Most don’t agree to the phrase “Winter in Chennai” thanks to the pretty much hot climate right through the year. Nevertheless the period between January 1st to February 15th technically could be called as Winter in Chennai after the Northeast Monsoon dies down and the cold dry air from Central India makes its way to the East Coast of Peninsular India.
Old Timers often remark Winter in Chennai was much cooler than what we are seeing today. Is there merit in this argument or is it like one of those many urban legends that exist in every city. Old Timers in Bangalore often remark they have never seen ceiling fans in their city while today Air Conditioners have become a necessity there than a luxury.
With the use of data for the last 3 decades or so we have tried to create an unbiased representation of how the temperatures over Chennai has changed during the month of January since 1979. These graphs have been plotted using data obtained from Climate Reanalyzer (http://cci-reanalyzer.org), Climate Change Institute, University of Maine, USA.
The first one is the mean temperature for the month of January over the period 1979 – 2015 using the Climate Forecast System Reanalysis (CFSR) of NOAA National Climatic Data Center. We have used this data to give the emerging pattern in the recent past as this data is noted to be well suited for Climate Study in the Satellite era thanks to the State-of-the-art 3rd generation reanalysis with robust physics and data assimilation.
As one can observe from the above chart the trend appears quite clearly the Mean temperature at 2 meters is showing an increase for Chennai & surrounding area.
If one were to look at minimum and maximum temperatures individually it holds the key on why the mean temperatures over Chennai is showing an increasing trend over the last 35 years or so.
The average minimum temperature for January pretty much shows a fairly similar picture over the last three decades or so with a very marginal increasing trend. Except for the early part of 1990s’ when it was low at around 18°C the average minimum temperature have been around 19-20°C.
It is the average maximum temperatures that is showing a clear increasing trend for Chennai. Effectively meaning the days are warmer than what it used to be earlier. While the night time minimum temperatures seem to be showing a stable trend the day time highs are showing a clear increasing trend. Is this due to possibly Urbanization we don’t know.
To end we provide the historical mean temperature data of Chennai. These are plotted using CCSM4 one of several general circulation models (GCMs) used in the Intergovernmental Panel on Climate Change (IPCC). This data is available till 2005 but if one were to see it in perspective with the earlier data shown from the recent times a clear pattern emerges “Winter in Chennai is getting warmer”.