April 12, 2010

India's Rising Temperature Affecting Everything !

Scorching — that’s what Bangalore has become. Sunday’s maximum temperature of 37.6 degrees Celsius and minimum temperature of 24.2 degrees Celsius has been the highest in the past 25 years. The all-time maximum and minimum temperatures for April till date has been 38.3 degrees Celsius (April 30, 1931) and 14.4 degrees Celsius (April 26, 1894).

"The month of April always experiences extreme summer heat during day and night. The trend is likely to continue into May,"  
April 11, 1983 had also recorded a very close 37.7 degrees Celsius and this was the last recorded highest temperature in the past 25 years. 
In an ominous sign of climate change hitting home, India has seen accelerated warming in the past few decades and the temperature-rise pattern is now increasingly in line with global warming trends. 
The most up-to-date study of temperatures in India, from 1901 to 2007, has found that while it’s getting warmer across regions and seasons, night temperatures have been rising significantly in almost all parts of the country. 
The rise in night temperatures — 0.2 degrees Celsius per decade since 1970, according to the study — could have potentially adverse impact on yields of cereal crops like rice. The paper also finds that
warming has been highest in post-monsoon and winter months (October to February).
‘‘Until the late 1980s, minimum (or night) temperatures were trendless in India. India was an odd dot in the global map as most regions worldwide were seeing a rise in night temperatures in sync with growing levels of greenhouse gases. Our analysis shows the global trend has caught up with India,’’ said K Krishna Kumar, senior scientist and programme manager at Indian Institute of Tropical Meteorology, Pune, and one of the authors.
Regional factors seem to be getting over-ridden by warming caused by greenhouse gases. For instance, the cooling trend in much of north India seen in the 1950s and 60s has been reversed, possibly because the effect of aerosols in the air can no longer compensate for greenhouse gas warming. 
The rising night temperatures are a major cause of worry. Said Jagdish K Ladha, principal scientist in the India chapter of International Rice Research Institute, ‘‘Minimum temperatures have a link with rice fertility. At higher than normal night temperatures, rice grains aren’t properly filled up, leading to a drop in yield.’’ 
During 1901 to 2007, the all-India mean, maximum and minimum annual temperatures rose at the rate of 0.51, 0.71 and 0.27 degrees Celsius per 100 years, respectively.

However, post 1970, the rise has been sharper with mean and minimum temperatures both increasing at the rate of 0.2 degrees per decade, faster than the maximum temperature which rose by 0.17 degrees. 
Among regions, the hardest hit seems to be the western Himalayas encompassing portions of Jammu & Kashmir, Himachal Pradesh and Uttarakhand. Here the mean temperature rise in the last century was 0.86 degrees while, more recently, temperatures have been going up by as much as 0.46 degrees per decade. The rapid warming of the region would have obvious fallouts on glacier melts.
On a seasonal scale, winter and post-monsoon temperatures show significant warming trends in recent decades though temperatures in other months have also been going up more modestly. 


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