One of the most worrying global trends in climate is a southward shift in the tropical rain belt during recent decades.
This has significantly affected rainfall patterns and caused severe impacts on water availability, food production and natural hazards. The impacts have been most pronounced in tropical Africa and South America but this phenomenon may also affect tropical Asia including Singapore.
The culprit has been assumed to be thermal forcing due to climate change but now a new ‘smoking gun’ has been identified.
A scientific publication in Nature Geoscience this month from the University of Miami Rosentiel School of Marine and Atmospheric Sciences (Nature Geoscience, doi:10.1038/ngeo2988) suggests that the tropical rain belt shift is not due to natural climate forcing or greenhouse gas emissions, but instead is primarily the result of increased particulate air pollution from burning of fossil fuels, mainly in the northern hemisphere.
The effect was thought to arise from particulates changing the radiative properties of clouds that in turn affects atmospheric circulation, regional climate and rainfall.
Air pollution is increasingly being linked to severe weather changes, for example in 2014 a team led by Texas A&M University demonstrated that Asian air pollution strengthened storm clouds by delaying release of precipitation and making the clouds live longer and grow bigger.