People across the world are becoming increasingly aware of the public health hazard posed by polluted air. Similarly, with filthy smog and other forms of air pollution being produced through industrial, fossil-fuel burning processes, most of us have a sense that airborne pollutants can’t be good for the environment either. Less obvious is the link between the world’s largest single killer and the biggest environmental challenge our planet has ever faced. What, if anything, do air pollution and climate change have to do with each other?
'Air pollution' describes any substance introduced to the indoor or outdoor environment which alters the atmosphere’s natural state. In this sense, greenhouse gases (GHGs) are air pollutants: gases such as methane and carbon dioxide entering the atmosphere in such unprecedented amounts that our planet’s climate system is changing, to the detriment of its ecosystems and inhabitants. However, in many areas such as policy-making, greenhouse gases are usually treated as a separate issue to air pollution. Whilst GHGs have a global effect on the planet, air pollution has a more local effect on health and the surrounding environment.
However, whilst the relationship between air pollution and climate change remains only partly understood, recent research suggests they may influence each other more than previously thought.
It is predicted that air quality will decline in response to climate change. Increased heat and sunlight may facilitate higher concentrations of ozone, which forms in sunlight, and prolong its duration.
Conversely, there are numerous ways in which air pollution may aggravate climate change.
Higher concentrations of particle pollution may affect various aspects of cloud formation, in turn altering traditional rainfall patterns, with significant potential consequences.
Particulate matter can affect global warming in various ways depending on its composition. In general, light-coloured particles will reflect sunlight away from and cool the earth, whilst dark particles absorb heat, having a warming effect. Sulphates and nitrates are light particles which cool; black carbon absorbs heat. Black carbon can have a particularly negative effect when it settles on Arctic ice, which accelerates melting. In a similar way, the more Arctic ice that melts, the less white space exists to reflect sunlight and heat away from Earth – so this contributes doubly toward global warming.
How can we effectively tackle these two environmental threats in a way that is mutually beneficial?
Often, air pollution and GHG emissions come from the same sources (e.g. fossil fuel combustion), so both issues can often be combated simultaneously by reducing harmful emissions. For example, cutting emissions of black carbon and ozone is mutually beneficial to human health, air quality and climate. But this is not always the case – some measures designed to curb greenhouse gas emissions may result in worsening air quality, or vice versa. For example, burning biomass as fuel is encouraged as a ‘carbon neutral’ energy source; whilst it helps meet CO2 reduction targets, it also increases harmful particle emissions.
As awareness of the link between these two problems grows, it is increasingly important for policymakers to consider air pollution and climate holistically, to ensure that positive steps are taken to address these urgent problems together.