Greenhouse gas (GHG) refers to gases in the atmosphere that are associated with the warming of the planet. In the provided context, GHG concentrations have increased since the Industrial Revolution due to the use of fossil fuels, contributing to the rise in global average temperature. The Earth has already warmed by about 1.1°C, and annual average GHG emissions in the 2010s have remained at the highest levels in human history. Although the rate of increase has slowed, emissions are still trending upward, making climate change a pressing global issue.
The context emphasizes that energy-related CO₂ accounts for roughly three-quarters of total GHG emissions. For this reason, climate mitigation depends heavily on reducing fossil fuel use, expanding electrification, improving energy efficiency, and shifting to renewable energy. Scientific assessments cited in the context indicate that stabilizing temperature rise requires global CO₂ emissions to fall to net zero. For a 1.5°C pathway, this would mean reaching CO₂ net zero around 2050. GHG reduction is therefore central to climate policy, while carbon dioxide removal (CDR) is described as a longer-term complement for offsetting residual emissions, not a substitute for rapid emissions cuts.