Cold air rises—what that means for Earth’s climate

Posted: May 6, 2020 by oldbrew in atmosphere, climate, Clouds, radiative theory, research, weather
Tags: , ,

Tropical beach

Are these researchers proposing a kind of reverse greenhouse effect in the tropics?

Conventional knowledge has it that warm air rises while cold air sinks, says

But a study from the University of California, Davis, found that in the tropical atmosphere, cold air rises due to an overlooked effect—the lightness of water vapor.

This effect helps to stabilize tropical climates and buffer some of the impacts of a warming climate.

The study, published today in the journal Science Advances, is among the first to show the profound implications water vapor buoyancy has on Earth’s climate and energy balance.

“It’s well-known that water vapor is an important greenhouse gas that warms the planet,” said senior author Da Yang, an assistant professor of atmospheric sciences at UC Davis and a joint faculty scientist with Lawrence Berkeley National Laboratory.

“But on the other hand, water vapor has a buoyancy effect which helps release the heat of the atmosphere to space and reduce the degree of warming. Without this lightness of water vapor, the climate warming would be even worse.”

Humid air is lighter than dry air under the same temperature and pressure conditions. This is called the vapor buoyancy effect. This study discovered this effect allows cold, humid air to rise, forming clouds and thunderstorms in Earth’s tropics.

Meanwhile, warm, dry air sinks in clear skies. Earth’s atmosphere then emits more energy to space than it otherwise would without vapor buoyancy.

The study found that the lightness of water vapor increases Earth’s thermal emission by about 1-3 watts per square meter over the tropics. That value compares with the amount of energy captured by doubling carbon dioxide in the atmosphere.

The authors’ calculations further suggest that the radiative effects of vapor buoyancy increase exponentially with climate warming.

Full article here.

Update – new research article published:
The lightness of water vapor helps to stabilize tropical climate
Seth D. Seidel and Da Yang
Science Advances 06 May 2020

Quote from the article:
Here, we offer a different explanation of the tropics’ climate stability by way of a robust clear-sky feedback. The magnitude of this feedback may be estimated with greater certainty than for feedbacks depending on changes in clouds and circulation.
. . .
This paper will show that the lightness of water vapor has a profound impact on Earth’s energy balance and climate stability.

  1. Stephen Richards says:

    I get so sick of these so called science based studies that are nothing more than crafted propaganda

  2. oldbrew says:

    SciTech Daily goes with this headline:

    Cold Air Rises – How Wrong Are Our Global Climate Models?

    *How wrong* 😆
    – – –
    This graphic is from the report:

  3. tallbloke says:

    “The authors’ calculations further suggest that the radiative effects of vapor buoyancy increase exponentially with climate warming.”

    So, a negative feedback to add to all the others then…

  4. hunterson7 says:

    Damp cool air rising is as old as physics.
    That it is being “discovered” in the era of climate madness implied a lot. That climate kooks imply convection has anything to do with the climate (non) emergency is just another bit of evidence of the endless corruption climate extremism yields.
    Next they will “discover” adiabatic cooling….

  5. Zoe Phin says:

    What are they saying?
    Warmed air rises and cools.

    Are they saying ”
    look at that air now! it’s cold, and it’s aloft” ?

    Is that what they are saying? Or is there something actually new here?

  6. oldbrew says:

    Here’s the paper:
    The Incredible Lightness of Water Vapor

    However, the lightness of water vapor has been completely overlooked in the context of climate feedbacks.
    . . .
    We propose that the vapor buoyancy effect can increase Earth’s OLR and help to stabilize Earth’s climate by regulating the atmosphere’s thermal structure.
    . . .
    In warmer climates, the vapor buoyancy effect would become more significant due to increasing water vapor. Therefore, we expect that the radiative effect due to the vapor buoyancy also increases with climate warming.
    This is a negative climate feedback (Fig. 2b). The proposed mechanism relies on ample atmospheric water vapor, so it would be most effective in stabilizing the tropical climate. In principle, this feedback should have been represented by climate models. However, it has not been evaluated or even discussed.
    [bold added]

  7. Paul Vaughan says:

    With discrete shh! UN a long north earn ice margin$ sang high saw dawn lee EU’V-E 88% win-D fall with lunisolar + 27.03 day leftovers ….4s knacks.

  8. Phoenix44 says:

    Seems to me they are saying the climate models overestimate the Greenhouse effect in the Tropics and really overestimate the effect increased CO2 will have in the Tropics.

    Good stuff!

  9. oldbrew says:

    ‘We propose that the vapor buoyancy effect can increase Earth’s OLR’

    Where does that leave the unscientific ‘heat trapping’ they keep claiming is a problem?

