http://www.ncdc.noaa.gov/oa/climate/...arming.html#Q3
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Large-scale measurements of sea-ice have only been possible since the satellite era, but through looking at a number of different satellite estimates, it has been determined that Arctic sea ice has decreased between 1973 and 1996 at a rate of -2.8 +/- 0.3%/decade. Although this seems to correspond to a general increase in temperature over the same period, there are lots of quasi-cyclic atmospheric dynamics (for example the Arctic Oscillation) which may also influence the extent and thickness of sea-ice in the Arctic. Sea-ice in the Antarctic has shown very little trend over the same period, or even a slight increase since 1979. Though extending the Antarctic sea-ice record back in time is more difficult due to the lack of direct observations in this part of the world.
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The warming has not been globally uniform. Some areas (including parts of the southeastern U.S.) have, in fact, cooled over the last century. The recent warmth has been greatest over North America and Eurasia between 40 and 70°N. Warming, assisted by the record El Niño of 1997-1998, has continued right up to the present, with 2001 being the second warmest year on record after 1998.
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If one calculates trends beginning with the commencement of radiosonde data in the 1950s, there is a slight greater warming in the record due to increases in the 1970s. There are statistical and physical reasons (e.g., short record lengths, the transient differential effects of volcanic activity and El Niño, and boundary layer effects) for expecting differences between recent trends in surface and lower tropospheric temperatures, but the exact causes for the differences are still under investigation (see National Research Council report "Reconciling Observations of Global Temperature Change").
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The last few years have shown an increase in Antarctic Sea Ice, and the Southern Hemisphere in general has shown a reducing in temperature.
In short the scientists don't know, nor can they explain much of what they find. Very few (if any) hold out that there is change to the global environment, the debate lays in the cause and effect it will hold on society.
I personally do not believe it will hold much of an impact. We have risen .2 Degree Celsius since the mid 19th Century according to the National Oceanic and Atmospheric Administration, and with that have seen the biggest economic, social, and technological boom ever in history. I'm not saying lets turn the heat up and keep it going, but it obviously is not as bad as Gore makes it out to be.