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Climate effects of global land cover change
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When changing from grass and croplands to forest, there are two competing effects of land cover change on climate: an albedo effect which leads to warming and an evapotranspiration effect which tends to produce cooling. It is not clear which effect would dominate. We have performed simulations of global land cover change using the NCAR CAM3 atmospheric general circulation model coupled to a slab ocean model. We find that global replacement of current vegetation by trees would lead to a global mean warming of 1.3°C, nearly 60% of the warming produced under a doubled CO2 concentration, while replacement by grasslands would result in a cooling of 0.4°C. It has been previously shown that boreal forestation can lead to warming; our simulations indicate that mid- latitude forestation also could lead to warming. These results suggest that more research is necessary before forest carbon storage should be deployed as a mitigation strategy for global warming.
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High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years
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The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.
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Greenhouse Gassed: Carbon Dioxide Spells Indigestion for Food Chains
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The author closes with a quote from a biologist who asks who will be chasing wild ungulates with nutrition supplements. CO2 is a fertilizer, with side effects. Plants may grow more rapidly, but at the cost of their nutritional value. Hessman interviews researchers studying this effect on a range of animals from insects to mammals.
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GREEN-TREE RETENTION IN HARVEST UNITS: BOON OR BUST FOR BIODIVERSITY?.pdf
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etween trees and man there is a rift in the perception of time, and forest managers have no choice but to yield to the pace of the trees. This can make innovations in forest management difficult to evaluate. Nonetheless, innovation is key to meeting society’s changing expectations. It is not just timber anymore. Biodiversity, recreation, aesthetics, and clean water all share top billing with a sustainable crop of timber. And although novel silvicultural strategies are being promoted to meet these complex demands, without the benefit of time, it is difficult to know exactly how well they will achieve their goals.
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SOME REFLECTIONS ON CLIMATE CHANGE, GREEN GROWTH ILLUSIONS AND DEVELOPMENT SPACE
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Many economists and policy makers advocate a fundamental shift towards “green growth” as the new, qualitatively-different growth paradigm, based on enhanced material/resource/energy efficiency and drastic changes in the energy mix. “Green growth” may work well in creating new growth impulses with reduced environmental load and facilitating related technological and structural change. But can it also mitigate climate change at the required scale (i.e. significant, absolute and permanent decline of GHG emissions at global level) and pace? This paper argues that growth, technological, population-expansion and governance constraints as well as some key systemic issues cast a very long shadow on the “green growth” hopes. One should not deceive oneself into believing that such evolutionary (and often reductionist) approach will be sufficient to cope with the complexities of climate change. It may rather give much false hope and excuses to do nothing really fundamental that can bring about a U-turn of global GHG emissions. The proponents of a resource efficiency revolution and a drastic change in the energy mix need to scrutinize the historical evidence, in particular the arithmetic of economic and population growth. Furthermore, they need to realize that the required transformation goes beyond innovation and structural changes to include democratization of the economy and cultural change. Climate change calls into question the global equality of opportunity for prosperity (i.e. ecological justice and development space) and is thus a huge developmental challenge for the South and a question of life and death for some developing countries (who increasingly resist the framing of climate protection versus equity).
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The Influence of Climate, Soils, Weather, and Land Use on Primary Production and Biomass Seasonality in the US Great Plains
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Identifying the conditions and mechanisms that control ecosystem processes, such as net primary production, is a central goal of ecosystem ecology. Ideas have ranged from single limiting-resource theories to colimitation by nutrients and climate, to simulation models with edaphic, climatic, and competitive controls. Although some investigators have begun to consider the influence of land-use practices, especially cropping, few studies have quantified the impact of cropping at large scales relative to other known controls over ecosystem processes. We used a 9-year record of produc- tivity, biomass seasonality, climate, weather, soil conditions, and cropping in the US Great Plains to quantify the controls over spatial and temporal patterns of net primary production and to esti- mate sensitivity to specific driving variables. We considered climate, soil conditions, and long-term average cropping as controls over spatial patterns, while weather and interannual cropping varia- tions were used as controls over temporal vari- ability. We found that variation in primary production is primarily spatial, whereas variation in seasonality is more evenly split between spatial and temporal components. Our statistical (multi- ple linear regression) models explained more of the variation in the amount of primary produc- tion than in its seasonality, and more of the spatial than the temporal patterns. Our results indicate that although climate is the most important variable for explaining spatial patterns, cropping explains a substantial amount of the residual variability. Soil texture and depth con- tributed very little to our models of spatial vari- ability. Weather and cropping deviation both made modest contributions to the models of temporal variability. These results suggest that the controls over seasonality and temporal variation are not well understood. Our sensitivity analysis indicates that production is more sensitive to climate than to weather and that it is very sen- sitive to cropping intensity. In addition to iden- tifying potential gaps in out knowledge, these results provide insight into the probable long- and short-term ecosystem response to changes in climate, weather, and cropping.
