Study suggests La Niña winters could keep on coming, but climate models are out of step with observations

The conclusions of a recent study are quite blunt: ‘We show that the spatial pattern of observed surface temperature changes since 1979 is highly unusual, and many aspects of it cannot be reproduced in current climate models, even when accounting for the influence of natural variability.’ Hardly inspiring, when such models are being relied upon by governments for radical so-called climate policies.
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Forecasters are predicting a “three-peat La Niña” this year, says Phys.org.

This will be the third winter in a row that the Pacific Ocean has been in a La Niña cycle, something that’s happened only twice before in records going back to 1950.

New research led by the University of Washington offers a possible explanation. The study, recently published in Geophysical Research Letters, suggests that climate change is, in the short term, favoring La Niñas.

“The Pacific Ocean naturally cycles between El Niño and La Niña conditions, but our work suggests that climate change could currently be weighing the dice toward La Niña,” said lead author Robert Jnglin Wills, a UW research scientist in atmospheric sciences. “At some point, we expect anthropogenic or human-caused influences to reverse these trends and give El Niño the upper hand.”

Scientists hope to predict the direction of these longer-term El Niño-like or La Niña-like climate trends in order to protect human life and property. [Talkshop comment – really?]

“This is an important question over the next century for regions that are strongly influenced by El Niño, which includes western North America, South America, East and Southeast Asia and Australia,” Wills said.
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But while Earth’s atmosphere has warmed in recent decades, the new study shows a surprising trend in the tropical ocean. The authors looked at temperatures at the surface of the ocean recorded by ship-based measurements and ocean buoys from 1979 to 2000.

The Pacific Ocean off South America has actually cooled slightly, along with ocean regions farther south. Meanwhile, the western Pacific Ocean and nearby eastern Indian Ocean have warmed more than elsewhere. Neither phenomenon can be explained by the natural cycles simulated by climate models. This suggests that some process missing in current models could be responsible.

The upshot of these changes on either side of the tropical Pacific is that the temperature difference between the eastern and western Pacific has grown, surface winds blowing toward Indonesia have strengthened, and people are experiencing conditions typical of La Niña winters.

The study focuses on temperature patterns at the ocean’s surface. Thirty years of data is too short to study the frequency of El Niño and La Niña events.

“The climate models are still getting reasonable answers for the average warming, but there’s something about the regional variation, the spatial pattern of warming in the tropical oceans, that is off,” Wills said.

Full article here.
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From the study: Plain Language Summary

Regional climate change depends not only on the magnitude of global warming, but also on the spatial pattern of warming. We show that the spatial pattern of observed surface temperature changes since 1979 is highly unusual, and many aspects of it cannot be reproduced in current climate models, even when accounting for the influence of natural variability. We find a particularly large discrepancy in the rate of warming within the western Pacific Ocean and eastern Indian Ocean, which suggests that models have systematic biases in the response of sea-surface temperature patterns to anthropogenic forcing, because the contribution of natural variability to multi-decadal trends is thought to be relatively small in this region. Our work raises the possibility that the recent trends toward more La-Niña-like conditions may be partly a response to anthropogenic forcing, even though most existing climate model and paleoclimate evidence suggests that trends will eventually reverse toward more El-Niño-like conditions, with an associated shift in regional climate trends.