Observed past and present climate trends and variability indicates an increasing trend of about 1 degree C in May and 0.5 degree C in November has been observed during the fourteen year period 1985-1998. Inter-seasonal, inter-annual and spatial variability in rainfall trend has been observed during the past few decades. Annual mean rainfall exhibits increasing trends. Observed changes in extreme climatic events revealed from new evidences on recent trends show increasing tendency in the intensity and frequency of extreme weather events over the last century and into the 21st century. Impacts of these observed changes have been significant on agriculture, particularly on food production and security. Another area critically affected is hydrology and water resources, characterized by water shortages. Our coastal zone is most threatened. Saltwater from the Bay of Bengal has penetrated 100 km or more inland along tributary channels during dry season. Evidences of the impacts of climate related factors on mangroves are the severe destruction of mangroves due to reduction of freshwater flows and salt water intrusion. Wetlands have been observed to suffer from precipitation decline and droughts in the delta region. The north is affected by floods and riverbank erosion, north and northwestern parts affected by droughts, while the northeast is ravaged by flash floods annually. In recent years, heat waves and cold spells have claimed hundreds of life. Vector borne diseases particularly dengue has become a health hazard claiming hundreds of lives every year.