Georeferencing Animal Specimen Datasets

For biodiversity research, the field of study that is concerned with the richness of species of our planet, it is of the utmost importance that the location of an animal specimen find is known with high precision. Due to specimens often having been collected over the course of many years, their accompanying geographical data is often ambiguous or may be very imprecise. In this article, we detail an approach that utilizes reasoning and external sources to improve the geographical information of animal finds. Our main contribution is to show that adding external domain knowledge improves the ability to georeference locations over traditional methods that focus solely on analyzing geographical information. Additionally, our system is able to output the confidence it has in its decisions through a confidence measure based on the difficulty of the instance and the steps undertaken to disambiguate it. Our results show that adding domain knowledge to the georeferencing process increases the accuracy @5km from 38.9% to 61.7% and from 47.0% to 74.5% @25km. Furthermore, we reduce the mean distance by more than half, from 251.1km to 114.5km, and decrease the number of records for which no reference can be found from 26.2% to 7.4%.     

The inner solar system cratering record and the evolution of impactor populations

We review previously published and newly obtained crater size-frequency distributions in the inner solar system. These data indicate that the Moon and the terrestrial planets have been bombarded by two populations of objects. Population 1,dominating at early times, had nearly the same size distribution as the present-day asteroid belt, and produced heavily cratered surfaces with a complex, multi-sloped crater size-frequency distribution. Population 2, dominating since about 3.8–3.7 Gyr,had the same size distribution as near-Earth objects(NEOs) and a much lower impact flux, and produced a crater size distribution characterized by a differential –3single-slope power law in the crater diameter range 0.02 km to 100 km. Taken together with the results from a large body of work on age-dating of lunar and meteorite samples and theoretical work in solar system dynamics, a plausible interpretation of these data is as follows. The NEO population is the source of Population 2 and it has been in near-steady state over the past ～ 3.7–3.8 Gyr; these objects are derived from the main asteroid belt by size-dependent non-gravitational effects that favor the ejection of smaller asteroids. However, Population 1 was composed of main belt asteroids ejected from their source region in a size-independent manner, possibly by means of gravitational resonance sweeping during orbit migration of giant planets;this caused the so-called Late Heavy Bombardment(LHB). The LHB began some time before ～3.9 Gyr, peaked and declined rapidly over the next ～ 100 to 300 Myr,and possibly more slowly from about 3.8–3.7 Gyr to ～2 Gyr. A third crater population(Population S) consisted of secondary impact craters that can dominate the cratering record at small diameters.     

Does temperature contain a stochastic trend: linking statistical results to physical mechanisms

By construction, the time series for radiative forcing that are used to run the 20c3m experiments, which are implemented by climate models, impart non-stationary movements (either stochastic or deterministic) to the simulated time series for global surface temperature. Here, we determine whether stochastic or deterministic trends are present in the simulated time series for global surface temperature by examining the time series for radiative forcing. Statistical tests indicate that the forcings contain a stochastic trend against the alternative hypothesis that the series are trend stationary with a one-time structural change. This result is consistent with the economic processes that impart a stochastic trend to anthropogenic emissions and the physical processes that integrate emissions in the atmosphere. Furthermore, the stochastic trend in the aggregate measure of radiative forcing also is present in the simulated time series for global surface temperature, which is consistent with the relation between these two variables that is represented by a zero dimensional energy balance model. Finally, we propose that internal weather variability imposed on the stochastic trend in radiative forcings is responsible for statistical results, which gives the impression that global surface temperature is trend stationary with a one-time structural change. We conclude that using the ideas of stochastic trends, cointegration, and error correction can generate reliable conclusions regarding the causes of changes in global surface temperature during the instrumental temperature record.