Stabilizing global climate will require major transformations to energy and food systems, including drastic reductions in the use of fossil fuels, improvements in energy and material efficiencies, extensive electrification of energy end uses, sustainable intensification of agriculture, and carbon management. Although progress has been made in researching these topics in recent years, several research questions central to framing global energy and agriculture policies deserve further study. In this dissertation, I explore several relevant research topics with the goal of contributing to our understanding of the opportunities and challenges for achieving net-zero emissions energy and food systems, including (1) the characteristics of modeled net-zero CO2 emissions energy systems; (2) the potential for seaweed farming to deliver globally-scaled carbon removal and emissions mitigation; and (3) potential solutions for hard-to-abate greenhouse gas emissions from the global food system. In scenarios that successfully reach net-zero CO2 emissions by the end of this century, renewable energy sources account for 60% of primary energy at net-zero on average (compared to ~14% today), with slightly less than half of that renewable energy derived from biomass. Meanwhile, electricity makes up approximately half of final energy consumed (compared to ~20% today), highlighting the extent to which solid, liquid, and gaseous fuels remain prevalent in the scenarios even when emissions reach net-zero. Residual emissions and offsetting negative emissions are not evenly distributed across world regions, which may have important implications for negotiations on burden-sharing, human development, and equity. Sinking farmed seaweed to the deep sea is a potential method to remove carbon from the atmosphere (i.e., negative emissions), and sequestering a gigaton of CO2 per year with this method may cost as little as $480/tCO2 on average. Instead, using farmed seaweed for products that avoid a gigaton of CO2-equivalent greenhouse gas emissions annually – by substituting for more emissions-intensive food or feed sources – could return a profit of $50/tCO2-eq. However, these costs depend on low farming costs, high seaweed yields, and assumptions that almost all carbon in seaweed is removed from the atmosphere (i.e., competition between phytoplankton and seaweed is negligible) and that seaweed products can displace products with substantial embodied non-CO2 GHG emissions, such as agricultural goods. Modern agriculture is extremely emissions-intensive, and sweeping systemic changes will be needed to reach net-zero. Shifting diets away from beef would have an outsized impact on decreasing the average emissions intensity of caloric production, and closing yield gaps is a top priority to increase production without increasing agricultural land area. Promising methods are being developed to suppress GHG emissions from enteric fermentation, soils, and rice paddies, although further research is needed to determine the long-term efficacy and scalability of solutions globally. Stopping deforestation is also a top priority, which will require aggressive policy action to enact strict land-use regulations. Ultimately, achieving net-zero emissions energy and food systems will entail an accelerated and coordinated global effort across multiple economic sectors.

Over the 20th century, critical advancements in energy generation and agriculture have revolutionized contemporary society, propelling many of the modern advancements enjoyed by humanity today. However, these developments have come at a considerable cost to the natural environment, resulting in, among others, global climate change, ecological decline, and wildlife extinction (IPCC, 2013; Masson-Delmotte et al., 2021; F. N. Tubiello et al., 2015). Recent international efforts to mitigate severe climate warming and minimize further environmental damage, aim for swift and significant reductions in annual anthropogenic CO2 emissions worldwide the vast majority of which originate from fossil energy generation (89%), and agriculture driven land-use expansion (11%) (Friedlingstein et al., 2021; Le Quéré et al., 2018; Ramankutty, Evan, Monfreda, & Foley, 2008). Thus, climate mitigation pathways that successfully limit future warming below 2°C require the swift transformation of modern agriculture and energy generating practices (Audoly, Vogt-Schilb, Guivarch, & Pfeiffer, 2018; Popp et al., 2017; Rogelj, Popp, et al., 2018; Rogelj, Schaeffer, et al., 2015a; Rogelj, Shindell, et al., 2018). However, fossil-burning infrastructure is generally long-lived (Davis, Caldeira, & Matthews, 2010; Davis & Socolow, 2014b; Seto et al., 2016; Shearer, Fofrich, & Davis, 2017) and current climate change mitigation scenarios do not track the magnitude and patterns of necessary power plant retirements (Fofrich et al., 2020). Here, we show fossil-fired power plants retiring up to three decades earlier than historically has been the case in scenarios consistent with international climate targets (i.e., keeping global warming well below 1.5°C or 2°C), potentially jeopardizing trillions of dollars in power generating assets. If instead, power generators continue to operate as they have historically, we find the resulting emissions are incompatible with more ambitious climate mitigation targets without the equivalent removal of atmospheric CO2.

We show China, India, the United States, and Western Europe hold the largest share of share of potentially stranded assets, risking trillion dollars in stranded fossil-fired power generating assets if these generators are forced to retire prematurely. However, the monetary and social cost of unabated climate change will be much greater than those accrued by stranded fossil-fired generators. For instance, climate change is projected to reduce agricultural productivity in historically warm regions of the planet (Lobell et al., 2013; Lobell, Schlenker, & Costa-Roberts, 2011; Rosenzweig et al., 2014; Schlenker & Roberts, 2009) and limit the availability of arable land over the remainder of this century. Therefore, we investigate potential shifts in the location of major grain crop (maize, rice, soybean, and wheat) cultivation under different scenarios of climate change and find that just 2°C of warming risks roughly 19% of global crop production, rising to 35% in scenarios where global temperatures approach or exceed 3°C of warming. Although the agricultural impacts of climate change might be lessened through adaption, our findings emphasize the large extent to which a warming planet may disrupt global food production in the coming years. Thus, unmitigated anthropogenic warming stems to jeopardize future food security and equity over the next century.

Stabilizing CO2 emissions at current levels for fifty years is not consistent with either an atmospheric CO2 concentration below 500 ppm or global temperature increases below 2 °C. Accepting these targets, solving the climate problem requires that emissions peak and decline in the next few decades, and ultimately fall to near zero. Phasing out emissions over 50 years could be achieved by deploying on the order of 19 'wedges', each of which ramps up linearly over a period of 50 years to ultimately avoid 1 GtC y−1 of CO2 emissions. But this level of mitigation will require affordable carbon-free energy systems to be deployed at the scale of tens of terawatts. Any hope for such fundamental and disruptive transformation of the global energy system depends upon coordinated efforts to innovate, plan, and deploy new transportation and energy systems that can provide affordable energy at this scale without emitting CO2 to the atmosphere.