Includes sea level rise; extreme weather; changes to ecosystems, plants and animals; melting ice and permafrost; ocean wamring; impacts to water resources, agriculture, public health and national security
For James Overland, an Arctic oceanographer at NOAA’s Pacific Marine Environmental Laboratory, six exceptionally slushy summers in a row in the Arctic demanded an explanation that went beyond the obvious: that global warming is raising the Arctic’s temperature. After analyzing winds and pressure patterns, Overland and several colleagues documented an unusual shift in the prevailing June winds—from westerlies to southerly—that amplified Arctic warming and sea ice melt.
In the mid-1980s, the winter sea ice pack in the Arctic was dominated by multi-year ice—ice that had survived at least one summer melt. Today, less than half of the sea ice at winter maximum has survived at least one summer.
Each summer, the seasonal unraveling of the Arctic’s blanket of ice exposes large areas of the ocean to solar heating. The smaller the ice extent, the larger the potential warming influence. Arctic sea ice extent in July 2011 was the lowest for that month in the satellite record.
When the winds are right, dust from the deserts of the U.S. Southwest blows onto the snow-capped Rocky Mountains. How do dirty snowfields contribute to the loss of more than 250 billion gallons of water in the Colorado River?
This report presents a comprehensive appraisal of Earth’s climate in 2009, and establishes the last decade as the warmest on record. Reduced extent of Arctic sea ice, glacier volume, and snow cover reflect the effects of rising global temperature.