The Copenhagen Primer, a user-friendly guide to the 2009 climate summit, lays out the essentials of history, science and negotiating points. Four pages of charts show timelines of previous summits; important scientific discoveries; the main political points nations are arguing over; and projections of what various actions—or inactions—are expected to cost in coming years. It includes a web bibliography of primary sources. The guide is produced by the Earth Institute’s Environmental and Science Policy program. It may be downloaded free here.