Sentences with phrase «effects of cloud feedbacks»

If the effects of cloud feedbacks are eliminated, this range is reduced to 1.7 - 2.3 C. 2 Many other feedbacks, particularly those involving chemistry and biology, may also be important.

Therefore when you ask about the general effects of cloud feedbacks on climate, you have moved well beyond the scope of a discussion about aerosol second indirect effects.

But the net effect of cloud feedbacks is less well known.

They usually separate it out as the effect of the cloud feedback on shortwave radiation (i.e., radiation from the sun) and the effect of the cloud feedback on longwave radiation (i.e., radiation from the earth).

Not exact matches

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.

When the CLIMAP data proved to be wrong, and was replaced by more reliable estimates showing a substantial tropical surface temperature drop, Lindzen had to abandon his then - current model and move on to other forms of mischief (first the «cumulus drying» negative water vapor feedback mechanism, since abandoned, and now the «Iris» effect cloud feedback mechanism).

Possible reasons include increased oceanic circulation leading to increased subduction of heat into the ocean, higher than normal levels of stratospheric aerosols due to volcanoes during the past decade, incorrect ozone levels used as input to the models, lower than expected solar output during the last few years, or poorly modeled cloud feedback effects.

This result suggests that models may not yet adequately represent the long - term feedbacks related to ocean circulation, vegetation and associated dust, or the cryosphere, and / or may underestimate the effects of tropical clouds or other short - term feedback processes.»

There was more ice around in the LGM and that changes the weighting of ice - albedo feedback, but also the operation of the cloud feedback since clouds over ice have different effects than clouds over water.

Absent understanding of cloud feedback processes, the best you can really do is mesh it into the definition of the emergent climate sensitivity, but I think probing (at least some of) the uncertainties in effects like this is one of the whole points of these ensemble - based studies.

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

Even if the total effect of clouds has not been nailed down yet, it is obviously a small effect compared to the rest of the forcings and feedbacks in the system.

«By comparing the response of clouds and water vapor to ENSO forcing in nature with that in AMIP simulations by some leading climate models, an earlier evaluation of tropical cloud and water vapor feedbacks has revealed two common biases in the models: (1) an underestimate of the strength of the negative cloud albedo feedback and (2) an overestimate of the positive feedback from the greenhouse effect of water vapor.

He goes so far as to say that the IPCC is biased against «internal radiative forcing,» in favor of treating cloud effects as feedback.

Data from satellite observations «suggest that greenhouse models ignore negative feedback produced by clouds and by water vapor, that diminish the warming effects» of human carbon dioxide emissions.

This result suggests that models may not yet adequately represent the long - term feedbacks related to ocean circulation, vegetation and associated dust, or the cryosphere, and / or may underestimate the effects of tropical clouds or other short - term feedback processes.»

It is my understanding that the uncertainties regarding climate sensitivity to a nominal 2XCO2 forcing is primarily a function of the uncertainties in (1) future atmospheric aerosol concentrations; both sulfate - type (cooling) and black carbon - type (warming), (2) feedbacks associated with aerosol effects on the properties of clouds (e.g. will cloud droplets become more reflective?)

It's possible that CO2 contributes about a.6 C increase in temperature and that the effects of clouds acts as a negative feedback to moderate further increases.

The relative importance of GHG warming and indirect effect and a revised version of the IPCC TAR of the cloud feedback is exactly what I am working on.

# 27 CCPO It's possible that CO2 contributes about a.6 C increase in temperature and that the effects of clouds acts as a negative feedback to moderate further increases.

[Response: These feedbacks are indeed modelled because they depend not on the trace greenhouse gas amounts, but on the variation of seasonal incoming solar radiation and effects like snow cover, water vapour amounts, clouds and the diurnal cycle.

The details of the physics of different forcings (i.e. ozone effects due to solar, snow albedo and cloud effects due to aerosols etc.) do vary the feedbacks slightly differently though.

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).

When the CLIMAP data proved to be wrong, and was replaced by more reliable estimates showing a substantial tropical surface temperature drop, Lindzen had to abandon his then - current model and move on to other forms of mischief (first the «cumulus drying» negative water vapor feedback mechanism, since abandoned, and now the «Iris» effect cloud feedback mechanism).

There will be Regionally / locally and temporal variations; increased temperature and backradiation tend to reduce the diurnal temperature cycle on land, though regional variations in cloud feedbacks and water vapor could cause some regions to have the opposite effect; changes in surface moisture and humidity also changes the amount of convective cooling that can occur for the same temperature distribution.

Cloud feedbacks may be complicated, but a simple rule of thumb that emerges from that complexity is that high clouds exert a strong greenhouse effect and low clouds don't.

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).

This is what I get out of it: the Arctic - ice - albedo situation is more complicated than earlier thought (due to clouds, sun - filled summers, dark winters, etc), but NET EFFECT, the ice loss and all these other related factors (some negative feedbacks) act as a positive feedback and enhance global warming.

Spencer et al (2007) is cited as evidence for the iris effect of Lindzen in order to conclude that the negative feedbacks to the greenhouse effect due to clouds will be substantial.

