Publications Published in 2007

1. A cold phase of the East Pacific triggers new phytoplankton blooms in San Francisco Bay. Cloern, James E.; Jassby, Alan D.; Thompson, Janet K.; Hieb, Kathryn A..
   Proceedings of the National Academy of Sciences: 2007
   DOI: 10.1073/pnas.0706151104
   Notes
   Ecological observations sustained over decades often reveal abrupt changes in biological communities that signal altered ecosystem states. We report a large shift in the biological communities of San Francisco Bay, first detected as increasing phytoplankton biomass and occurrences of new seasonal blooms that began in 1999. This phytoplankton increase is paradoxical because it occurred in an era of decreasing wastewater nutrient inputs and reduced nitrogen and phosphorus concentrations, contrary to the guiding paradigm that algal biomass in estuaries increases in proportion to nutrient inputs from their watersheds. Coincidental changes included sharp declines in the abundance of bivalve mollusks, the key phytoplankton consumers in this estuary, and record high abundances of several bivalve predators: Bay shrimp, English sole, and Dungeness crab. The phytoplankton increase is consistent with a trophic cascade resulting from heightened predation on bivalves and suppression of their filtration control on phytoplankton growth. These community changes in San Francisco Bay across three trophic levels followed a state change in the California Current System characterized by increased upwelling intensity, amplified primary production, and strengthened southerly flows. These diagnostic features of the East Pacific "cold phase" lead to strong recruitment and immigration of juvenile flatfish and crustaceans into estuaries where they feed and develop. This study, built from three decades of observation, reveals a previously unrecognized mechanism of oceanestuary connectivity. Interdecadal oceanic regime changes can propagate into estuaries, altering their community structure and efficiency of transforming land-derived nutrients into algal biomass.
   
   
   
2. Adaptation to climate change in the Northeast United States: opportunities, processes, constraints. Moser, Susanne; Kasperson, Roger; Yohe, Gary; Agyeman, Julian.
   Mitigation and Adaptation Strategies for Global Change: 2007
   Notes
   Scientific evidence accumulating over the past decade documents that climate change impacts are already being experienced in the US Northeast. Policy-makers and resource managers must now prepare for the impacts from climate change and support implementing such plans on the ground. In this paper we argue that climate change challenges the region to maintain its economic viability, but also holds some opportunities that may enhance economic development, human well-being, and social justice. To face these challenges and seize these opportunities effectively we must better understand adaptation capacities, opportunities and constraints, the social processes of adaptation, approaches for engaging critical players and the broader public in informed debate, decision-making, and conscious interventions in the adaptation process. This paper offers a preliminary qualitative assessment, in which we emphasize the need for (1) assessing the feasibility and side effects of technological adaptation options, (2) increasing available resources and improving equitable access to them, (3) increasing institutional flexibility, fit, cooperation and decision-making authority, (4) using and enhancing human and social capital, (5) improving access to insurance and other risk-spreading mechanisms, and (6) linking scientific information more effectively to decision-makers while engaging the public. Throughout, we explore these issues through illustrative sectoral examples. We conclude with a number of principles that may guide the preparation of future adaptation plans for the Northeast.
   
   
   
3. Aerosol-cloud interaction inferred from MODIS satellite data and global aerosol models. Myhre, G.; Stordal, F.; Johnsrud, M.; Kaufman, Y. J.; Rosenfeld, D.; Storelvmo, T.; Kristjansson, J. E.; Berntsen, T. K.; Myhre, A.; Isaksen, I. S. A..
   Copernicus Publications Atmos Chem Phys: 2007
   Notes
   We have used the MODIS satellite data and two global aerosol models to investigate the relationships between aerosol optical depth (AOD) and cloud parameters that may be affected by the aerosol concentration. The relationships that are studied are mainly between AOD, on the one hand, and cloud cover, cloud liquid water path, and water vapour, on the other. Additionally, cloud droplet effective radius, cloud optical depth, cloud top pressure and aerosol Ångström exponent, have been analysed in a few cases. In the MODIS data we found, as in earlier studies, an enhancement in the cloud cover with increasing AOD. We find it likely that most of the strong increase in cloud cover with AOD, at least for AOD<0.2, is a result of aerosol-cloud interactions and a prolonged cloud lifetime. Large and mesoscale weather systems seem not to be a cause for the increase in cloud cover with AOD in this range. Sensitivity simulations show that when water uptake of the aerosols is not taken into account in the models the modelled cloud cover mostly decreases with AOD. Part of the relationship found in the MODIS data for AOD>0.2 can be explained by larger water uptake close to the clouds since relative humidity is higher in regions with higher cloud cover. The efficiency of the hygroscopic growth depends on aerosol type, the hygroscopic nature of the aerosol, the relative humidity, and to some extent the cloud screening. By analysing the Ångström exponent we find that the hygroscopic growth of the aerosol is not likely to be a main contributor to the cloud cover increase with AOD. Since the largest increase in cloud cover with AOD is for low AOD (~0.2) and thus also for low cloud cover, we argue that cloud contamination is not likely to play a large role. However, interpretation of the complex relationships between AOD and cloud parameters should be made with great care and further work is clearly needed.
   
