Physical Address
Plot 123 Kampala, Uganda
While it is widely acknowledged that human activities have significantly warmed the planet by burning coal, oil, and gas, fewer people are aware that these same activities also contribute to cooling. The Earth has warmed by nearly 1.2 degrees Celsius (2.2 degrees Fahrenheit) since preindustrial times, and it is on track to surpass the 1.5 degrees Celsius warming threshold.
Burning fossil fuels releases tiny particles that reflect sunlight and encourage cloud formation, thereby cooling the planet. Despite being deadly and linked to millions of deaths, this pollution has mitigated some of the impacts of global warming. Since the 1980s, these particles have offset between 40 and 80 percent of the warming caused by greenhouse gases.
However, efforts to reduce air pollution are diminishing this cooling effect. New regulations have reduced sulfur aerosols from global shipping, and China has drastically cut its sulfur pollution over the past decade. This reduction in pollution results in warmer temperatures, but the exact increase remains uncertain and critically impacts climate goals.
“We’re starting from an area of deep, deep uncertainty,” said Zeke Hausfather, a climate scientist at Stripe. “It could be a full degree of cooling being masked.”
Sulfur aerosols are primarily responsible for the cooling effect. These particles reflect sunlight and make clouds more reflective, thus cooling the Earth. When diseases and burned, sulfur is released into the atmosphere, causing severe health issues, including respiratory problems and chronic diseases, and contributing to about 1 in 10 deaths worldwide.
Over recent decades, many countries have made significant strides in reducing sulfur emissions. The United States and the European Union led these efforts, followed by China and India. China has reduced its sulfur dioxide emissions by over 70 percent since 2005 by implementing new technologies. In 2020, the International Maritime Organization introduced regulations limiting sulfur in shipping fuels, leading to an 80 percent drop in sulfur emissions from shipping. Mediterranean countries are planning similar regulations for 2025.
“There’s been a pretty steep decline over the last 10 years,” said Duncan Watson-Parris, an assistant professor at the Scripps Institution of Oceanography.
These regulatory measures have saved lives—around 200,000 premature deaths have been prevented in China, and the new shipping regulations could save approximately 50,000 lives annually. However, these efforts have inadvertently contributed to global warming. Scientists estimate that the reduction in aerosols due to the new shipping rules could add between 0.05 and 0.2 degrees Celsius of warming over the next few decades.
In the context of Africa and Uganda, where pollution control measures are still developing, the dynamics of sulfur aerosols and their impact on climate change could differ significantly. The challenge for these regions will be to balance air quality improvements with the potential impacts on climate, considering both public health and environmental sustainability.
