Debunk of the Week... El Niño/La Niña Update... Toon of the Week... Coming Soon on SkS... Poster of the Week... SkS Week in Review...
CLAIM: "Man-made Climate Change Doesn't Exist In Practice... During the last hundred years the temperature is increased [sic] about 0.1°C because of carbon dioxide. The human contribution was about 0.01°C."
Some news outlets are publishing articles stating that this claim is based on a new study. In reality, there is no new published study. The claim comes from a six-page document uploaded to arXiv, a website traditionally used by scientists to make manuscripts available before publication. This means that this article has not been peer-reviewed, so there is no guarantee to its credibility.
If the blogs that covered this as a new study had contacted independent scientists for insight, instead of accepting this short document as revolutionary science, they would have found that it does not have any scientific credibility.
As the scientists who examined this claim explained, the document relies on circular reasoning to claim that cloud cover and relative humidity have caused the change in global temperature, and ignores many additional factors affecting global temperature—including aerosol pollution, volcanic eruptions, and natural ocean oscillations. The published, peer-reviewed scientific research on this topic clearly shows that human activities are responsible for climate change.
Non-peer-reviewed manuscript falsely claims natural cloud changes can explain global warming, Claims Review Edited by Scott Johnson, Climate Feedback, July 12, 2019
El Niño is hanging on by its fingernails, but forecasters predict this event will wind down within the next couple of months. It’s likely that the temperature of the tropical Pacific Ocean surface will return to near-average soon, qualifying for “ENSO-neutral” conditions. Neutral conditions are favored to remain through the fall and winter.
Not dead yet
The June Niño3.4 index, our primary ENSO measurement, was 0.6°C above the long-term average, just above the El Niño threshold of 0.5°C. There is some evidence that the atmosphere over the central Pacific is still responding to that extra heating, as a bit more clouds and rain than average were present in June.
The Southern Oscillation Index and Equatorial Southern Oscillation Index were both slightly negative in June, also indicating some continuation of the weakened Walker circulation we expect to see with El Niño. But the upper-level and near-surface winds over the equatorial Pacific, another component of the Walker circulation, were close to average during June. All in all, El Niño is still present, but just barely.
That’s no ordinary rabbit
As frequent readers of this blog will know, we closely monitor the temperature of the water under the surface of the tropical Pacific. This can tell us if there is a source of warmer-than-average water to supply the surface, continuing to fuel El Niño, or not. In early June, there was a small downwelling Kelvin wave of warmer waters moving eastward under the surface of the Pacific, but this wave has dissipated recently.
Overall, the heat content in the top 300 meters of the equatorial Pacific is just about average now, in early July. This is one of the major factors in our forecast for a return to near-average surface temperatures and neutral ENSO conditions. Once the surface temperatures return to average, and the source of extra heat to the air above the central Pacific is gone, the atmospheric component of El Niño—that weakened Walker circulation—will also return to average.
July 2019 El Niño update: I think I’ll go for a walk by Emily Becker, NOAA's Climate.gov, July 11, 2019
Posted by John Hartz on Sunday, 14 July, 2019
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