How have human activities affected atmospheric greenhouse gas levels during the last 275 years and especially in the last 30 years? List the major human activities that add CO2, CH4, and N2O to the...

How have human activities affected atmospheric greenhouse gas levels during the last 275 years and especially in the last 30 years? List the major human activities that add CO2, CH4, and N2O to the atmosphere. What is a carbon footprint? How do scientists use models to make projections about future temperature changes? What do climate models project about temperature changes during this century? Explain how each of the following might contribute to atmospheric warming and climate change: (a) solar energy changes, (b) the oceans, (c) cloud cover, and (d) air pollution.