    Update – just found this by the same authors:
    The lightness of water vapor helps to stabilize tropical climate
    Seth D. Seidel and Da Yang
    Science Advances 06 May 2020

    Moist air is lighter than dry air at the same temperature, pressure, and volume because the molecular weight of water is less than that of dry air. We call this the vapor buoyancy effect. Although this effect is well documented, its impact on Earth’s climate has been overlooked. Here, we show that the lightness of water vapor helps to stabilize tropical climate by increasing the outgoing longwave radiation (OLR). In the tropical atmosphere, buoyancy is horizontally uniform. Then, the vapor buoyancy in the moist regions must be balanced by warmer temperatures in the dry regions of the tropical atmosphere. These higher temperatures increase tropical OLR. This radiative effect increases with warming, leading to a negative climate feedback. At a near present-day surface temperature, vapor buoyancy is responsible for a radiative effect of 1 W/m2 and a negative climate feedback of about 0.15 W/m2 per kelvin. [bold added]

  10. oldbrew says:

    This paper tests the hypothesis that the vapor buoyancy effect stabilizes Earth’s climate in the tropics. Using 2D CRM simulations, we have demonstrated that the radiative effect of vapor buoyancy is approximately 1 W/m2 in the reference climate, a value comparable to the direct radiative forcing due to doubling atmospheric CO2. Our calculations suggest that this radiative effect exponentially increases with climate warming. This effect results in a negative feedback of around 0.15 W/m2 per kelvin in the reference climate, which is of the same order of magnitude as the net cloud feedback and surface albedo feedback. [bold added]
    – – –
    So even if radiative theories without convection were all in order, the models would still be wrong?

  11. ivan says:

    Interesting that they calculate ‘Results Using a Real-Gas Radiative Transfer Model’. Therefore I question just how reliable are their results.

    It looks more like clutching at straws to keep the UN Church of Climatology rhetoric afloat than real research.

  12. oldbrew says:

    Another point from the second paper:

    ‘The origin and amplitude of the vapor buoyancy feedback depend on the horizontal distributions of temperature and moisture. Understanding the vapor buoyancy feedback, therefore, requires at least two columns or even two dimensions. This is fundamentally different from the conventional explanation of the tropical lapse rate feedback based on a single-column process—the temperature profile (the moist adiabat) is steepening from additional latent heating with warming.’

  13. pochas94 says:

    Consider thunderstorms. The intense upwelling of moisture laden air, often associated with tornadoes, that can actually punch moisture into the stratosphere, the anvil shaped top where the adiabatic cooling causes the moisture to suddenly dump, their dominance along the equator over the oceans where insolation is maximized. They charge the whole atmosphere leading to the Birkeland currents in the Arctic and probably affecting efficiency of precipitation worldwide. They provide a “heat pipe,” that totally bypasses any so-called “Greenhouse Effect.” Water vapor in action.

  14. oldbrew says:

    The abstract of the first paper starts with this:
    The molar mass of water vapor is much less than that of dry air. This makes a moist parcel lighter than a dry parcel of the same temperature and pressure. This effect is referred to as the vapor buoyancy effect and has often been overlooked in climate studies. We propose that the vapor buoyancy effect increases Earth’s outgoing longwave radiation (OLR) and that this negative radiative effect increases with warming, stabilizing Earth’s climate.
    – – –
    Time to stop overlooking it, then.

  15. Ron Clutz says:

    Reading this reminds of a recent analysis of the properties of CMIP6 climate models. AGU publication Causes of Higher Climate Sensitivity in CMIP6 Models by Mark D. Zelinka et al. (2019).

    In that paper the authors say this:
    “The severity of climate change is closely related to how much the Earth warms in response to greenhouse gas increases. Here we find that the temperature response to an abrupt quadrupling of atmospheric carbon dioxide has increased substantially in the latest generation of global climate models. This is primarily because low cloud water content and coverage decrease more strongly with global warming, causing enhanced planetary absorption of sunlight—an amplifying feedback that ultimately results in more warming. Differences in the physical representation of clouds in models drive this enhanced sensitivity relative to the previous generation of models. It is crucial to establish whether the latest models, which presumably represent the climate system better than their predecessors, are also providing a more realistic picture of future climate warming.”

    “Conceptually, this equation states that the TOA energy imbalance can be expressed as the sum of the radiative forcing and the radiative response of the system to a global surface temperature anomaly. The assumption that the radiative damping can be expressed as a product of a time‐invariant and global mean surface temperature anomaly is useful but imperfect (Armour et al., 2013; Ceppi & Gregory, 2019).”

    “ECS therefore depends on the magnitude of the CO2 radiative forcing and on how strongly the climate system radiatively damps planetary warming. A climate system that more effectively radiates thermal energy to space or more strongly reflects sunlight back to space as it warms (larger magnitude urn:x-wiley:grl:media:grl60047:grl60047-math-0007 ) will require less warming to restore planetary energy balance in response to a positive radiative forcing, and vice versa.”

    So it’s all about water and clouds and the degree to which an energy perturbation is amplified or reduced by the hydrological cycle. The models, of course, presume warming from additional GHGs, but the same issue arises regarding solar or oceanic variability.

    Zelinka et al. paper is here:

    My synopsis is here:

    Once again the Good Model INM-CM4-8 is bucking the model builders’ consensus. The new revised INM model has a reduced ECS and it flipped its cloud feedback from positive to negative.The description of improvements made to the INM modules includes how clouds are handled.

  16. oldbrew says:

    ‘This is primarily because low cloud water content and coverage decrease more strongly with global warming’

    But more heat causes more evaporation i.e. more water vapour – over water at least, which is > 70% of the planet’s surface.

  17. oldbrew says:

    MAY 6, 2020
    Decoding the skies: The impact of water vapor on afternoon rainfall

    Understanding the role of water vapor in weather is important because its effects are felt everywhere

  18. Bobby Lynch says:

    “the climate warming would be even worse.”

    Worse than what?