LowEmissionAsphalt-136pg-WhitePaper-May2023

P a g e | 70 CO 2 is widely understood as a key GHG, 132 contributing significantly to global warming and is the “common currency” or standard of measurement for the global warming potential (GWP) 133 of various thermo-trapping gases. Collectively, GHGs are sometimes referenced as carbon dioxide equivalents (CO 2 e) and valued based on each gas species GWP. NOx as an indirect greenhouse gas (IGHG) 134 135 is a bit more complex. Through various processes nitrogen oxides (NO, NO 2 ) interact with trace gases in the troposphere and stratosphere which do absorb (hold) energy in the spectral range relevant to the greenhouse effect . The net impact is an enhancement of the greenhouse effect . Figure 40 – U.S. GHG Emissions by Sector 2020 Source: EPA 132 EPA: carbon dioxide is 79% of all GHGs. 133 global warming potential (GWP) is a measure of how much energy the emissions of 1 ton of a gas will absorb over a given timeframe, relative the emissions of 1 ton of carbon dioxide. 134 indirect greenhouse gas : emissions that are a result of natural atmospheric chemical reactions such as NOx as a precursor to ozone, where the resultant is a heat trapping gas. 135 chemistry-climate model initiative (CCMI) ; World Climate Research Programme; United Nations IPCC.