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Causes: Cooling effect of carbon emissions 

 Image: Peggy Anke

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The cooling effect of carbon emissions

Summary

  • 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:

“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 results in 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. 
  • The cooling effect lasts for hours to months, but as emissions are continuous, the cooling is ongoing. The exception was when global industries and international travel largely shut down due to Covid in 2020-2021. This led to an abrupt spike in temperatures and heat-related impacts (Videos 1 &2).
  • 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 now continues to rise at an alarming pace.
  • Figures used in the IPCC Sixth Assessment Report WG1 estimate the impact of pollutants is less than 1°C. Others (Video 1) suggest this is a dangerously conservative under-estimate (the research supporting this is more recent than IPCC AR6 WGI).
  • 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.

  Causes

Other sections

Home > Climate wiki > What causes climate change? > Greenhouse gases > Emissions pollution

Summary

  • 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:

“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 results in 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. 
  • The cooling effect lasts for hours to months, but as emissions are continuous, the cooling is ongoing. The exception was when global industries and international travel largely shut down due to Covid in 2020-2021. This led to an abrupt spike in temperatures and heat-related impacts (Videos 1 &2).
  • 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 now continues to rise at an alarming pace.
  • Figures used in the IPCC Sixth Assessment Report WG1 estimate the impact of pollutants is less than 1°C. Others (Video 1) suggest this is a dangerously conservative under-estimate (the research supporting this is more recent than IPCC AR6 WGI).
  • 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.

Video 1: November 2022 at COP27, Dr. Ye Tao covers some of the latest research, with a critique of the IPCC 6th Assessment Report (2021) use of the lowest estimate of 0.7C, when the range is much higher. As the IPCC has consistently underestimated the speed and impacts of climate change, Tao argues that it would be prudent to prepare for a higher figure. 

Video 2: Methane comes from production and transport of fossil fuels, but instead of tumbling during the global COVID lockdowns, they spiked upwards.

Fig. 1: SO2 concentrations 14 December, 2022. Click on the image for an updated view and to track other data. Image: Google mapping project earth.nullschool.net.
Fig. 1: SO2 concentrations 14 December, 2022. Click on the image for an updated view and to track other data. Image: Google mapping project earth.nullschool.net.

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