simplified diagram of the Earth's heat budget
This is a hUgE topic and one that I intend to expand upon in the near future. However, we will come across this issue repeatedly as we study other topics so I've only included a few links here from Planet Ocean. Just be aware that Global Climate Change is probably one of the most intensely debated environmental topics in the world today!
Please read these links from Planet Ocean.
Also, familiarize yourself with this graph of carbon dioxide concentrations versus time.
CO2 concentrations in the atmosphere since 1958, from Garrrison
From NOVA: What would happen to sea-level if the West Antarctic Ice Sheet
NASA Climate News and Research
Global Warming Central, from Pace University
EPA's Global Warming Site
Global Warming International Center
Sierra Club's Global Warming Site
Environmental Defense Fund Site About Global Warming