A new study published Thursday in Science suggests that human-caused warming is intensifying El Nino, the periodic Pacific Ocean pattern that disrupts weather worldwide. Researchers estimate that El Nino events are now more than 36% stronger than before industrialization, including a 16% increase during the past 40 years, according to the Associated Press. The result arrives as a powerful El Nino is developing and could become the strongest in the modern record.
El Nino occurs when part of the equatorial Pacific becomes unusually warm, altering atmospheric circulation and raising global temperatures. Strong events can amplify heat waves, droughts and floods, damage fisheries and coral reefs, worsen food insecurity and generate enormous economic losses. The conventional instrumental record spans only about 75 years, making it difficult to distinguish a long-term trend from the system's large natural swings.
University of Michigan paleoclimate scientist Julia Cole and colleagues extended the record by studying 29 fossil corals from the Galapagos Islands. Fourteen samples predated the industrial era, 14 came from the modern period and one covered the transition; the oldest dated to around 1100. Ratios of calcium to strontium and oxygen isotopes produced two independent estimates of past seawater conditions, while uranium-thorium measurements dated the skeletons.
Cole told AP that the reconstructed change closely tracks the rise in global temperature caused mainly by fossil-fuel emissions. The study argues that the acceleration raises the prospect of stronger El Nino and La Nina cycles increasing the frequency and severity of climate extremes. Columbia University's tracker reported a recent weekly El Nino anomaly of 2.7 degrees Celsius, above the 2-degree threshold used for a very strong event, with further growth expected for two to four months.
Outside experts remain divided. Brown University coral scientist Kim Cobb described corals as a leading archive for reconstructing El Nino and said broader paleoclimate evidence points toward intensification with warming. University of Pennsylvania scientist Michael Mann and University of North Carolina marine scientist John Bruno countered that recent Galapagos observations show declining variability and that the coral signal may partly reflect general greenhouse warming rather than a change in El Nino itself.
The authors acknowledge that the 900-year reconstruction contains gaps and that El Nino varies sharply from one event to another. Cole said unusually large events can distort short comparisons and argued that the longer coral perspective reveals the trend. Researchers will continue testing the finding against instrumental data and other Pacific climate archives, while the current event provides an immediate test of forecasts and the study's wider implications.
Comments