Scientists know greenhouse gas emissions cause climate change, but what causes greenhouse gas emissions in the first place? We assessed how many greenhouse gases are released to support the lifestyles of people living in different parts of Europe – in other words, we figured out people’s carbon footprint. We found that different lifestyle choices resulted in very different carbon footprints. In general, people with higher incomes (who bought more things and traveled more) had much higher carbon footprints than people who lived more modestly. Understanding how our purchases affect greenhouse gas emissions is an important step to designing policies and guidelines for cutting emissions and addressing climate change.