Look at how snobby your lungs look! I don't think we can be friends anymore.
First off, breathing through your nose is much actually healthier if you consider the contaminants in the air. One very special area that your nose has and your mouth doesn't, is the nostrils/sinuses. Through the use of the nostril hair, mucus, and nitric oxide, foreign objects and bacteria are mainly prevented from entering the body. What this means is that if you happen to inhale at the same time a large mosquito flies across your face, there's a smaller chance that it'll follow down your respiratory system. (The hairs in your nostril will likely prevent it from entering) In a manner of speaking, you can think of your nostrils as life's natural gas masks.
However, if your town becomes the target of a biological cluster-bomb, you may want to put one of these on.
On the other hand, the tighter/smaller the diameter of the nostrils are, the better your nose may help in building pressure onto the lungs during inhalation. (More so than your mouth) Why is this important? The pressure allows the lungs to exercise it's natural elasticity, allowing it to remain healthy, longer. Along with that, the extra pressure allows the lungs to have more time to extract the precious oxygen that your body needs. While it may feels that you're taking in less oxygen per breath, you might actually be taking in more.
Alternatively, you could buy a oxygen tank and live forever.
In terms of taking in oxygen, breathing through your mouth might actually cause you to take in less oxygen in comparison of breathing through your nostrils? Why? Because your body has a natural inclination for homeostasis, or balance. By increasing your CO2 output, your body must decrease O2 input in order to maintain a balanced pH level in your blood. Just because you're breathing in a higher volume, doesn't mean it's going to get used.
If you think about it for about a twenty million picoseconds, you might realize that your nose was made to be your breathing apparatus. Each individual nostril has special jobs to do that allow the air you breath to be optimal for consumption. Things like filtering, humidifying, and even warming the air is ideal for your lungs. In all honestly, haven't we all taken a deep gulp of cold dry air during our winterly activities, and end up choking buckets from the sharp, intense pain?
Along with that, you increase your chances of drying out your mouth/throat, (which can make it easier for microbes to enter your body) losing your voice, and more severely, risking dehydration. Your nose on the other hand, is equipped to deal with whatever nature throws as it.
Tornadoes on the other hand.
