Within the last century, the amount of carbon-di-oxide in the atmosphere (a) ———dramatically because people (b)———— vast amounts of fossil, coal and petroleum. Average global temperature has also increased by about 0-6° Celsius within the past century. Scientists (c) ——– that human activities are responsible for at least half of that temperature increase, They (d) ———– that unless drastic action is taken, global temperature (e)——-— to rise by 1-4° to 5-8° Celsius over the next century.