[ 155 ] Earth and Space Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Since the Industrial Revolution, when the consumption of energy to power machinery began to substantially expand, people have increased the concentration of carbon dioxide in the atmosphere by ___ by burning fossil fuels and cutting down forests that reduce the concentration of carbon dioxide. A. 10% B. 50% C. 30% D. 80% Burning fossil fuels and forests also releases nitrogen. All forms of fixed nitrogen are greenhouse gases that cause global warming. What can you conclude from this pair of statements? Earth’s upper mantle is rigid and, together with the crust, is part of the lithosphere. The lower mantle flows slowly at a rate of ________ per year. A. a foot B. a few centimeters C. a mile D. a kilometer