Chennai, India

A scientific analysis of the December 2015 Chennai floods found no detectable effect of human-induced climate change on the extreme one-day rainfall event, likely due to the masking effect of aerosol pollution in the region.

• On 1 December 2015, Chennai experienced record rainfall, with some stations recording as much as 494 mm (19.45 inches) in 24 hours. This event was meteorologically extreme, with a probability of occurrence in the current climate estimated between one in 600 and one in 2,500 per year.
• The scientific analysis concluded that human-induced climate change had no detectable effect on the extreme one-day rainfall in Chennai on 1 December 2015, covering periods from 1900-1970 and 1970-2014.
• The lack of detectable human-caused influence is attributed to the 'aerosol effect,' where high levels of aerosol pollution (the 'brown cloud') block sunlight and counteract the warming effects of greenhouse gases, particularly in the western Bay of Bengal.
• The 2015 rainy season occurred alongside several climatic factors, including a strong El Niño, record warm global surface temperatures, and high Indian Ocean temperatures. SST-forced regional models showed a small but clear increase in the probability of extremes associated with El Niño and other non-anthropogenic SST anomalies.
• Chennai's high vulnerability to the floods was exacerbated by unplanned urban growth, including an estimated 150,000 illegal buildings, the loss of water bodies, encroachment of drainage channels, and inadequate flood zone planning and desilting.
• The economic costs to India resulting from the flood waters in Chennai are estimated at US$3 billion.

APA

AchutaRao, K., van Oldenborgh, G. J., Otto, F. E., & Haustein, K. (2017). Chennai, India. Climate and Development Knowledge Network. https://cdkn.org/sites/default/files/files/CDKN_RRA_Chennai_Floods_proof5.pdf

Chicago

AchutaRao, Krishna, Geert Jan van Oldenborgh, Friederike E.L. Otto, and Karsten Haustein. Chennai, India. Climate and Development Knowledge Network, 2017. https://cdkn.org/sites/default/files/files/CDKN_RRA_Chennai_Floods_proof5.pdf.

Wikipedia

{{cite report |last1=AchutaRao |first1=Krishna |last2=van Oldenborgh |first2=Geert Jan |last3=Otto |first3=Friederike E.L. |last4=Haustein |first4=Karsten |title=Chennai, India |publisher=Climate and Development Knowledge Network |date=2017 |url=https://cdkn.org/sites/default/files/files/CDKN_RRA_Chennai_Floods_proof5.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{achutarao2017chennai, author = {AchutaRao, Krishna and van Oldenborgh, Geert Jan and Otto, Friederike E.L. and Haustein, Karsten}, title = {{Chennai, India}}, institution = {Climate and Development Knowledge Network}, year = {2017}, url = {https://cdkn.org/sites/default/files/files/CDKN_RRA_Chennai_Floods_proof5.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }