A new study that used comprehensive
surface temperature data to record changes in daily mean temperatures
across India over seven decades has found “a consistent pattern of warming”
over the northwestern and southern parts of the country from the 1950s
to the 2000s, even as the “broad zone anchored over northeastern India and
extending southwestward across central India” saw “a pattern of cooling”
during this period.
The results, published recently
in Scientific Reports, a journal of the Nature group, have been reported by
Robert S Ross and T N Krishnamurti of Florida State University, Sandeep
Pattnaik of IIT-Bhubaneswar, and D S Pai of the India Meteorological
Department. The study has examined the patterns in the overall warming
of the planet that has accelerated since the 1950s, and its possible impact
on Indian agriculture. (‘Decadal surface temperature trends in India based on a
new high resolution data set’: Scientific Reports 8: 2018)
What is the key finding of the
study?
Essentially that while the “decade
mean maximum surface temperatures over India in the pre-monsoon months in the
1950s showed limited areas with values as high as 40°C”, by the 2010s,
the “area with values exceeding 40°C had expanded to include the majority of
the Indian peninsula, with peak values in south-central India reaching
42°C”. At the same time, there is “a definite, and somewhat surprising, cooling
(or in some instances, reduced warming)” in the Northeast over these
decades — a pattern of warming and cooling that is explained by “the
presence of a large region of anthropogenic brown haze over India and the
adjacent ocean regions”, especially in the winter and spring. “The haze”,
the researchers say, “is composed of aerosols that absorb solar
radiation, which reduces insolation at the Earth’s surface leading to cooling,
while increasing absorption in the aerosol layer leading to warming”.
On what data is the study
based?
An examination of all-India
surface mean temperature anomalies for 1901-2016 reveals an “unmistakable
rapid rise, particularly since about 1980, as seen in annual, winter,
pre-monsoon, monsoon and post-monsoon period depictions”, notes the study.
Beginning from this observation, the researchers focussed on a recently
developed comprehensive surface temperature data set for India for 1969-2005, a
range that was subsequently expanded to 1951-2013. Temperature data from 395
Indian meteorological stations were categorised into the periods April 1-May 31
(pre-monsoon), July 1-September 30 (monsoon), and January 1-March 31 (winter),
for which researchers looked at the maximum, minimum and daily mean
temperatures.
And what do the data suggest?
In the 1950s, the area with a
mean maximum temperature higher than 40°C was small — only one spot in
south-central India showed values ~ 41°C. “The region with values greater than
40°C begins to expand in the 1970s and 1980s and (that) with values greater
than 41°C in south-central India enlarges”, says the study. A very slight fall
is seen in the 1990s, and then, “the region with temperatures greater than 40°C
expands dramatically in the 2000s and the 2010s, (that) with temperatures
greater than 41°C expands, and a region with temperature greater than 42°C
appears in south-central India in the 2010s”. Also, a notable warming trend
that begins in northwestern India in the 1970s, accelerates in the 2000s ad
2010s. The broad conclusion: “These decadal mean temperature patterns
suggest that global warming is manifesting itself over parts of India in the
maximum temperatures observed during the warm pre-monsoon period, with an
accelerating pace noted, particularly in the last two decades.”
What do these findings imply?
India, the researchers underline,
is “more vulnerable to climate change because its agricultural system must
feed 17.5% of the world’s population with only 2.4% of the land and 4% of the
water resources of the planet”. A mid-range projection of climate change
for 2020-39 has indicated a reduction in crop yields of between 4.5% and 9%,
the study says. One point of comfort: maps of multi-decadal temperature change
show that the primary rice- and sorghum-growing regions “lie directly in
the swath of multi-decadal temperature cooling (or reduced warming)”,
which may indicate relatively “less stress” for these “critical growing
areas”.
Credit: Indian Express Explained
(http://indianexpress.com/article/explained/simply-put-how-heat-footprint-has-grown-monsoon-forecast-5185892/)
Reach Us
if you face difficulty in understanding the above article.
No comments:
Post a Comment