Sentences with phrase «as water vapor feedback»

Indirectly, human activity that increases global temperatures will increase water vapor concentrations, a process known as water vapor feedback.

There is nothing in the climate models that says that the positive feedbacks such as the water vapor feedback and the ice albedo feedback, etc. operate only for CO2 warming and not on natural warming.

They most certainly don't cancel one another as the water vapor feedback is much larger and the cloud feedback either adds or is small to allow for measured values of 2 C per doubling.

First, for changing just CO2 forcing (or CH4, etc, or for a non-GHE forcing, such as a change in incident solar radiation, volcanic aerosols, etc.), there will be other GHE radiative «forcings» (feedbacks, though in the context of measuring their radiative effect, they can be described as having radiative forcings of x W / m2 per change in surface T), such as water vapor feedback, LW cloud feedback, and also, because GHE depends on the vertical temperature distribution, the lapse rate feedback (this generally refers to the tropospheric lapse rate, though changes in the position of the tropopause and changes in the stratospheric temperature could also be considered lapse - rate feedbacks for forcing at TOA; forcing at the tropopause with stratospheric adjustment takes some of that into account; sensitivity to forcing at the tropopause with stratospheric adjustment will generally be different from sensitivity to forcing without stratospheric adjustment and both will generally be different from forcing at TOA before stratospheric adjustment; forcing at TOA after stratospehric adjustment is identical to forcing at the tropopause after stratospheric adjustment).

The atmosphere and surface might very well heat up from enhanced GHE, but as soon as water vapor feedback kicks in it will actually act as both a positive and a negative feedback.

Not exact matches

The conclusion that limiting CO2 below 450 ppm will prevent warming beyond two degrees C is based on a conservative definition of climate sensitivity that considers only the so - called fast feedbacks in the climate system, such as changes in clouds, water vapor and melting sea ice.

The theory of dangerous climate change is based not just on carbon dioxide warming but on positive and negative feedback effects from water vapor and phenomena such as clouds and airborne aerosols from coal burning.

While the ECS factors in such «fast» feedback effects as changes in water vapor — water itself is a greenhouse gas, and saturates warm air better than cold — they argued that slow feedbacks, such as changes in ice sheets and vegetation, should also be considered.

Sure, there might be a few papers that take climate sensitivity as a given and somehow try to draw conclusions about the impact on the climate from that... But, I hardly think that these are swamping the number of papers trying to determine what the climate sensitivity is, studying if the water vapor feedback is working as expected, etc., etc..

However, this climate sensitivity includes only the effects of fast feedbacks of the climate system, such as water vapor, clouds, aerosols, and sea ice.

[1] CO2 absorbs IR, is the main GHG, human emissions are increasing its concentration in the atmosphere, raising temperatures globally; the second GHG, water vapor, exists in equilibrium with water / ice, would precipitate out if not for the CO2, so acts as a feedback; since the oceans cover so much of the planet, water is a large positive feedback; melting snow and ice as the atmosphere warms decreases albedo, another positive feedback, biased toward the poles, which gives larger polar warming than the global average; decreasing the temperature gradient from the equator to the poles is reducing the driving forces for the jetstream; the jetstream's meanders are increasing in amplitude and slowing, just like the lower Missippi River where its driving gradient decreases; the larger slower meanders increase the amplitude and duration of blocking highs, increasing drought and extreme temperatures — and 30,000 + Europeans and 5,000 plus Russians die, and the US corn crop, Russian wheat crop, and Aussie wildland fire protection fails — or extreme rainfall floods the US, France, Pakistan, Thailand (driving up prices for disk drives — hows that for unexpected adverse impacts from AGW?)

Specific humidity content of the air has increased, as expected as part of the conventional water vapor feedback, but in fact relative humidity also increased between 1950 and 1990, indicating a stronger water vapor feedback than given by the conventional assumption of fixed relative humidity.

Water vapor as a stabilizing (negative) feedback — what happens to water content as temperature goeWater vapor as a stabilizing (negative) feedback — what happens to water content as temperature goewater content as temperature goes up?

«It is now widely known that the water vapor feedback in general circulation models (GCMs) is close to that which would result from a climate ‐ invariant distribution of relative humidity [Soden and Held, 2006], as long anticipated before the advent of such models [e.g., Arrhenius, 1896; Manabe and Wetherald, 1967].»

If the CO2 rise is a carbon cycle feedback, this is still perfectly compatible with its role as a radiative agent and can thus «trigger» the traditional feedbacks that determine sensitivity (like water vapor, lapse rate, etc).

