Just thirty years ago, experts were still at a loss as to whether the earth was warming or cooling, and they could not tell whether the future world was an ice store or a greenhouse. In 1975, the first batch of sophisticated computer models show that if the carbon dioxide in the atmosphere doubles, the global temperature will rise by about three degrees. However, the scientists and the public at the time were still calm. For a while, some researchers even believed that the excess carbon dioxide in the atmosphere will lead to that farmland of the world will be fertile, and farmers will usher in a prosperous era.
Which of the following options can be introduced?
The severity of global warming is unexpected.