Climate Change: Pollution's Impact And Influence

Air pollution and climate change are two sides of the same coin. Air pollution is the leading environmental cause of illness and premature death, with fine air pollution particles or aerosols causing 6.4 million deaths every year. Air pollution also has adverse impacts on biodiversity, ecosystems, and human capital. The sources of outdoor air pollution are often the same as those for high carbon dioxide emissions, such as the use of fossil fuels for power generation, industry, and transport. These sources are key contributors to climate warming. Greenhouse gases, a significant component of air pollution, cause the climate to warm by trapping heat from the sun in the Earth's atmosphere. The recent increase in greenhouse gas pollution is causing the planet to warm more than it did in the 20th century.

Greenhouse gases, such as carbon dioxide, trap heat from the Sun

Greenhouse gases are essential for keeping the Earth warm enough for life to exist. However, human activities have been increasing the amount of greenhouse gases in the atmosphere, causing the planet to warm beyond normal levels. Greenhouse gases, such as carbon dioxide, trap heat from the Sun by absorbing the light and radiation that would otherwise escape back into space.

The greenhouse effect is a natural process responsible for keeping the Earth's temperature habitable. Sunlight, or solar energy, reaches the Earth's surface, where it is absorbed or reflected. The energy that is reflected bounces back into the atmosphere in the form of heat. As this heat escapes back into space, greenhouse gases absorb it, trapping it within the atmosphere. This process has been occurring constantly and has kept the planet warm enough to support life.

The greenhouse effect is caused by gases in the atmosphere with a complex molecular structure that can absorb heat. These gases include carbon dioxide, water vapour, methane, and nitrous oxide. Carbon dioxide, for example, is made up of one carbon atom and two oxygen atoms, with bonds between the atoms that can vibrate and absorb photons. These photons are particles of light that carry energy from the Sun. When greenhouse gases absorb photons, they trap the Sun's energy, preventing it from escaping into space, and causing the atmosphere to heat up.

The recent increase in greenhouse gas pollution is primarily due to the burning of fossil fuels, as well as vehicle exhaust, emissions from agriculture, and pollutants released from factories and power plants. This has led to higher concentrations of greenhouse gases in the atmosphere, amplifying the greenhouse effect and causing global warming. As a result, the Earth's climate is warming, with scientists predicting that the planet will warm more this century than it did in the 20th century.

Carbon dioxide is of particular concern due to its long atmospheric lifetime. Unlike methane, which reacts with oxygen and is removed from the atmosphere within around 12 years, carbon dioxide does not react with oxygen and can remain in the atmosphere for over a century. As a result, the added carbon dioxide from human activities accumulates much faster than it can be naturally removed, leading to a net increase in the atmosphere. This increase in carbon dioxide and other greenhouse gases is a significant contributor to climate change.

Black carbon, a particulate pollutant, warms the Earth

Black carbon, a particulate pollutant, is formed by the incomplete combustion of wood, waste, fossil fuels, biofuels, and biomass. It is a major constituent of soot and is commonly known as such.

Black carbon is a powerful short-lived climate pollutant (SLCP) that contributes to climate change and ill health. Although SLCPs persist in the atmosphere for a short time, their global warming potential is often much greater than carbon dioxide (CO2). Black carbon has a warming impact up to 1,500 times stronger than CO2 per unit of mass. It is the second-largest contributor to climate change after CO2.

Black carbon warms the Earth's atmosphere by absorbing sunlight and converting it into heat. It is very effective at absorbing light, and its warming effect is similar to that of asphalt surfaces creating islands of heat in urban areas. When black carbon is suspended in the atmosphere, it converts incoming solar radiation to heat. This accelerates the melting of snow and ice, reducing their albedo (reflectivity). This effect is particularly pronounced in snow-covered regions like the Arctic, the Himalayas, the Andes, the Rocky Mountains, the Canadian Rockies, and the Alps.

Black carbon also influences cloud formation and precipitation. It affects the reflectivity, stability, and duration of clouds. Depending on the amount of soot in the air and its position in the atmosphere, black carbon can either evaporate clouds or stabilize them, thereby having a cooling effect. It also alters regional weather and rainfall patterns, impacting ecosystems and human livelihoods. For example, changing rain patterns can disrupt monsoons critical for agriculture in large parts of Asia and Africa.

In combination with tropospheric ozone, black carbon contributes to significant staple crop losses globally each year. It also has adverse effects on human health, as the tiny particles can penetrate deep into the lungs and facilitate the transport of toxic compounds into the bloodstream.

The main sources of black carbon emissions include the burning of fossil fuels, wood, and other biomass fuels, as well as waste. Household energy, industrial production, agricultural burning, and the transport sector are significant contributors to black carbon emissions.

Reducing black carbon emissions is crucial for slowing climate change, improving air quality, and protecting human health and ecosystems.

Aerosols, like sea salt particles, reflect sunlight away from Earth

Aerosols are suspensions of liquid, solid, or mixed particles with highly variable chemical compositions and size distributions. They are released into the atmosphere through human activity, such as burning fossil fuels, and natural processes, such as volcanic eruptions, dust storms, and sea spray. Aerosols influence climate change by interacting with sunlight, either reflecting it away from Earth or absorbing it.

