A STUDY OF GREENHOUSE EFFECTS USING ZERO, ONE AND TWO-DIMENSIONAL CLIMATE MODELS

In this study a hierarchy of simple climate models is built and used to assess the impact of changes in the trace gas abundance of Earth's atmosphere on the global and zonal surface temperatures. Two of the four models presented use the Equivalent Radiative Atomosphere approximation to treat the greenhouse effect of water vapor, carbon dioxide and ozone. The other two models have vertically resolved atmospheres and use broad band absorptance and emissivity models in the treatment of radiative exchanges. Two of the models have resolution in the meridional direction and the horizontal energy transport is approximated by a linear, constant coefficient diffusion. A series of sensitivity experiments is conducted with these models to assess the relative importance of various parameters and modeling assumptions. All of the models are sensitive to variations in solar irradiance: the range of the response, quantified in terms of the (beta) parameter, ranges from 71 K to 186 K. The response is highly dependent on the strength of the water vapor feedback in the particular model. Another series of calculations is concerned with the impact of changes in the CO(,2) abundance of the atmosphere on the surface temperatures. The range of the response to a doubling of the CO(,2) abundance is from 2.5 K to 10 K for ERA based models and from 1.9 K to 6 K for the others. The response depends on the latitude and most importantly on the water vapor feedback strength. The effect of minor trace gases O(,3), CH(,4) and N(,2)O on the globally averaged temperature is also studied. A 50% decrease in O(,3) column density lowers the surface temperature by 0.28 K. A doubling of the present atmospheric abundance of CH(,4) and N(,2)O heats the surface by 0.25 K and 0.42 K, respectively

Tree-ring growth of Pinus nigra Arn. subsp. pallasiana under different climate conditions throughout western Anatolia

Pinus nigra Am. subsp. pallasiana (black pine) is one of the most widely grown tree in Turkey. It is the third most widely distributed tree species after Quercus L. and Pinus brutia Ten. Black pine grows in 20% of all forested areas in Turkey. In this dendroecological study, we identified the most important climate factors affecting radial growth of black pine in western Anatolia and classified its responses to climate. Twenty-eight site chronologies developed by different researchers were used in the analysis. Response functions were calculated for each chronology to identify the effect of climate on radial growth. Hierarchical cluster analysis was used to sort response functions and to classify the chronologies into groups based on climate responses. The individual responses of these chronologies to temperature and precipitation were classified in four main groups. Climatic and phytogeographic differences were the major factors influencing the formation of clusters. The results suggest that the major limiting factor is drought caused by low precipitation, especially in May, in almost all sites. The drought effect is much stronger in the transition region to the steppe, Central Anatolia and Mediterranean Regions than the Black Sea Region. Black pine trees respond positively to higher temperature at the beginning of growing season in almost all areas except in transition region to the steppe. (C) 2012 Elsevier GmbH. All rights reserved