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For the second consecutive month, the snowcover footprint over North America was the smallest on record for the month. A record-small snow footprint was also observed over Eurasia and the Northern Hemisphere as a whole.

Based on satellite measurements taken during a baseline period from 1980-2000, the ice covering the Arctic Ocean ranges from an average late winter peak of about 6 million square miles (more than twice the area of the lower 48 states), to a typical late summer minimum of well less than half of that. The melt is in full swing by the summer solstice each year, when the baseline ice extent averages about 4.6 million square miles. But this year, according to NASA and the National Snow and Ice Data Center , the melt-back reached that level by June 1, three weeks early, and since that time, has been at record low levels for the period. This is particularly remarkable because throughout April, daily ice extents hovered very close to average baseline levels (as noted at the time by some commentators eager to suggest the globe is not warming). In other words, the ice retreated with exceptional speed this May — a speed close to the average melt rate of July.

The 2009 State of the Climate report released today draws on data for 10 key climate indicators that all point to the same finding: the scientific evidence that our world is warming is unmistakable. More than 300 scientists from 160 research groups in 48 countries contributed to the report, which confirms that the past decade was the warmest on record and that the Earth has been growing warmer over the last 50 years. Based on comprehensive data from multiple sources, the report defines 10 measurable planet-wide features used to gauge global temperature changes. The relative movement of each of these indicators proves consistent with a warming world. Seven indicators are rising: air temperature over land, sea-surface temperature, air temperature over oceans, sea level, ocean heat, humidity and tropospheric temperature in the “active-weather” layer of the atmosphere closest to the Earth’s surface. Three indicators are declining: Arctic sea ice, glaciers and spring snow cover in the Northern hemisphere.

“For the first time, and in a single compelling comparison, the analysis brings together multiple observational records from the top of the atmosphere to the depths of the ocean,” said Jane Lubchenco, Ph.D., under secretary of commerce for oceans and atmosphere and NOAA administrator. “The records come from many institutions worldwide. They use data collected from diverse sources, including satellites, weather balloons, weather stations, ships, buoys and field surveys. These independently produced lines of evidence all point to the same conclusion: our planet is warming,”