In Spencer and Braswell (2008), and to an even greater extent in his blog article, Spencer tries to introduce the rather peculiar notion of «internal radiative forcing» as distinct from cloud or water vapor feedback.

Since Milankovitch factors are excluded as small, BUT they do exist and by ignoring them you are introducing an increasing underestimation of the incoming solar radiation (& its impact on solar irradiance and on water vapor etc feedbacks), then why is there not an uncertainty estimate for this or better yet an actual estimate of what the under estimation is?

A small correction: Lindzen's «Iris» speculation is not the same as his earlier proposal that water vapor should have a zero or negative feedback.

(PS regarding Venus — as I have understood it, a runaway water vapor feedback would have occured when solar heating increasing to become greater than a limiting OLR value (Simpson - Kombayashi - Ingersoll limit — see http://chriscolose.wordpress.com/2010/08/23/climate-feedbacks-part-1/ — although I should add that at more «moderate» temperatures (warmer than today), stratospheric H2O increases to a point where H escape to space becomes a significant H2O sink — if that stage worked fast enough relative to solar brightening, a runaway H2O case could be prevented, and it would be a dry (er) heat.

(ie all these things are important, but would be minor contributors (so far as I know) to climate feedbacks, relative to the Planck response, water vapor, snow, ice, lapse rate, biological stuff, etc..)

That doens» t affect the equilibrium increase in the upward flux at TRPP in response, though it may change how much of that is absorbed by the stratosphere (perhaps a reduction due to shielding of water vapor and CO2 wings in the stratosphere by increased tropospheric water vapor (as it would by an increase in clouds, particularly higher clouds)-- PS feedbacks also change the baseline spectral flux in the vicinity of the CO2 band.

Positing that there have been any times with zero volcanic aerosols is almost as ludicrous as positing there is no water vapor feedback; neither compares with trying to use them as the basis for a long winded attempt at justification for a wished for «safe» climate sensitivity.

But then there's feedbacks within the stratosphere (water vapor), which would increase the stratospheric heating by upward radiation from below, as well as add some feedback to the downward flux at TRPP that the upward flux at TRPP would have to respond to via warming below TRPP.

Perhaps it's worth mentioning that other feedbacks can come into play, too, such as water vapor and albedo changes.

Warming must occur below the tropopause to increase the net LW flux out of the tropopause to balance the tropopause - level forcing; there is some feedback at that point as the stratosphere is «forced» by the fraction of that increase which it absorbs, and a fraction of that is transfered back to the tropopause level — for an optically thick stratosphere that could be significant, but I think it may be minor for the Earth as it is (while CO2 optical thickness of the stratosphere alone is large near the center of the band, most of the wavelengths in which the stratosphere is not transparent have a more moderate optical thickness on the order of 1 (mainly from stratospheric water vapor; stratospheric ozone makes a contribution over a narrow wavelength band, reaching somewhat larger optical thickness than stratospheric water vapor)(in the limit of an optically thin stratosphere at most wavelengths where the stratosphere is not transparent, changes in the net flux out of the stratosphere caused by stratospheric warming or cooling will tend to be evenly split between upward at TOA and downward at the tropopause; with greater optically thickness over a larger fraction of optically - significant wavelengths, the distribution of warming or cooling within the stratosphere will affect how such a change is distributed, and it would even be possible for stratospheric adjustment to have opposite effects on the downward flux at the tropopause and the upward flux at TOA).

If a doubling of CO2 resulted in a temperature increase of approximately 1 K before any non-Planck feedbacks (before water vapor, etc.), then assuming the same climate sensitivity to the total GHE, removing the whole GHE would result in about a (setting the TOA / tropopause distinction aside, as it is relatively small relative to the 155 W / m2 value) 155/3.7 * 1 K ~ = 42 K. Which is a bit more than 32 or 33 K, though I'm not surprised by the difference.

16 (DBB) If more water vapor leads to more precipitation then water vapor will act as a negative feedback on rising global temperature.

Re 9 wili — I know of a paper suggesting, as I recall, that enhanced «backradiation» (downward radiation reaching the surface emitted by the air / clouds) contributed more to Arctic amplification specifically in the cold part of the year (just to be clear, backradiation should generally increase with any warming (aside from greenhouse feedbacks) and more so with a warming due to an increase in the greenhouse effect (including feedbacks like water vapor and, if positive, clouds, though regional changes in water vapor and clouds can go against the global trend); otherwise it was always my understanding that the albedo feedback was key (while sea ice decreases so far have been more a summer phenomenon (when it would be warmer to begin with), the heat capacity of the sea prevents much temperature response, but there is a greater build up of heat from the albedo feedback, and this is released in the cold part of the year when ice forms later or would have formed or would have been thicker; the seasonal effect of reduced winter snow cover decreasing at those latitudes which still recieve sunlight in the winter would not be so delayed).

