Prior to any climate change impact study, it is important that a model has been thoroughly evaluated for the crop or production system of interest. Once the evaluation is acceptable, simulating a future climate change scenario is no more difficult than simulating a crop under current or historic conditions. One needs an accurate estimate of the future weather conditions and data for the additional crop, soil and management inputs. The model is simply run with the future weather data and if considered relevant, the projected [CO2] level. This process is the core of any simulation analysis of climate change impacts in agriculture and is found in the earliest applications of ecophysiological models (Rosenzweig 1985). However, in the selection of the appropriate model, it is important to consider whether a model will not only respond to the expected changes in climate, but also to the projected ranges. As an example, the first crop simulation models that were used for climate change studies did not include a response to the projected [CO2] level. Most current models also have difficulties with proper responses to extreme high temperatures.
A first consideration usually is what climate change and [CO2] scenarios to consider (see Chapters 3, 10). Comparing simulations from a single historic year with a single future year would be misleading since the results would be highly dependent on the weather conditions for that pair of years. Thus, simulations usually are conducted for sets of historic and future data that are run for 20 or more years in order to provide a more robust estimate of impacts and to account for the annual variability. Furthermore, this allows one to analyze production risk and to examine which weather variables appear to dominate predicted changes in production, resource use and environmental impact.
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.