The World's Annual Pollution Problem

Human activities are responsible for the increase in greenhouse gases in the atmosphere, with carbon dioxide (CO2) being the most significant contributor. The largest sources of greenhouse gas emissions are electricity and heat production, followed by transportation, manufacturing, construction, and agriculture. The distribution of emissions has changed over time, with Europe and the United States previously dominating global emissions. However, in recent decades, Asia, particularly China, has seen a significant rise in emissions due to rapid economic growth and industrialization. While CO2 emissions growth has slowed in recent years, it has yet to reach its peak, and if global energy demands continue to be met primarily by fossil fuels, annual emissions could reach 75 billion tons or more by the end of the century.

CO2 emissions by country

Global CO2 emissions have been increasing since the mid-18th century, with a notable surge during the Industrial Revolution. In 1950, global emissions were around 6 billion tonnes of CO2, rising to over 20 billion tonnes by 1990. As of 2022, global emissions have exceeded 35 billion tonnes annually. The top six emitting countries in 2022 were China, the United States, India, the EU27, Russia, and Brazil, together accounting for 61.6% of global greenhouse gas emissions.

China has been the largest emitter of CO2 since 2006, experiencing a surge of over 4,500% in emissions from 1950 to 2000. This can be attributed to its economic surge in the 1970s, particularly with Deng Xiaoping's new economic strategy in 1978. However, when analysed per capita, China's emissions are lower than those of the United States, due to its large population. The United States, on the other hand, has released more historical carbon dioxide emissions, with over 400 GtCO2 emitted since 1750.

The United States and China together account for about 40% of cumulative CO2 emissions since the Industrial Revolution. Other notable emitters include India, Japan, and the broader Asian region, which have all experienced emission growth exceeding 1,000% between 1950 and 2000.

Within the EU27, Germany is the largest emitter, contributing 21.9% of the bloc's emissions, followed by France (12.0%) and Poland (11.2%). Luxembourg, Belgium, Lithuania, Estonia, and the Netherlands have seen the largest relative decreases in emissions between 2021 and 2022, while Bulgaria, Spain, Portugal, Greece, Ireland, and Malta have experienced increases.

It is worth noting that the choice of energy sources plays a significant role in CO2 emissions. Countries with lower emissions, such as the UK, Portugal, and France, produce a higher proportion of their electricity from nuclear and renewable sources.

Greenhouse gas emissions by sector

Greenhouse gas emissions are distributed across various sectors, with the energy sector being the most significant contributor. Within the energy sector, electricity and heat production are the largest sources of emissions, accounting for around 30% of all emissions globally. This is followed by transportation, which contributes about 14% of global emissions, with over 94% of the fuel used in this sector being petroleum-based. Manufacturing and construction are also notable sub-sectors within the energy sector, making up about 13% of emissions.

The industrial sector is another major source of greenhouse gas emissions, with industrial processes accounting for a large proportion of emissions. This includes burning fossil fuels for energy and emissions from chemical reactions necessary for producing goods from raw materials. The manufacturing sector, in particular, has witnessed a decrease in emissions intensity, with a projected increase in emissions expected by 2050.

Agriculture is a significant contributor to greenhouse gas emissions, especially in the form of methane and nitrous oxide. Livestock production, agricultural soils, and rice cultivation are the primary sources of emissions within this sector. Methane is produced during the digestive processes of livestock, while nitrous oxide is released through the application of nitrogen-based fertilizers.

The commercial and residential sector also contributes to emissions, primarily through the burning of fossil fuels for heat and the use of gases for refrigeration and cooling in buildings. When including indirect emissions from electricity end-use, this sector's emissions increase substantially.

Lastly, the land use, land-use change, and forestry sector play a role in greenhouse gas emissions. While land areas can act as carbon sinks, absorbing CO2 from the atmosphere, certain activities within this sector can also release emissions.

Nitrous oxide emissions by sector

The majority of nitrous oxide emissions come from the agricultural sector. Nitrous oxide is produced by microbes in soil, and the application of nitrogen fertilisers makes more nitrogen available for microbes to convert to nitrous oxide. This process also occurs when organic fertilisers such as animal manure are used. As the use of nitrogen fertilisers has increased over the past 50 years, so have nitrous oxide emissions. In 2022, agricultural soil management was the largest source of nitrous oxide emissions in the US.

Nitrous oxide is also a byproduct of fuel combustion in mobile and stationary sources, such as passenger cars, light trucks, and other motor vehicles. In 2009, about 19% of total US nitrous oxide emissions came from energy sources, with two-thirds of that coming from mobile sources. Nitrous oxide emissions from mobile combustion decreased by 56% between 1990 and 2022 due to criteria pollutant emission standards for on-road vehicles.

