Is a global warming signature emerging in the tropical Pacific?

The tropical pacific experienced a hitherto-unseen anomalous basinwide warming from May 2009 through April 2010 with the maximum warming to the east of the dateline, but for a weak anomalous cooling west of 140°E after early boreal fall. Our observed analysis and model experiments isolate the potential teleconnections from TP during the summer of 2009. Further, we show through an empirical orthogonal function analysis of the tropical Pacific SSTA that the anomalous conditions in TP during this period could have manifested as a canonical El Nio, but for a slowly intensifying background west-east gradient. This zonal SST gradient is subject to an increasing trend associated with global warming. A possible implication is that any further increase in global warming may result in more basinwide warm events in place of canonical El Nios, along with the occurrence of more intense La Niaños and El Nio Modokis

Projected response of the Indian Ocean Dipole to greenhouse warming

International audienceNatural modes of variability centred in the tropics, such as the El Nino/Southern Oscillation and the Indian Ocean Dipole, are a significant source of interannual climate variability across the globe. Future climate warming could alter these modes of variability. For example, with the warming projected for the end of the twenty-first century, the mean climate of the tropical Indian Ocean is expected to change considerably. These changes have the potential to affect the Indian Ocean Dipole, currently characterized by an alternation of anomalous cooling in the eastern tropical Indian Ocean and warming in the west in a positive dipole event, and the reverse pattern for negative events. The amplitude of positive events is generally greater than that of negative events. Mean climate warming in austral spring is expected to lead to stronger easterly winds just south of the Equator, faster warming of sea surface temperatures in the western Indian Ocean compared with the eastern basin, and a shoaling equatorial thermocline. The mean climate conditions that result from these changes more closely resemble a positive dipole state. However, defined relative to the mean state at any given time, the overall frequency of events is not projected to change [mdash] but we expect a reduction in the difference in amplitude between positive and negative dipole events