Worldwide air pollution has fallen sharply due to COVID19 lockdowns, in the UK it’s estimated that NOx concentrations have been reduced by 30 to 40%. As a result, there’s been widespread media coverage and it’s got people stating that this is an opportunity to meet climate targets. However, despite efforts, it’s likely that low levels won’t be sustained when normality returns. This was the case when looking back at the financial crisis in 2010, at the end of the year annual CO2 emissions were the greatest they’d ever been.
Air pollution and climate change are two of the world’s main environmental problems. The two are closely linked by their common origin and they are both worsened by anthropogenic behaviour, particularly the burning of fossil fuels. But, there are complex interactions between them.
Climate change is a large-scale and long term shift in the planet’s weather patterns and average global temperatures. This has seen a shift since the mid 1800s, between the 20th and 21st century CO2 in the atmosphere rose by 40% and subsequently, global warming is happening at an unprecedented rate.
Air pollution has also experienced changes as a result of economies growing. Air pollution occurs when air contains gases, dust and smoke in concentrations that are detrimental to human health and the planet. Sources of pollutants can be both natural and anthropogenic. Natural sources include: the erosion of land, salt spraying, volcanic injection, biological decay, forest fires and chemical reactions. Human generated air pollutants originate from industry, agriculture, transport and construction.
Whilst climate change has been a hot topic for many years, air quality hasn’t. The impacts of future climate extremes on air quality are not well recognized or quantified.
How does climate change affect air pollution?
Shifts in the planet’s weather patterns and global temperatures can alter the chemical composition of the atmosphere and therefore outdoor air pollution. Atmospheric warming caused by the burning of fossil fuels has led to an increase in the frequency and duration of extreme weather events. In recent years heatwaves are occurring more regularly, which causes levels of ground-level ozone to significantly increase. Ground-level ozone is a serious pollutant, which at high levels, damages human health and vegetation. Another resultant of heatwaves is bushfires, this phenomenon can have detrimental impacts on air quality. Last year in June 2019, Australia experienced the worst recorded bushfires, whereby 46 million acres of land were destroyed. Consequently, this caused huge implications to Australia’s air quality, levels of PM2.5 were 40 times World Health Organisation standards (10 ug/m3).
Climate change can also affect the quality of air in the indoor environment. Outdoor air quality heavily influences Indoor Air Quality (IAQ), thus changes to outdoor concentrations will affect those inside. Additionally, changes in occupant behaviour and buildings responses to a changing climate such as ventilation rates all determine IAQ.
What are the effects of air pollution on climate change?
As mentioned previously, air pollution is due to the presence of high levels of pollutants in the air. These pollutants include gases and tiny atmospheric particles, otherwise known as aerosols, which have a measurable effect on climate change. Aerosols and gases contribute to climate change, through their effect on the balance of incoming and outgoing radiation from the Earth and its atmosphere. Different air pollutants impact climate change in different ways, for example: sulfate particles cool the atmosphere by reflecting solar radiation, whilst particles such as black carbon, methane and ozone absorb solar radiation. Tiny atmospheric particles can also create cloud droplets in the lower atmosphere, however, clouds can cool and warm the climate depending on the altitude. As water droplets and ice particles are ‘white’ they reflect solar radiation, but condensed water droplets trap and emit long wave radiation.
The composition and effect of atmospheric aerosols and gases vary depending on their source, natural or anthropogenic. Unfortunately, the majority of air pollution contributing to climate change is the result of human activity, and with increasing human consumption patterns driven by population growth and growing economies this isn’t set to decrease.
What does this mean for future climate change and air pollution?
It’s known that human activity is the main driver for both environmental issues, COVID19 has recently highlighted this. How governments respond to the COVID19 crisis could either amplify or benefit both climate change and air pollution. With the last four years being the hottest on record, there’s already widespread concern that the world is presently way off course to meet the global limit of 1.5℃ warming. This will cause air pollution to continually rise but because there are many unknown variables relating to aerosol particles, their influence on climate change is still being researched. However, research has shown that pollutants such as methane, black carbon, ground-level ozone are top contributors to atmospheric warming after CO2. Therefore, in order to achieve a limit of 1.5℃ warming, we need to reduce levels of air pollutants alongside CO2 emissions. It is clear then, that climate change and air pollution are directly correlated, they heighten the effects of one another hence when one gets worse, so does the other. They both have to be addressed as a matter of priority.