Arnold Schwarzenegger Governor OBSERVATION OF METHANE AND OTHER NON-CARBON DIOXIDE GREENHOUSE GAS EMISSIONS FROM CALIFORNIA

..................................................................................................................................................... xi Executive Summary ................................................................................................................................... 1 1.0 Introduction .................................................................................................................................... 5 1.1. Background and Overview ....................................................................................................... 5 1.1.1. Methane and Other Non‐Carbon Dioxide Greenhouse Gases .................................... 5 1.1.2. Atmospheric Inverse Methods ......................................................................................... 5 1.1.3. Project Goal and Objectives .............................................................................................. 6 1.1.4. Report Organization .......................................................................................................... 6 2.0 Approach ......................................................................................................................................... 7 2.1. Identification of Measurement Stations .................................................................................. 7 2.1.1. Inventory Estimates of Methane, Nitrous Oxide, and Radon Emissions ................... 7 2.1.2. Predicted Maps of Time Varying Methane and Radon Mixing Ratios ...................... 8 2.1.3. Candidate Measurement Stations .................................................................................... 9 2.2. Measurement of Methane and Other Gases ........................................................................... 9 2.2.1. Measurements ..................................................................................................................... 9 2.3. Preliminary Estimation of Regional Methane and Nitrous Oxide Emissions ................. 10 2.3.1. Radon Mixing Model Emission Estimates .................................................................... 11 2.3.2. Lagrangian Model Prediction of Greenhouse Gas Mixing Ratios............................. 11 2.3.3. Linear Regression Analysis of Predicted and Measured Methane Signals .............. 15 2.3.4. Bayesian Inverse Estimates of Methane Emissions ..................................................... 15 2.4. Design of an Enhanced Monitoring Network ...................................................................... 18 2.4.1. Benefit of Additional Measurement Sites ..................................................................... 18 2.4.2. Use of Radiocarbon Methane (14 CH4) to Identify Fossil Methane Emissions ......... 18 3.0 Results and Discussion ................................................................................................................ 19 3.1. Identification of Observing Stations ...................................................................................... 19 3.1.1. Inventory Estimates of Methane, Nitrous Oxide, and Radon Emissions ................. 19 3.1.2. Predicted Maps of Time Varying Methane Mixing Ratios ......................................... 22 3.1.3. Locations of Potential Measurement Stations .............................................................. 24