The amount of water vapour in the atmosphere is
expected to increase at a rate governed by the Clausius–
Clapeyron (*7% °C
−1 ) under conditions of warming
(Willett et al. 2007; Boucher et al. 2013). The all India
averaged annual and seasonal mean specific humidity and
relative humidity are found to be increasing significantly for
both gridded observations (HadISDH, Willet et al. 2014) and
reanalysis (ERA-Interim, Dee et al. 2011) datasets during the
period 1979–2015 (Fig. 2.5 and Table 2.3).
The estimated magnitude of the annual specific humidity
trend is similar for both datasets and is found to be comparable with the earlier assessment using IMD station data
(Mukhopadhyay et al. 2017). The significant increasing
trend in specific humidity assessed during the pre-monsoon
season is consistent with the largest surface warming trend
found for this season (see Table 2.1). Past studies had also
reported a rise in the moisture content of the atmosphere
associated with warming over the Indian region (Krishnan
et al. 2016; Mukhopadhyay et al. 2017). This increased
water vapour under conditions of regional warming may
lead to significant positive feedback on human-induced climate change, as water vapour is the most important contributor to the natural greenhouse effect (Willett et al. 2007;
Boucher et al. 2013).
2.2.2 Causes of Observed Changes
The surface air temperature changes over India between
1956 and 2005 are attributed to anthropogenic forcing
mostly by greenhouse gases and partially offset by other
anthropogenic forcings including aerosols and land use land
cover change (Dileepkumar et al. 2018). The observed
changes in maximum temperature during the post-monsoon
Fig. 2.4 Spatial distribution of observed annual and seasonal trends
(°C per decade) for (top panel) mean, (middle panel) maximum and
(bottom panel) minimum temperatures in (left to right panels) annual
(ANN), winter (December–February, DJF), pre-monsoon (March–May,
MAM), monsoon (June–September, JJAS) and post-monsoon
(October–November, ON) seasons during the period 1986–2015. The
grid boxes are hatched where the trends are insignificant (i.e. a trend of
zero lies inside the 95% confidence interval)
26
J. Sanjay et al.
expected to increase at a rate governed by the Clausius–
Clapeyron (*7% °C
−1 ) under conditions of warming
(Willett et al. 2007; Boucher et al. 2013). The all India
averaged annual and seasonal mean specific humidity and
relative humidity are found to be increasing significantly for
both gridded observations (HadISDH, Willet et al. 2014) and
reanalysis (ERA-Interim, Dee et al. 2011) datasets during the
period 1979–2015 (Fig. 2.5 and Table 2.3).
The estimated magnitude of the annual specific humidity
trend is similar for both datasets and is found to be comparable with the earlier assessment using IMD station data
(Mukhopadhyay et al. 2017). The significant increasing
trend in specific humidity assessed during the pre-monsoon
season is consistent with the largest surface warming trend
found for this season (see Table 2.1). Past studies had also
reported a rise in the moisture content of the atmosphere
associated with warming over the Indian region (Krishnan
et al. 2016; Mukhopadhyay et al. 2017). This increased
water vapour under conditions of regional warming may
lead to significant positive feedback on human-induced climate change, as water vapour is the most important contributor to the natural greenhouse effect (Willett et al. 2007;
Boucher et al. 2013).
2.2.2 Causes of Observed Changes
The surface air temperature changes over India between
1956 and 2005 are attributed to anthropogenic forcing
mostly by greenhouse gases and partially offset by other
anthropogenic forcings including aerosols and land use land
cover change (Dileepkumar et al. 2018). The observed
changes in maximum temperature during the post-monsoon
Fig. 2.4 Spatial distribution of observed annual and seasonal trends
(°C per decade) for (top panel) mean, (middle panel) maximum and
(bottom panel) minimum temperatures in (left to right panels) annual
(ANN), winter (December–February, DJF), pre-monsoon (March–May,
MAM), monsoon (June–September, JJAS) and post-monsoon
(October–November, ON) seasons during the period 1986–2015. The
grid boxes are hatched where the trends are insignificant (i.e. a trend of
zero lies inside the 95% confidence interval)
26
J. Sanjay et al.