Abstracts on Global Climate Change

Dec 2003

Analysis of the duration, seasonal timing, and location of North Atlantic tropical cyclones: 1950-2002

Balling, RC Cerveny, RS


Many scientists have suggested that a warmer world with elevated atmospheric moisture levels could increase the frequency, intensity, or duration of future tropical cyclones or alter their mean locations. While others have examined historical patterns in tropical cyclone frequency and intensity, and generally found no trends in recent decades, we analyzed tropical cyclone records from the Caribbean, Gulf of Mexico, and tropical sector of the western North Atlantic over the period 1950-2002 with a focus on the duration, seasonal timing, and geographic position of the events. We found no significant trends in the start date, ending date, or duration of the storm season (defined in various ways) and no trends in the average geographic position of the storms. Furthermore, these measures of hurricane season timing and storm locations were not related to regional sea surface temperature or the northern hemispheric or global temperatures.

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Soil and rhizosphere microorganisms have the same Q(10) for respiration in a model system

Baath, E Wallander, H


We compared the Q(10) relationship for root-derived respiration (including respiration due to the root, external mycorrhizal mycelium and rhizosphere microorganisms) with that of mainly external ectomycorrhizal mycelium and that of bulk soil microorganisms without any roots present. This was studied in a microcosm consisting of an ectomycorrhizal Pinus muricata seedling growing in a sandy soil, and where roots were allow to colonize one soil compartment, mycorrhizal mycelium another compartment, and the last compartment consisted of root- and mycorrhiza-free soil. The respiration rate in the bulk soil compartment was 30 times lower than in the root compartment, while that in the mycorrhizal compartment was six times lower. There were no differences in Q(10) (for 5-15degreesC) between the different compartments, indicating that there were no differences in the temperature relationship between root-associated and non-root-associated organisms. Thus, there are no indications that different Q(10) values should be used for different soil organism, bulk soil or rhizosphere-associated microorganisms when modelling the effects of global climate change.

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Ecosystem responses to global climate change: Moving beyond color mapping

Schmitz, OJ Post, E Burns, CE Johnston, KM

BIOSCIENCE 53:12 1199-1205

Current assessments of climate-change effects on ecosystems use two key approaches: (1) empirical synthesis and modeling of species range shifts and life-cycle processes that coincide with recent evidence of climate warming, from which scenarios of ecosystem change are inferred; and (2) experiments examining plant-soil interactions under simulated climate warming. Both kinds of assessment offer indisputable evidence that climate change and its effects on ecosystems are ongoing. However, both approaches often provide conservative estimates of the effects of climate change on ecosystems, because they do not consider the interplay and feedback among higher trophic levels in ecosystems, which may have a large effect on plant species composition and on ecosystem services such as productivity, Understanding the impacts of these top-down processes on ecosystems is critical for determining large-scale ecosystem response to climate change. Using examples of links between climate forcing, trophic interactions, and changes in ecosystem state in selected terrestrial, freshwater, and marine systems, we show that the ability to understand and accurately forecast future effects of climate change requires an integrated perspective, linking climate and the biotic components of the ecosystem as a whole.

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Elevated sea-surface temperature, reduced provisioning and reproductive failure of wedge-tailed shearwaters (Puffinus pacificus) in the southern Great Barrier Reef, Australia

Smithers, BV Peck, DR Krockenberger, AK Congdon, BC


During the 2002 austral summer abnormally high sea-surface temperatures (SST) occurred in the southern Great Barrier Reef (GBR), Australia. This phenomenon was accompanied by reduced provisioning, decreased growth rates and reproductive failure of wedge-tailed shearwaters in the region. In 2002, adults were unable to compensate for changes in either the availability and/or accessibility of forage-fish by increasing food loads or foraging rates. This is one of few studies to explicitly correlate decreases in chick provisioning with above-average annual variation in SST and is the first to do so for a tropical seabird species in the western Pacific. It adds to an increasing number of data sets identifying the potential negative impacts of increasing SST at upper-trophic levels. As SST continue to rise with global climate change, our results predict substantial detrimental effects on seabird populations of the GBR. This finding has important implications for both seabird and coral reef ecosystem management in the region. Our results also suggest that wedge-tailed shearwaters are sensitive indicators to changes in forage-fish availability/accessibility associated with SST variation that can be used to develop models of, and monitor for, these potential impacts.

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Holocene yellow silt layers and the paleoclimate event of 8200 a BP in Lop Nur, Xinjiang, NW China

Liu, CL Wang, ML Jiao, PC Li, S Chen, YZ


Many yellow silt layers have been identified in the Holocene sediments in the last lake of Lop Nur (playa), Xinjiang, northwestern China. Statistics of drill-hole cores have revealed more than one hundred layers, which exhibit regularity in time sequence. Study has further verified that these yellow silt layers were deposited through eolian processes. The time-frequency distribution diagram shows an obvious peak occurring at about 8200 a B.P., which is consistent with the dry, windy and cold climate event occurring at 8200 a in other places around the world. Therefore, this event is regarded as a response to the global climate change.

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