The AgResearch study shows 80% of those carbon emissions were generated on the farm, which scientists say was "broadly consistent with other international studies of products derived from farmed, ruminant livestock."
However, productivity gains by sheep farmers in the last 20 years mean more sheep meat is produced now than in 1990, even though the sheep flock is now 43% smaller.
The report, released yesterday, calculated the drop in numbers reduced by 22% lamb's total carbon footprint over that period.
The report was designed to benchmark lamb's carbon footprint and identify areas that could be targeted to reduce the sector's emissions.
It was funded by the Meat Industry Association, Ballance Agri-Nutrients, Landcorp and the Ministry of Agriculture and Forestry's greenhouse gas footprinting strategy.
Agriculture minister David Carter welcomed the efforts to measure and improve the sector's carbon footprint, saying primary industries could not manage their emissions if they did not measure them first.
"New Zealand operates some of the most efficient on-farm production systems in the world, but we are facing the growing challenge of producing more food with fewer emissions," he said.