Importance of non-CO₂emissions in carbon management

Abstract

Background and framingAt the Durban 2011 climate negotiations, it was decided 'to adopt a universal legal agreement on climate change as soon as possible, and no later than 2015' [1]. This decision thereby fails to agree measures to curb emissions commensurate with the global ambition of avoiding a 2°C temperature rise above pre-industrial levels. According to the IPCC Working Group III, future global temperatures can be limited to a 2-2.4°C rise above pre-industrial levels, but only if global emissions peak by 2015 [2]. Without a legally binding and widely adopted agreement by 2015, the most likely outcome is continued high emissions growth well beyond this, leaving little chance of remaining below the 2°C threshold [3][4][5]. The apparently conflicting messages emerging from the negotiations -that emissions must commensurate with avoiding 2°C [6], but that agreement will not be reached in time to achieve this-stress the importance of developing emission mitigation strategies that, at the same time, consider climate impacts and hence adaptation. A risk-averse strategy would frame adaptation by the most extreme global emission scenarios and mitigation by the lowest; for example, mitigate for 2°C, adapt for 4°C or higher [7]. Arguably, the reverse currently underpins climate policies -mitigation measures are more closely aligned with 4°C of warming [3,8], whilst adaptation research tends to focus on preparing for impacts associated with 2°C, largely because many emission scenarios will reach a 2°C warming around 2050. Addressing climate adaptation and mitigation in unison adds complexity but is essential in the case of the food system, where the climate has direct impacts on agricultural production. In this paper, bottom-up UK scenarios focused on the food system are used to infer global non-CO 2 emission pathways, by exploring different levels of mitigation and climate change impacts in the context of shifting levels and patterns of consumption. Understanding constraints on curbing non-CO 2 provides additional guidance for managing CO 2 budgets constrained to avoid a 2°C temperature rise. Background: GHG budgets highlight a need for urgency, yet analyses are often CO 2 -focused, with less attention paid to non-CO 2 . Results: In this paper, scenarios are used to explore non-CO 2 drivers and barriers to their mitigation, drawing out implications for CO 2 management. Results suggest that even optimistic technological and consumption-related developments lead to on-going increases in global N 2 O, largely to improve food security within a changing climate. This contrasts with existing analysis, where lower levels of N 2 O by 2050 are projected. Conclusions: As avoiding '2°C' limits the emissions budget, constraints on reducing non-CO 2 add pressure to energy system decarbonization. Overlooking how a changing climate and rising consumption restricts efforts to curb non-CO 2 will result in policies aiming to avoid 2°C falling short of the mark.© 2014 The Author(s). Published by Taylor & Francis. This is an Open Acces...

How Do Dietary Choices Influence the Energy-System Cost of Stabilizing the Climate?

“…Our findings corroborate [2]: it is not the quantity of meat that determines food-related GHG emission levels; it is the quantity of ruminant products, i.e., beef, lamb, and dairy. A switch from diets rich in ruminant meat to diets with meat from monogastric animals (pork, chicken) reduces CH 4 emissions by almost the same amount as a switch to an entirely vegan diet and N 2 O emissions by about half the reduction achieved by switching to the vegan diet, in line with references [46,47].…”

The Contribution of Non-CO2 Greenhouse Gas Mitigation to Achieving Long-Term Temperature Goals

“…In addition, a number of mitigation options associated with demand-side measures, notably human dietary changes, are not included. These could yield significant additional non-CO 2 emissions reductions [17,42]. Finally, the analysis does not assume technological development and associated cost reductions in the non-CO 2 mitigation measures over time.…”

Climate change reduces warming potential of nitrous oxide by an enhanced Brewer‐Dobson circulation

“…To diagnose the strength of the BDC in our simulations, we compute the residual mean vertical velocity at the 70 hPa level, characterizing vertical mass transport by the BDC. The residual mean vertical velocity w* is calculated following the transformed Eulerian mean framework, which approximates the Lagrangian-mean mass transport [Andrews et al, 1987;Butchart, 2014]. Results for the CTRL simulation and the final 10 years of the 1PCT simulation are shown in Figure 1a.…”

“…The tropical mass flux across the 70 hPa pressure level is calculated by the area weighted integral of the residual mean vertical velocity times the air density. By using log-pressure coordinate scaling [Andrews et al, 1987], the density at 70 hPa is given by p S À1 g À1 where S is the scale height (7000 m), g the gravity (9.81 m s À2 ), and p the pressure (70 hPa). The mass flux was calculated for tropical grid cells with w* directed upwards (w* > 0).…”

“…The GWP is a measure to normalize the climate efficiencies of greenhouse gases (GHGs) relative to that of CO 2 . This allows for a comparison of different GHG emissions according to their relevance for global warming [Bows-Larkin et al, 2014]. It is also applied in assessing the efficiency of mitigation strategies and has been used by Crutzen et al [2007] to reveal potential offsets of the CO 2 sequestration of biofuel plantations by additional emissions of N 2 O.…”