Greenhouse gases in the atmosphere hit a record high last year despite temporary declines during the pandemic. Greenhouse gas concentrations grew at a faster pace than the annual average from 2011 through 2020, according to the World Meteorological Organization's (WMO) Greenhouse Gas Bulletin published Monday. Specifically, levels of carbon dioxide, the most important greenhouse gas, surged to 149 percent of the pre-industrial level or the levels before 1750, when humans “started disrupting Earth’s natural equilibrium.”