TL;DR — While carbon dioxide is the most well-known greenhouse gas, many other air pollutants have either direct or indirect impacts on the climate. Many substances in the atmosphere, in addition to acting as air pollutants with negative health and environmental impacts, also play a role in atmospheric warming and climate change. The complex relationship between climate change and air quality means that many of these substances have an array of negative impacts over time scales that can also vary broadly. Given the critical and increasingly time-sensitive nature of stopping climate change, it's important for us to take stock of all of the mitigation opportunities available to us. Doing so will require looking past CO2 — the traditional barometer for climate change — and starting to rigorously measure and reduce emissions from other sources.

The complex ties between air quality and climate change

Climate change is an incredibly dynamic, complex phenomenon that involves the interaction of many different air pollutants and atmospheric processes. Over time, these dynamics result in long-term shifts in temperatures and weather patterns driven by human activity.

In addition to warming temperatures, climate change also presents secondary consequences such as:

  • Severe droughts
  • Water scarcity
  • Intense fires
  • Rising sea levels
  • Flooding
  • Melting of polar ice
  • Catastrophic storms
  • Reduced biodiversity
  • Reduction of GDP

Feedback loops and climate tipping points

In the context of climate change, a feedback loop occurs when one change triggers a series of additional changes that ultimately reinforce the initial change. These loops create a domino effect where the impacts of climate change lead to further climate warming. Here are some examples of feedback loops that can occur as a result of climate change:

  • The albedo effect: As sea ice melts due to warming, the Earth's surface becomes darker, which means it absorbs more solar radiation and warms further. This increased warming causes more sea ice to melt — creating a vicious cycle.
  • Water vapor feedback: As the atmosphere warms, it becomes capable of holding more moisture. This increase in water vapor amplifies the warming effect.
  • Permafrost feedback: As permafrost thaws due to rising temperatures, it releases stored carbon dioxide and methane (a potent greenhouse gas). This released greenhouse gas causes additional warming, which melts more permafrost — a self-reinforcing cycle.
  • Cloud feedback: The influence of clouds on climate is complex. Depending on the type and altitude of clouds, they can either trap heat in the atmosphere or reflect incoming solar radiation back to space. As the climate changes, the distribution and altitude of clouds changes, which can either amplify or reduce warming.

These feedback loops have the potential to trigger tipping points in the climate system — critical thresholds beyond which the climate shifts to a new equilibrium state. Once triggered, tipping points can lead to abrupt and irreversible changes in regional climate patterns and ecosystem functioning. Some examples include the disruption of ocean circulation patterns (which regulate global climate), the collapse of ice sheets, and the transformation of forests into grasslands.

Air pollutants and their role in climate change

While carbon dioxide is the most well-known greenhouse gas, many other air pollutants also play significant roles in climate change. Here are some key examples:

Methane (CH4)

Methane is a potent greenhouse gas that is approximately 84-86 times more effective at trapping heat than CO2 over a 20-year period. Although CO2 remains in the atmosphere for much longer than methane, the short-term warming impact of methane is significant. Methane is emitted from a variety of sources including:

  • Agriculture (particularly livestock farming)
  • Landfills
  • Wastewater treatment plants
  • Fossil fuel extraction and refinement (including natural gas and oil)
  • Thawing permafrost

Nitrous oxide (N2O)

Nitrous oxide is another potent greenhouse gas that is approximately 265-298 times more effective at trapping heat than CO2 over a 100-year period. The primary anthropogenic (human-caused) sources of nitrous oxide emissions are:

  • Agricultural soil management (including the use of synthetic fertilizers)
  • Manure management
  • Wastewater treatment
  • Industrial chemical production
  • Combustion of fossil fuels

Particulate matter and aerosols

While not typically thought of as greenhouse gases, aerosols and particulate matter in the atmosphere can have a significant impact on climate change. These particles can either reflect sunlight back to space (which has a cooling effect) or trap heat in the atmosphere (which has a warming effect). The net effect depends on the type and distribution of the aerosol and its interactions with clouds. Some aerosols that have warming effects include:

  • Black carbon (soot): When deposited on ice and snow, black carbon absorbs solar radiation, reducing the albedo (reflectivity) of the surface and accelerating melting. Some studies suggest that black carbon may be responsible for 25% of observed Arctic warming.
  • Brown carbon: Like black carbon, brown carbon absorbs solar radiation and can reduce the albedo of ice and snow, contributing to warming.

Other aerosols, such as sulfate aerosols, can have a net cooling effect by reflecting sunlight. However, this does not mean they are beneficial — these aerosols cause significant public health issues.

Tropospheric ozone (O3)

While stratospheric ozone protects us from harmful UV radiation, tropospheric (ground-level) ozone is a greenhouse gas that contributes to climate warming. Tropospheric ozone is a secondary pollutant formed through chemical reactions involving:

  • Nitrogen oxides (NOx)
  • Volatile organic compounds (VOCs)
  • Carbon monoxide (CO)
  • Methane

These precursor pollutants come from sources such as vehicle emissions, power plants, industrial facilities, and wildfires.

Hydrofluorocarbons (HFCs) and other halogenated compounds

HFCs are potent greenhouse gases used in refrigeration and air conditioning systems. Although they do not deplete the ozone layer like their predecessor CFCs (chlorofluorocarbons), they have global warming potentials (GWPs) thousands of times higher than CO2. They are being phased out under the Kigali Amendment to the Montreal Protocol.

The interconnection between air quality and climate change

Air quality and climate change are deeply interconnected. For example:

  • Climate change worsens air quality: Rising temperatures increase the formation of ground-level ozone and other secondary pollutants, and can increase the frequency and intensity of wildfires (which emit large amounts of particulate matter).
  • Air pollution affects climate: Many of the pollutants that harm air quality (such as black carbon and methane) also contribute to climate warming.
  • Both affect human health: Climate change and air pollution together pose significant threats to human health, contributing to respiratory diseases, cardiovascular diseases, and premature mortality.
  • Mitigation strategies can address both: Many mitigation strategies address both climate change and air quality simultaneously. For example, transitioning to renewable energy sources reduces both CO2 emissions and air pollutant emissions from fossil fuel combustion.

This interconnection means that efforts to address climate change should also consider impacts on air quality, and vice versa. The Montreal Protocol, for example, was originally designed to protect the ozone layer but has also significantly reduced greenhouse gas emissions.

Measuring air quality to support climate action

As the importance of addressing both air quality and climate change becomes increasingly clear, the role of air quality measurement becomes more critical. Governments and businesses need to:

  • Monitor emissions: Accurate measurement of air pollutants is essential for understanding current emission sources and tracking progress towards emission reduction targets.
  • Inform policy: Air quality data helps policymakers develop evidence-based strategies to reduce emissions and improve public health.
  • Support accountability: As governments and businesses commit to emission reduction targets, regular air quality monitoring is necessary to verify progress and ensure accountability.
  • Drive innovation: Air quality data can help identify pollution hotspots and inform the development of solutions tailored to local needs.

The EPA has also started to recognize the role that air pollution control can play in climate change mitigation. As stated in their recent guidance on air quality and climate change, "the air quality improvements achieved through pollution control efforts contribute to climate change mitigation." In fact, as the EPA works toward developing national ambient air quality standards (NAAQS), air quality measurement becomes more important than ever as the EPA can use air pollution control as a way to cap emissions.

Interested in measuring air quality as we take the step towards cleaner air and a healthier climate? Get in touch with our team to learn more about our Sensing-as-a-Service solution for governments, businesses, and community organizations!