Background Paragraph: Pollutants also affect the atmosphere through their contribution to global warming. Global warming is an increase in the Earth’s temperature. It is thought to be caused mostly by the increase of greenhouse gases like carbon dioxide. Greenhouse gases can be released by factories that burn fossil fuels. Over the past 20 years, burning fossil fuels has produced about three-quarters of the carbon dioxide from human activity. The rest of the carbon dioxide in the atmosphere is there because of deforestation, or cutting down trees ( Figure below ). Trees absorb carbon dioxide during cellular respiration, so when trees are cut down, they cannot remove carbon dioxide from the air. 
Story: There are two planets, Glarnak and Bornak, that share the same atmospheric composition. The planets have nearly identical ecosystems and topography. The main difference between the two planets is the level of global warming on each planet. Glarnak is experiencing a strong impact from global warming. Bornak, though, is experiencing practically no effects of global warming.
Is it more or less likely that Bornak has more trees than Glarnak? Is it more or less likely that Glarnak has more trees than Bornak? Is the average temperature of Bornak higher or lower than Glarnak? Is the average temperature of Glarnak higher or lower than Bornak? Which planet has less pollutants in the atmosphere? Which planet has more pollutants in the atmosphere? Which planet is less likely to use fossil fuels as their main source of energy? Which planet is more likely to use fossil fuels as their main source of energy? Which planet probably produces less carbon dioxide? Which planet probably produces more carbon dioxide?