Benjamin S. Felzer

Indirect Emissions from Biofuels: How Important?

Biofuel Backfire For compelling economical, geopolitical, and environmental reasons, biofuels are considered an attractive alternative to fossil fuels for meeting future global energy demands. Melillo et al. (p. 1397, published online 22 October), however, suggest that a few serious drawbacks related to land use need to be considered. Based on a combined biogeochemistry and economic model, indirect land use (for example, clearing forested land for food crops to compensate for increased biofuel crop production on current farmlands) is predicted to generate more soil carbon loss than directly harvesting biofuel crops. Furthermore, increased fertilizer use for biofuels will add large amounts of nitrous oxide—a more effective heat-trapping molecule than carbon dioxide—to the atmosphere. Policy decisions regarding land and crop management thus need to consider the long-term implications of increased biofuel production. Land-use changes associated with biofuel production are predicted to increase greenhouse gas emissions. A global biofuels program will lead to intense pressures on land supply and can increase greenhouse gas emissions from land-use changes. Using linked economic and terrestrial biogeochemistry models, we examined direct and indirect effects of possible land-use changes from an expanded global cellulosic bioenergy program on greenhouse gas emissions over the 21st century. Our model predicts that indirect land use will be responsible for substantially more carbon loss (up to twice as much) than direct land use; however, because of predicted increases in fertilizer use, nitrous oxide emissions will be more important than carbon losses themselves in terms of warming potential. A global greenhouse gas emissions policy that protects forests and encourages best practices for nitrogen fertilizer use can dramatically reduce emissions associated with biofuels production.

Probabilistic Forecast for Twenty-First-Century Climate Based on Uncertainties in Emissions (Without Policy) and Climate Parameters

Abstract The Massachusetts Institute of Technology (MIT) Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model’s first projections were published in 2003, substantial improvements have been made to the model, and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections; for example, the median surface warming in 2091–2100 is 5.1°C compared to 2.4°C in the earlier study. Many changes contribute to the stronger warming; among the more important ones are taking into account the cooling in the second half of the twentieth century due to volcanic eruptions for input parameter estimation and a more sophisticated method for projecting gross domestic product (GDP) growth, which eliminated many low-emission scenarios. However, if recently published data, suggesting stronger twentieth-century ocean warming, are used to determine...

Sensitivity of the Australian Monsoon to insolation and vegetation: Implications for human impact on continental moisture balance

General circulation model experiments test the geologically based correlation of high monsoon rainfall over interior Australia with Northern Hemisphere insolation and evaluate the sensitivity of the Australian Monsoon to ecosystem change. Our results suggest that Northern Hemisphere insolation control on the intensity of the Siberian High, rather than summer insolation over the Australian continent, determines the strength of the Australian Monsoon on millennial time scales, unlike a classic monsoon regime. Additional simulations show that the penetration of monsoon moisture into the interior is sensitive to biosphere-atmosphere feedbacks linked to vegetation type and soil properties. This sensitivity offers a resolution to the observed failure of the Australian Monsoon to penetrate the interior in the Holocene. Postulated regular burning practiced by early humans may have converted a tree-shrub-grassland mosaic across the semiarid zone to the modern desert scrub, thereby weakening biospheric feedbacks and resulting in long-term desertification of the continent.

Sensitivity of a general circulation model to changes in northern hemisphere ice sheets

Sensitivity experiments with a general circulation model demonstrate the role of ice sheet size on the local, regional, and global climate. Model experiments isolate the effects of albedo, height, and area of the ice sheets and show how the National Center for Atmospheric Research Community Climate Model 1 responds to changes in the size of northern hemisphere ice sheets. A flat ice sheet with full glacial areal extent but no elevation is used to study albedo effects. A full ice sheet with full glacial areal extent and elevation is used to represent height effects. An ice sheet with half the glacial area of the others but the full glacial elevation is used to represent area effects. All of the sensitivity experiments have (1) interactive sea surface temperatures calculated by a slab ocean and (2) modern boundary conditions except for the ice sheets. The experiments show that both the full and flat ice sheets lower the global mean surface temperatures (GMT) by 2.5°C and that the GMT is dependent upon the area, rather than the height, of the ice sheets. High ice sheets maintain colder temperatures than lower ice sheets over the ice sheets themselves, but compensating warmer temperatures occur downstream from the high ice sheets. The downstream warmer temperatures are the result of (1) glacial anticyclones that cause subsidence and reduced cloud cover during summer as well as reduced soil moisture and (2) increased southwesterly flow across the Atlantic Ocean that results in increased southerly advection of warm air during winter. A dynamical effect of the high ice sheets during summer is to change the wave number of the planetary waves in the midlatitudes, whereas a thermodynamic effect of the flat ice sheets during summer is to lower the geopotential heights throughout the northern hemisphere. In general, northern hemisphere ice sheets induce both a local response over the ice sheets and a regional response downstream from the ice sheets but have little impact on the southern hemisphere except where sea ice expands.

Holocene lake sediment records of Arctic hydrology

Although paleoclimatic research in the Arctic has most often focused on variations in temperature, the Arctic has also experienced changes in hydrologic balance. Changes in Arctic precipitation and evaporation rates affects soils, permafrost, lakes, wetlands, rivers, ice and vegetation. Changes in Arctic soils, permafrost, runoff, and vegetation can influence global climate by changing atmospheric methane and carbon dioxide concentrations, thermohaline circulation, and high latitude albedo. Documenting past variations in Arctic hydrological conditions is important for understanding Arctic climate and the potential response and role of the Arctic in regards to future climate change. Methods for reconstructing past changes in Arctic hydrology from the stratigraphic, isotopic, geochemical and fossil records of lake sediments are being developed, refined and applied in a number of regions. These records suggest that hydrological variations in the Arctic have been regionally asynchronous, reflecting the impacts of different forcing factors including orbitally controlled insolation changes, changes in geography related to coastal emergence, ocean currents, sea ice extent, and atmospheric circulation. Despite considerable progress, much work remains to be done on the development of paleohydrological proxies and their application to the Arctic.

