revealed that the actual climate sensitivity is too far-fetched to be in the lowest part of the 1.5 °C–4.5 °C range. The research was written over four years and has been described in a 165-page, peer-reviewed journal article commissioned by the World Climate Research Programme (WCRP). It indicates that if carbon dioxide levels in the air increase by two-fold from their pre-industrial levels and continue to persist, the world is likely to experience ultimate warming from 2.3 °C to 4.5 °C. The scientists observed that there would be a 6%–18% chance of surpassing 4.5 °C and less than 5% chance of remaining below 2 °C. The temperature of the Earth has already touched about 1.2 °C higher than preindustrial levels. Furthermore, if greenhouse gas emissions trajectories continue to persist, the world is likely to witness a doubling of atmospheric carbon dioxide in the next six to eight decades. Narrowing the range of climate sensitivity has been a major challenge since the seminal US National Research Council paper came up with a 1.5 °C–4.5 °C range in 1979 (Charney et al). That same range was still quoted in the most recent IPCC report. Steven Sherwood, Study Lead Author and Professor, UNSW Sydney Sherwood is also the chief investigator with the ARC Centre of Excellence for Climate Extremes. The collaboration of an international team of researchers from a broad range of climate disciplines has led to this latest research. During the study, the team used paleoclimate records to predict prehistoric temperatures, temperature records since the industrial revolution, satellite observations, and comprehensive models that analyze the physics of communications within the climate system. Following this, the researchers integrated more individual lines of proof than provided by any previous studies to obtain their results. These independent lines of proof were subsequently integrated in a statistically stringent manner that allowed the researchers to spot where exactly the results overlapped. This approach enabled the team to converge on the best estimate of climate sensitivity. The researchers also observed that, with the latest developments, the numerous lines of proof validated each other, resulting in more confidence in the outcome. The 2.3 °C–4.5 °C temperature range carefully accounts for alternative assumptions or views and “unknown unknowns,” with a more upfront calculation producing a likely range that is even narrower from 2.6 °C to 3.9 °C. This paper brings together what we know about climate sensitivity from measurements of atmospheric processes, the historical warming, and warm and cold climates of the past. Statistically combined, these estimates make it improbable that climate sensitivity is at the low end of the IPCC range and confirm the upper range. This adds to the credibility of climate model simulations of future climate. Gabi Hegerl, Study Co-Author, University of Edinburgh “An important part of the process was to ensure that the lines of evidence were more or less independent,” added Professor Sherwood. “You can think of it as the mathematical version of trying to determine if a rumour you hear separately from two people could have sprung from the same source; or if one of two eyewitnesses to a crime has been influenced by hearing the story of the other one.” Subsequently, the scientists went one step further and detected the conditions that would be needed for the climate sensitivity to lie beyond this most probable range. The scientists demonstrated that low climate sensitivities, which were earlier believed to be credible, around 1.5 °C–2 °C, could only happen if the data analysis contains numerous unconnected and unforeseen errors (for instance, unforeseen cloud patterns and behavior of long-term ocean warming), reinforcing their judgment that such low values are quite unlikely today. Another set of situations makes it implausible that global temperatures would increase over 4.5 °C for a doubling of atmospheric carbon dioxide from preindustrial times, even though these responses of higher temperatures are still more likely than extremely low sensitivities. In spite of this qualification, the three-year-long research procedure launched by the WCRP with cross-checking at each step, a comprehensive analysis of the physical procedures, and an inference of the conditions needed for the estimate has eventually consolidated an advance on the four-decade issue. These results are a testament to the importance of cross-disciplinary research along with slow, careful science and perfectly highlight how international co-operation can unpick our most vexing problems. Eelco Rohling, Study Co-Author and Professor, Australian National University “If international policymakers can find the same focus and spirit of co-operation as these researchers then it will give us hope that we can forestall the worst of global warming,” Rohling concluded. Sherwood, S., et al. (2020) An assessment of Earth’s climate sensitivity using multiple lines of evidence. Reviews of Geophysics. doi.org/10.1029/2019RG000678. Source: https://unsw.edu.au