AIR POLLUTION

Air pollution and climate change are closely related. As well as driving climate change, the main cause of CO2 emissions – the extraction and burning of fossil fuels – is also a major source of air pollutants. What’s more, many air pollutants contribute to climate change by affecting the amount of incoming sunlight that is reflected or absorbed by the atmosphere, with some pollutants warming and others cooling the Earth. These short-lived climate-forcing pollutants (SLCPs) include methane, black carbon, ground-level ozone, and sulfate aerosols. They have significant impacts on the climate: black carbon and methane in particular are among the top contributors to global warming after CO2.

Health and ecosystem impacts of key short-lived climate-forcing pollutants

Black carbon (BC, also known as soot) is a component of fine particulate matter (PM2.5). Particulate matter is the air pollutant that is most harmful to human health and the primary driver of air pollutant-induced mortality.

Methane (CH4) does not have any direct human health effects in the sense that inhaling typical ambient concentrations of methane is not harmful to human health. However, methane has a very important indirect human health impact, because it is a precursor to ground-level ozone (O3, also known as tropospheric ozone), which causes asthma and other respiratory diseases and contributes to air pollution-related premature deaths. Ozone also damages plants and leads to USD 11–18 billion worth of crop losses each year.

Climate change: We need action on air pollution and greenhouse gases

First of all, emissions from additional sectors are also important: for instance, methane and black carbon emissions from agriculture have important health and climate impacts, and emissions of coolants (particularly hydrofluorocarbons, or HFCs) from the cooling sector are especially potent climate warmers. Second, it is important to consider both CO2 and air pollutants when designing and selecting climate and air quality measures in order to ensure that the desired benefits can actually be achieved. Some technologies that are promoted as climate-friendly – combustion of biomass and other biofuels for home heating or transport, for example – may emit more particulate matter, including black carbon, than the technology it replaced, and thus continue to harm human health and potentially warm the climate.

Multiple benefits for climate, air quality, health, and sustainable development

Aside from contributing to limiting global warming, strong reductions in methane, black carbon and ground-level ozone have other key benefits for sustainable development: they protect health and avoid premature deaths by improving air quality; they prevent millions of tonnes of crop losses yearly; and they can prevent the climate from reaching tipping points that can exacerbate long-term climate impacts and make adapting to climate change harder, especially for the poor and most vulnerable. By acting on climate and air pollution together we have the opportunity to take advantage of synergies between the Paris Agreement climate goals and the UN Sustainable Development Goals to improve lives now and limit future climate warming.

Air Quality and Climate Change Research

Climate change can impact air quality and, conversely, air quality can impact climate change. 

Changes in climate can result in impacts to local air quality. Atmospheric warming associated with climate change has the potential to increase ground-level ozone in many regions, which may present challenges for compliance with the ozone standards in the future. The impact of climate change on other air pollutants, such as particulate matter, is less certain, but research is underway to address these uncertainties.

Emissions of pollutants into the air can result in changes to the climate. Ozone in the atmosphere warms the climate, while different components of particulate matter (PM) can have either warming or cooling effects on the climate. For example, black carbon, a particulate pollutant from combustion, contributes to the warming of the Earth, while particulate sulfates cool the earth's atmosphere.