David Merron/500px Prime/Getty Images

Climate change models are running hotter than expected and scientists aren’t sure why

Climate modeling is a science, but not an exact one. There are hundreds of tiny details to take into account in order to produce predictions of potential outcomes. These models help us establish goals like those set forth by the Paris Climate Agreement, and how we get an idea of what might happen if we fail to meet those benchmarks and watch global temperatures climb past the current goal of a 1.5 degree Celsius increase. But over the last year or so, those climate models have started to heat up. According to a report from Bloomberg, climate models have suddenly started to produce projections that push us dangerously closer to doomsday scenarios — and scientists are unsure as to why.

Historically, climate models have been our guide to what could happen to the planet based on the level of carbon emissions that humans are pumping into the atmosphere. For the most part, modeling projects from around the world have produced a similar baseline projection: if we double up on the amount of carbon in our atmosphere compared to what was present during pre-industrial levels, we will see a global temperature increase of three degrees Celsius. This has been the baseline that scientists have been working with for some time now, using it to project things like the rate of ice melting, ocean water levels rising and effects on soil and wildlife. But now it appears that the models have taken a major upswing, suggesting that the planet may experience significantly warmer temperatures — throwing everything we know about what the future might bring for a loop. According to Bloomberg, some major climate models have seen jumps in temperature levels of 30 percent or higher. The Swedish Meteorological and Hydrological Institute's model now projects we could see warming of 4.3 degrees Celsius; France's National Center for Meteorological Research is now projecting a 4.9 degree Celsius rise; the United States Department of Energy model says temperatures could jump 5.3 degrees; the United Kingdom's Met Office Hadley Center says it temperatures could jump 5.5 degrees; and Canada's Earth System Model projects a 5.6 degree increase.


These changes are unexpected and in large part unexplained. According to Bloomberg, many scientists are hopeful that the results are not accurate — that some unforeseen wrench has been thrown into the process and is currently causing a temporary disruption. This is entirely possible, seeing as these models are complicated, sensitive tools that contain tens of thousands of lines of code meant to account for all sorts of details. Most climate models operate by taking into account the known history of the climate, replicating the conditions of past centuries, then building on that to predict what the future might bring. These simulations can account for all sorts of different conditions, ranging from pollution and emissions levels, to rain and heat waves and everything in between. The end result of these simulations is the closest proximity to what we can realistically expect to occur to our planet, based on trends and human behaviors.

Because these are predictive models, they can change based on different conditions — and they tend to be quite finicky. Earlier this year, a study published in the journal Geophysical Research Letters suggested that cloud cover could significantly screw with these models. Clouds are incredibly challenging to account for in these models because they are ephemeral, changing constantly, and account for a relatively small portion of the overall atmosphere. Yet, their effect cannot be ignored. Depending on the type of cloud in the sky and its latitude, it can serve to either cool or warm the planet. Accurately modeling those clouds and their location in the sky is a struggle for these predictive engines, and the end result can fluctuate significantly based on cloud modeling. According to the Geophysical Research Letters study, some models saw as much as a 0.5 degree Celsius increase based on changes in clouds. Paired with the prediction of a doubling in greenhouse gas emissions — as most models often use as a baseline — and warming in the model was predicted to exceed 4.5 degrees Celsius.


Given that level of sensitivity, it's up to scientists responsible for the models to figure out what exactly went wrong — if anything. Two papers published by groups responsible for climate models suggest that there may be something to this newfound sensitivity to clouds in recent predictions. In a paper published in the journal Geoscientific Model Development, one group of scientists found that switching off new cloud modeling and predictions related to aerosol production reverted the model back to its previous baseline. Another paper from the Lawrence Livermore National Lab had similar results: ditch the virtual clouds and return to more familiar results. Scientists around the world will likely continue to tweak the model and determine what information may be responsible for the sudden uptick in temperature rises.

The fear, of course, is that the models aren't wrong — that the new predictions of increased temperature are accurate and previous predictions failed to properly account for cloud cover. If that's the case, we're all in a lot more trouble than we may have imagined. For some time now, the goal set forth by experts has been to limit global warming to a 1.5 degree Celsius increase. A doomsday, worst-case scenario has always been a five degree Celsius rise — and that assumed that humans made no effort to mitigate their impact on the planet. It seemed like that scenario was off the table at this point — that a global effort to cut back on fossil fuels and greenhouse emissions along with a concerted effort to adopt environmentally friendly policies was enough to take us off the course of complete destruction. But if the newest model readouts prove to be correct, we've actually been on a far worse track the whole time and we've only just recently lowered the risk to what we once viewed as the absolute worst of the worst. A global temperature rise of three degrees Celsius — where previous predictions have placed us — would be devastating for millions of people and could wipe out entire populations of plants and wildlife. If we're closer to a path toward a five degree Celsius rise, the effects will be multitudes worse. Now we simply have to hope that virtual clouds haven't obscured our view from what we truly face.