Cropping Systems to Improve Carbon Sequestration for Mitigation of Climate Change (Report‪)‬

1. Introduction Rapid increase in carbon dioxide (C[O.sub.2]) concentration in the atmosphere associated with other greenhouse gases (GHGs), such as nitrous oxide ([N.sub.2]O) and methane (C[H.sub.4]), since the industrial revolution is a major concern with respect to its impact on climate change. Therefore, there is an urgency to adopt effective measures for mitigating the threat of global climate change [1]. The concentration of C[O.sub.2] in the atmosphere increased from 280 to 387 ppmv in 1750 to 2007, and continues to increase at the rate of 1.5 ppmv per year. During the same period, [N.sub.2]O was increased from 270 to 314 ppbv, and C[H.sub.4] increased from 700 to 1745 ppbv (Table 1) [2,3]. Increased concentration of GHGs impacts the temperature of the Earth by absorbing and emitting radiation within the thermal infrared range. The anthropogenic enrichment of GHGs in the atmosphere and the cumulative radiative forcing (factors affect the balance between incoming solar radiation and outgoing infrared radiation within the Earth's atmosphere) has led to a substantial increase in global surface temperature. The major sources to enrich the atmospheric GHGs are fossil fuel combustion and land use changes. For instance, about 25% of C[O.sub.2], 50% of C[H.sub.4] and up to 70% of [N.sub.2]O released globally through human sources [4]. Increased frequency of natural disasters, such as floods, tsunami, hurricane, etc., during the recent years might be attributed to the climate change associated to increased accumulation of GHGs in the atmosphere. The global surface temperature increased by 0.6[degrees]C since the late 19th century with a current average warming rate of 0.17[degrees]C per decade [2]. Such temperature increase would considerably alter the distribution of precipitation, e.g., 0.5-1% of precipitation increase per decade in the most of Northern Hemisphere and 0.3% increase in the tropics and sub-tropics [1]. Consequently, land productivity, biomass accumulation, biodiversity, and the whole environmental system would be negatively impacted. The US EPA has released its final findings on greenhouse gases and has declared that "GHGs threaten the public health and welfare of the American people" [5]. Therefore, it is urgent to adopt practical and effective approaches to controlling the GHG emission for mitigating global climate change for a sustainable development of the environment. The objective of this review is to briefly elucidate the main sources of GHG emission and particularly address the sustainable development of cropping systems for carbon sequestration to mitigate the threat of the global climate change.