Why are the concern over global cooling replaced with a concert over global warming?

Because global warming warms up the earth and even though it only warmed it up 4C, it is estimated to warm up more and more each year. 

With all the pollution that the world puts into the atmosphere, it is slowly destroying the ozone layer. The ozone layer protects us from harmful rays that the sun gives off. If that ozone layer disappears, The earth will be much warmer, and you will probably get skin cancer. Human life will be drastically different if we couldn't go outside because of this.

When the ball is rising up, it gains kinetic energy. when the ball reaches the very top, it will have all potential energy, until it falls back down and gains it kinetic energy. finally when you catch the ball or it falls back down, it would have gained its potential energy back.