Climate change deniers are running out of arguments as cloud coverage, often proposed as a potential thermostat for the planet, turns out to be something that could make global warming worse. And while it is nice to hear that they are once again wrong, this finding is bad news for everyone.  

The study, published in Nature, estimated a new value for the equilibrium climate sensitivity (ECS), which measures the temperature differences if we were to double the amount of CO2 in the atmosphere. The temperature increase if this was to happen is estimated at around 3°C (5.4°F), but the new research suggests it might be closer to 3.7°C (6.66°F). This revision is based on a series of comparisons between several different models and how they predict the current climate. This "performance against observations" led the team to show that certain clouds actually have a warming effect on the ECS.

The ECS depends on several climate feedbacks both positive and negative. Ice reflects light back into space, while greenhouse gases absorb the heat and so too does water vapor. Clouds were always seen as a big uncertainty. Yes, the water vapor traps heat, but the cloud's whiteness could reflect some of the light back into space.

Climate change deniers jumped at this uncertainty as if it was proof that the Earth will simply regulate itself, although there were studies (here and here for example) suggesting that the role of clouds was underestimated. Deniers also claimed that since models are imperfect and might not simulate the current climate with a high degree of precision, they should be discarded. These claims are completely disproven in the study.

"We do not find that model errors can be taken as evidence that global warming is over-projected by climate models," the researchers wrote in the study. "On the contrary, our results add to a broadening collection of research indicating that models that simulate today’s climate best tend to be the models that project the most global warming over the remainder of the twenty-first century"

The models might still give us some wiggle room for what the actual warming within the next 80 years will be, but it's clear now is the time to act to curb global warming.