By an elegant and complex process a particular group of bacteria take the atmospheric nitrogen and turn it into forms that can be used for biological purposes. These are just a few examples of how every living thing is dependent on natural processes, intimately linked to the Earth's biophysical systems. Many more such linkages are at work during your morning routine - the pollinating insects that make orange juice possible, the hydrologic cycles that put water in the coffee pot, the ozone that protects you when you walk out into the sunlight. It is unlikely that any amount of technological ingenuity could come up with replacements for these natural systems. Temperature control is good example of how hard it would be to re-create these systems.
Humans can only survive within a narrow range of warmth and cold.
Without clothing or shelter, that range might be a few dozen degrees Fahrenheit. Without the atmosphere regulating the climate, the Earth's year round temperature would average around zero degrees Fahrenheit. Under those circumstances, with no liquid water to be found, staying warm would actually not be our biggest problem. Although nature might seem quite distant from the modern world, look far enough and you will find natural systems and substances at the foundation of all activities. It is not always easy to grasp the immensity of these systems nor the role they play in our lives.