You would be forgiven for thinking the COP21 climate talks in Paris would take on some of the biggest polluters.

If governments have any hope of reaching the goal of capping global temperatures, environmentalists say there must be binding targets to cut emissions on food, aviation and shipping.

Not one is on the agenda, and that's on purpose. It just proved too politically sensitive.

Airplanes and Shipping

Environmentalists have dubbed aviation and shipping the "Elephants in the Room" in Paris. They claim that air travel is responsible for 5% of man-made emissions and shipping 3%.

Aviation is expected to boom in the coming decades and environmentalists want binding caps on the sector.

The European parliament called for transport to face binding emissions targets, saying the sector is the "second-largest sector generating greenhouse gas emissions."

The U.N. has encouraged aviation and shipping to work "with a view to agreeing to concrete measures addressing these emissions."

Aviation says it accounts for only 1.3% of man-made carbon emissions and that each new airplane that takes flight brings a 15% to 20% drop in emissions compared to older planes.

The International Maritime Organization says it will "continue its endeavors to reduce environmental impacts from international maritime transport," noting 900 new ships meet enhanced fuel efficiency standards.

Agriculture

Blame the animals. As the world eats more meat and converts forests into farm land, carbon emissions will surely rise. Agriculture already accounts for about 14% of global emissions and 25% when deforestation and other land use is included, according to the Brookings Institution. It warns food production will have to increase by 50% by 2050 as populations increase.

Think tank Chatham House says demand for meat will rise 76% by mid century and says livestock alone accounts for 15% of carbon emissions, equal to "tailpipe emissions from all the world's vehicles."

Emissions caused by the livestock sector range from converting land to grow feed, to transporting the livestock, and particularly the methane emitted, especially from belching cattle.

But how do you slow the uptake of pork in India and beef in China, and tell Americans to eat less steak? Chatham House says nothing less than a radical shift in our eating patterns will cap agriculture emissions.