Role of historical land-cover changes as a mechanism for global and regional climate change

Spring 1999.Also issued as author's dissertation (Ph.D.) -- Colorado State University, 1999.Includes bibliographical references.This paper describes the results from several modeling studies and an observational analysis as to the effect of historical land-cover change on regional and global climates. We discuss methods for determining historical vegetation change and present results from model simulations at the global and regional scale which compare climates generated using currently observed vegetation versus natural vegetation as a boundary condition. We also compare these modeling studies with recent observational data and with simulations of climate change resulting from increased greenhouse gases. We conclude from this research that vegetation change, as it has already occurred, globally and regionally, can have significant effects on both global and regional climates. These effects are not limited to the regions of direct land-cover change forcing. For example, as a result of tropical deforestation, the position and intensity of the ITCZ is affected by the change in land surface characteristics resulting in global-scale effects which are similar in nature to the climatic effects associated with El Nino Southern Oscillation (ENSO). These include changes in high-latitude circulations, the generation of low frequency waves which appear to propagate to the extratropic s in well-defined teleconnection patterns, and reduced low-level easterlies over most of the tropical Pacific basin under current vegetation. This implies an interaction mechanism between tropical deforestation and ENSO. The model simulations of climate change due to landcover change compare favorably in spatial pattern and amplitude with recently observed temperature trends. Additionally, a comparison between simulations of climate changes due to landcover disturbance and changes due to rising atmospheric CO2 concentration show that global land-cover changes, as they have already occurred, are responsible for shifts in climate which are of similar amplitude and occur in the same regions as simulated climate changes resulting from increased CO2. A comparison of three independent observational datasets shows strong disagreement not only in the sign of recent globally-averaged temperature trends but also disagree as to regions where significant climate shifts are occurring. Unlike model simulations of greenhouse gas warming, warm anomalies do not occur preferentially over land during t his period and do not increase with height in the tropics.Sponsored by NPS contracts CA 1268-2-9004 and COLR-R92-0204; USGS contract 99CR-AG0005 and SA 9005CS0014; and NASA grant NAG8-1511

Role of historical land-cover changes as a mechanism for global and regional climate change, The

1999 Spring.Includes bibliographical references (pages 99-117).This paper describes the results from several modeling studies and an observational analysis as to the effect of historical land-cover change on regional and global climates. We discuss methods for determining historical vegetation change and present results from model simulations at the global and regional scale which compare climates generated using currently observed vegetation versus natural vegetation as a boundary condition. We also compare these modeling studies with recent observational data and with simulations of climate change resulting from increased greenhouse gases. We conclude from this research that vegetation change, as it has already occurred, globally and regionally, can have significant effects on both global and regional climates. These effects are not limited to the regions of direct land-cover change forcing. For example, as a result of tropical deforestation, the position and intensity of the ITCZ is affected by the change in land surface characteristics resulting in global-scale effects which are similar in nature to the climatic effects associated with El Niño Southern Oscillation (ENSO). These include changes in high-latitude circulations, the generation of low frequency waves which appear to propagate to the extratropics in well-defined teleconnection patterns, and reduced low-level easterlies over most of the topical Pacific basin under current vegetation. This implies an interaction mechanism between tropical deforestation and ENSO. The model simulations of climate change due to land-cover change compare favorably in spatial patterns and amplitude with recently observed temperature trends. Additionally, a comparison between simulations of climate changes due to land-cover disturbance and changes due to rising atmospheric CO2 concentration show that global land-cover changes as they have already occurred, are responsible for shifts in climate which are of similar amplitude and occur in the same regions as simulated climate changes resulting from increased CO2. A comparison of three independent observational datasets shows strong disagreement not only in the sign of recent globally-averaged temperature trends but also disagree as to regions where significant climate shifts are occurring. Unlike model simulations of greenhouse gas warming, warm anomalies do not occur preferentially over land during this period and do not increase with height in the tropics

Sensitivity of a general circulation model to large scale vegetation changes, The

Summer 1995.Bibliography: pages 52-57.Sponsored by National Park Service 0479-8-8001.Sponsored by National Science Foundation ATM-930675

