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Administrative Draft Environmental Impact Report Gill Medical Center Project 4.10 GREENHOUSE GAS EMISSIONS This section evaluates the effects of Project-generated greenhouse gas (GHG) emissions. This section is based on the Air Quality and Greenhouse Gas Emissions Assessment prepared by ECORP Consulting, Inc. (2020). The information provided below is an abridged version of this report. This analysis was prepared using methodologies and assumptions recommended by the San Joaquin Valley Air Pollution Control District (SJVAPCD). Regional and local existing conditions are presented, along with pertinent emissions standards and regulations. The purpose of this assessment is to estimate Project-generated GHG emissions attributable to the Project and to determine the level of impact the Project would have on the environment. 4.10.1 Environmental Setting 4.10.1.1 Greenhouse Gas Emissions Certain gases in the earth's atmosphere, classified as GHGs, play a critical role in determining the earth's surface temperature. Solar radiation enters the earth's atmosphere from space.A portion of the radiation is absorbed by the earth's surface and a smaller portion of this radiation is reflected back toward space. This absorbed radiation is then emitted from the earth as low-frequency infrared radiation.The frequencies at which bodies emit radiation are proportional to temperature. Because the earth has a much lower temperature than the sun, it emits lower-frequency radiation. Most solar radiation passes through GHGs; however, infrared radiation is absorbed by these gases.As a result, radiation that otherwise would have escaped back into space is instead trapped, resulting in a warming of the atmosphere. This phenomenon, known as the greenhouse effect, is responsible for maintaining a habitable climate on earth.Without the greenhouse effect, the earth would not be able to support life as we know it. Prominent GHGs contributing to the greenhouse effect are CO2, methane (CH4), and N20. Fluorinated gases also make up a small fraction of the GHGs that contribute to climate change. Fluorinated gases include chlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride; however, it is noted that these gases are not associated with typical land use development. Human-caused emissions of these GHGs in excess of natural ambient concentrations are believed to be responsible for intensifying the greenhouse effect and leading to a trend of unnatural warming of the earth's climate, known as global climate change or global warming. It is "extremely likely"that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in GHG concentrations and other anthropogenic factors together (Intergovernmental Panel on Climate Change [IPCC] 2014). Table 4.10-1 describes the primary GHGs attributed to global climate change, including their physical properties, primary sources, and contributions to the greenhouse effect. Each GHG differs in its ability to absorb heat in the atmosphere based on the lifetime, or persistence, of the gas molecule in the atmosphere. CH4 traps over 25 times more heat per molecule than CO2, and N20 absorbs 298 times more heat per molecule than CO2 (IPCC 2014). Often, estimates of GHG emissions are presented in carbon dioxide equivalents (CO2e), which weight each gas by its global warming potential. Greenhouse Gas and Climate Change 4.10-1 October 2021