Role Of Climate Variability Research Articles

SCALE, CONTEXT, AND DECISION MAKING IN AGRICULTURAL ADAPTATION TO CLIMATE VARIABILITY AND CHANGE

This work presents a framework for viewing agricultural adaptation, emphasizing the multiple spatial and temporal scales on which individuals and institutions process information on changes in their environment. The framework is offered as a means to gain perspective on the role of climate variability and change in agricultural adaptation, and developed for a case study of Australian agriculture. To study adaptation issues at the scale of individual farms we developed a simple modelling framework. The model highlights the decision making element of adaptation in light of uncertainty, and underscores the importance of decision information related to climate variability. Model results show that the assumption of perfect information for farmers systematically overpredicts adaptive performance. The results also suggest that farmers who make tactical planting decisions on the basis of historical climate information are outperformed by those who use even moderately successful seasonal forecast information. Analysis at continental scales highlights the prominent role of the decline in economic operating conditions on Australian agriculture. Examples from segments of the agricultural industry in Australia are given to illustrate the importance of appropriate scale attribution in adapting to environmental changes. In particular, adaptations oriented toward short time scale changes in the farming environment (droughts, market fluctuations) can be limited in their efficacy by constraints imposed by broad changes in the soil/water base and economic environment occuring over longer time scales. The case study also makes the point that adaptation must be defined in reference to some goal, which is ultimately a social and political exercise. Overall, this study highlights the importance of allowing more complexity (limited information, risk aversion, cross-scale interactions, mis-attribution of cause and effect, background context, identification of goals) in representing adaptation processes in climate change studies.

The role of climate variability and global warming in the dieback of Northern Hardwoods

The severity of dieback in Northern Hardwood Forests of Canada and the United States this century (1910–1990) was reconstructed from pathology records and compared to indices of extreme weather stresses in the region, and to changes in global temperatures and climatic variability over the same period. Thaw-freeze and root-freeze events in winter and early spring were key factors intriggering (and synchronizing) severe episodes of dieback. Once trees were injured by freezing, forest dieback correlated significantly with heat and drought stress. Freezing (but not drought) stresses in Northern Hardwoods correlated significantly (r = 0.70, p < 0.001) with increasing global mean annual temperatures and low values of the Pacific tropical Southern Oscillation Index. Major diebacks did not occur early in the century at a time of notable freezing stress. Prior to 1940, the Northern Hardwoods consisted of relatively young populations of trees regrowing following extensive cutting and forest burning in the late 19th century (1860–1890). It appears that forest maturation is the key factorpreconditioning trees to climatic injury, and dieback. A simple projection of climate and forest maturation ages suggested the recurrence of major dieback episodes on white/yellow birch, sugar maple and red spruce in the latter half of the 21st century (2045–2085).

Glacial records of Global climate: A 1500-year tropical ice core record of climate

A general discussion is given of climate variability over the last 1500 years as interpreted from two ice cores from the Quelccaya ice cap, Peru. The possible role of climatic variability in prehistory over this period is discussed with emphases on (1) relationships between climate and the rise and decline of coastal and highland cultures; (2) the possible causes of two major dust events recorded in the Quelccaya ice cores around AD 920 and AD 600; and (3) implications of climatic variation for the occupation and abandonment of the Gran Pajaten area. The remarkable similarity between changes in highland and coastal cultures and changes in accumulation as determined from the Quelccaya ice cores implies a strong connection between human activities and climate in this region of the globe. Two ice cores drilled to bedrock from the 6047 masl col of Huascaran in the Cordillera Blanca, Peru in 1993 offer the potential of an annual to decadal climatic and environmental record which should allow the study of human-climate and human-environmental relationships over 10,000+ years. The 1991 and 1993 evidence from the Quelccaya ice cap indicates that recent and rapid warming is currently underway in the tropical Andes. Thus many of the unique glacier archives are in imminent danger of being lost forever.