Six or four seasons? An evidence for seasonal change in Bangladesh

Bangladesh is reported to suffer from climatic changes, and many local people begin to wonder that six seasons in Bangladeshi annual calendar transition to four seasons where the traditional one (Bangla calendar) is considered to have consisted of the six seasons. We collected observations of key climate variables (1953-2010) from the weather station located in Dhaka, and conducted face-to-face surveys with 1,011 respondents and seven experts to elicit their current perception about whether six seasons are becoming four seasons. To scientifically confirm this, we apply nonparametric statistical methods to the key climate variables and test whether any pair of two neighboring seasons in Bangla calendar is converging into one. The statistical analysis shows "convergence" for specific two pairs of two neighboring seasons, meaning that the annual calendar now consists of four seasons, not six. Approximately 65% of respondents believe that annual calendar transitions to four seasons from six seasons. Overall, people's perception and the statistical analysis are consistent each other. The effect of global climatic changes now becomes significant to the extent that local people correctly perceive some fundamental seasonal changes of annual calendar and it is really ongoing on the basis of our statistical analysis.