The idea that we should get our hamburgers from a lab and not from a slaughterhouse — the basic premise of the “cultured meat” or “clean meat” movement — tends to get people excited for two main reasons: It could save billions of animals from immense suffering, and it could fight global warming by reducing the number of methane-producing cattle.

But a new study suggests that the second reason may be wrong, and that lab-grown meat could actually be worse for climate change.

Published February 19 in the journal Frontiers for Sustainable Food Systems, the report argues that lab-grown meat, in the long run, may accelerate climate change more than regular beef does.

The authors note that other studies calculating the greenhouse gas emissions of cattle have lumped the gases together as if they’re all equivalent. But not all gases are created equal. Yes, cows produce a lot of methane, and methane is very bad for global warming. Yet it only lasts in the atmosphere for a dozen years. Carbon dioxide, on the other hand, lasts more than a century. And you know what releases a lot of CO2? Labs — including those that make cultured meat.

In the couple of days since it came out, the study has already produced several chagrined headlines concluding that clean meat doesn’t make for a cleaner environment. The report has us questioning our old assumptions, and that’s a good thing. But let’s not replace them with new assumptions that are just as problematic.

The authors emphasize that their study is based on highly speculative modeling, which is itself based on some pretty strong assumptions. Two of them are especially glaring. The study models what will happen assuming that 1) lab-grown meat will keep being produced using the same methods of energy generation that currently power production, and 2) this will continue over the course of 1,000 years.

To be fair, the researchers had to pick some time frame for the sake of running their model, and any time frame is going to be fairly arbitrary. But 1,000 years is such a long span that it seems very unlikely we’ll still be using such energy-inefficient methods to make lab-grown meat by the end of it.

Whether because clean meat companies will face pressure from their climate-conscious consumers, or because policymakers will step forward to regulate emissions, or because scientists will come up with a way to use cleaner energy to power production (solar and energy storage technology are improving and getting cheaper as it is), cultured meat will probably not be made using current methods, even a century from now.

In other words, it’s hard to imagine a future scenario where assumptions 1 and 2 will both hold true, producing the most pessimistic of the possible outcomes modeled in the report.

There’s another reason to be cautious about the study’s findings, as the authors are the first to note: The companies making cultured meat generally don’t release data on their production process and how much energy it uses up. They’re especially inclined to treat that information as proprietary now that several competitors — from Memphis Meats and Just in the US to Aleph Farms and Future Meat Technologies in Israel — are racing to get their products to market.

“We did the best we could,” lead author John Lynch told Quartz this week. “We surveyed all the literature, but it’s still a fundamental problem that we have no idea whether [the data] correspond with what the companies are doing or not.”

For now, no one’s making cultured meat on a massive commercial scale — production is still a relatively small, lab-based affair. Companies are still trying to figure out how to make clean meat more appealing while also making it less wildly expensive. So there would be limited data on how the process works at scale even if the companies were keen to share it.

It may be in the companies’ interest to become more forthcoming, though.

Lynch’s study only proves we can’t assume lab-grown meat will necessarily be better for the environment; the research doesn’t prove it will necessarily be worse. But his report isn’t the first to warn about cultured meat’s potential impact on our climate, and it won’t be the last. As more studies come out, consumers are likely to join academic researchers in calling for more transparency. Many of them won’t be content to reduce animal suffering if they fear they might be harming the environment in the process.

Over the past decade, the clean meat movement has become associated with twin promises — saving animals and saving the planet. So, naturally, people now want both — and clean meat producers will have to adapt to meet that demand.

Sign up for the Future Perfect newsletter. Twice a week, you’ll get a roundup of ideas and solutions for tackling our biggest challenges: improving public health, decreasing human and animal suffering, easing catastrophic risks, and — to put it simply — getting better at doing good.