The document discusses the greenhouse effect and its impacts. It provides background on the carbon cycle and increasing levels of carbon dioxide measured since 1958. The greenhouse effect creates moderate temperatures by trapping heat, while the enhanced greenhouse effect from human emissions may cause climate change. Scientists cannot agree on exact impacts but they could include increased droughts, flooding, food shortages, disease, and loss of biodiversity. The Arctic is especially vulnerable, as melting permafrost releases methane and species struggle with habitat changes.