Because the NASA-funded researchers say so.
The media release is below.
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Long-term global warming not driven naturally
Study debunks argument that warming is driven by natural factors
DUKE UNIVERSITY
DURHAM, N.C. — By examining how Earth cools itself back down after a period of natural warming, a study by scientists at Duke University and NASA’s Jet Propulsion Laboratory confirms that global temperature does not rise or fall chaotically in the long run. Unless pushed by outside forces, temperature should remain stable.
The new evidence may finally help put the chill on skeptics’ belief that long-term global warming occurs in an unpredictable manner, independently of external drivers such as human impacts.
“This underscores that large, sustained changes in global temperature like those observed over the last century require drivers such as increased greenhouse gas concentrations,” said lead author Patrick Brown, a PhD student at Duke’s Nicholas School of the Environment. Natural climate cycles alone are insufficient to explain such changes, he said.
Brown and his colleagues published their peer-reviewed research Feb. 1 in the Journal of Climate.
Using global climate models and NASA satellite observations of Earth’s energy budget from the last 15 years, the study finds that a warming Earth is able to restore its temperature equilibrium through complex and seemingly paradoxical changes in the atmosphere and the way radiative heat is transported.
Scientists have long attributed this stabilization to a phenomenon known as the Planck Response, a large increase in infrared energy that Earth emits as it warms. Acting as a safety valve of sorts, this response creates a negative radiative feedback that allows more of the accumulating heat to be released into space through the top of the atmosphere.
The new Duke-NASA research, however, shows it’s not as simple as that.
“Our analysis confirmed that the Planck Response plays a dominant role in restoring global temperature stability, but to our surprise we found that it tends to be overwhelmed locally by heat-trapping positive energy feedbacks related to changes in clouds, water vapor, and snow and ice,” Brown said. “This initially suggested that the climate system might be able to create large, sustained changes in temperature all by itself.”
A more detailed investigation of the satellite observations and climate models helped the researchers finally reconcile what was happening globally versus locally.
“While global temperature tends to be stable due to the Planck Response, there are other important, previously less appreciated, mechanisms at work too,” said Wenhong Li, assistant professor of climate at Duke. These other mechanisms include a net release of energy over regions that are cooler during a natural, unforced warming event. And there can be a transport of energy from the tropical Pacific to continental and polar regions where the Planck Response overwhelms positive, heat-trapping local effects.
“This emphasizes the importance of large-scale energy transport and atmospheric circulation changes in restoring Earth’s global temperature equilibrium after a natural, unforced warming event,” Li said.
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Jonathan H. Jiang and Hui Su of NASA’s Jet Propulsion Laboratory, managed by the California Institute of Technology, co-authored the new study.
Funding came from the National Science Foundation (#AGS-1147608) as well as the NASA ROSES13-NDOA and ROSES13-NEWS programs.
CITATION: “Unforced Surface Air Temperature Variability and Its Contrasting Relationship with the Atmospheric TOA Energy Flux at Local and Global Spatial Scales,” Patrick T. Brown, Wenhong Li, Jonathan H. Jiang, Hui Su, Feb. 1, 2016, Journal of Climate; DOI: http://dx.doi.org/10.1175/JCLI-D-15-0384.1
If we know the models are terribly flawed, and better than 95% of them have been defeated by the data that NASA ITSELF espouses, why would you use them to “study” past climate changes? Their hindcasting ability is as useless as their forecasting ability, and yet we merrily go forward trusting them more than we trust the actual DATA.
“The new evidence may finally help put the chill on skeptics’ belief that long-term global warming occurs in an unpredictable manner, independently of external drivers such as human impacts.”
The closest I have seen to “unpredictable” is more “we do not know how to predict.” And is our sun not external to our planet?
I am willing to believe humans can affect climate, possibly even globally, but not to the extent postulated by most past or current models. There have certainly been large-scale changes before (compare North Africa of the First Egyptian dynasty with that of the Eighteenth or later. And the models ignore, rather than explain, Medieval Warm and Little Ice Age alike.
Assistant Professor PhD Student MODEL S go figure
Give them a break, folks. These people are desperate to get careers of feeding from the federal tax (or fiat Fed counterfeit money) funded trough started. To do that they have to talk the right talk and tow the party line, you know, then, being able to demonstrate satisfactory success at those, they will be invited to belly up to the publicly funded trough. Fiat money must have fiat physics for support, y’know.
The whole thing really is disgusting, isn’t it. But….. ya know what…..The whole system is wheezing up to death’s doorstep. Truth and reality WILL win.
Ever notice how these folks love all the NASA satellite data, except the ones that tell them the temperature?
“NASA’s Jet Propulsion Laboratory confirms that global temperature does not rise or fall chaotically in the long run.” Apparently NASA never heard of the Younger Dryas when temperatures quickly plunged back to a 900-years cold spell with glacial temperatures.
NASA also ‘debunked’ the threat of frost to O-rings.
When you read an article like that, you wonder exactly how it passed peer review. The only answer I could come up with is the ‘peer review’ must have consisted of a spell checker. I mean, the logic that ice ages occurred naturally, but the warm up after the ice ages is not natural, even before humans made significant impact on the Earth, how does any rational person let that get through peer review.