11. Of the following related to greenhouse gases and global warming, the true statement is (explain): (A) levels of greenhouse gas methane are increasing by about l ppm per year in the atmosphere, (B) per molecule, methane has a greater effect on greenhouse warming
than does carbon dioxide, (C) rediative forcing of CO2 is about 25 times that of CH4 , (D) carbon dioxide is the only gas considered significant as a cause of greenhouse warming, (E) although models predict greenhouse warming, there is no evidence in recent in recent years that it may have in fact begun.