The polar regions exert controls on global sea level, the carbon cycle, and atmospheric and ocean circulation. The climate of is controlled by complex interactions between the sun, the atmosphere, ocean and sea ice, making accurate prediction of regional climate a formidable challenge. Predicting how polar climate may change is therefore an essential part of understanding the global climate system. The BAS Climate Programme uses observations from both polar regions to improve our understanding of how natural and human-induced factors contribute to climate change. Programme goals are: a) to explain changes in atmospheric circulation, temperatures and sea-ice extent in both polar regions over the past 50 years and to determine how much of this change is due to human activity and how much is a result of natural factors (including solar variability); b) to improve the representation of polar climate processes in large-scale models, using targeted observations; c) to improve climate predictions in the polar regions on the space and timescales needed by the international scientific community (including glaciologists, oceanographers and biologists); d) to maintain a programme of high-quality, long-term observations in the Antarctic using instruments at BAS research stations and remote field sites; e) to understand the controls on energetic particle precipitation in the upper atmosphere, and the ways in which particle precipitation can impact on the middle and lower atmosphere through changes in chemistry and wave propagation.