Completing the data life cycle: using information management in macrosystems ecology research

An important goal of macrosystems ecology (MSE) research is to advance understanding of ecological systems at both fine and broad temporal and spatial scales. Our premise in this paper is that MSE projects require integrated information management at their inception. Such efforts will lead to improved communication and sharing of knowledge among diverse project participants, better science outcomes, and more transparent and accessible (ie “open”) science. We encourage researchers to “complete the data life cycle” by publishing well-documented datasets, thereby facilitating re-use of the data to answer new and different questions from the ones conceived by those involved in the original projects. The practice of documenting and submitting datasets to data repositories that are publicly accessible ensures that research results and data are available to and use-able by other researchers, thus fostering open science. However, ecologists are often unfamiliar with the requirements and information management tools for effectively preserving data and receive little institutional or professional incentive to do so. Here, we provide recommendations for achieving these ends and give examples from current MSE projects to demonstrate why information management is critical for ensuring that scientific results can be reproduced and that data can be shared for future use.

CLIMATE CHANGE SCENARIOS FOR THE U.S. NATIONAL ASSESSMENT

In support of the U.S. National Assessment of the Potential Consequences of Climate Variability and Change, climate scenarios were prepared to serve as the basis for evaluating the vulnerability of environmental and societal systems to changes projected for the twenty-first century. Since publication of the results of the assessment at the end of 2000, the National Research Councils report Climate Change Science: An Analysis of Some Key Questions, and the U.S. governments U.S. Climate Action Report—2002 have both relied on the assessments findings. Because of the importance of these findings, it is important to directly address questions regarding the representativeness and usefulness of the model-based projections on which the findings were based. In particular, criticisms have focused on whether the climate models that were relied upon adequately represented twentieth-century conditions and whether their projections of conditions for the twenty-first century were outliers. Reexamination of the approa...

Quantitative reflectance spectroscopy of buddingtonite from the Cuprite mining district, Nevada

Buddingtonite, an ammonium-bearing feldspar diagnostic of volcanic-hosted alteration, can be identified and, in some cases, quantitatively measured using short-wave infrared (SWIR) reflectance spectroscopy. In this study over 200 samples from Cuprite, Nevada, were evaluated by X ray diffraction, chemical analysis, scanning electron microscopy, and SWIR reflectance spectroscopy with the objective of developing a quantitative remote-sensing technique for rapid determination of the amount of ammonium or buddingtonite present, and its distribution across the site. Based upon the Hapke theory of radiative transfer from particulate surfaces, spectra from quantitative, physical mixtures were compared with computed mixture spectra. We hypothesized that the concentration of ammonium in each sample is related to the size and shape of the ammonium absorption bands and tested this hypothesis for samples of relatively pure buddingtonite. We found that the band depth of the 2.12-micron NH4 feature is linearly related to the NH4 concentration for the Cuprite buddingtonite, and that the relationship is approximately exponential for a larger range of NH4 concentrations. Associated minerals such as smectite and jarosite suppress the depth of the 2.12-micron NH4 absorption band. Quantitative reflectance spectroscopy is possible when the effects of these associated minerals are also considered.

A systematic study of GCM sensitivity to latitudinal changes in solar radiation

Abstract Paleoclimatic data and climate model simulations have demonstrated that orbitally forced changes in solar radiation can have a pronounced effect on global climate. Key questions remain, however, about the spatial patterns in the climatic sensitivity to these changes in solar radiation. The authors use GCM simulations of Kutzbach and Guetter and Prell and Kutzbach that were made with the NCAR Community Climate Model (CCM), version CCM0. The results of these simulations are employed to compute linear equilibrium sensitivity coefficients and jackknife uncertainties relating the response of key climate variables to orbitally forced changes in solar radiation. The spatial distributions of the sensitivities and the corresponding uncertainties reveal the synoptic patterns of climate response for these climate variables and identify areas of high and low sensitivity. The sensitivity of CCM0 to solar radiation changes such as those experienced during the Quaternary is large and predominately linear for ma...

Evaluation of a regional climate model for paleoclimate applications in the Arctic

The Paleoclimates From Arctic Lakes and Estuaries (PALE) project has been investigating methods of doing high-resolution model-data comparisons for the Arctic. As a prelude to a paleosimulation of the North Atlantic region, a modern simulation using observationally driven reanalysis data has been completed. The ARCSyM mesoscale model has been configured for the North Atlantic region, including Labrador, Ungava, Baffin Island, Ellesmere Island, Greenland, and Iceland, with a resolution of 70 km. This high resolution is necessary to predict sub-GCM grid-scale climate processes, such as precipitation and storm patterns that depend upon the detailed topography and coastlines of the region. Experiments were performed for the time period of September 1987 to March 1990, driven by observational analyses. The model accurately captures the major summer and winter circulation systems in the North Atlantic region. Comparisons with meteorological station data show high correlations for winter and summer surface temperatures, with a cold bias in winter and a warm bias in summer. Winter precipitation is well simulated by the model because it is driven by the large-scale circulation. The orographically driven summer precipitation is overrepresented and does not correlate well with observations, although the overall pattern is correct. These results show that the model is capable of capturing the correct temperature and precipitation patterns, although grid-to-grid comparisons are not possible. The mesoscale model is therefore useful for regionally based data-model comparisons, but should not be used to compare individual cores with specific model grids.