Sentences with phrase «clouds as a positive feedback»

They seem to believe that CO2 interacts with H2O in a way that multiplies its effect, and that may tie into their modeling of clouds as positive feedback.

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.

As I understand it the issue of whether the feedback of clouds is positive or negative has nothing whatsoever to do with the contribution clouds make to the earth's albedo.

Simon said:» As I understand it the issue of whether the feedback of clouds is positive or negative has nothing whatsoever to do with the contribution clouds make to the earth's albedo.»

As far as I know all the GCM's assume positive cloud feedbacks to get to some of the higher temperature increaseAs far as I know all the GCM's assume positive cloud feedbacks to get to some of the higher temperature increaseas I know all the GCM's assume positive cloud feedbacks to get to some of the higher temperature increases.

Gavin has already pointed out that ceteris probably ain't paribus, as there could be negative feedbacks due to clouds that diminish the positive albedo feedbacks.

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).

I think it is not fair to spin these findings in a way that suggests that overall there would be positive feedback in such a situation, as proposed by Brian Dodge («high clouds may give a positive feedback»).

-- These storms should penetrate higher as climate warms according to the models, a positive feedback, and satellite data looking at cloud height changes over El Nino time scales show something similar and show the models getting that about right also, for physical reasons we think we understand

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.

All the evidence says there is probably a negative cloud feedback, not positive as AR5 asserts.

As the total cloud cover increases, the first effect acts to reduce the warming (a negative feedback) while the second effect acts to increase it (positive feedback).

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.

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.

I personally think IPCC will lose less by openly conceding that clouds have always been «the largest source of uncertainty» and that it now appears that some of tis «uncertainty» is being cleared up, with the models no longer predicting a net positive cloud feedback as before.

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.

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.

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.

Callendar implicitly discounted the arguments for substantial positive feedbacks on initial forcing that characterize subsequent GCMs, observing the nagative feedback from clouds as follows:

More water vapour means also more clouds, which in the models are used as positive feedback.

The idea that low solar states will increase cloud cover is irrational as that amounts to a large positive feedback.

Re: «atmospheric water vapor acts as feedback magnifier» How do you quantify and validate the global magnitude of impacts (INCLUDING CLOUDS) or even whether they are positive or negative?

It's not looking good for strongly positive WV and cloud feedbacks (as predicted by the IPCC AR4 models), BBD.

It's not looking good for strongly positive WV and cloud feedbacks (as predicted by the IPCC AR4 models)

Models assume that relative humidity will stay the same over the tropics as the world warms, that clouds are a positive feedback and not a negative one, and that cloud changes are a feedback and not a forcing in their own right.

A slight change of ocean temperature (after a delay caused by the high specific heat of water, the annual mixing of thermocline waters with deeper waters in storms) ensures that rising CO2 reduces infrared absorbing H2O vapour while slightly increasing cloud cover (thus Earth's albedo), as evidenced by the fact that the NOAA data from 1948 - 2008 shows a fall in global humidity (not the positive feedback rise presumed by NASA's models!)

Basically, Dr Ferenc Miskolczi's life as a NASA climate research scientist was made hell because he discovered that the extra water vapour being evaporated is not having a positive - feedback (increasing the CO2 warming effect by absorbing more infrared from the sun), instead it is going into increased cloud cover, which reflects incoming sunlight back to space.

Spencer & Braswell (2008) found: «we obtain positive cloud feedback biases in the range -0.3 to -0.8 Wm ^ -2 K ^ -1... our results suggest the possibility of an even larger discrepancy between models and observations than is currently realized» See Spencer's discussion on Foster's comments «As can be seen, most models exhibit large biases — as much as 50 deAs can be seen, most models exhibit large biases — as much as 50 deas much as 50 deas 50 deg.

«He also * claims * clouds have negative feedback, completely neglecting studies that show clouds to have both negative and positive feedback» he does indeed state that clouds can act as a positive and negative feedback, but he claims that he believes based upon his own observations that mostly clouds act as a negative feedback, might I also say that this observation is also made by Professor.

Do you feel equally as comfortable to argue, paleosensitivity = 2 - 4.5 K Therefore, the net cloud feedback is positive If no, then you must admit that it would be hard to test a net negative cloud feedback against paleo data without having any models available that include such a feedback.

As we both know, physical observations of CERES satellites since AR4 was published (Spencer + Braswell) have shown that the net cloud feedback over the tropics is strongly negative, rather than positive, as assumed by IPCAs we both know, physical observations of CERES satellites since AR4 was published (Spencer + Braswell) have shown that the net cloud feedback over the tropics is strongly negative, rather than positive, as assumed by IPCas assumed by IPCC.

This doesn't preclude a revolutionary discovery that reverses the developing understanding of cloud feedbacks as positive, not negative.

If these new findings can not be refuted, it appears that the net cloud feedback is very likely to be strongly negative rather than positive, as assumed by the IPCC models.

Spencer + Braswell showed, based on CERES observations, that the net feedback from clouds with warming temperature over the tropics was negative, instead of positive as estimated earlier by the IPCC models while conceding «cloud feedbacks remain the largest source of uncertainty»

If cloud feedback is positive and clouds are decreasing as a result of GHG forced warming — people probably ought to pay a bit more attention to the warnings from Hansen.

Cloud formation not only acts as a positive feedback but as negative feedbacks as well.

This could perhaps be the identification of cyclical patterns in the temperature records that explain recent warming, the GCR experiments, an unkown feedback (or the full understanding of clouds, removing their possibility as a positive feedback as described by thr IPCC) or something else.

Notable among these are Wentz et al. (2007), who suggest that the IPCC has failed to allow for two - thirds of the cooling effect of evaporation in its evaluation of the water vapor - feedback; and Spencer (2007), who points out that the cloud - albedo feedback, regarded by the IPCC as second in magnitude only to the water - vapor feedback, should in fact be negative rather than strongly positive.

After the publication of AR4, a study by Spencer et al., using physical observations from CERES satellites over the tropics, showed that the net feedback from clouds is strongly negative, rather than positive, as assumed by the climate models.

I would say that all the papers cited by IPCC as evidence for the assumed strongly positive feedback from clouds provide even less «robust observational evidence that clouds provide a net positive feedback».

Using the estimate of Wyant, this would point to a 2xCO2 climate sensitivity of 1.5 C (rather than 3.2 C, as estimated by IPCC using the strongly positive net feedback assumption for clouds).

But I also believe it is reasonable to conclude, based on all the recent data out there, that the net feedback from clouds (LW+SW) is very likely to be negative (rather than strongly positive, as assumed by all the models cited by IPCC), and that the 2xCO2 climate sensitivity is very likely to be below 1.5 C (probably closer to 1C).

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