Through June, the eastern Pacific was warmer than average, but the lack of a strong gradient in sea surface temperature anomalies between the eastern and western Pacific may have kept the atmosphere from getting in sync with the developing El Niño.
A pool of warm water lurking beneath the surface of the western Pacific has been slowly sloshing eastward in the past few months. This traveling wave of warm water is one of the signs that climate conditions are favorable for the emergence of El Niño later this year.
Everyone's asking if the arrival of El Niño guarantees that 2015 will set a new record for warmest global temperature. In his latest blog, Deke Arndt explains why it's possible--maybe even likely--but not guaranteed.