**6.3 Attribution assessment**

Studies of tropical cyclones Ana and Batsirai that devastated Southeastern Africa deduced that human acts are at least in part liable for climate change. [9, 10, 28]. So did a study of the desert locust (*Schistocerca gregaria*) outbreak that impacted Ethiopia, Kenya, and Somalia [68, 69]. Anthropogenic GHGs are linked to energy and

#### *Dialing Back the Doomsday Clock with Circular Bioeconomy DOI: http://dx.doi.org/10.5772/intechopen.113181*

agricultural industries (**Table 3**). Agriculture is also a big aerosols emitter [48, 63, 70]. About 20% of the 3.3 million premature mortalities incurred in the world in 2010 from ozone and PM2.5 pollution were attributed to agriculture [71]. A good amount of agriculture's GHG and aerosol burden emanates from fertilizer manufacture and use. The Haber-Bosch fertilizer process via ammonia synthesis is a gargantuan fossil energy consumer and GHG emitter [72]. In the USA corn (maize) production system, for instance, baseline GHG emission is ≈ 2469 kg CO2 eq per ha, and nitrogen fertilizer alone (manufacture and field losses) accounts for about 56% [73]. In livestock production, pig feed accounted for 79% of fossil fuel consumption and 88% of GHG emissions. The values for chicken feed were respectively 84% and 91%. In these studies, corn and soybean were basic inputs, and inorganic fertilizer was used in their cultivation [74]. In view of these values and recalling that nitrogen fertilizer and manure contribute 92% of all N2O attributable to agriculture in the USA [75], and because fertilizer is required for the cultivation of maize and rapeseed, used for bioethanol and biodiesel creation respectively, a Nobel Laureate invested some computations. The results motivated the Nobel Laureate to caution that due to the larger GWP of N2O relative to CO2, and contingent upon the uptake efficiency of nitrogen fertilizer, the production of bioethanol from maize, and biodiesel from rapeseed, may lead to the emission of enough N2O that wipes out the benefits of using biofuels to replace CO2 emitting fossil fuels [76]. So, how may humanity manage and mitigate GHG emissions, to constrain climate change?
