unit test Earth scientists have concluded that the methods of harnessing energy that have been used over the past two centuries, such as the burning of fossil fuels, are causing climates around the world to change more quickly and suddenly than ever before in human history. Evidence includes increased air temperatures, rising sea levels, and the shrinking of glaciers in Greenland, Alaska, and other regions of Earth. The most complex level of organizational hierarchy that climate change could potentially affect is Earth’s