It is generally accepted that global warming is happening, and that the protective ozone layer remains in danger. Much of the atmospheric pollution – which in part is responsible for global warming – is caused by the burning of fossil fuels in the creation of energy to support city life. Global warming and its possible effects on, for example, European ski slopes, the submerging of populated islands, the loss to Britain of our climate-moderating Gulf Stream and the increasing occurrence of violent storms, is common knowledge. However, these are by no means the only environmental hazards stemming directly from current urban lifestyles on the planet. Other hazards include: contamination of water sources, overloading of environmental sinks such as the great river estuaries, acid rain, and air pollution in cities. Much of the pollution causing environmental damage can be attributed directly to the building process. For example, 50 per cent of the world's fossil fuel consumption is directly related to the servicing and use of buildings. In addition, energy is used to make building materials, to transport them to the site, and in their erection as part of the building. The servicing and use of buildings alone, results in the production of 50 per cent of the world's output of carbon dioxide, amounting to about one-quarter of the greenhouse gases.