extreme changers in climate are nothing new on earth. In its long history,there have been times when the Earth's climate became warmer, causing ice to melt and sea levels to rise, so that much more of our planet was covered in water.At other times the Earth has been very cold; these ice ages saw huge areas of the planet covered in snow and ice. These might sonnd like drastic changes in Earth's climate,but they happened very gradually over thousands of years.