Aerosols, like sea salt particles, play a crucial role in regulating Earth's climate by reflecting sunlight back into space. These particles are often brighter than the Earth's land or ocean surfaces, and this reflection of sunlight leads to a cooling effect on the planet. The degree of reflection or absorption depends on the composition and colour of the particles. Bright-coloured or translucent particles tend to reflect radiation back towards space, while darker aerosols absorb more radiation. Salt particles, specifically, tend to reflect all the sunlight they encounter.

The cooling effect of aerosols is particularly evident after volcanic eruptions, which inject large amounts of aerosols into the stratosphere. For example, the 1991 eruption of Mount Pinatubo ejected over 20 million tons of sulfur dioxide, creating particles in the stratosphere that reflected sunlight and caused a temporary drop in global temperatures.

Aerosols also influence cloud formation. They can act as cloud condensation nuclei, leading to an increase in cloud droplets and enhanced reflection of solar radiation. This is known as the cloud albedo effect, which contributes to the cooling of the Earth's climate.

While the cooling effect of aerosols like sea salt particles can temporarily counteract the warming caused by greenhouse gases, it is important to note that the overall impact of aerosols on climate change is complex. Different types of aerosols have varying effects, and their distribution and concentration can vary regionally. Additionally, the warming effect of greenhouse gases is more prolonged due to their longer atmospheric lifetimes compared to aerosols.

Short-lived climate pollutants, like methane, are more potent warmers than CO2

Short-lived climate pollutants (SLCPs) are powerful climate forcers that remain in the Earth's atmosphere for a much shorter time than carbon dioxide (CO2). However, their potential to warm the atmosphere is much greater. Black carbon, methane, tropospheric ozone, and hydrofluorocarbons (HFCs) are the most significant SLCPs, and they are the most important contributors to global warming after CO2. These SLCPs are responsible for up to 45% of current global warming, with methane alone contributing to about 45% of today's net global warming.

Methane is a potent greenhouse gas that is 84 times more powerful than CO2 at warming the planet in its first two decades in the atmosphere. It is a precursor to tropospheric ozone, which is a toxic pollutant that inhibits plant photosynthesis, thereby reducing plant biomass and crop yields. Tropospheric ozone is responsible for significant yield losses in soybean, wheat, corn, and rice crops. Black carbon, on the other hand, is the largest contributor to global warming after CO2. It warms the Earth's atmosphere by absorbing sunlight, accelerating the melting of snow and ice, and contributing to climate change feedback loops.

The relatively short atmospheric lifetime of SLCPs, ranging from days to a few decades, means that reduction efforts can have rapid effects. By reducing SLCP emissions, we can quickly bend the global warming curve in the coming decades. For example, reducing methane emissions can be achieved through improving agricultural practices, reducing food waste, and capturing emissions from landfills and oil and gas production. Cutting SLCPs now can avoid up to 0.6°C of global warming by 2050 and help prevent dangerous climate tipping points, such as the loss of Arctic summer sea ice, which would cause irreversible and catastrophic changes.

While CO2 is the primary driver of long-term climate change, SLCPs play a critical role in near-term global warming. Their potent warming effects and short atmospheric lifetimes mean that reducing SLCP emissions is the fastest way to slow down temperature rise in the immediate future. Therefore, addressing both CO2 and SLCPs is essential to combat climate change effectively and meet the goals of the Paris Agreement.

Air pollution and climate change should be tackled together to protect health

Air pollution and climate change are two sides of the same coin, but they are often addressed separately. To protect human health, particularly in low- and middle-income countries, these issues should be tackled together.

Air pollution is the leading environmental cause of illness and premature death worldwide, causing 6.4 million deaths each year. The health impacts of air pollution disproportionately affect people in developing countries, where billions are exposed to harmful concentrations of fine particulate matter (PM2.5). These particles, emitted from sources such as coal-fired power plants and diesel-fueled vehicles, contribute to a range of diseases, including ischemic heart disease, stroke, lung cancer, and respiratory issues like asthma and allergies.

Air pollution and climate change are linked in a vicious cycle. Air pollution, particularly greenhouse gases like carbon dioxide, methane, and black carbon, traps heat in the Earth's atmosphere, causing global warming. This warming leads to more extreme weather events, such as heatwaves and droughts, which further degrade air quality. For example, heatwaves can cause stagnant air and increase ground-level ozone pollution, which is a health hazard. Additionally, higher temperatures extend the growing season for plants, increasing pollen concentrations and airborne allergens that negatively affect respiratory health.

Climate change also impacts ecosystems, with drastic changes observed in the Arctic due to warming. The warming climate contributes to the melting of snow and ice, which changes the Earth's surface and leads to further warming. This positive feedback loop has severe consequences for the environment and human health.

To break this cycle, interventions are needed to reduce air pollution and mitigate climate change. Addressing the sources of toxic air pollution, such as coal combustion and traffic emissions, can have dual benefits. By reducing emissions from these sources, we can improve air quality and protect human health in the short term while also slowing down climate change over a longer period.

Additionally, it is crucial to measure and monitor air pollution levels to effectively manage the problem. Developing countries, where the impact of air pollution is most severe, often lack the infrastructure for monitoring air quality. Establishing ground-level monitoring networks and disseminating air quality data to the public are essential steps in tackling air pollution and its associated health risks.

By addressing air pollution and climate change jointly, with a focus on protecting human health, we can strengthen economies, reduce poverty, and build a more resilient future for vulnerable communities worldwide.

Frequently asked questions