• Burning fossil fuels emits both long-lived greenhouse gases and short-lived aerosols such as sulfur dioxide (SO₂) and nitrogen oxides (NO). Along with an increasing number of wildfires globally, these contribute to the formation of smog and acid rain, and are directly linked to the deaths of millions, including some 3,300 in Aoteaora.

More than 8 million people died in 2018 from fossil fuel pollution, significantly higher than previous research suggested, according to new research from Harvard University. – Harvard School of Engineering

• When these pollutants interact with clouds, they make them brighter and more reflective. The resulting albedo effect has led to artificial cooling that masks around 1°C of warming. A sudden reduction in emissions would, perversely, result in the abrupt rise of temperatures beyond 2°C.
• The effects are more pronounced over the localised regions that emit the most greenhouse gases; that is, heavily industrialised areas such as China, and large fossil-fuel uses such as India.
• Figures used in the IPCC Sixth Assessment Report WG1 estimate the impact of pollutants is less than 1°C. Others suggest this is a dangerously conservative under-estimate. The research supporting this is more recent than IPCC AR6 WGI, and attributed to the abrupt spike in record-breaking global temperatures in 2023 (Fig. 1 and Video 1).
• International laws to reduce these toxic aerosols from shipping came into effect in 2022, and are gradually being rolled out. By reducing this toxic aerosol pollution the cooling effect of these aerosols is also being removed (Fig. 1)

Without aerosols’ cooling effect, the world would already have reached the temperature threshold of dangerous climate change… Until recently, ships’ aerosol emissions probably cooled the planet more than their greenhouse-gas emissions warmed it. – Pierce, 2024

• Pollutants include hydroxyl radicals, which are present in tiny quantities and have a lifetime of less than a second. However, they remove about 85% of methane from the atmosphere. The abrupt reduction in these during Covid has been attributed to the sudden, abrupt rise of atmospheric methane 2021-2022 (Video 2). Due to feedback effects and a possible tipping point being breached, methane continues to rise at an alarming pace.
• Volcanoes also emit sulfates. Eruptions have masked some warming over the last few hundred years, causing global temperatures to drop slightly for short periods. 
• See also ‘water vapour and clouds‘ and ‘ozone‘, as both influence the amount of warming or cooling depending on the type of cloud and where they are in the atmosphere.