Preface
Human activities since the nineteenth century have contributed to substantial increases in the
atmospheric concentrations of heat-trapping greenhouse gases (GHG), such as carbon dioxide
(CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), and fluorinated gases. Carbon dioxide is the main
long-lived GHG in the atmosphere related to human activities. Burning of fossil fuels, deforestation, and land use changes, among other human (anthropogenic) activities, have led to a
rapid increase of atmospheric CO 2 levels from 280 parts per million during 1850 to more than
416 parts per million in February 2020. The series of assessment reports of the United Nations
Intergovernmental Panel on Climate Change (IPCC) provides unequivocal evidence for the role
of anthropogenic forcing in driving the observed warming of the Earth’s surface by about 1
o C
during the last 150 years. Consequences of this warming have already manifested in several
other global-scale changes such as melting glaciers, rising sea levels, changing precipitation
patterns, and an increasing tendency of weather and climate extremes. These changes are projected to continue through the twenty-first century, as the GHG concentrations continue to rise.
Robust attributions and projections of regional-scale changes to anthropogenic forcing are
inherently more complex than global-scale changes because of the strong internal variability at
local scales. For example, the IPCC Fifth Assessment Report (AR5) reported large inter-model
spread in the climate change response of the Indian monsoon precipitation, Indian Ocean
regional sea-level rise, Himalayan snow cover, and other aspects of the regional climate
system. In this context, this book presents a comprehensive assessment of climate change over
the Indian region and its links to global climate change. This assessment report is based on
peer-reviewed scientific publications, analyses of long-term observed climate records, paleoclimate reconstructions, reanalysis datasets and climate model projections from the Coupled
Model Intercomparison Project (CMIP) and the COordinated Regional climate Downscaling
EXperiment (CORDEX). This book is the first ever climate change report for India from the
Ministry of Earth Sciences, Government of India, and its preparation was led and coordinated
by the Centre for Climate Change Research (CCCR) at the Indian Institute of Tropical
Meteorology (IITM), Pune.
The aim of this assessment report is to describe the physical science basis of regional
climate change over the Indian subcontinent and adjoining areas. The first chapter briefly
introduces global climate change, sets the regional context, and synthesizes the key points
from the subsequent chapters. Apart from GHGs, emissions of anthropogenic aerosols over the
Northern Hemisphere have substantially increased during the last few decades, and their
impacts on the regional climate are also assessed. Chapters 2–11 of the report assess changes
in several aspects of regional climate and their drivers, viz., temperature, precipitation, GHGs,
atmospheric aerosols and trace gases, droughts and floods, synoptic systems, tropical cyclones
and extreme storms, Indian Ocean warming and sea-level rise, and the Himalayan cryosphere.
While impacts and policy lie beyond the scope of this report, Chapter 12 closes this report with
a brief outline of the potential implications of climate change for the country’s natural
ecosystems, water resources, agriculture, infrastructure, environment, and public health, along
with some policy-relevant messages towards realizing India’s sustainable development goals
by mitigating these risks.
ix
Human activities since the nineteenth century have contributed to substantial increases in the
atmospheric concentrations of heat-trapping greenhouse gases (GHG), such as carbon dioxide
(CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), and fluorinated gases. Carbon dioxide is the main
long-lived GHG in the atmosphere related to human activities. Burning of fossil fuels, deforestation, and land use changes, among other human (anthropogenic) activities, have led to a
rapid increase of atmospheric CO 2 levels from 280 parts per million during 1850 to more than
416 parts per million in February 2020. The series of assessment reports of the United Nations
Intergovernmental Panel on Climate Change (IPCC) provides unequivocal evidence for the role
of anthropogenic forcing in driving the observed warming of the Earth’s surface by about 1
o C
during the last 150 years. Consequences of this warming have already manifested in several
other global-scale changes such as melting glaciers, rising sea levels, changing precipitation
patterns, and an increasing tendency of weather and climate extremes. These changes are projected to continue through the twenty-first century, as the GHG concentrations continue to rise.
Robust attributions and projections of regional-scale changes to anthropogenic forcing are
inherently more complex than global-scale changes because of the strong internal variability at
local scales. For example, the IPCC Fifth Assessment Report (AR5) reported large inter-model
spread in the climate change response of the Indian monsoon precipitation, Indian Ocean
regional sea-level rise, Himalayan snow cover, and other aspects of the regional climate
system. In this context, this book presents a comprehensive assessment of climate change over
the Indian region and its links to global climate change. This assessment report is based on
peer-reviewed scientific publications, analyses of long-term observed climate records, paleoclimate reconstructions, reanalysis datasets and climate model projections from the Coupled
Model Intercomparison Project (CMIP) and the COordinated Regional climate Downscaling
EXperiment (CORDEX). This book is the first ever climate change report for India from the
Ministry of Earth Sciences, Government of India, and its preparation was led and coordinated
by the Centre for Climate Change Research (CCCR) at the Indian Institute of Tropical
Meteorology (IITM), Pune.
The aim of this assessment report is to describe the physical science basis of regional
climate change over the Indian subcontinent and adjoining areas. The first chapter briefly
introduces global climate change, sets the regional context, and synthesizes the key points
from the subsequent chapters. Apart from GHGs, emissions of anthropogenic aerosols over the
Northern Hemisphere have substantially increased during the last few decades, and their
impacts on the regional climate are also assessed. Chapters 2–11 of the report assess changes
in several aspects of regional climate and their drivers, viz., temperature, precipitation, GHGs,
atmospheric aerosols and trace gases, droughts and floods, synoptic systems, tropical cyclones
and extreme storms, Indian Ocean warming and sea-level rise, and the Himalayan cryosphere.
While impacts and policy lie beyond the scope of this report, Chapter 12 closes this report with
a brief outline of the potential implications of climate change for the country’s natural
ecosystems, water resources, agriculture, infrastructure, environment, and public health, along
with some policy-relevant messages towards realizing India’s sustainable development goals
by mitigating these risks.
ix