Gram for gram for gram, beef and lamb generate around three times more carbon than pork, five times more than kangaroo, six times more than chicken, egg and fish, thirteen times more than nuts and forty times more than grains and legumes.
Do you eat beef or lamb once a week? Instead, try eating it once a month. Eat a serve of chicken, duck or kangaroo in the other weeks. Swapping a serve of red meat for once each month instead of once each week cuts 0.2 tonnes carbon from your footprint each year.
Data and references in the 'Notes' section.