Editing IPCC:AR6/WGI/Chapter-10 (section)

==== 10.6.3.4 Relevant Anthropogenic and Natural Drivers for Long-term Change ====

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The relevant drivers for long-term change in the mean Indian summer monsoon are summarized briefly:

* Increased greenhouse gas (GHG) concentrations (chiefly CO <sub>2</sub> ) are a strong contributor to changes in the monsoon, with repercussions for the meridional temperature contrast driving the monsoon circulation ( [[#Ueda--2006|Ueda et al., 2006]] ; [[#Roxy--2015|Roxy et al., 2015]] ), for the monsoon winds in the lower troposphere ( [[#Cherchi--2011|Cherchi et al., 2011]] ; [[#Krishnan--2013|Krishnan et al., 2013]] ), or for the availability of moisture from the Indian Ocean ( [[#May--2011|May, 2011]] ).
* Industrial emissions of sulphate aerosol predominantly in the Northern Hemisphere could change inter-hemispheric energy transports and weaken the monsoon ( [[#Polson--2014|Polson et al., 2014]] ; [[#Undorf--2018|Undorf et al., 2018]] ). The effect of local anthropogenic emissions of black carbon (chiefly from cooking fires) is uncertain ( [[#Lau--2006|Lau and Kim, 2006]] ; [[#Nigam--2010|Nigam and Bollasina, 2010]] ).
* India’s green revolution over the late-20th century led to considerable land-use change, with massive expansion of agriculture at the expense of forest and shrublands. As a result, India’s northern plains feature widespread irrigation, suggested to be a cause of drying ( [[#Mathur--2020|Mathur and AchutaRao, 2020]] ).
* Decadal modes of variability such as the Pacific Decadal Variability (PDV, Annex IV) and Atlantic Multi-decadal Variability (AMV, Annex IV), which may be partly forced ( [[IPCC:Wg1:Chapter:Chapter-3#3.7.7|Section 3.7.7]] ), are known to cause decadal modulation of the monsoon ( [[#Krishnamurthy--2014|Krishnamurthy and Krishnamurthy, 2014]] ; [[#Naidu--2020|Naidu et al., 2020]] ).

The interplay of these external and internal drivers is key to understanding past and future monsoon change.

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