evidence: 5 things you should know about the greenhouse gases warming the planet [...] However, human activity is resulting in the increased emission of so-called greenhouse gases (GHGs) which, unlike other atmospheric gases such as oxygen and nitrogen, becomes trapped in the atmosphere, unable to escape the planet. This energy returns to the surface, where it is reabsorbed. [...] GHG emissions are critical to understanding and addressing the climate crisis: despite an initial dip due to COVID-19, the latest UNEP Emissions Gap Report shows a rebound, and forecasts a disastrous global temperature rise of at least 2.7 degrees this century, unless countries make much greater efforts to reduce emissions.