   
   
4. Aerosol partitioning between the interstitial and the condensed phase in mixed-phase clouds. Verheggen, Bart; Cozic, Julie; Weingartner, Ernest; Bower, Keith; Mertes, Stephan; Connolly, Paul; Gallagher, Martin; Flynn, Michael; Choularton, Tom; Baltensperger, Urs.
   Journal of Geophysical Research: 2007
   Notes
   The partitioning of aerosol particles between the cloud and the interstitial phase (i.e., unactivated aerosol) has been investigated during several Cloud and Aerosol Characterization Experiments (CLACE-3, CLACE-3 and CLACE-4) conducted in winter and summer 2004 and winter 2005 at the high alpine research station Jungfraujoch (3580 m altitude, Switzerland). Ambient air was sampled using different inlets in order to determine the activated fraction of aerosol particles,
   
   
   
5. Aerosol Pollution Impact on Precipitation: A Scientific Review. Andreae, Meinrat O., Artaxo, Paulo, Barrie, Leonard. A., Brenguier, Jean-Louis, Cotton, William R., Feingold, Graham, Gong, Sunling L., Hegg, Dean A., Kaufman, Yoram (Deceased), Levin, Zev, Lohmann, Ulrike, Tanre, Didier, Yuter, Sandra.
   The WMO/IUGG INTERNATIONAL AEROSOL PRECIPITATION SCIENCE ASSESSMENT GROUP (IAPSAG): 2007
   Notes
   The WMO and IUGG resolutions handed a mandate to IAPSAG to review the effects of aerosol pollution, including biomass burning, on precipitation. The initial set up and framework of IAPSAG were illustrated by List [2004]. This document is a review of our knowledge of the relationship between aerosols and precipitation reaching the Earth's surface and it includes a list of recommendations that could help to advance our knowledge in this area.
   
   
   
6. Altered soil microbial community at elevated CO2 leads to loss of soil carbon. Carney, Karen M.; Hungate, Bruce A.; Drake, Bert G.; Megonigal, J. Patrick.
   PNAS: 2007
   DOI: 10.1073/pnas.0610045104
   Notes
   Increased carbon storage in ecosystems due to elevated CO2 may help stabilize atmospheric CO2 concentrations and slow global warming. Many field studies have found that elevated CO2 leads to higher carbon assimilation by plants, and others suggest that this can lead to higher carbon storage in soils, the largest and most stable terrestrial carbon pool. Here we show that 6 years of experimental CO2 doubling reduced soil carbon in a scrub-oak ecosystem despite higher plant growth, offsetting {approx}52% of the additional carbon that had accumulated at elevated CO2 in aboveground and coarse root biomass. The decline in soil carbon was driven by changes in soil microbial composition and activity. Soils exposed to elevated CO2 had higher relative abundances of fungi and higher activities of a soil carbon-degrading enzyme, which led to more rapid rates of soil organic matter degradation than soils exposed to ambient CO2. The isotopic composition of microbial fatty acids confirmed that elevated CO2 increased microbial utilization of soil organic matter. These results show how elevated CO2, by altering soil microbial communities, can cause a potential carbon sink to become a carbon source.
   
   
   
7. Analysis of farm performance in Europe under different climatic and management conditions to improve understanding of adaptive capacity. Reidsma, Pytrik; Ewert, Frank; Oude Lansink, Alfons.
   Climatic Change: 2007
   Notes
   Abstract&nbsp;&nbsp;The aim of this paper is to improve understanding of the adaptive capacity of European agriculture to climate change. Extensive data on farm characteristics of individual farms from the Farm Accountancy Data Network (FADN) have been combined with climatic and socio-economic data to analyze the influence of climate and management on crop yields and income and to identify factors that determine adaptive capacity. A multilevel analysis was performed to account for regional differences in the studied relationships. Our results suggest that socio-economic conditions and farm characteristics should be considered when analyzing effects of climate conditions on farm yields and income. Next to climate, input intensity, economic size and the type of land use were identified as important factors influencing spatial variability in crop yields and income. Generally, crop yields and income are increasing with farm size and farm intensity. However, effects differed among crops and high crop yields were not always related to high incomes, suggesting that impacts of climate and management differ by impact variable. As farm characteristics influence climate impacts on crop yields and income, they are good indicators of adaptive capacity at farm level and should be considered in impact assessment models. Different farm types with different management strategies will adapt differently.
   
