CLORPT allows for a theoretical framework when creating natural experiments for the study of soil formation. (Retallack 2001) Climate When soil science was first founded, climate was considered one of the most important factors regarding the formation of soil. For instance, temperate regions have widespread acidic sand Spodosols, and in tropical regions red clayey Oxisols are common. The tendency to use climatic data for the classification of soils has been challenged by efforts to base the classification of soil on observable features within the soils. This tendency is unfortunate because paleoclimates cannot be interpreted from paleosols identified using paleoclimatic data. Fortunately, the identification of paleosols using climatic data is changing. For example, Aridisols have been redefined (Soil Survey Staff 1998) as soils that possess a calcic horizon of less than 1 meter in depth. The terms climate and weather are sometimes used interchangeably in modern languages, but have very different scientific meanings. Weather is the record of temperature, rainfall, and humidity as reported daily online, by newspapers, and by television. Conversely, climate is the average of data collected from weather reports, usually over a 30-year period, that reflects these observations. The weather data used to determine climate is based on particular weather stations that are generally chosen to reflect the conditions that exist in the surrounding region (Müller 1982). However, exposed high ridges and local frost hollows are not considered regarding regional weather stations because they represent microclimates and are significantly different from regional climate even though they are important for small flora and fauna. Like exposed high ridges and local frost hollow microclimates, soil climate is also a special kind of microclimate. It refers to the moisture, temperature, and other climatic indicators that are found within the pores of soil. For example, in well-drained soils, the soil climate is a somewhat subdued version of the regional climate. In waterlogged soils, soil climate is not related to regional climate because the temperature and oxygenation of waterlogged soils is more dependent on local groundwater paths and rates than on atmospheric conditions. Estimates of other types of soil climate are now beginning to find their way into the classification of soils, the models for soil formation, and into the study of soil biology. The classification of climate from paleosols can be related using climatically sensitive features of soils that are sensitive to particular climatic variables, but even the best of these features