Overline: Links between greenhouse gases, climate change and air quality
Headline: Air Pollution and Climate Change

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.

Air pollution: a critical health risk worldwide

At the first WHO Global Conference on Air Pollution and Health in 2018 WHO Director General Dr. Tedros Adhanom Ghebreyesus called air pollution a “silent public health emergency”. Approximately 7 million premature deaths annually are due to the effects of air pollution, about 4 million of which are due to ambient (outdoor) air pollution. Beyond shortening lives, air pollution can negatively impact our day-to-day lives, causing respiratory illness and leading to days of missed work and school. Children are especially vulnerable to the impacts of air pollution: exposure to air pollution in early childhood, when the lungs are still developing, can lead to reduced lung capacity that persists through adulthood.

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

To reach the Paris Agreement goal of limiting warming to 1.5 (or even 2) degrees Celsius, rapid reduction of CO2 emissions is absolutely necessary, but will not in itself be sufficient. The IPCC special report on the impacts of global warming of 1.5 °C stresses that deep reductions in emissions of non-CO2 climate forcers, particularly the air pollutants methane and black carbon, are also crucial. And while the decarbonisation of the economy will generally reduce emissions of both CO2 and air pollutants, pursuing the phaseout of fossil fuels is not enough – for either air quality or climate. 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.

If we are to achieve the goals of the Paris Agreement, then emissions of other climate drivers such as methane, black carbon, and ground-level ozone must be reduced alongside carbon dioxide. These reductions would benefit the climate and foster sustainable development by delivering better health outcomes through improved air quality, preventing crop losses, and ensuring that we avoid climate tipping points that would exacerbate long-term impacts and impede efforts to adapt to climate change.

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.

Kathleen Mar on the importance of reducing short-lived climate-forcing pollutants

RIFS research on air pollution and climate change

Air Quality Modelling for Policy Advice (AQ) does basic scientific research to understand the effects of emission sources on ambient levels of air pollution and its associated impacts. The primary methodology is numerical modelling, and a special focus of the group is long-range transport of ground-level ozone. The group participates in the Task Force on Hemispheric Transport of Air Pollution, which provides science-based advice to the Convention on Long-Range Transboundary Air Pollution.

ClimAct examines the potentials and limits of an integrated approach to air quality and climate in the context of the Paris Agreement and Sustainable Development Goals, in particular via its participation in and study of the Climate and Clean Air Coalition (CCAC), a voluntary transnational partnership that aims to reduce near-term global warming and improve air quality through action on short-lived climate-forcing pollutants.

ClimPol conducts research in support of transformations towards more integrated policymaking on climate change and air quality. It focuses on a range of issues relating to air quality in urban areas and explores the connections between air pollution, climate change, and mobility. The research team also fosters greater awareness of these issues by establishing dialogues among policymakers, civil society actors, and the scientific community.

SusKat aims to reduce air pollution levels in Nepal by improving scientific understanding, identifying effective measures, and raising awareness of the problem and its solutions among policymakers and the general public. Now in its third phase, the project is currently focused on capacity building and stakeholder engagement to support the implementation of the most promising mitigation measures.