short-term changes that span over diurnal to
inter-annual timescale. The lack of robust observational records is a severe constraint to make a reliable
assessment of the trends in GHGs fluxes. In this
chapter, we provide an overview of the measurement
of a few GHGs concentration, how carbon is sequestered in natural ecosystems as determined by the eddy
covariance technique and some model-based results
for India. The chapter provides a summary assessment
of GHGs (mainly CO 2 , CH 4 and N 2 O)-related research
in India. Other trace gases, such as ozone, SO 2 and
CFCs, have been discussed in Chap. 5. A brief discussion on the upper ocean carbon cycle in the Indian
Ocean has been presented in Chap. 10.
4.1 Introduction
There is a general scientific consensus that radiative processes associated with increasing concentrations of greenhouse gases (GHGs) and related feedback processes are
responsible for the global warming and climate change
(IPCC 2013). The important GHGs in the earth’s environment are carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide
(N 2 O), halocarbons and ozone in the lower atmosphere. The
concentrations of CO 2 , CH 4 and N 2 O have significantly
increased since the beginning of the industrial era (Ciais et al.
2013). Among the GHGs of anthropogenic origin, the
increase of atmospheric carbon is of primary concern because
CO 2 has a long lifetime in the atmosphere (*100 years). The
concentration of atmospheric CO 2 was ca. 280 ppm during
the pre-industrial period. This has exceeded 400 ppm in
recent time (https://www.esrl.noaa.gov/gmd/ccgg/trends).
The average growth rate has been estimated at 2.11 ppm per
year during the last decade, and a value of 410 ppm was
observed in 2018 (https://www.esrl.noaa.gov/gmd). However, the CO 2 mixing ratio shows considerable variability on
local to regional scale. For example, the amplitude of CO 2
variations observed in the west peninsular India (*25 ppm)
was much higher than that observed in the Mauna Loa
observatory in the Pacific region (*6 ppm) (see Fig. 4.1),
though both the sites are situated within a narrow latitude
band (Sinhagad: 18.35° N; Mauna Loa: 19.4° N). The measurement in India is likely affected by regional terrestrial
biospheric processes and marine sources (Tiwari et al. 2014).
The concentration of CH 4 has increased from 700 to
1857 ppb and that of N 2 O from 270 to 321 ppb since
pre-industrial era (IPCC 2007). Although the concentrations
of CH 4 and N 2 O are small compared to that of CO 2 , their
global warming potential (GWP) in terms of radiative forcing is several times (28 and 265 for CH 4 and N 2 O, respectively, to 100-year time horizon) higher than that of an
equivalent amount of CO 2 . Residence time of CO 2 in the
atmosphere is *100 years, whereas that of CH 4 and N 2 O is
about 10 years and 120 years, respectively. The increase in
CH 4 concentration is mainly dominated by agricultural and
animal husbandry operations, and that of N 2 O is due to
agricultural practices (Liu et al. 2019).
4.2 Observational Aspects of GHGs Research
in India
In India, there are very few research organizations involved
in the observational aspects of GHGs research with a
long-term perspective. One of the earliest attempts was made
by a group at the National Institute of Oceanography
(NIO) in Goa and Physical Research Laboratory (PRL) in
Ahmedabad, which took a major initiative in measuring
GHGs at a coastal site in western India, Cabo de Rama, also
known as Cape Rama (acronym CRI: 15.08° N, 73.83° E,
50 m ASL) in association with the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia (Bhattacharya et al. 2009). The CRI site is located
closer to the shoreline, free from any major vegetation and
away from habitation (Tiwari et al. 2011). Routine measurement of the concentrations of CO 2 , CH 4 , CO, N 2 O and
H 2 was carried out at the bimonthly time intervals. Additionally, carbon (d
13 C) and oxygen (d
18 O) isotopic ratios of
CO 2 were also measured. The observational record is
available for about a decade (1992–2002) and also for a
period of 2009–2013.
In the next phase of the carbon cycle study in India, the
Indian Space Research Organisation (ISRO) started the
National Carbon Project (NCP) under the auspices of the
ISRO Geosphere-Biosphere Program (IGBP) in the early
phase of the 2010s. The NCP endeavors to understand the
GHGs dynamics and estimate their budget by means of a
robust observational network across the country (Chanda
et al. 2013, 2014; Sharma et al. 2013, 2014; Patel et al. 2011;
Mahesh et al. 2014, 2016, 2019; Sreenivas et al. 2016, 2019;
Jha et al. 2013, 2014; Rodda et al. 2016). At about the same
time, another GHGs observational program (CO 2 and CH 4 )
at a semi-urban hilly site near Pune, called Sinhagad (SNG),
was initiated by the Indian Institute of Tropical Meteorology, Pune, under the patronage of the Ministry of Earth
Sciences (MoES), Government of India. The SNG site is
200 km east of the Arabian Sea (73.75° E, 18.35° N,
1600 m ASL) situated over the Western Ghats mountainous
terrain of southwestern peninsular region of the Indian
subcontinent. The location is relatively free from major
vegetation and local habitation disturbances for GHGs
measurement on a long-term perspective. Routine air sampling at SNG, from a 10 m meteorological tower at weekly
intervals, has been operational since November 2009 (Tiwari
4 Observations and Modeling of GHG Concentrations and Fluxes …
75
inter-annual timescale. The lack of robust observational records is a severe constraint to make a reliable
assessment of the trends in GHGs fluxes. In this
chapter, we provide an overview of the measurement
of a few GHGs concentration, how carbon is sequestered in natural ecosystems as determined by the eddy
covariance technique and some model-based results
for India. The chapter provides a summary assessment
of GHGs (mainly CO 2 , CH 4 and N 2 O)-related research
in India. Other trace gases, such as ozone, SO 2 and
CFCs, have been discussed in Chap. 5. A brief discussion on the upper ocean carbon cycle in the Indian
Ocean has been presented in Chap. 10.