If C02 is the largest single contributing factor to the Greenhouse Effect (because supposedly water vapor is only involved as a feedback to primary chemistry involving C02 itself), and C02 lags temperature increases (as has been stated on this very blog), how has the Earth ever returned to colder glacial conditions following periods of warming?

While the amounts and distribution of water vapor and clouds are feedbacks, the intrinsic properties are «externally - imposed» by the physics, as is the case with snow and ice, etc..

Obviously, sensitivity to radiative forcing of greenhouse gases (not water vapor, but CO2 and CH4) can't include feedbacks of those same gases — those are defined as forcings in such a sensitivity.

If CO2 in the Anthropocene atmosphere contributes to re-vegetating currently arid areas as it did post-LGM, we should expect an even greater warming feedback from CO2 than is assumed from water vapor and albedo feedbacks, due to decreased global dust - induced albedo and increased water vapor from transpiration over increased vegetated area.

Is less poleward transport of heat by the Gulf Stream as the AMOC weakens a positive feedback for global warming, since that energy will escape more slowly in the humid (higher water vapor GHG effect) tropics than near the poles?

35, L20704, doi: 10.1029 / 2008GL035333, 2008], due to Andrew Dessler and his colleagues, who (as you would know) used the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite to show that the water - vapor feedback is strongly positive, tending to double the initial warming due to CO2 itself.

Lindzen also suggested that water vapor would act as a negative feedback on global warming because the upper troposphere would dry out as it warmed (which also fits the «sky will open up» ideas) but the fact is that the troposphere has gotten wetter.

So does the warming of the ocean, or for that matter, even the water vapor feedback as the increasing partial pressure water vapor is both a response to higher temperatures and a cause of higher temperatures — but can raise temperatures only against the thermal inertia of the ocean.

Physically, the Stefan - Boltzmann feedback becomes more negative and the water vapor feedback becomes less positive as the temperature increases.»

I think it's more a matter of the physics of the situation, and the sky is just too big a lab and the experiment still ongoing to get exact results and there are these pesky «internal» feedbacks — such as water vapor and clouds.

Skeptics also see CO2 as increasing water vapor, but they see this water vapor acting as a net negative feedback.

You have mentioned a MGT feedback loop of diminishing water vapor as the only thing that explains the hiatus well but it could also occur with increasing water vapor as clouds might reflect more sunlight back restoring the new system to its temperature mean.

This acts as a positive feedback on the surface warming, because water vapor itself is a powerful greenhouse gas that, like CO2, absorbs and re-emits longwave radiation back to the surface.

Disputes within climate science concern the nature and magnitude of feedback processes involving clouds and water vapor, uncertainties about the rate at which the oceans take up heat and carbon dioxide, the effects of air pollution, and the nature and importance of climate change effects such as rising sea level, increasing acidity of the ocean, and the incidence of weather hazards such as floods, droughts, storms, and heat waves.

I certainly never said individual positive feedbacks don't exist, and even mentioned some related to climate, such as ice albedo and increases in water vapor in air.

It appears to me that the new «scientific evidence» is suggesting that water vapor feedback is not as strong as had been estimated by the models previously and that net cloud feedback may be neutral to slightly negative, rather than strongly positive, as predicted previously by the models.

The supposed water vapor amplification mechanism will simply accelerate the water cycle slightly and produce little actual temperature rise, certainly less than the 1 C rise touted as a no - feedback case.

Niche Modelling concludes from the Leviticus data that net total global radiative feedback from water vapor, etc. is negative, rather than strongly positive, as estimated by the models cited in IPCC AR4.

manacker December 19, 2012 at 8:00 pm said:» It appears to me that the new «scientific evidence» is suggesting that water vapor feedback is not as strong as had been estimated by the models previously and that net cloud feedback may be neutral to slightly negative, rather than strongly positive, as predicted previously by the models»

Cloud feedback for example is pushed as being negative, and some also attack the idea of water vapor feedback being positive too.

A substantial reduction in water vapor (shown below, from Lacis et al (2010) as well as increase in the surface albedo are important feedbacks here, showing that removing the non-condensing greenhouse gases (mostly CO2) in the atmosphere can collapse nearly the entire terrestrial greenhouse effect.

There is much discussion as to the value of the climate sensitivity, which swirls around whether there is net positive or negative feedback from things like clouds and water vapor.