Issue link: https://hi.iaq.net/i/670243
Every breath we take: the lifelong impact of air pollution 7.3 How local air pollution affects our climate Average global temperatures are dictated by the balance between the incoming energy from the sun that is retained by, and warms, the Earth's surface, and the energy that is reflected back into space. When human activity pollutes the air, it upsets the Earth's energy balance, producing a warming effect. Both gases and particles are involved in this process. Greenhouse gases, such as CO 2 and CH 4 , act directly, trapping radiation in the atmosphere. Others, such as oxides of nitrogen (NOx), impact indirectly on the concentrations of CH 4 and O 3 (another powerful greenhouse gas). The role of aerosols in global warming is complex and can be positive and negative. By 2013, the concentration of CO 2 in the atmosphere had increased by around 42% over the levels present before the Industrial Revolution. In 2013, the Intergovernmental Panel on Climate Change (IPCC) concluded that, unless very stringent emission standards are achieved, by the end of the 21st century global surface temperatures will be more than 1.5°C above their 19th-century levels. 7 Disturbingly, the IPCC expressed medium confidence that a 'business as usual' scenario, in which emissions remain high, carries a 50:50 chance that warming will exceed 4°C by 2100. Such a rise will have huge implications for health, wellbeing and the global community itself. 8–11 A tragic but timely indication of the consequences of the extreme weather events likely to become more common in the world was provided by the devastation wrought by Cyclone Pam on Vanuatu in March 2015. 7.4 How climate change affects the air we breathe Atmospheric chemistry is complex and, just as climate change is primarily caused by the release of greenhouse gases, the warming climate itself alters atmospheric chemistry in ways that can damage health and wellbeing. This can be illustrated by reference to O 3 . Global warming increases levels of O 3 in the lower atmosphere, giving rise to airway damage, reduced lung function and increases in respiratory symptoms in exposed persons, as we have discussed throughout this report. Yet, the highest levels of atmospheric O 3 exist in the stratosphere (the second major layer of the Earth's atmosphere), where the 'O 3 layer' reduces the amount of ultraviolet radiation reaching the Earth's surface and, with it, damage to our DNA. In the 1970s, thinning of the O 3 layer prompted measures to tackle release of the chlorofluorocarbons (CFCs) present in aerosols that were primarily responsible. However, more recently it has been proposed that the 50–60-year timescale predicted for O 3 layer recovery may not in fact be achieved owing to climate change. 12,13 The Air Quality Expert Group report Air quality and climate change: a UK perspective provides an in- depth assessment of the interactions between the climate and aspects of the air we breathe. 4 7.5 Health and wellbeing implications Even in outline, the interconnections between air quality and climate change present a complex and sometimes confusing picture. However, the headline message for society, supported by an overwhelming scientific consensus, is that climate change is a product of human activity and, especially, emissions from the combustion of fossil fuels. By extension, any consideration of the health effects of human-induced air pollution is incomplete without including the many and diverse health and wellbeing impacts that are already taking place owing to the changing climate. In a recent report, a working group of the IPCC observed that, through shifts in weather patterns and other consequences, climate change is both a direct and an indirect risk to health. 14 Through its impacts on air quality, water and food, it is already affecting lives and livelihoods across the globe. In 2014 the 96 © Royal College of Physicians 2016