Author
Christina Williamson
Other affiliations: National Oceanic and Atmospheric Administration, University of Colorado Boulder, Earth System Research Laboratory ...read more
Bio: Christina Williamson is an academic researcher from Cooperative Institute for Research in Environmental Sciences. The author has contributed to research in topics: Aerosol & Troposphere. The author has an hindex of 23, co-authored 43 publications receiving 3450 citations. Previous affiliations of Christina Williamson include National Oceanic and Atmospheric Administration & University of Colorado Boulder.
Papers
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TL;DR: It is found that wolves who were raised by humans do not show these same skills, whereas domestic dog puppies only a few weeks old, even those that have had little human contact, do show these skills.
Abstract: Dogs are more skillful than great apes at a number of tasks in which they must read human communicative signals indicating the location of hidden food. In this study, we found that wolves who were raised by humans do not show these same skills, whereas domestic dog puppies only a few weeks old, even those that have had little human contact, do show these skills. These findings suggest that during the process of domestication, dogs have been selected for a set of social-cognitive abilities that enable them to communicate with humans in unique ways.
917 citations
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CERN1, Goethe University Frankfurt2, University of Helsinki3, Paul Scherrer Institute4, University of Beira Interior5, University of Innsbruck6, Carnegie Mellon University7, California Institute of Technology8, University of Leeds9, University of Eastern Finland10, University of Vienna11, Lebedev Physical Institute12, Finnish Meteorological Institute13, Kyoto University14, Helsinki Institute of Physics15, Stockholm University16, Leibniz Association17
TL;DR: The results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.
Abstract: Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei(1). Aerosols can cause a net cooling of climate by scattering sun ...
738 citations
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Paul Scherrer Institute1, Carnegie Mellon University2, CERN3, Goethe University Frankfurt4, University of Helsinki5, Stockholm University6, ETH Zurich7, Cooperative Institute for Research in Environmental Sciences8, Earth System Research Laboratory9, California Institute of Technology10, Helsinki Institute of Physics11, University of Innsbruck12, University of Eastern Finland13, Finnish Meteorological Institute14, National Center for Atmospheric Research15, Karlsruhe Institute of Technology16, University of Leeds17, University of California, Irvine18, University of Vienna19, University of Beira Interior20
TL;DR: It is shown that organic vapours alone can drive nucleation, and a particle growth model is presented that quantitatively reproduces the measurements and implements a parameterization of the first steps of growth in a global aerosol model that can change substantially in response to concentrations of atmospheric cloud concentration nuclei.
Abstract: About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday. Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres. In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles, thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth, leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer. Although recent studies predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon, and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Kohler theory), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10(-0.5) micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.
507 citations
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TL;DR: Observational evidence is provided that at high altitudes, NPF occurs mainly through condensation of highly oxygenated molecules (HOMs), in addition to taking place through sulfuric acid–ammonia nucleation, which is more than 10 times faster than ion-induced nucleation and growth rates are size-dependent.
Abstract: New particle formation (NPF) is the source of over half of the atmosphere's cloud condensation nuclei, thus influencing cloud properties and Earth's energy balance. Unlike in the planetary boundary layer, few observations of NPF in the free troposphere exist. We provide observational evidence that at high altitudes, NPF occurs mainly through condensation of highly oxygenated molecules (HOMs), in addition to taking place through sulfuric acid-ammonia nucleation. Neutral nucleation is more than 10 times faster than ion-induced nucleation, and growth rates are size-dependent. NPF is restricted to a time window of 1 to 2 days after contact of the air masses with the planetary boundary layer; this is related to the time needed for oxidation of organic compounds to form HOMs. These findings require improved NPF parameterization in atmospheric models.
336 citations
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University of Leeds1, CERN2, Goethe University Frankfurt3, Helsinki Institute of Physics4, university of lille5, University of Helsinki6, Paul Scherrer Institute7, University of Hawaii8, Carnegie Mellon University9, California Institute of Technology10, University of Vienna11, University of Eastern Finland12, Lebedev Physical Institute13, Georgia Institute of Technology14, Foundation for Research & Technology – Hellas15, University of Beira Interior16
TL;DR: In this article, the authors build a global model of aerosol formation using extensive laboratory-measured nucleation rates involving sulfuric acid, ammonia, ions and organic compounds, and a comparison with atmospheric observations show that nearly all nucleation throughout the present-day atmosphere involves ammonia or biogenic organic compounds.
Abstract: Fundamental questions remain about the origin of newly formed atmospheric aerosol particles because data from laboratory measurements have been insufficient to build global models In contrast, gas-phase chemistry models have been based on laboratory kinetics measurements for decades Here we build a global model of aerosol formation using extensive laboratory-measured nucleation rates involving sulfuric acid, ammonia, ions and organic compounds The simulations and a comparison with atmospheric observations show that nearly all nucleation throughout the present-day atmosphere involves ammonia or biogenic organic compounds in addition to sulfuric acid A significant fraction of nucleation involves ions, but the relatively weak dependence on ion concentrations indicates that for the processes studied variations in cosmic ray intensity do not significantly affect climate via nucleation in the present-day atmosphere
260 citations
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TL;DR: It is argued and present evidence that great apes understand the basics of intentional action, but they still do not participate in activities involving joint intentions and attention (shared intentionality), and children's skills of shared intentionality develop gradually during the first 14 months of life.
