2023 March Board Book

Pressman et al.

10.3389/fsufs.2022.1072805

FIGURE 2 California 1950–2017 total historical CH 4 emissions, comparison of these emissions converted to CO 2 eq and CO 2 we using GWP and GWP*, respectively, and cumulative CO 2 eq and CO 2 we with emissions-forced warming. The x -axis represents years and the y -axis represents annual CH 4 emissions (A) , annual CO 2 eq or CO 2 we (B) , or cumulative CO 2 eq or CO 2 we (C) . CO 2 we are represented in (B, C) by the blue solid line (“GWP*”), GWP-based CO 2 eq are represented by the red solid line (“GWP”), and temperature is given in (C) by the dashed black line (“Warming”). The temperature axis in (C) is scaled by 0.001 mK/TgCO 2 , or 1 K/TtCO 2 . The scaling factor that relates cumulative CO 2 emissions to temperature change is known as transient climate response to cumulative carbon emissions (TCRE). The scaling factor here (approximate TCRE) exceeds the IPCC likely range, likely due to a large increase in annual CH 4 emissions in the 1950s leading to a larger GWP of CH 4 in this period (see Section 4). This large GWP may be responsible for the “bulge” in warming between 1950 and 1990 (C) .

Frontiers in Sustainable Food Systems

08

frontiersin.org