Observed changes
The IPCC reports are conservative. Researchers from countries as different as USA, Russia, China, Qatar, Saudi Arabia and Norway are expected to reach consensus on how to compile the research going on worldwide. Nevertheless, the IPCC has managed to agree on several points. Due to the IPCC being conservative, the new empirical data from the field are as a rule at the higher end of IPCC predictions.
  1. The global average surface temperature has increased by about 0.7°C over the last hundred years.

    Globally, the first decade of this century was the warmest in instrumental records since 1861. The 1990's was the second warmest decade. 1998 the warmest year recorded, but that was partly due to unusually high solar activity and a very strong El Nino. It now seems 2010 sails up as the warmest year recorded, with several countries reporting new records. This despite of low solar activity, a very strong negative NAO and a very strong and prolonged La Nina.


    Graph: National Aeronautics and Space Administration

  1. Night-time daily minimum air temperatures over land increased by about 0.2°C per decade between 1950 and 1993.

    Global average temperature of the lowest 8 kilometres of the atmosphere has changed by +0.05 ± 0.10°C per decade since the start of the satellite record in 1979.

  1. The extent of snow cover has been reduced by 10% since the late 1960's

    The annual duration of lake and river ice cover in the mid- and high latitudes of the Northern Hemisphere has been reduced by two weeks over the 20th century.

  1. Northern Hemisphere spring and summer sea-ice extent has decreased by about 10 to 15% since the 1950's

    The global average sea level rose between 0.1 and 0.2 metres during the 20th century.
    The waves are growing

    There has been a widespread retreat of mountain glaciers in non-polar regions during the 20th century.