Contents lists available at ScienceDirect Ecotoxicology and Environmental Safety journal homepage: www.elsevier.com/locate/ecoenv Climate change impact of livestock CH 4 emission in India: Global temperature change potential (GTP) and surface temperature response Shilpi Kumari a, ⁎ , Moonmoon Hiloidhari b , Nisha Kumari c , S.N. Naik d , R.P. Dahiya a a Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi 110016, India b School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, India c Deenbandhu Chhotu Ram University of Science and Technology, Murthal 131039, Haryana, India d Centre for Rural Development and Technology, Indian Institute of Technology Delhi, New Delhi 110016, India ARTICLE INFO Keywords: Livestock CH 4 emission Climate change Global temperature change potential (GTP) Absolute GTP (AGTP) ABSTRACT Two climate metrics, Global surface Temperature Change Potential (GTP) and the Absolute GTP (AGTP) are used for studying the global surface temperature impact of CH 4 emission from livestock in India. The impact on global surface temperature is estimated for 20 and 100 year time frames due to CH 4 emission. The results show that the CH 4 emission from livestock, worked out to 15.3 Tg in 2012. In terms of climate metrics GTP of livestock-related CH 4 emission in India in 2012 were 1030 Tg CO 2 e (GTP 20 ) and 62 Tg CO 2 e (GTP 100 ) at the 20 and 100 year time horizon, respectively. The study also illustrates that livestock-related CH 4 emissions in India can cause a surface temperature increase of up to 0.7 mK and 0.036 mK over the 20 and 100 year time periods, respectively. The surface temperature response to a year of Indian livestock emission peaks at 0.9 mK in the year 2021 (9 years after the time of emission). The AGTP gives important information in terms of temperature change due to annual CH 4 emissions, which is useful when comparing policies that address multiple gases. 1. Introduction Methane (CH 4 ) is the most abundant non-CO 2 greenhouse gas (GHG) and contributes 0.97 W/m 2 of forcing, or about 1/3rd of the forcing from well-mixed GHGs (IPCC, 2014). Although emitted in much less quantity by mass than CO 2 , CH 4 can cause significant climate da- mage because of its high radiative forcing (IPCC 2013; Ripple et al., 2014; Xie et al., 2016). Thus, mitigation of methane emissions can yield large benefits to climate, health, and agriculture. The livestock sector is a major source of anthropogenic CH 4 emis- sion, with annual contributions of 14.5% to the global CH 4 emission budget (Kebreab et al., 2010; Martin et al., 2010; Gerber et al., 2013). The IPCC has also reported that the global animal sector can cause surface temperature to rise by ~5 m K over 20 year time horizon (IPCC, 2014). More than 90% of livestock CH 4 emission occur through the enteric fermentation process in ruminant animals (Monteny et al., 2006; Kumari et al., 2014). In India, district level assessment has been reported for the year 2003 from livestock, which was 14.3 Tg yr -1 (Chhabra et al., 2013). The first Biennial Update Report presented to the United Nations Framework Convention on Climate Change gives an overall estimation of greenhouse gas emission amounting to 2137 Tg in 2010 from India (MOEF, 2015). The agriculture sector was reported to contribute 18% of the total greenhouse gas emissions and methane emission through enteric fermentation was nearly 60% of the agri- cultural emissions. Thus, bolstering researches to understand the cli- mate change impact of livestock emission is relevant for effective cli- mate mitigation policies and also to promote sustainable livestock farming. Such research is particularly important in livestock dominant countries like India, China, Brazil and USA. For instance, India has the world's largest livestock population (> 500 million), contributing nearly 10–15 Tg CH 4 emission annually (Chhabra et al., 2013; Kumari et al., 2016). Since the IPCC's first assessment report in 1990, the global warming potential (GWP) has been used as a method for comparing the potential climate impact of different GHGs (Shine et al., 2005). But, the use of GWP has been criticized by many climate scientists because GWP does not explain the magnitude of climate change due to GHGs emission (i.e. impact on temperature rise) and the GWP exchange value does not give the exact radiative forcing caused in a longer time frame (Shine et al., 2005; Sarofim et al., 2012). Therefore, Shine et al. (2005) proposed the global surface temperature change potential (GTP) as an alternative metric to GWP to assess climate change impact of GHGs emission. As defined in the IPCC 4th assessment report (IPCC, 2007), the GTP is the ratio between the global mean surface temperature change at a given http://dx.doi.org/10.1016/j.ecoenv.2017.09.003 Received 29 April 2017; Received in revised form 1 September 2017; Accepted 5 September 2017 ⁎ Corresponding author. E-mail address: shilpidas.iit@gmail.com (S. Kumari). Ecotoxicology and Environmental Safety 147 (2018) 516–522 0147-6513/ © 2017 Elsevier Inc. All rights reserved. MARK