The burning of coal at electric power plants accounted for 60% of all nitrous oxide emissions from stationary combustion in the US in 2009. US industrial sources emitted 11 million metric tons of carbon dioxide equivalent (MMTCO2e) of nitrous oxide in 2009, a decrease of 10.8% from 2008. The two main industrial sources of nitrous oxide emissions are the production of adipic acid and nitric acid. Adipic acid is produced by oxidizing a ketone-alcohol mixture with nitric acid, and the chemical reaction results in nitrous oxide emissions.

Nitrous oxide is also emitted from wastewater that contains nitrogen-based organic materials, such as those found in human or animal waste. In 2009, treatment of residential and commercial wastewater produced 92% of all nitrous oxide emissions from waste management in the US.

Global emissions over time

Global emissions have been increasing over time, with the current rate of carbon dioxide in the atmosphere being 50% higher than it was before the Industrial Revolution. Before the Industrial Revolution, emissions were very low, and growth in emissions was slow until the mid-20th century. In 1950, the world emitted 6 billion tonnes of CO2, which had increased to more than 20 billion tonnes by 1990. Emissions have continued to grow, and we now emit over 35 billion tonnes each year. The annual rate of increase in atmospheric carbon dioxide over the past 60 years is 100-200 times faster than the increase that occurred at the end of the last ice age 11,000-17,000 years ago.

The biggest contributor to global emissions is Asia, which accounts for around half of global emissions. China is the largest emitter in Asia and the world, with more than a quarter of global emissions. This is due to rapid economic growth and industrialization in recent decades, with a 450% increase in CO2 emissions since 1990. The second-largest emitter is North America, dominated by the United States, which accounts for about one-fourth of global emissions. Europe is the third-largest emitter, with some countries, such as Germany, having higher emissions than others, such as France, due to a greater reliance on fossil fuels.

While global emissions have continued to rise, there have been some periods where global events have caused emissions to decrease. For example, the COVID-19 pandemic caused global CO2 emissions to decrease by 5.5% in 2020 due to lockdowns and restrictions. Similarly, the global recession in 2009 resulted in a 2% decrease in CO2 emissions.

The increase in global emissions has had significant impacts on health and the environment. Air pollution is a leading risk factor for death, contributing to an estimated 7 to 8.1 million deaths globally in 2021. The majority of these deaths occur in low- and middle-income countries, with indoor air pollution being a significant contributor. Exposure to air pollution has also been linked to various health issues, including heart disease, stroke, lower respiratory infections, lung cancer, diabetes, and chronic obstructive pulmonary disease (COPD).

If global energy demand continues to grow and is met primarily by fossil fuels, human emissions of carbon dioxide could reach 75 billion tons per year or more by the end of the century. This would result in atmospheric carbon dioxide amounts of 800 ppm or higher, which have not been seen on Earth for close to 50 million years.

Impact of pollution

Human activities have had a profound impact on the environment, with pollution being one of the most significant concerns. The Industrial Revolution marked a turning point, as it led to a massive increase in pollutants emitted into the air, causing harmful effects on both human health and the environment. Today, industrialization and urbanization continue to contribute to air pollution, which poses a major threat to public health, with nearly 9 million deaths attributed to it annually.

One of the most visible impacts of pollution is on water bodies, including rivers and oceans. Marine pollution is primarily due to land-based activities, with plastic being a significant contributor. More than 10 million metric tons of plastic end up in the oceans each year, and this number is expected to triple by 2040. The fishing industry contributes to a significant portion of this plastic waste. Nutrient pollution, caused by nitrogen and phosphorus waste from fertilizers and manure, leads to eutrophication, resulting in the blooming of harmful algae and the creation of "dead zones" with extremely low oxygen levels, making it impossible for life to survive.

Water pollution also extends to the contamination of water sources with heavy metals, such as mercury, arsenic, copper, iron, and lead. The presence of these substances in water bodies can lead to poisoning and bioaccumulation in species, particularly those higher up on the food chain, such as fish consumed by humans. For example, the combustion of coal can result in mercury pollution in water, leading to high concentrations of methylmercury in fish like tuna and striped bass. Consumption of these contaminated fish poses health risks, including an increased risk of fetal anomalies, cardiovascular diseases, and dementia in adults.

Additionally, the presence of pharmaceutical products in water bodies has raised concerns. Oral contraceptives, for instance, have led to the feminization of male fish, and the release of antibiotics has contributed to antimicrobial resistance. These issues highlight the need for proper regulation and governance to prevent the harmful impacts of pharmaceutical pollution on the environment and human health.

Pollution also affects the air we breathe. Greenhouse gas emissions from various sectors, including electricity and heat production, transportation, manufacturing, and construction, contribute to climate change and poor air quality. The choice of energy sources plays a crucial role, as some countries rely more heavily on fossil fuels, which have higher emissions. While economic growth and industrialization have improved living standards, they have also resulted in increased carbon dioxide emissions, particularly in countries like China, which has seen a nearly 450% increase in emissions since 1990.

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