Traffic contributes to a high amount of total greenhouse gas emission. This paper examines the issue whether road slope has a significant influence on carbon dioxide emission when driving a car. CO2 measurements are temporally and spatially restricted when using conservative methods, so this work makes use of extended floating car data (xFCD). An experiment is being set up for collecting data, which has been acquired for four months using an xFCD-equipped vehicle. In this time period, about 100 recordings have been acquired. Findings include a moderate positive correlation between road slope and CO2 pollution. This fact has been substantiated by a Pearson Correlation analysis. Consequently, an influence of slope on greenhouse gas emissions appears to be present for a certain local area