Which statement best defines decarbonization of the energy system?

• A. A reduction in carbon emissions from energy use achieved by increasing efficiency and switching to low-carbon energy sources.
• B. A policy that taxes all carbon-based fuels equally.
• C. Removing carbon dioxide from the atmosphere.
• D. Reducing the price of fossil fuels.

Answer: (A)

Decarbonization of the energy system means lowering the carbon emitted for each unit of energy used, which happens by making energy use more efficient and by replacing high-carbon energy with low-carbon or zero-carbon sources. This combines two pathways: reducing demand through efficiency improvements (like better insulation, efficient appliances, and electrifying heat and transport where powered by clean electricity) and changing the energy supply mix toward renewables, nuclear, or carbon-free options. This is why the best statement is the one that describes cutting carbon emissions from energy use through both efficiency gains and switching to low-carbon sources.

Other options miss the core idea: a carbon tax can help drive decarbonization but isn’t the act of decarbonizing itself; removing CO2 from the atmosphere is about carbon dioxide removal rather than reducing emissions from energy use; lowering fossil fuel prices could actually raise emissions if demand rises.