By rename do you mean turn into an improper fraction?
if so, it is because without turning it into an improper fraction, you cannot subtract 3/4 from 1/4 because you would get a negative answer and that would be incorrect
Weather is a complex phenomena. in order to solve engineering problems such as the prediction of weather, we utilize degrees of freedom (DoF)... weather is one of the many elements that need millions of DoF and still cannot accurately predict it. mainly it's a vector analysis much akin to finite element analysis where each micro degree of freedom or say molecule of air is represented as one point interconnected in a web of points and each point's properties are altered relatively (similar principles how autonomous mini drones coordinate synchoronously) to each other.
many factors are considered: pressure, temperature and density of the air for sure. friction factors. drag factors. rotation of the earth. and that's the natural phenomena. include the heat given off the land, the radiation from the sun, airplanes, people, etc... its highly complicated. having done a weather station project, it's fair to say that there isn't a simple answer to your simple question. we measured wind direction, wind current, temp and humidity, visibility, pressure, etc... and we couls measure these things, but can't really say why say the wind went east or west... except tell you that its because of millions of degrees of freedom interacting with each other simultaneously and some things like weather are just like that.
I dont know lol I think vast weather changes such as global warming may cause extinction to species or adaptation to heat. But it depends solely on the lifeform
A. the surface area of rocks decreases because of acid rain