Key words: primary production; carbon; land use; agriculture; climate; weather; soil; seasonality; cropping; grassland; US Great Plains.
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Timing of climate variability and grassland productivity
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Future climates are forecast to include greater precipitation variability and more frequent heat waves, but the degree to which the timing of climate variability impacts ecosystems is uncertain. In a temperate, humid grassland, we examined the seasonal impacts of climate variability on 27 y of grass productivity. Drought and high- intensity precipitation reduced grass productivity only during a 110-d period, whereas high temperatures reduced productivity only during 25 d in July. The effects of drought and heat waves declined over the season and had no detectable impact on grass productivity in August. If these patterns are general across ecosystems, predictions of ecosystem response to climate change will have to account not only for the magnitude of climate variability but also for its timing.
Konza | net primary production | streamflow | critical climate periods
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Climate change and the world economy: short-run determinants of atmospheric CO2
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Volcanic eruptions, the El Nin ̃ o Southern oscillation (ENSO), world population, and the world economy are the four variables usually discussed as influencing the short-run changes in CO2 atmospheric levels through their influence on CO2 emissions and sinks. Using proper procedures of detrending, we do not find any observable relation between the short-term growth of world population and the increase of CO2 concentrations. Results suggest that the link between volcanic eruptions, ENSO activity, and CO2 concentrations may be confounded by the coincidence of the Pinatubo eruption with the breakdown of the economies of the Soviet Bloc in the early 1990s. Changes in world GDP (WGDP) have a significant effect on CO2 concentrations, so that years of above-trend WGDP are years of greater rise of CO2 concentrations. Measuring WGDP in constant US dollars of 2000, for each trillion WGDP deviates from trend, the atmospheric CO2 concentration has deviated from trend, in the same direction, about half a part per million.
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GLOBAL WARMING AND FISH MIGRATIONS
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Ocean temperatures are expected to rise over the next decades. This is likely to affect the distribution of fish stocks between the exclusive economic zones (EEZs) of different countries. Such changes are likely to be triggered as temperatures rise beyond certain threshold levels, and they are likely to be irregular because temperatures are likely to vary around a rising trend. The paper looks at the case where temperature changes would displace a fish stock out of the EEZ of one country and into the EEZ of another, with a transition period in which the stock is shared. It is examined how this might affect the risk of extinction and degree of overfishing, under different cost scenarios and different assumptions about how countries react to observed changes in the distri- bution of the stock between their economic zones.
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Relationship between fire, climate oscillations, and drought in British Columbia, Canada, 1920–2000
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Climate oscillations such as El Nin ̃o–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) are known to affect temperature and precipitation regimes and fire in different regions of the world. Understanding the relationships between climate oscillations, drought, and area burned in the past is required for anticipating potential impacts of regional climate change and for effective wildfire-hazard management. These relationships have been investigated for British Columbia (BC), Canada, either as part of national studies with coarse spatial resolution or for single ecosystems. Because of BC’s complex terrain and strong climatic gradients, an investigation with higher spatial resolution may allow for a spatially complete but differentiated picture. In this study, we analyzed the annual proportion burned– climate oscillation–drought relationships for the province’s 16 Biogeoclimatic Ecosystem Classification (BEC) zones. Analyses are based on a digital, spatially explicit fire database, climate oscillation indices, and monthly precipitation and temperature data with a spatial resolution of 400 m for the period 1920–2000. Results show that (1) fire variability is better related to summer drought than to climate oscillations, and that (2) fire variability is most strongly related to both, climate oscillations and summer drought in southeastern BC. The relationship of area burned and summer drought is strong for lower elevations in western BC as well. The influence of climate oscillations on drought is strongest and most extensive in winter and spring, with higher indices being related to drier conditions. Winter and spring PDO and additive winter and spring PDO ENSO indices show BC’s most extensive significant relationship to fire variability. Western BC is too wet to show a moisture deficit in summer that would increase annual area burned due to teleconnections.
Keywords: area burned, aridity index, Canada, ENSO, PDO, wildfire
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