Global warming ISN'T slowing down: Anomalies in climate models can be explained by El Niño, researchers claim
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One of the major arguments of those who deny climate change is that, over the last 15 years, global warming has been slowing down.
Research, now claims, has shown that this is consistent with models of climate change and can be explained by the weather phenomenons El Niño and La Niña.
By reviewing data from 1950 to 2013 scientists found models under and overestimated warming trends when El Niño and La Niña respectively were taken into account.
A study claims temperature changes in the Pacific can help explain over and underestimates in climate models. The study shows these trends are consistent with El Nino and La Nina. Shown is an anomaly image from 2007, during La Niña, where strong bands of blue (cool) water and red (warm) water are shown
The study in Nature Climate Change shows that El Niño and La Niña could explain discrepancies in climate models.
WHAT ARE EL NINO AND LA NINA?
El Niño and La Niña are opposite phases of what is known as the El Niño/Southern Oscillation (Enso) cycle, says the NOAA.
The Enso cycle is a scientific term that describes the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific (approximately between the International Date Line and 120 degrees West).
La Niña is sometimes referred to as the cold phase of Enso and El Niño as the warm phase.
These deviations from normal surface temperatures can have large-scale impacts not only on ocean processes, but also on global weather and climate.
El Niño and La Niña episodes typically last nine to 12 months, but some prolonged events may last for years.
They often begin to form between June and August, reach peak strength between December and April, and then decay between May and July of the following year.
While their periodicity can be quite irregular, El Niño and La Niña events occur about every three to five years.
Typically, El Niño occurs more frequently than La Niña.
The global warming slowdown over the last 15 years had raised questions about the accuracy and credibility of climate models.
But now experts say that the models are accurate when natural weather systems are considered.
The paper was led by climatologist Dr James Risbey, based in Australia.
Risbey and colleagues investigated the ability of present models to reproduce temperature observations for the past 15-year period.
Over time weather patterns like El Niño and La Niña cancel each other out, but in the short term they can skew climate data and make models seem inaccurate.
The findings of the research were that periods of global warming increasing or decreasing were consistent with temperature changes caused by El Niño and La Niña.
The authors studied a collection of 18 global climate models that are able to represent El Niño/Southern Oscillation (Esno) through sea surface temperatures.
Of these they identify a subset which accurately represent the current state of El Niño/Southern Oscillation through comparison with observations.
By reviewing data from 1950 to 2013 scientists found models under and overestimated warming trends when El Niño and La Nina respectively were taken into account. Shown is Laguna Blanca in Chile, a dry lakebed flooded by El Niño storms. The storms restarted the growth of polygonal salt formations
The selected models are able to provide more accurate estimations of temperature trends over the past 15 years as well as the recent spatial trends in Pacific Ocean surface temperature.
'The question of how climate model projections have tracked the actual evolution of global mean surface air temperature is important in establishing the credibility of their projections,' the researchers write.
'Some studies and the IPCC Fifth Assessment Report suggest that the recent 15-year period (1998–2012) provides evidence that models are overestimating current temperature evolution.
'Such comparisons are not evidence against model trends because they represent only one realisation where the decadal natural variability component of the model climate is generally not in phase with observations.'
The scientists go on to say that climate models have actually been successful in estimating Pacific trend patterns with regards to El Nino and La Niña with surprising accuracy, albeit by accident.
The research shows how the climate in the short term can be affected by weather patterns like El Niño and La Niña, but it does not disprove man-made climate change is occurring.
The predictions of weather patterns by climate models isn't perfect, as on occasion it has been a few years out, but nonetheless the anomalies in the models seem not to have been explained.
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