ENSO, volcanoes and record-breaking temperatures



Monthly-mean, near-surface temperatures are examined for records and trends after accounting for the influences of ENSO and the volcanic eruptions of Agung, El Chichón and Pinatubo. Of the 16 consecutive record-breaking months in 1997–98, at least six can be attributed to ENSO-associated warmth. The period is still unusual, but no more unusual than 1990–91 when an equal number of records occurred in the ENSO-adjusted data. The warming trend over the past two decades is also shown to be unusual, but is found (in the raw data) to be not significantly different from the warming trend of the 1910s–1930s. When ENSO and volcanic effects are removed, however, the recent warming trend increases (to 0.25°C/decade) and becomes highly significant compared to the earlier period.