According to a Google blog post, estimates are both flight-specific and seat-specific, and they show up next to the price and duration of flights in search results. Flights with low emissions have a green badge, and people can sort results, and the greenest ones show up at the top. But it’s also possible to get a search result with no low-emission flights, Google said. This can happen when flights in the search pollute more than that particular route’s median carbon emissions. In that case, Google recommends trying different dates. The carbon emission estimates are part of a new sustainability effort by Google. Last month, the company said it’s created a team specifically tasked with highlighting greener options within its travel tools and added the ability to find eco-certified hotels to its search engine. It also just implemented a new feature in Google Maps that shows the most fuel-efficient routes, in addition to the fastest ones. Google is working with the European Environment Agency, airlines, and other providers to collect its carbon emissions data. For example, newer airplanes generally pollute less than older ones, the company said, while flying first class increases a person’s carbon footprint because the seats take up more space. Surprisingly, non-stop flights aren’t always the greenest; a flight with multiple stops can have a lighter impact on the environment if it’s on a fuel-efficient aircraft and it’s traveling less distance. Google also recently joined the Travalyst coalition, a non-profit organization focused on sustainable travel, and promised to help develop an open model for calculating aircraft carbon emissions and push for standardization in the travel industry.