   
   
8. Analysis of rainwater samples: comparison of single particle residues with ambient particle chemistry from the northeast Pacific and Indian oceans. Holecek, J.C.; Spencer, M.T.; Prather, K.A..
   Journal of Geophysical Research: 2007
   DOI: 10.1029/2006JD008269
   Notes
   Individual particles produced from atomized rainwater samples collected in California and the Indian Ocean were analyzed with an aerosol time-of-flight mass spectrometer (ATOFMS) to investigate the chemical composition of the individual rain residue particles. Insoluble residue particle types were determined on the basis of a comparison of the rainwater particle mass spectra with ambient particle spectra. Major particle types found in rainwater include dust, organic carbon with sodium, aromatic organic carbon, vegetative detritus, and an internally mixed sea salt and elemental carbon class. A unique internally mixed sea salt–elemental carbon particle type was detected in both the ambient and rainwater samples, suggesting this particle type was most likely formed by cloud processing occurring during long-range transport. The presence of this particle type in remote marine locations has important climate ramifications as it is anticipated it will be strongly absorbing on the basis of the combination of an absor ng particle (elemental carbon) mixed with a high refractive index material (sea salt). Most of the particle types detected in rainwater were detected in the ambient particles with the exception of a unique aromatic particle type detected in rainwater samples from both locations. The presence of the aromatic type coupled with the absence of biomass particles in the rainwater samples leads to the hypothesis the aromatic components were originally associated with atmospheric biomass burning particles. The ubiquitous presence of this aromatic type in rainwater samples highlights the potential importance of biomass burning and/or humic-like substances (HULIS) compounds in cloud formation and rain processes.
   
   
   
9. An inter-comparison of regional climate models for Europe: model performance in present-day climate. Jacob, Daniela; Bärring, Lars; Christensen, Ole; Christensen, Jens; de Castro, Manuel; Déqué, Michel; Giorgi, Filippo; Hagemann, Stefan; Hirschi, Martin; Jones, Richard; Kjellström, Erik; Lenderink, Geert; Rockel, Burkhardt; Sánchez, Enrique; Schär, Christoph; Seneviratne, Sonia; Somot, Samuel; van Ulden, Aad; van den Hurk, Bart.
   Climatic Change: 2007
   Notes
   The analysis of possible regional climate changes over Europe as simulated by 10 regional climate models within the context of PRUDENCE requires a careful investigation of possible systematic biases in the models. The purpose of this paper is to identify how the main model systematic biases vary across the different models. Two fundamental aspects of model validation are addressed here: the ability to simulate (1) the long-term (30 or 40&nbsp;years) mean climate and (2) the inter-annual variability. The analysis concentrates on near-surface air temperature and precipitation over land and focuses mainly on winter and summer. In general, there is a warm bias with respect to the CRU data set in these extreme seasons and a tendency to cold biases in the transition seasons. In winter the typical spread (standard deviation) between the models is 1&nbsp;K. During summer there is generally a better agreement between observed and simulated values of inter-annual variability although there is a relatively clear signal that the modeled temperature variability is larger than suggested by observations, while precipitation variability is closer to observations. The areas with warm (cold) bias in winter generally exhibit wet (dry) biases, whereas the relationship is the reverse during summer (though much less clear, coupling warm (cold) biases with dry (wet) ones). When comparing the RCMs with their driving GCM, they generally reproduce the large-scale circulation of the GCM though in some cases there are substantial differences between regional biases in surface temperature and precipitation.
   
   
   
10. An overview of regional land-use and land-cover impacts on rainfall. Pielke, R. A.; Adegoke, J.; Beltran-Przekurat, A.; Hiemstra, C. A.; Lin, J.; Nair, U. S.; Niyogi, D.; Nobis, T. E..
    Tellus B: 2007
    DOI: doi:10.1111/j.1600-0889.2007.00251.x
    Notes
    This paper documents the diverse role of land-use/land-cover change on precipitation. Since land conversion continues at a rapid pace, this type of human disturbance of the climate system will continue and become even more significant in the coming decades.