Editorial
The State of Earth's Climate 2009: How can so many people be so wrong?

Medieval Warm Period Record of the Week
This issue's Medieval Warm Period Record of the Week comes from the Central Scandinavian Mountains, Sweden.

Subject Index Summary
Ocean Acidification (Effects on Marine Plants: Macroalgae): How do marine macroalgae respond to increases in the CO2 concentration of the air that is in intimate contact with the waters in which they live?

Journal Reviews
Extreme Paleofloods of the Southwestern United States: Will there be more or fewer of the hydrologic catastrophes if the climate continues to warm?

Millennial Cycling of Climate in West Africa During the Holocene: What is the evidence for it?

Yellow Fever and Dengue in Tomorrow's Europe: Would they become greater threats to the continent's populace if the world began to warm again?

Effect of Elevated CO2 on the Root Mass Fraction of Plants: Do above- and below-ground plant parts respond differently to atmospheric CO2 enrichment?

Seventy Years of High Arctic Plant Responses to Climate Change: How dramatic have they been?