Further, it is often ambiguous whether a "carbon footprint" refers only to carbon emissions or to all greenhouse gas emissions weighted to a C02-equivalent scale (using, for example, a Global Warming Potential), implying the need for clear description whenever footprints are published. We use carbon footprint to refer to either carbon dioxide or all greenhouse gas emissions, relying on context to clarify. If a carbon footprint includes all greenhouse gas emissions, the policy context is much the same, but there is a shift in emphasis towards food and agriculture.