Climate Sense

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Assessment of climate change

and adaptation in India

Ajit Tyagi, India Meteorological Department, New Delhi;

and B. N. Goswami, Indian Institute of Tropical Meteorology, Pune

he vulnerability of society to rising temperatures, chang-

ing precipitation patterns and increasing climatic extremes

has become one of the most discussed issues in the global

economic, social, scientific and political fora. Global and regional

models have been used to produce climate change scenarios focus-

ing on the frequency and intensity of extreme events such as heat

waves, cold spells, severe thunderstorms, tropical cyclones, storm

surges, severe storms and drought. Extensive observational data

from the past is required for any such assessment. It is widely

acknowledged that better forecasting capability is central to an

effective adaptation strategy, particularly in the Indian context

where livelihoods are strongly tied to the physical environment.

Therefore, India has taken steps to develop capabilities in regional

climate modelling and impact assessment, as well as to evolve

sector-specific impact minimization and adoption strategies.

Status of climate change in India

India has maintained a well disributed network of about 200 mete-

orological observatories across the country for more than a century

and about 500 observatories since 1947. Findings derived from the

data, and its subsequent analysis, have helped in climate monitoring

and climate change studies.

Mean annual surface air temperature over India rose by 0.52°C

during 1901-2008 and has been above normal since 1990 over a

base period of 1961-1990. This warming is primarily due to a rise

in maximum temperature across the country. However, since 1990

the minimum temperature has steadily risen at a slightly higher rate

than the maximum value.

Upper air temperatures have increased in the lower troposphere,

with the trend significant at 850 hectopascals, while a small decreas-

ing trend was observed in the upper troposphere.

The spatial

pattern of trends in the mean annual temperature shows significant

positive (increasing) trends over most of the country, except over

parts of Rajasthan, Gujarat and Bihar, where significant negative

(decreasing) trends were observed.

During the last century the Indian summer monsoon season rainfall

(June to September) has shown no significant trend. However, three

subdivisions – Jharkhand, Chattisgarh and Kerala – have shown

a significant decreasing trend, while eight subdivisions – Gangetic

West Bengal, West Uttar Pradesh, Jammu and Kashmir, Konkan and

Goa, Madhya Maharashtra, Rayalaseema, Coastal Andhra Pradesh and

North Interior Karnataka – have shown a significant increasing trend

during the same period.

A significant increasing trend has been observed in the frequency

of heavy rainfall events over the west coast.

Many extreme rain-

fall indices have shown significant positive trends over

the west coast and north western parts of the Indian

Peninsula with the exception of Mahabaleshwar, which

shows a decreasing trend in some of the extreme rainfall

indices.

Long-term linear results from the frequency of tropi-

cal cyclones over the north Indian Ocean, the Bay of

Bengal and the Arabian Sea for different seasons and

years, generally show a significant decreasing trend.

addition, a sharp decrease in the frequency of cyclones

during the monsoon season was observed.

However, an

increasing trend in the frequency of tropical cyclones

over the Bay of Bengal in the months of May and

November was also observed.

Prediction of climate over India

South Asian summer monsoon (SASM) rainfall and

its potential for change were evaluated under the

World Climate Research Program Coupled Model

Inter-comparison Project data set. The response of

SASM rainfall to a transient increase in anthropogenic

radiative forcing was investigated for two time-slices

– 2031-2050 and 2081-2100 – in the non-mitigated

Special Report on Emission Scenarios B1, A1B and

A2. Only 10 out of 25 models are able to simulate the

annual cycle and the space-time characteristics of SASM

precipitation reasonably well.

Almost all models show an increase in precipita-

tion and weakening of monsoon circulation for future

projections.

A substantial increase in precipitation

was observed over the western equatorial Indian Ocean

and southern parts of India when using ten selected

models.

However, the monsoon circulation weakens

under all the three climate change experiments. While

global atmosphere-ocean coupled models can provide

a good representation of the planetary-scale features,

their application to regional studies is limited by their

coarse resolution (around 300 kilometres).

The regional climate modelling system Providing

Regional Climates for Impacts Studies (PRECIS), devel-

oped by the Hadley Centre for Climate Prediction and

Research, has been applied in India to develop high

resolution climate change scenarios. The model has a

resolution of approximately 50 kilometres and is forced

at its lateral boundaries by a high resolution (around

overnance

and

olicy