Donepezil Plus Solifenacin (CPC-201) Treatment for Alzheimer's Disease

Available cholinergic drugs for treating Alzheimer's disease (AD) provide modest symptomatic benefit. We hypothesized that co-administration of a peripheral anticholinergic to reduce dose-limiting adverse effects (AEs) would enable the safe/tolerable use of higher cholinesterase inhibitor doses and thus improve their antidementia efficacy. A modified single-blind, ascending-dose, phase IIa study of donepezil plus solifenacin (CPC-201) lasting 26 weeks was conducted in 41 patients with probable AD of moderate severity. Entry criteria included the use of donepezil at a dose of 10 mg/day during the preceding 3 months. The primary outcome measure was the maximum tolerated dose (MTD) of donepezil achieved (to protocol limit of 40 mg/day) when administered with the anticholinergic solifenacin 15 mg/day. Secondary measures included assessments of cognitive and global function, as well as of AEs. The mean ± SD donepezil MTD increased to 38 ± 0.74 mg/day (median 40 mg/day; p < 0.001); 88% of the study population safely attained this dose at the end of titration. Markedly reduced donepezil AE frequency, especially gastrointestinal, allowed this dose increase. There were no drug-related serious AEs or clinically significant laboratory abnormalities. At 26 weeks, Alzheimer's Disease Assessment Scale Cognitive Component scores in the efficacy evaluable population improved by 0.35 ± 0.85 points over baseline (p < 0.05), an estimated 2.5 ± 0.84 points above 10 mg/day donepezil and 5.4 ± 0.84 points above historic placebo (both p < 0.05). Clinical Global Impression of Improvement scores improved by 0.94 ± 0.20 to 3.1 ± 0.20 points (p < 0.001). The findings suggest that limiting donepezil AEs by co-administration of solifenacin allows the safe administration of substantially higher cholinesterase inhibitors doses that may augment cognitive and global benefits in patients with AD

Global vegetation cover changes from coarse resolution satellite data

Land cover plays a key role in various biophysical processes related to global climate and terrestrial biogeochemistry. Although global land cover has dramatically changed over the last few centuries, until now there has been no consistent way of quantifying the changes globally. In this study we used long-term climate and soils data along with coarse resolution satellite observations to quantify the magnitude and spatial extent of large-scale land cover changes attributable to anthropogenic processes. Differences between potential leaf area index (LAI), derived from climate-soil-leaf area equilibrium, and actual leaf area index obtained from satellite data are used to estimate changes in land cover. Further, changes in LAI between potential and actual conditions are linked to climate by expressing them as possible changes in radiometric surface temperatures (Tr) resulting from changes in surface energy partitioning. As expected, areas with high population densities, such as India, China, and western Europe showed large reductions in LAI. Changes in global land cover expressed as summer, midafternoon Tr, ranged from −8° to +16°C. Deforestation resulted in an increase in Tr, while irrigated agriculture reduced the Tr. Many of the current general circulation models (GCMs) use potential vegetation maps to represent global vegetation. Our results indicate that there are widespread changes in global land cover due to deforestation and agriculture below the resolution of many GCMs, and these changes could have a significant impact on climate. Potential and actual LAI data sets are available for climate modelers at 0.5° × 0.5° resolution to study the possible impacts of land cover changes on global temperatures and circulation patterns

A search for rapidly pulsating hot subdwarf stars in the GALEX survey

NASA's Galaxy Evolution Explorer (GALEX) provided near- and far-UV observations for approximately 77 percent of the sky over a ten-year period; however, the data reduction pipeline initially only released single NUV and FUV images to the community. The recently released Python module gPhoton changes this, allowing calibrated time-series aperture photometry to be extracted easily from the raw GALEX data set. Here we use gPhoton to generate light curves for all hot subdwarf B (sdB) stars that were observed by GALEX, with the intention of identifying short-period, p-mode pulsations. We find that the spacecraft's short visit durations, uneven gaps between visits, and dither pattern make the detection of hot subdwarf pulsations difficult. Nonetheless, we detect UV variations in four previously known pulsating targets and report their UV pulsation amplitudes and frequencies. Additionally, we find that several other sdB targets not previously known to vary show promising signals in their periodograms. Using optical follow-up photometry with the Skynet Robotic Telescope Network, we confirm p-mode pulsations in one of these targets, LAMOST J082517.99+113106.3, and report it as the most recent addition to the sdBVr class of variable stars.Comment: 11 Pages, 8 Figures, Accepted for publication in the Astrophysical Journa