4.1 Introduction
There is a general scientific consensus that radiative processes associated with increasing concentrations of greenhouse gases (GHGs) and related feedback processes are
responsible for the global warming and climate change
(IPCC 2013). The important GHGs in the earth’s environment are carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide
(N 2 O), halocarbons and ozone in the lower atmosphere. The
concentrations of CO 2 , CH 4 and N 2 O have significantly
increased since the beginning of the industrial era (Ciais et al.
2013). Among the GHGs of anthropogenic origin, the
increase of atmospheric carbon is of primary concern because
CO 2 has a long lifetime in the atmosphere (*100 years). The
concentration of atmospheric CO 2 was ca. 280 ppm during
the pre-industrial period. This has exceeded 400 ppm in
recent time (https://www.esrl.noaa.gov/gmd/ccgg/trends).
The average growth rate has been estimated at 2.11 ppm per
year during the last decade, and a value of 410 ppm was
observed in 2018 (https://www.esrl.noaa.gov/gmd). However, the CO 2 mixing ratio shows considerable variability on
local to regional scale. For example, the amplitude of CO 2
variations observed in the west peninsular India (*25 ppm)
was much higher than that observed in the Mauna Loa
observatory in the Pacific region (*6 ppm) (see Fig. 4.1),
though both the sites are situated within a narrow latitude
band (Sinhagad: 18.35° N; Mauna Loa: 19.4° N). The measurement in India is likely affected by regional terrestrial
biospheric processes and marine sources (Tiwari et al. 2014).
The concentration of CH 4 has increased from 700 to
1857 ppb and that of N 2 O from 270 to 321 ppb since
pre-industrial era (IPCC 2007). Although the concentrations
of CH 4 and N 2 O are small compared to that of CO 2 , their
global warming potential (GWP) in terms of radiative forcing is several times (28 and 265 for CH 4 and N 2 O, respectively, to 100-year time horizon) higher than that of an
equivalent amount of CO 2 . Residence time of CO 2 in the
atmosphere is *100 years, whereas that of CH 4 and N 2 O is
about 10 years and 120 years, respectively. The increase in
CH 4 concentration is mainly dominated by agricultural and
animal husbandry operations, and that of N 2 O is due to
agricultural practices (Liu et al. 2019).
4.2 Observational Aspects of GHGs Research
in India
In India, there are very few research organizations involved
in the observational aspects of GHGs research with a
long-term perspective. One of the earliest attempts was made
by a group at the National Institute of Oceanography
(NIO) in Goa and Physical Research Laboratory (PRL) in
Ahmedabad, which took a major initiative in measuring
GHGs at a coastal site in western India, Cabo de Rama, also
known as Cape Rama (acronym CRI: 15.08° N, 73.83° E,
50 m ASL) in association with the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia (Bhattacharya et al. 2009). The CRI site is located
closer to the shoreline, free from any major vegetation and
away from habitation (Tiwari et al. 2011). Routine measurement of the concentrations of CO 2 , CH 4 , CO, N 2 O and
H 2 was carried out at the bimonthly time intervals. Additionally, carbon (d
13 C) and oxygen (d
18 O) isotopic ratios of
CO 2 were also measured. The observational record is
available for about a decade (1992–2002) and also for a
period of 2009–2013.
In the next phase of the carbon cycle study in India, the
Indian Space Research Organisation (ISRO) started the
National Carbon Project (NCP) under the auspices of the
ISRO Geosphere-Biosphere Program (IGBP) in the early
phase of the 2010s. The NCP endeavors to understand the
GHGs dynamics and estimate their budget by means of a
robust observational network across the country (Chanda
et al. 2013, 2014; Sharma et al. 2013, 2014; Patel et al. 2011;
Mahesh et al. 2014, 2016, 2019; Sreenivas et al. 2016, 2019;
Jha et al. 2013, 2014; Rodda et al. 2016). At about the same
time, another GHGs observational program (CO 2 and CH 4 )
at a semi-urban hilly site near Pune, called Sinhagad (SNG),
was initiated by the Indian Institute of Tropical Meteorology, Pune, under the patronage of the Ministry of Earth
Sciences (MoES), Government of India. The SNG site is
200 km east of the Arabian Sea (73.75° E, 18.35° N,
1600 m ASL) situated over the Western Ghats mountainous
terrain of southwestern peninsular region of the Indian
subcontinent. The location is relatively free from major
vegetation and local habitation disturbances for GHGs
measurement on a long-term perspective. Routine air sampling at SNG, from a 10 m meteorological tower at weekly
intervals, has been operational since November 2009 (Tiwari
4 Observations and Modeling of GHG Concentrations and Fluxes …
75