Climate change scenario

This article is about climate change scenarios. Socioeconomic scenarios are used by analysts to make projections of future greenhouse gas (GHG) emissions and to assess future vulnerability to climate change (Carter et al., 2001:151). Producing scenarios requires estimates of future population levels, economic activity, the structure of governance, social values, and patterns of technological change. Economic and energy modelling (such as via the World3 or the POLES models) can be used to analyse and quantify the effects of such drivers.

These scenarios can be thought of as stories of possible futures. They allow the description of factors that are difficult to quantify, such as governance, social structures, and institutions. Morita et al. (2001:137-142) assessed the literature on global futures scenarios. They found considerable variety among scenarios, ranging from variants of sustainable development, to the collapse of social, economic, and environmental systems. In the majority of studies, the following relationships were found:

Morita et al. (2001) noted that these relationships were not proof of causation.

No strong patterns were found in the relationship between economic activity and GHG emissions. Economic growth was found to be compatible with increasing or decreasing GHG emissions. In the latter case, emissions growth is mediated by increased energy efficiency, shifts to non-fossil energy sources, and/or shifts to a post-industrial (service-based) economy.

A baseline scenario is used as a reference for comparison against an alternative scenario, e.g., a mitigation scenario (IPCC, 2007c:810). Fisher et al. (2007:178-194) assessed the baseline scenarios literature. They found that baseline CO₂ emission projections covered a large range. In the United States, electric power plants emit about 2.4 billion tons of carbon dioxide (CO2) each year, or roughly 40 percent of the nation's total emissions. The EPA has taken important first steps by setting standards that will cut the carbon pollution from automobiles and trucks nearly in half by 2025 and by proposing standards to limit the carbon pollution from new power plants.

Factors affecting these emission projections are described below:

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