Climate change is a global issue affecting every industry. Automotive companies have been working to address this issue by reducing the greenhouse gas emissions of their vehicles. EPA has encouraged this by providing incentives in the Greenhouse Gas Emissions Rule of 2009. Improving the efficiency of MACs (mobile air conditioning systems) is part of this effort. Life-cycle climate performance (LCCP) is a comprehensive metric for estimating the greenhouse gases emissions produced by the construction, operation, and end-of-life recycling of a vehicle MAC (Mobile Air Conditioning) system. Many companies and organizations have conducted LCCP for their vehicles using various software tools. The IMAC-GHG-LCCP (Improved Mobile Air Conditioning related to Green-House-Gas LCCP) model is a new comprehensive software tool that follows a similar approach as the current automotive LCCP modeling standard, GREEN-MAC-LCCP ([Global Refrigerants Energy & Environmental Mobile Air Condition LCCP), but with a focus on simplicity and ease-of-use. The tool has added support for water plumbing, multiple evaporators and chillers, electric compressors and user-defined refrigerants. Vehicle usage data for each city including vehicle lifetime, driving distance, and driving duration are open for user edit. Inputs to the software include refrigerant leakage data, MACs capacity and power consumption data, vehicle component mass data, fan data, updated weather data, and drive cycle data to calculate the indirect and direct CO2-equivalent emissions for a given vehicle in each selected city. Curve fits of the cooling capacity and power consumption are used to estimate the performance of the MAC at a range of different engine/vehicle speeds and ambient conditions. The emissions of the vehicle at each time step of the selected drive cycle are calculated. A results report provides the calculated direct and indirect emissions for each city. A model example estimating the effects of improving the efficiency of the MAC system on the direct and indirect emissions of a vehicle is presented.