Abstract: We propose that the crucial difference between human cognition and that of other species is the ability to participate with others in collaborative activities with shared goals and intentions: shared intentionality. Participation in such activities requires not only especially powerful forms of intention reading and cultural learning, but also a unique motivation to share psychological states with oth- ers and unique forms of cognitive representation for doing so. The result of participating in these activities is species-unique forms of cultural cognition and evolution, enabling everything from the creation and use of linguistic symbols to the construction of social norms and individual beliefs to the establishment of social institutions. In support of this proposal we argue and present evidence that great apes (and some children with autism) understand the basics of intentional action, but they still do not participate in activities involving joint intentions and attention (shared intentionality). Human children's skills of shared intentionality develop gradually during the first 14 months of life as two ontogenetic pathways intertwine: (1) the general ape line of understanding others as animate, goal-directed, and intentional agents; and (2) a species-unique motivation to share emotions, experience, and activities with other persons. The develop- mental outcome is children's ability to construct dialogic cognitive representations, which enable them to participate in earnest in the collectivity that is human cognition.
3,660 citations
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01 Jan 2008TL;DR: For instance, the authors argues that human cooperative communication is grounded in a psychological infrastructure of shared intentionality (joint attention, common ground), evolved originally for collaboration and culture more generally.
Abstract: Winner, 2009 Eleanor Maccoby Book Award in Developmental Psychology, presented by the American Psychological Association. and Honorable Mention, Literature, Language & Linguistics category, 2008 PROSE Awards presented by the Professional/Scholarly Publishing Division of the Association of American Publishers. Human communication is grounded in fundamentally cooperative, even shared, intentions. In this original and provocative account of the evolutionary origins of human communication, Michael Tomasello connects the fundamentally cooperative structure of human communication (initially discovered by Paul Grice) to the especially cooperative structure of human (as opposed to other primate) social interaction. Tomasello argues that human cooperative communication rests on a psychological infrastructure of shared intentionality (joint attention, common ground), evolved originally for collaboration and culture more generally. The basic motives of the infrastructure are helping and sharing: humans communicate to request help, inform others of things helpfully, and share attitudes as a way of bonding within the cultural group. These cooperative motives each created different functional pressures for conventionalizing grammatical constructions. Requesting help in the immediate you-and-me and here-and-now, for example, required very little grammar, but informing and sharing required increasingly complex grammatical devices. Drawing on empirical research into gestural and vocal communication by great apes and human infants (much of it conducted by his own research team), Tomasello argues further that humans' cooperative communication emerged first in the natural gestures of pointing and pantomiming. Conventional communication, first gestural and then vocal, evolved only after humans already possessed these natural gestures and their shared intentionality infrastructure along with skills of cultural learning for creating and passing along jointly understood communicative conventions. Challenging the Chomskian view that linguistic knowledge is innate, Tomasello proposes instead that the most fundamental aspects of uniquely human communication are biological adaptations for cooperative social interaction in general and that the purely linguistic dimensions of human communication are cultural conventions and constructions created by and passed along within particular cultural groups. Jean Nicod Lectures A Bradford Book
2,639 citations
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TL;DR: Supporting the cultural intelligence hypothesis and contradicting the hypothesis that humans simply have more “general intelligence,” it is found that the children and chimpanzees had very similar cognitive skills for dealing with the physical world but that theChildren had more sophisticated cognitive skills than either of the ape species for dealingWith the social world.
Abstract: Humans have many cognitive skills not possessed by their nearest primate relatives. The cultural intelligence hypothesis argues that this is mainly due to a species-specific set of social-cognitive skills, emerging early in ontogeny, for participating and exchanging knowledge in cultural groups. We tested this hypothesis by giving a comprehensive battery of cognitive tests to large numbers of two of humans' closest primate relatives, chimpanzees and orangutans, as well as to 2.5-year-old human children before literacy and schooling. Supporting the cultural intelligence hypothesis and contradicting the hypothesis that humans simply have more "general intelligence," we found that the children and chimpanzees had very similar cognitive skills for dealing with the physical world but that the children had more sophisticated cognitive skills than either of the ape species for dealing with the social world.
1,138 citations
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TL;DR: The authors exploit newly available massive natu- ral language corpora to capture the language as a language evolution phenomenon. But their work is limited to a subset of the languages in the corpus.
826 citations
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TL;DR: Going into the future, scientists can help humanity to domesticate nature more wisely by quantifying the tradeoffs among ecosystem services, such as how increasing the provision of one service may decrease ecosystem resilience and the provisionof other services.
Abstract: Like all species, humans have exercised their impulse to perpetuate and propagate themselves. In doing so, we have domesticated landscapes and ecosystems in ways that enhance our food supplies, reduce exposure to predators and natural dangers, and promote commerce. On average, the net benefits to humankind of domesticated nature have been positive. We have, of course, made mistakes, causing unforeseen changes in ecosystem attributes, while leaving few, if any, truly wild places on Earth. Going into the future, scientists can help humanity to domesticate nature more wisely by quantifying the tradeoffs among ecosystem services, such as how increasing the provision of one service may decrease ecosystem resilience and the provision of other services.
791 citations