This study examines the impact of electric vehicle (EV) adoption on greenhouse gas (GHG) emissions in California's transportation sector from 2000-2021. Using data from the California Air Resources Board's GHG Emissions Inventory, the analysis focuses on three primary factors affecting transportation emissions: EV population, fuel economy of light-duty vehicles, and gasoline sales. Through correlation and regression analyses, the study finds that gasoline sales have the most substantial impact on emissions. Improvements in fuel economy and increases in EV population both contribute to reducing emissions, with fuel economy showing a stronger impact than EV adoption. Specifically, for every 1 MPG increase in fuel economy, emissions decrease by approximately 1.7644 MMTCO2e, while for every 1,000 increase in EV population, emissions decrease by about 0.0416 MMTCO2e. The findings suggest that while promoting EV adoption is important, it should be complemented with policies that enhance fuel economy and reduce gasoline consumption to achieve more significant and immediate reductions in transportation emissions. The study concludes that a multifaceted approach addressing fuel economy, gasoline consumption, and EV adoption is needed to substantially reduce transportation emissions and achieve California's long-term climate goals.