There is something that the average person can do to slow down climate change, and it can be accomplished without leaving the house. Don’t waste food.

Some 931 million tons of it went to waste in 2019, according to the United Nations Environment Programme. Individual households were responsible for more than half of that, with the rest coming from retailers and the food service industry.

New estimates show that about 17% of food available to consumers worldwide that year ended up being wasted. The matter is even more urgent when considered alongside another UN analysis that tracks the problem further up the supply chain, and shows 14% of food production is lost before it reaches stores. Waste is happening at every point, from the field to the dinner table.

Food waste and loss are responsible for as much as 10% of global emissions, according to the Intergovernmental Panel on Climate Change. If it were a country, this discard would rank third in the ranking of the world’s sources of greenhouse gases, after China and the U.S. Among the most effective climate solutions, non-profit Project Drawdown ranks cutting food waste ahead of moving to electric cars and switching to plant-based diets.

Last week's UNEP report suggests the amount of food wasted by consumers could be about double the previous estimate. The analysis conducted by the UN's Food and Agriculture Organization in 2011 relied on data from fewer countries.

The methodology has advanced, and now there’s data for 54 countries. This has revealed that the problem isn’t limited to the richest countries. The report nevertheless indicated varying degrees of confidence in national inputs, and there are still only 14 countries that have household food-waste data that is compatible with UNEP’s index.

The findings should still help countries set food-waste reduction targets and create ways to track progress. So far, few have included reducing waste in their planned submissions under the Paris climate agreement. Ensuring progress in tackling this source of carbon emissions will depend in part on nations adopting a common methodology.

“It comes down to straight measurement,” said Martina Otto, who leads UNEP’s cities unit. “If you can’t measure it, you can’t take the right action.”

Some governments are putting in nudges and incentives to change behavior, and this goes beyond creating awareness campaigns. For example, in South Korea, rubbish collectors charge homes based on the weight of their food waste. 

“Food waste is really an area where individuals can impact their personal carbon footprint,” said Clementine O’Connor, who spearheaded the UNEP research. “With the food that you buy, with how you take care of it and consume it, it’s a daily chance to affect your own impact.”