Time filter

Source Type

Melbourne, Australia

Wakker B.P.,University of Wisconsin - Madison | Lockman F.J.,U.S. National Radio Astronomy Observatory | Brown J.M.,University of Wisconsin - Madison | Brown J.M.,Institute of Public Affairs
Astrophysical Journal

We present a study of the small-scale structure of the interstellar medium (ISM) in the Milky Way. We used HST STIS data to measure N(H I) in a pencil beam toward 59 active galactic nuclei and compared the results with the values seen at 9'-36' resolution in the same directions using radio telescopes (Green Bank Telescope, Green Bank 140-ft, and LAB survey). The distribution of ratios N(Ly α)/N(H I) has an average of 1 and a dispersion of about 10%. Our analysis also revealed that spectra from the Leiden-Argentina-Bonn (LAB) all-sky Hi survey need to be corrected, taking out a broad Gaussian component (peak brightness temperature 0.048 K, FWHM 167 km s-1, and central velocity -22 km s-1). The column density ratios have a distribution showing similarities to simple descriptions of hierarchical structure in the neutral ISM as well as to a more sophisticated three-dimensional magnetohydrodynamic simulation. From the comparison with such models, we find that the sonic Mach number of the local ISM should lie between 0.6 and 0.9. However, none of the models yet matches the observed distribution in all details, but with many more sightlines (as will be provided by the Cosmic Origins Spectrograph) our approach can be used to constrain the properties of interstellar turbulence. © 2011. The American Astronomical Society. Source

Quirk T.,Institute of Public Affairs
Energy and Environment

The role of methane in the atmosphere has been emphasised by the IPCC to the point that many governments regard methane as almost as important as carbon dioxide amongst the greenhouse gases. The IPCC emphasis has resulted in emissions from natural gas pipelines, coal seams and agricultural livestock being included in schemes to limit the growth of greenhouse gas concentrations. Analysis of changes to atmospheric methane within the last one hundred years suggests that the annual increases from 1930 to 1970 were due to losses from the production, transmission and distribution of natural gas. Further, the substantial reduction in these losses from 1970 to 1990 has brought the annual increases back to the rate seen at the start of the twentieth century. Measurements over the last fifteen years show only natural variability. They provide no justification for any attempts to reduce methane from industrial or agricultural activity. While methane variability remains restricted to natural causes, the best policy is to do nothing. Source

Babajanian B.,Institute of Public Affairs
Central Asian Survey

This article examines the extent to which the World Bank's community-driven Village Investment Project empowered people to influence the choice of local investments (micro-projects) and to exact accountability from their leaders. It is based on qualitative interviews and group discussions in 16 rural communities. The research demonstrates that the project provided an effective mechanism for responsive infrastructure delivery to address local priority needs. However, it did not improve accountability either within or outside the micro-project boundaries. The project's bottom-up development model was not by itself sufficient to enable people to exercise power over local government officials and informal leaders in the absence of effective horizontal accountability institutions within the state. © 2015 Southseries Inc. Source

Quirk T.,Institute of Public Affairs
Asia-Pacific Journal of Atmospheric Sciences

The apparent leveling of the global temperature time series at the end of the 1990s may represent a break in the upward trend. A study of the time series measurements for temperature, carbon dioxide, humidity and methane shows changes coincident with phase changes of the Atlantic and Pacific Decadal Oscillations. There are changes in carbon dioxide, humidity and methane measurement series in 2000. If these changes mark a phase change of the Pacific Decadal Oscillation then it might explain the global temperature behavior. © 2012 Korean Meteorological Society and Springer Science+Business Media Dordrecht. Source

Soon W.,Harvard - Smithsonian Center for Astrophysics | Velasco Herrera V.M.,National Autonomous University of Mexico | Selvaraj K.,Xiamen University | Traversi R.,University of Florence | And 7 more authors.
Earth-Science Reviews

We report on the existence and nature of Holocene solar and climatic variations on centennial to millennial timescales. We introduce a new solar activity proxy, based on nitrate (NO3-) concentration from the Talos Dome ice core, East Antarctica. We also use a new algorithm for computing multiple-cross wavelet spectra in time-frequency space that is generalized for multiple time series (beyond two). Our results provide a new interpretive framework for relating Holocene solar activity variations on centennial to millennial timescales to co-varying climate proxies drawn from a widespread area around the globe. Climatic proxies used represent variation in the North Atlantic Ocean, Western Pacific Warm Pool, Southern Ocean and the East Asian monsoon regions. Our wavelet analysis identifies fundamental solar modes at 2300-yr (Hallstattzeit), 1000-yr (Eddy), and 500-yr (unnamed) periodicities, leaves open the possibility that the 1500-1800-yrcycle may either be fundamental or derived, and identifies intermediary derived cycles at 700-yr and 300-yr that may mark rectified responses of the Atlantic thermohaline circulation to external solar modulation and pacing. Dating uncertainties suggest that the 1500-yr and 1800-yrcycles described in the literature may represent either the same or two separate cycles, but in either case, and irrespective too of whether it is a fundamental or derived mode in the sense of Dima and Lohmann (2009), the 1500-1800-yr periodicity is widely represented in a large number of paleoclimate proxy records. It is obviously premature to reject possible links between changing solar activity at these multiple scales and the variations that are commonly observed in paleoclimatic records. © 2014 Elsevier B.V. Source

Discover hidden collaborations