Hydrofluorocarbons (HFCs) are increasing in the atmosphere, acting as greenhouse gases that warm the climate. Even though HFCs don't harm the ozone layer, they contribute to climate change. In 2011, the total heat caused by all HFCs was only a small fraction compared to carbon dioxide or methane. HFCs have Global Warming Potentials (GWPs) much higher than CO2, indicating their long-term warming impact. If high-GWP HFCs continue to be used more in the future, their warming effect will grow substantially, undoing some of the environmental progress made by phasing out older harmful substances. Choosing alternative chemicals with lower GWPs could help reduce the climate impact of future HFC use.