NOAA's National Centers for Environmental Information
Use the form below to select from a collection of monthly summaries recapping climate-related occurrences on both a global and national scale.
Global Snow and Ice ReportAnnual 2007
Northern Hemisphere Sea Ice Extent
According to the National Snow and Ice Data Center, the Northern Hemisphere sea ice extent, which is measured from passive microwave instruments onboard NOAA satellites, reached the least sea ice extent on record during the month of September with 4.28 million square kilometers (39 percent below the 1979-2000 mean). The anomalous warmth that covered much of the Northern Hemisphere during January-September 2007, contributed to the sea ice extent being well below the record set in 2005 by a remarkable 23%. For further information on Northern Hemisphere snow and ice conditions, please see the NSIDC News page, provided by the NOAA's National Snow and Ice Data Center (NSIDC).
Arctic sea ice conditions are inherently variable from year to year in response to wind, temperature and oceanic forcings. Quite often a "low" ice year is followed by recovery the next year. But increasing surface temperatures in high latitudes have contributed to progressively more summer melt and less ice growth in the fall and winter. While natural variability is responsible for year-to-year variations in sea ice extent, three extreme minimum extent years along with evidence of thinning of the ice pack suggest that the sea ice system is experiencing changes which may not be solely related to natural variability.
Northern Hemisphere Snow Cover Extent
As shown in the time series to the right, mean Northern Hemisphere snow cover extent during the boreal winter (December 2006-February 2007) was below average. Much of this was due to anomalously warm conditions across Asia, Europe, Canada, and the northeast half of the U.S. The boreal winter 2007 snow cover extent over the Northern Hemisphere was the 8th lowest extent in the historical record. Mean Northern Hemisphere winter snow cover extent for the 1967-2007 period of record was 45.4 million square kilometers.
Snow cover for the boreal winter 2007 across North America was above average and was the 13th largest extent over the 41-year historical record. This was in part due to a series of snow and ice storms that struck the U.S. during the month of February. Average North America boreal winter snow cover extent is 17.0 million square kilometers for the 1967-2007 period of record.
Mean Northern Hemisphere snow cover extent during boreal spring (March-May) 2007 was below average. Much of this was due to anomalously warm conditions across Asia, Europe, and most of the contiguous U.S. Spring 2007 snow cover extent on the Northern Hemisphere was the 3rd lowest extent on record. Mean Northern Hemisphere spring snow cover extent for the 1967-2007 period of record is 30.8 million square kilometers.
Snow cover for boreal spring across North America was below average, giving March-May 2007 a rank of 8th lowest extent on record. Mean North America boreal spring snow cover extent is 12.9 million square kilometers for the 1967-2007 period of record.
Data were provided by the Global Snow Laboratory, Rutgers University.
