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Steve Drake's avatar

In Kevin’s doc a couple of times he uses language that tends to confuse people on both sides of the climate change issue. For instance, “ Climate change is brought on by human activities, most notably burning of fossil fuels putting increasing amounts of carbon dioxide into the atmosphere.” It should say, “Accelerated climate change……”. Too often, in the general public, the misleading “Climate change” causes unnecessary confusion and polarizes the issue.

His article overall is VERY interesting, but reliable sources should be more careful with the wording to avoid confusion and division in the general public.

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Dennis Horne's avatar

Human activity - producing and burning fossil fuels, agriculture - is responsible for more 100% of the present global warming (aerosols lower the temperature). Immediately prior to industrialisation Earth was cooling a fraction of a degree per thousand years.

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Bruce Gelin's avatar

This brings to mind the theories of ten or so years ago that no, carbon dioxide has nothing to do with global warming, it’s all due to galactic cosmic rays striking clouds and creating nucleation sites for aerosols ... long since refuted but probably still around as one of many zombie theories deniers cling to. The current paper gives a great summary of the true contributions from various sources.

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Thomas L. Hutcheson's avatar

A useful "explainer/" debunker of the idea that water vapor is an explanation alternative to CO2 accumulation of climate change.

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Dennis Horne's avatar

Yes every climate denier pontificating on the subject knows water vapour is a powerful GHG, but how much WV would there be if Earth were at -18C - the temperature its distance from the Sun would indicate.

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LT3's avatar

I am puzzled why people cannot see that commercial aviation is the driver of Global Warming. Currently there is 95+ billion gallons of water vapor equivalency being exhausted into the Tropopause / Lower Stratospheric boundary. And this feed has been increasing since the late 60's and perfectly explains why the climate diverged from the Solar trend starting in the mid 70's. My models indicate that if humanity stopped emitting water vapor into the stratosphere, Earth's climate would cool 0.9C within 12 months. Co2 is irrelevant, until the aviation exhaust is removed from the equation. This postulation has been proven by Trumps no fly during the pandemic, in which cut aviation in activity in half for a 12 month period and the climate cooled rapidly (0.35C in 6 months) and caused a triple dip La-Nina. The HT volcano erupted shortly thereafter and more than replaced the water vapor missing from aviation and took the world new record temperatures, and we are still living under elevated Stratospheric water vapor levels.

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LivingWithEntropy's avatar

Thank you Dr's. Dessler and Trenberth. I especially appreciated seeing the "positive feedback loop" and reading your discussion.

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Dennis Horne's avatar

Whatever the contribution to Earth's temperature CO2 makes, and climate deniers like Judith Curry delights her followers by saying it's only 25%, the simple fact is adding CO2 to the atmosphere causes warming.

When CO2 is added, the level CO2 molecules radiate energy to space rises, where the air is cooler, so there is less cooling (radiation related to fourth power temperature, Stefan-Boltzmann), so Earth warms until a steady state is regained.

Even on a dry planet there would be significant warming.

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Kevin Hester's avatar

The water vapour feedback loop has been grossly underestimated, like the other 6 dozen feedback loops we've triggered.

https://kevinhester.live/2016/06/07/for-every-1-degree-c-we-warm-the-planet-we-will-see-7-more-moisture-in-the-atmosphere/

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Dennis Horne's avatar

Your name rings a bell. Did you bring Guy McPherson to NZ? Your science is wrong but our biology might doom us.

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Ian Walker's avatar

Ah yes, the role of fugacity, a funny term, and much misunderstood. And then we have the difference between water in gaseous form, and water in a mist form, and all of them near various critical points, depending on micro-climate and weather. Not hard at all :( ...

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Joel Huberman's avatar

Does this mean that regions experiencing high humidity (ground level) are also experiencing enhanced greenhouse warming?

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Andrew Dessler's avatar

Not really. Water vapor near the surface doesn't trap much heat; it's really water vapor in the upper atmosphere (where it's cold) that traps the heat.

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LT3's avatar

Of course it does, high humidity regions (the tropics) do not allow radiational cooling as quickly as low humidity (the desert).

There really is no debate on this fact, that is meteorology 101.

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