“A collective picture of a warming world”

• Over the 20th century:

  • global-average surface temperature has increased (0.6° C)
  • temperature in lowest 8km increased in past 4 decades
  • global-average sea level has risen (0.1- 0.2 m)
  • snow & ice extent decreased - widespread retreat of glaciers
  • precipitation has increased (up to 1% per decade)

• In Northern hemisphere increase in temperature in C20th likely to have been largest of any century, 1990s the warmest decade & 1998 the warmest year during past 1000 years.

• Since 1750 there has been an increase of:

  • CO2 (31%), CH4 (151%) and N2O (17%)
  • present CO2 likely not exceeded in past 20, 000 years