A Lacis: You don't seem to appreciate the fact that water vapor and clouds are feedback effects, which means that the water vapor and cloud distributions depend directly on the local meteorological conditions, and are therefore constrained by the temperature dependence of the Clausius - Clapeyron relation.

Because the net effect of clouds — whilst still one of the major sources of uncertainty in relation to climate sensitivity is likely a positive feedback

You don't seem to appreciate the fact that water vapor and clouds are feedback effects, which means that the water vapor and cloud distributions depend directly on the local meteorological conditions, and are therefore constrained by the temperature dependence of the Clausius - Clapeyron relation.

Spencer + Braswell have shown that over the tropics on a shorter - term basis, the net overall feedback from clouds with warming is negative; this is largely due to an increase in reflection of incoming radiation by increased clouds with a smaller effect from the reduction of energy trapping high altitude clouds, which slow down outgoing radiation by absorbing and re-radiating energy.

This «climate sensitivity» not only depends on the direct effect of the GHGs themselves, but also on natural «climate feedback» mechanisms, particularly those due to clouds, water vapour, and snow cover.

These models suggest that if the net effect of ocean circulation, water vapour, cloud, and snow feedbacks were zero, the approximate temperature response to a doubling of carbon dioxide from pre-industrial levels would be a 1oC warming.

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.

Cumulus clouds will have the same effect, but more in balance with the positive effects, resulting in less negative net feedback, but with the same result, much lower climate sensitivity than the IPCC would have you believe.I realize that climate sensitivity is not usually discussed as a local phenomenon, but it should be, since it is the integral of all local phenomena.

If, for instance, CO2 concentrations are doubled, then the absorption would increase by 4 W / m2, but once the water vapor and clouds react, the absorption increases by almost 20 W / m2 — demonstrating that (in the GISS climate model, at least) the «feedbacks» are amplifying the effects of the initial radiative forcing from CO2 alone.

Modelers have chosen to compensate their widely varying estimates of climate sensitivity by adopting cloud feedback values countering the effect of climate sensitivity, thus keeping the final estimate of temperature rise due to doubling within limits preset in their minds.

Could tropical cloud feedbacks, or the coupling to ENSO, amplify the effects of low latitude hydrological responses to high - latitude anomalies in these models?

Cloud variations are obviously an important element on a global scale, but the effects of Arctic ice melting are important locally and also a non-trivial fraction of global albedo feedbacks, which are a contributor to total feedback that is smaller than those from water vapor and probably from cloud feedbacks, but not insignifiCloud variations are obviously an important element on a global scale, but the effects of Arctic ice melting are important locally and also a non-trivial fraction of global albedo feedbacks, which are a contributor to total feedback that is smaller than those from water vapor and probably from cloud feedbacks, but not insignificloud feedbacks, but not insignificant.

Its warming effect, however, is simultaneously amplified and dampened by positive and negative feedbacks such as increased water vapor (the most powerful greenhouse gas), reduced albedo, which is a measure of Earth's reflectivity, changes in cloud characteristics, and CO2 exchanges with the ocean and terrestrial ecosystems.

He assumes a feedback of 1.6 for water vapor, 1.3 for clouds, and 1.1 for ice / albedo effects.

''... the warming is only missing if one believes computer models where so - called feedbacks involving water vapor and clouds greatly amplify the small effect of CO2.»

The shortwave effect of low clouds is often discussed in terms of a feedback mechanism, however they show here that the LW effect easily dominates the energy budget.

If not either the CO2 / temp relationship is wrong [I do not think so] or the effect of the CO2 rise is being variably effected by negative feedbacks such as increased cloud formation and albedo thus offsetting the CO2 related temperature rise.

One important feedback, which is thought to approximately double the direct heating effect of carbon dioxide, involves water vapor, clouds and temperature.

However, I am not a «warmista» by any means — we do not know how to properly quantify the albedo of aerosols, including clouds, with their consequent negative feedback effects in any of the climate sensitivity models as yet — and all models in the ensemble used by the «warmistas» are indicating the sensitivities (to atmospheric CO2 increase) are too high, by factors ranging from 2 to 4: which could indicate that climate sensitivity to a doubling of current CO2 concentrations will be of the order of 1 degree C or less outside the equatorial regions (none or very little in the equatorial regions)- i.e. an outcome which will likely be beneficial to all of us.

This led to a nasty scene, when he said I was unable to see what was obvious, ever - accelerating cooling which would lead to a runaway «Neptune Effect» because of mechanisms of positive feedback (his best examples were clouds which collect over the winter solstice — the «in - law» effect — persisting through to mid-February — the «Cupid» effect — and combining forces to wreck the climate for the entire first half of the Effect» because of mechanisms of positive feedback (his best examples were clouds which collect over the winter solstice — the «in - law» effect — persisting through to mid-February — the «Cupid» effect — and combining forces to wreck the climate for the entire first half of the effect — persisting through to mid-February — the «Cupid» effect — and combining forces to wreck the climate for the entire first half of the effect — and combining forces to wreck the climate for the entire first half of the year.)

but this is the full CMIP3 ensemble, so at least the plot is sampling the range of choices regarding if and how indirect effects are represented, what the cloud radiative feedback & sensitivity is, etc. across the modelling community.