1.) tends to raise co2 levels in the atmosphere, but 2.) tends to lower co2 levels in the atmosphere. 1. a.) carpooling instead of driving alone b.) cutting down trees instead of growing trees c.) reusing an item instead of buying new d.) using energy-efficient cars instead of gas guzzlers 2. a.) driving instead of walking b.) releasing emission instead of storing them c.) throwing food in the trash instead of composting d.) using clean energy sources instead of fossil fuels