New research published in the journal Science this week spells some bad news for our fight against climate change, as a group of scientists warned that our current climate models are overstating the cooling effect cloud cover can have. The New York Times reports:

The new paper suggests the effects of a flaw in the model could be serious: Based on its analysis of one model of climate change, the cloud error could mean an additional 1.3 degrees Celsius of warming than expected. […]

“Unfortunately, it means staying below 2 degrees is going to be even harder,” said Trude Storelvmo, an atmospheric scientist and another author of the paper, and an associate professor in the Yale department of geology and geophysics. “We have to emit even less CO2 to stay below those limits.”

The average green is likely going to seize on this study as more evidence that humanity is doomed—the modern environmental movement seems to work best when it’s predicted the end to be nigh. But there’s another, more general concern about climate science here beyond just this warning that one variable in our best climate models isn’t properly calibrated: this serves as another reminder that we know precious little about our planet’s climate.

Too often the science behind climate change is described by eco-activists as “settled,” but we can’t go a month without learning about new research disproving some climate process that was previously assumed to be true. Yes, human-caused greenhouse gas emissions are trapping more of the sun’s radiation in our atmosphere and heating up surface temperatures, but we can acknowledge that without pretending like climate science is somehow done and dusted.

Our models are woefully inaccurate, and no wonder—there are an astounding number of variables they need to account for, and countless relationships between those variables that also require study. This latest study offers a correction to just one of these variables, and it alone is enough to raise new doubts over hitting climate targets. There’s so much more we don’t know, and while researchers work towards a more complete understanding of our planet’s immensely complex climate, environmentalists would do well not to pretend we know more than we do—it only sets them up to look foolish when the models get it wrong.