The epic series of sci-fi books by Frank Herbert, Dune, which has recently been adapted into a film of the same name, is set in the far future on the desert planet of Arrakis. Herbert sketched out a beautifully detailed world that, at first glance, seemed so real that we could picture ourselves in it.
But, if such a universe did exist, what would it be like?
We are experts with expertise in climate modeling, therefore we simulated Arrakis' climate to find out. We were curious to see how the physics and ecology of such a world stacked up against an actual climate model.
At our website Climate Archive, you may zoom in on certain elements and highlight things like temperature or wind speed.
When we were finished, we were ecstatic to learn that Herbert had imagined a setting that, for the most part, met our expectations. We might have to suspend our disbelief from time to time, but much of Arrakis would be habitable, albeit inhospitable.
We began with a climate model that is routinely used to forecast weather and climate on Earth. To utilize these models, you must first decide on the physical rules (which are well-known in the case of planet Earth) and then input data on anything from the geometry of mountains to the strength of the sun or the composition of the atmosphere. The model can then mimic the climate and provide an estimate of what the weather will be like.
We choose to adhere to the same fundamental physical laws that regulate weather and climate on Earth. If our model revealed anything completely weird and exotic, it may imply that the laws of Arrakis were different, or that Frank Herbert's imaginative picture of Arrakis was simply that, a fantasy.
Then, based on the precise information available in the main novels and the companion Dune Encyclopedia, we had to teach the climate model-specific characteristics of Arrakis. These included the planet's terrain and orbit, which was generally circular, similar to Earth's present. The shape of an orbit can have a significant impact on climate, as evidenced by Game of Thrones' long and unpredictable winters.
Finally, we informed the model on the composition of the atmosphere. It is, for the most part, comparable to Earth today, albeit with less carbon dioxide (350 parts per million as opposed to our 417 ppm). The concentration of ozone is the most significant difference. On Earth, the lower atmosphere contains relatively little ozone, barely about 0.000001 percent. It is 0.5 percent on Arrakis. Over a 20-year period, ozone is approximately 65 times more effective at warming the atmosphere than CO2.
After entering all of the essential information, we sat back and waited. Complex models like these take longer to run, more than three weeks in this case. To conduct the hundreds of thousands of calculations required to replicate Arrakis, we needed a massive supercomputer. However, what we discovered was well worth the wait.
The literature and film depict a world with an unforgiving sun and desolate sand and rock wastelands. However, as you approach the frigid areas and the cities of Arrakeen and Carthag, the environment in the novel begins to transform into something more habitable.
Our model, on the other hand, reveals a different narrative. In our Arrakis model, the warmest months in the tropics reach roughly 45°C, while the coldest months do not fall below 15°C. The same as on Earth. The highest temperatures would occur in the mid-latitudes and polar areas. Summer temperatures on the sand can reach 70°C (also suggested in the book). Winters are as harsh, with temperatures as low as -40°C in the mid-latitudes and as low as -75°C at the poles.
This is counterintuitive given that the equatorial region receives more solar radiation. However, the polar regions of Arrakis in the model contain substantially greater atmospheric moisture and high cloud cover, which acts to warm the climate because water vapor is a greenhouse gas.
According to the book, there is no rain on Arrakis. However, our model predicts that very little rainfall will fall, confined to the higher latitudes in the summer and autumn, and only on mountains and plateaus. There would be clouds in the tropics as well as the polar latitudes, with the amount shifting depending on the season.
The book also claims that polar ice caps exist and have done so for a long time, at least in the northern hemisphere. But this is where the books and our model diverge the most: summer temperatures would melt any polar ice, and there would be no snowfall to restore the ice caps in winter.
Could people live in such a desolate world? To begin, we must assume that the human-like characters in the novel and movies have thermal tolerances equivalent to humans today. If this is the case, it appears that, contrary to the book and movies, the tropics would be the most habitable region. Survivable wet-bulb temperatures, a measure of "habitability" that combines temperature and humidity, are never exceeded since there is so little humidity.
In terms of heat, the mid-latitudes, where most humans reside on Arrakis, are actually the most deadly. Monthly average temperatures in the lowlands are frequently above 50–60°C, with maximum daily temperatures significantly higher. These temperatures are lethal to humans.
We do know that outside of habitable areas, all humanoid life on Arrakis must wear "stillsuits," which are meant to keep the wearer cool and recapture body moisture from perspiration, urinating, and breathing to create drinkable water. This is significant since, as described in the novel, Arrakis has no rainfall, no standing bodies of open water, and very little atmospheric moisture that may be retrieved.
Outside of the tropics, the earth also gets exceedingly cold, with winter temperatures that would be uninhabitable without technology. Cities such as Arrakeen and Carthag would suffer from both heat and cold stress, similar to a more extreme version of Siberia on Earth, which can have both unbearably hot summers and brutally frigid winters.
It's worth remembering that Herbert authored the first Dune novel in 1965. Herbert was working two years before recent Nobel laureate Syukuro Manabe published his seminal first climate model, yet he didn't have the benefit of modern supercomputers or even any computer. Given that, the world he constructed six decades ago appears amazingly consistent.
(The authors adapted a well-known climate model for exoplanet research and applied it to Dune's world. The work was done in their spare time and is meant to serve as a suitable outreach piece to highlight how climate scientists utilize mathematical models to better understand our globe and exoplanets. It will contribute to future academic publications on desert worlds and exoplanets.)