Sensitivity of a general circulation model to global changes in leaf area index

Methods have recently become available for estimating the amount of leaf area at the surface of the Earth using satellite data. Also available are modeled estimates of what global leaf area patterns would look like should the vegetation be in equilibrium with current local climatic and soil conditions. The differences between the actual vegetation distribution and the potential vegetation distribution may reflect the impact of human activity on the Earth\u27s surface. To examine model sensitivity to changes in leaf area index (LAI), global distributions of maximum LAI were used as surface boundary conditions in the National Center for Atmospheric Research community climate model (NCAR CCM2) coupled with the biosphere atmosphere transfer scheme (BATS). Results from 10-year ensemble averages for the months of January and July indicate that the largest effects of the decreased LAI in the actual LAI simulation occur in the northern hemisphere winter at high latitudes despite the fact that direct LAI forcing is negligible in these regions at this time of year. This is possibly a result of LAI forcing in the tropics which has long-ranging effects in the winter of both hemispheres. An assessment of the Asian monsoon region for the month of July shows decreased latent heat flux from the surface, increased surface temperature, and decreased precipitation with the actual LAI distribution. While the statistical significance of the results has not been unambiguously established in these simulations, we suspect that an effect on modeled general circulation dynamics has occurred due to changes of maximum LAI suggesting that further attention needs to be paid to the accurate designation of vegetation parameters. The incorporation of concomitant changes in albedo, vegetation fractional coverage, and roughness length is suggested for further research

Relative climatic effects of landcover change and elevated carbon dioxide combined with aerosols: A comparison of model results and observations

In this study we examine the possibility that the historical total of human landcover changes have had a comparable effect on climate to that of historical increases in CO2 and aerosols. We compared results from two coupled climate model simulations which investigated transient climate changes produced by observed historical changes of CO2 combined with sulfate aerosol forcing with two other climate model simulations that examined the equilibrium climatic effects of currently observed changes in landcover from its natural state. We found that simulated, near-surface temperature anomalies due to transient increases in atmospheric CO2 combined with aerosols at the level currently observed are of similar amplitude as simulated temperature anomalies due to the direct and remote (nonlocal) equilibrium effects of historical anthropogenic landcover change in all models. Both effects are of comparable amplitude to observed temperature trends in the past 2 decades, the period of largest global surface warming. These results provide evidence for a confounding influence on surface temperatures and may be an indication that the problem of detection of the radiative warming effect of increased CO2 in the observational record may be more complicated than previously appreciated

Evidence for concerted ring opening and C-Br bond breaking in UV-excited bromocyclopropane

Photodissociation of gaseous bromocyclopropane via its A-band continuum has been studied at excitation wavelengths ranging from 230 nm to 267 nm. Velocity-map images of ground-state bromine atoms (Br), spin-orbit excited bromine atoms (Br*) and C3H5 hydrocarbon radicals reveal the kinetic energies of these various photofragments. Both Br and Br* atoms are predominantly generated via repulsive excited electronic states in a prompt photodissociation process in which the hydrocarbon co-fragment is a cyclopropyl radical. However, the images obtained at the mass of the hydrocarbon radical fragment identify a channel with total kinetic energy greater than that deduced from the Br and Br* images, and with a kinetic energy distribution that exceeds the energetic limit for Br + cyclopropyl radical products. The velocity-map images of these C3H5 fragments have lower angular anisotropies than measured for Br and Br*, indicating molecular restructuring during dissociation. The high kinetic energy C3H5 signals are assigned to allyl radicals generated by a minor photochemical pathway which involves concerted C-Br bond dissociation and cyclopropyl ring-opening following single UV-photon absorption. Slow photofragments also contribute to the velocity map images obtained at the C3H5 radical mass, but corresponding slow Br atoms are not observed. These features in the images are attributed to C3H5+ from the photodissociation of the C3H5Br+ molecular cation following two-photon ionization of the parent compound. This assignment is confirmed by 118-nm vacuum ultraviolet ionization studies that prepare the molecular cation in its ground electronic state prior to UV photodissociation

Modeling Progressive Fibrosis with Pluripotent Stem Cells Identifies an Anti-fibrotic Small Molecule.

Progressive organ fibrosis accounts for one-third of all deaths worldwide, yet preclinical models that mimic the complex, progressive nature of the disease are lacking, and hence, there are no curative therapies. Progressive fibrosis across organs shares common cellular and molecular pathways involving chronic injury, inflammation, and aberrant repair resulting in deposition of extracellular matrix, organ remodeling, and ultimately organ failure. We describe the generation and characterization of an in&nbsp;vitro progressive fibrosis model that uses cell types derived from induced pluripotent stem cells. Our model produces endogenous activated transforming growth factor β (TGF-β) and contains activated fibroblastic aggregates that progressively increase in size and stiffness with activation of known fibrotic molecular and cellular changes. We used this model as a phenotypic drug discovery platform for modulators of fibrosis. We validated this platform by identifying a compound that promotes resolution of fibrosis in in&nbsp;vivo and ex&nbsp;vivo models of ocular and lung fibrosis