One Thing You Can Do: Smarter Laundry

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There are steps you can take to reduce those emissions.

“Laundry temperature is a big deal,” said Elizabeth Morgan, director of Innoweaver, a British consulting firm. That’s because about 90 percent of the energy a washing machine uses goes toward heating water.

There are some situations where you probably should use hot water: cleaning bed linens after being sick, for instance, or washing sweaty gym gear. An occasional hot wash can also help with general hygiene, Ms. Morgan said. Aside from that, though, stick to cold water.

It’s worth noting that the cold setting may still heat the water in your machine to as much as 80 degrees Fahrenheit, or about 27 Celsius. Check to see if your washer has a “tap cold” option and, if so, use it.

Another thing to keep in mind: The temperature recommendations on clothing labels represent “the highest spectrum clothes can handle,” said Melissa Hockstad, president and chief executive of the American Cleaning Institute. So you don’t necessarily need to go that hot.

The benefits of cold washing are numerous. One calculation from the cleaning institute, using Energy Star data, estimated that a household could cut its emissions by 864 pounds of carbon per year by washing four out of five loads in cold water.

Cold water also means fabrics won’t break down as much. That could reduce the amount of microplastics getting into the environment. (A single wash can release up to 700,000 tiny synthetic fibers into freshwater systems.) Not to mention, your clothes will likely look better and last longer.

Drying, though, is the major contributor to emissions. “It takes a lot of energy,” said Kyle R. Gluesenkamp, a researcher at the Oak Ridge National Laboratory. He said dryers often use five to 10 times more power than a washing machine.

Current technology is part of the problem. Most dryers in the United States suck in air, heat it and use it to evaporate water from the clothes, then vent it outside. Dr. Gluesenkamp compared that with boiling off water on the stove. It takes a lot of time and energy.

There are more energy efficient alternatives. Heat-pump dryers, for example, recycle hot air so the machine’s heating unit doesn’t have to work as hard. These dryers don’t always need vents and tend to be common in Europe, where you can’t always punch a hole in the wall of your 19th century building.

Whatever kind of machine you use for drying, Dr. Gluesenkamp said, the best thing you can do to reduce energy consumption is take full advantage of the high-speed spin cycle on your washing machine. That means less water needs to be evaporated off.

The Energy Department also recommends only doing full loads, and using dryer balls to help separate your clothes.

But the most efficient drying method requires almost no energy; just enough to haul your basket to a rack or clothesline. Air drying avoids the machine altogether and could save millions of tons of greenhouse gas emissions each year.

Old laundry routines, like any old habits, can be hard to break, but a few simple changes could reduce emissions sharply and save you money. “Be consistent and do it every time,” Ms. Hockstad said. “That’s really how we’re all going to do our part.”

This week, researchers got into a fierce public debate over whether eating red meat is really as bad for you as we’d thought. It was sparked by a new series of papers arguing that we just don’t have airtight evidence about the health risks of beef or pork.

Here on the climate team, we tend to focus on the environmental consequences of food. And this seemed like a good occasion to revisit what we really know. How sturdy is the scientific evidence on the climate impacts of meat eating?

Let’s start with what experts can say with a fair amount of confidence: Meat usually has a much larger greenhouse gas impact than plant-based foods. And beef has the biggest impact of all, with a climate footprint that’s about five times as large as chicken or pork, on average.

How can researchers be so sure? Partly, there are good common sense reasons to think so: Raising cows, chickens or pigs for food tends to take up a lot more land than growing crops. That’s because you need room not just for the animals but also for crops to feed them. On top of that, cow stomachs contain bacteria that help them digest grass but that also produce methane, a potent planet-warming gas that’s emitted through burps. So you’d expect cows to have the biggest impact.

The catch, however, is that production systems can vary hugely. If a farmer clears a patch of rain forest to raise cattle, that’s much worse for global warming than a farmer raising cattle on existing pasture. So when scientists try to measure the emissions from different foods, the precise numbers can vary widely depending on where they’re looking.

But there have now been hundreds of studies and when researchers tally them up, a clear pattern emerges. “Study after study shows that even when you have all this variation, the greenhouse impacts of beef are, on average, still many times greater than chicken, and another order of magnitude greater than, say, beans,” said Diego Rose, a professor at Tulane University who has studied both the nutritional and environmental aspects of diets. “Those results are pretty solid.”

That still leaves some unanswered questions. For example, researchers are still hotly debating whether grass-fed beef is any better for the climate than conventional feedlot beef. The answer can vary from location to location, and hinges on tricky questions about whether cattle grazing can help local soils take more carbon out of the air.

And, in another recent study, a team of scientists warned that we still don’t know nearly enough to understand the consequences of lots and lots of people worldwide all shifting their diets at once. While there’s been plenty of research on the climate impacts of beef and chicken, the scientists noted, a lot less is known about the environmental effects of many of the foods that might replace them.

Bottom line? We know food is a major contributor to climate change, accounting for about one-quarter of humanity’s greenhouse gases. And we know that meat tends to have an outsize impact. But that still leaves all sorts of important nuances that are going to be crucial for scientists to figure out if we hope to get global warming under control.