Offsetting carbon emissions. Conceptual image showing an aeroplane balanced on a set of scales against trees. This represents the environmental strategy known as carbon offsetting. This strategy involves the planting of trees (which absorb carbon dioxide) to offset the release of carbon dioxide elsewhere. Carbon offset credits can be traded between companies to meet their targets. Carbon dioxide is the main greenhouse gas that contributes to man-made global warming. Emissions from aviation are a significant contributor to climate change.