•extremely unlikely without external forcing •very unlikely due to known natural causes alone
Observed widespread warming
Global ocean
1955
2005
1980
Annual       Trend 1979 to 2005
Surface
Troposphere
The spatial pattern of observed temperature change shown on the left panel indicates widespread warming. We also have evidence that the lower troposphere warmed (right, shown from the late 70ies on), and that the global ocean gained heat since the mid 20th century.
This strengthens our confidence that variability generated within the climate system cannot explain these changes.

We therefore conclude (READ)