In mountain climbing, the death zone refers to altitudes above 26,000 feet (7,900 meters). At that height, the atmospheric pressure is only 35 percent of what it is at sea level. Irrespective of physical conditioning or acclimatization, it is not possible for any human at that altitude to breathe in enough oxygen to prevent widespread cell death in the body’s vital organs, and especially in the brain. Above 26,000 feet it becomes very difficult to sleep and near impossible to digest food. Any climber that spends more than about 12 hours above 26,000 feet without supplemental oxygen will experience permanent brain damage, increasing risk of loss of consciousness, and ultimately death.1
Among all Earth’s terrestrial life, animals that use lungs for respiration are the most sensitive to changes in atmospheric pressure. Lungs cease to mechanically function at air pressures three times greater or three times lower than the air pressure at sea level.
Effect of Atmospheric Pressure on Surface Temperature
In 2009, a team of four geologists and planetary astronomers published a paper in which they explained the impact atmospheric pressure has on the surface temperature of a planet.2 They showed how the atmospheric pressure plays a critical role in determining the magnitude of the greenhouse effect of a planet’s atmosphere. Atmospheric pressure affects the broadening of infrared spectral absorption lines, especially the spectral absorption lines of carbon dioxide and nitrogen. In the words of the four geologists and planetary astronomers, “If the total atmospheric pressure were lower, the climate forcing of greenhouse gases would be smaller, the magnitude of the greenhouse effect would be less, and the global mean temperature would drop.”3
In their paper, the team pointed out how the apparently imminent extinction of all life on Earth—as a consequence of the ongoing brightening of the Sun—might be significantly delayed if Earth’s atmospheric pressure were to decrease at a rate that near perfectly compensates for the brightening of the Sun. Other astronomers published papers in which they showed how different levels of atmospheric pressure on an extrasolar planet could provide more possible options for the planet’s habitability.4
Effect of Atmospheric Pressure on Life
As noted already, atmospheric pressure must be fine-tuned for lungs to be able to mechanically function. Therefore, lowering Earth’s atmospheric pressure to compensate for the future brightening of the Sun has a limit for animals dependent on lungs.
Lowering Earth’s atmospheric pressure also has a limit for life dependent on atmospheric oxygen and nitrogen. Together, oxygen and nitrogen comprise 99.03 percent of Earth’s atmosphere. A significant lowering of Earth’s atmospheric pressure, therefore, requires a substantial removal of oxygen and/or nitrogen.
Lowering the oxygen content would lower the elevation at which land animals could survive. Lowering it to less than half its present level would bring about the extinction of not only most land animals, but also most marine animals as well. A lower atmospheric oxygen content would also weaken Earth’s ozone shield. Such weakening would lower plant productivity in addition to impacting all land animals.
Lowering the nitrogen content would lower the amount of nitrogen fixation from the atmosphere. Less nitrogen fixation means less of an important nutrient critical for all plants, but especially for vascular plants. Lowering the ratio of nitrogen to oxygen in the atmosphere would seriously degrade the respiration of animals.
As the team of four geologists and planetary astronomers pointed out in their paper, any reasonable scenario that lowers Earth’s atmospheric pressure would also lower the quantity of carbon dioxide in the atmosphere. While carbon dioxide is the fourth most abundant gas in Earth’s atmosphere (after nitrogen, oxygen, and argon), it is only slightly above the minimum level needed for unimpeded photosynthesis. As I wrote in a previous blog,5 during the last ice age the carbon dioxide level in Earth’s atmosphere dropped down to 180–190 parts per million. The minimum for C3 photosynthesis at sea level = 150 parts per million, at 3,000 feet elevation it = 167 parts per million, at 6,000 feet elevation it = 187 parts per million, and at 9,000 feet it = 210 parts per million. Thus, any significant lowering of Earth’s atmospheric pressure will greatly reduce or eliminate C3 photosynthesis productivity. Currently, C3 photosynthesis plants comprise about 95 percent of Earth’s total plant biomass and 100 percent of the plant biomass used to feed humans and their domesticated animals.
Any reduction of Earth’s atmospheric pressure will lower the boiling point of water. For example, if Earth’s atmospheric pressure were lowered to half its present value, the boiling point of water at sea level would be 178° Fahrenheit (81° Centigrade) and at 9,000 feet elevation it would be 164° Fahrenheit (73° Centigrade). Water boiling points this low would dramatically alter the precipitation of rain and snow. Some regions on Earth would experience much greater precipitation rates. Others would experience much lower precipitation rates. This greater precipitation variability combined with the much higher wind velocities generated by lower atmospheric pressure would dramatically increase weather disasters worldwide.
Fine-Tuned Air Pressure
Recent research studies on the impact of atmospheric pressure for life on Earth and the possibility of life on extrasolar planets reveals that we should not take the atmospheric pressure of our planet for granted. While unicellular life-forms can tolerate a comparatively wide range of sea level atmospheric pressures, complex life, and especially human life, cannot. That the sea level air pressure on Earth is precisely at the best possible value for humans beings and global human civilization adds to the growing list of fingerprints that a supernatural, super-intelligent Being purposely designed Earth for the specific benefit of humans and their civilization.
Featured image credit: NASA