Unit 4 Global warming Record high readings of CO 2 raise concern據測定，大氣的二氧化碳濃度日均值于今年5月初達到了400 ppm，這是人類歷史上的最高紀錄。 According to Pieter Tans，a researcher at the National Oceanic and Atmospheric Administration，the last time the earth reached this high a level of CO2 was about 2 million years ago.During this time the earth was much warmer.Greenland was actually green，consisting of forest instead of ice and the sea levels were at least 3366 feet higher.So how important is this number which happens to be a daily figure？Its importance is to warn us that unless something extreme is done soon to change this trend，things can only get worse. The good news is that the trend can be changed，because the increase in CO2 which is the byproduct of the burning of fossil fuels like coal for electricity and oil for petrol，is a direct result of human activity.According to experts，in 2011 we managed to add an average of 2.4 million pounds of CO2 into the air every second. Whats concerning scientists more than this unprecedented (空前的) milestone of 400 parts per million，is the rapid pace at which the greenhouse gas is increasing.They believe that plants and animals can adapt (適應) when climate changes occur slowly over thousands of years，but not if the changes come within a short period of time，which is what is happening now.What is even more alarming is that if the oceans were not absorbing some of the gas，the levels would be even higher！Hopefully，the world will try to change this rapidly worsening situation. 謝謝觀看！