See which countries and sectors, both in the EU and worldwide, are the biggest emitters of greenhouse gases. Greenhouse gas emissions contribute to accelerating climate change. Who are the biggest producers? Which sector produces the most emissions? As the infographic above shows, the most emitted gas into the atmosphere is CO2. This gas is produced by all normal human activities. Although other greenhouse gases are present in the atmosphere in lower concentrations, they trap heat several times more than CO2. For example, methane is more than 80 times more powerful than CO2 over 20 years.