Climate change is a change in the "average weather" that a given region experiences, including such factors as storm frequency, temperature, wind patterns and precipitation. The rate and magnitude of global climate changes over the long term have many implications for natural ecosystems. As society becomes increasingly reliant on energy consumption in work at home and for mobility, the heat-trapping nature of the atmosphere has increased. As our scientific understanding of this situation increases, so does public concern and the requirement for a policy response. Aviation contributes a small but growing proportion to this problem (less than 4% of man-made atmospheric emissions). A key factor however, is that some of aviation's emissions are emitted in the upper atmosphere and may have a more direct effect. The science of climate change is still relatively new and the future is uncertain. However, there is a broad consensus that policy needs to be enacted now if climate change related problems and costs are to be avoided.