Sentences with phrase «water vapour feedback in»

(2) It made the point (not an original point, but on the other hand one that is not widely known even among the cognoscenti) that water vapour feedback in the global warming story is very largely determined by the response of water vapour in the middle and upper troposphere.

And if the pattern were to continue into the future, one would expect water vapour feedback in the climate system to halve rather than double the temperature rise due to increasing CO2.

Your thermostat proposition means that the water vapour feedback in particular will be less than assumed and will operate at a faster rate than assumed (I might even convert it into a lapse rate discussion).

«Positive Water Vapour Feedback in Climate Models Confirmed by Satellite Data.»

Presumably the water vapour feedback in models is dealt with by determining / estimating / calculating the radiative forcing from water vapour and then making some assumption about the water vapour response to atmospheric warming (e.g. assuming constant relative humidity).

Minschwaner, K., A.E. Dessler, and S. Parnchai, 2006: Multi-model analysis of the water vapour feedback in the tropical upper troposphere.

Hall, A., and S. Manabe, 1999: The role of water vapour feedback in unperturbed climate variability and global warming.

Skeptical Science has covered cloud feedback here, and as an interesting aside, amongst many papers on this subject, Dessler has a new paper on water vapour feedbacks in the Journal of Climate.

Not exact matches

What is certain is that, in the jargon of climate science, water vapour is a feedback, but not a forcing.

First that CO2 is the main climate driver, second that in calculating climate sensitivity the GHE due to water vapour should be added to that of CO2 as a feed back effect and third that the GHE of water vapour is always positive.As to the last point the feedbacks can not be positive otherwise we wouldn't be here to talk about it.

If carbon dioxide melts the Arctic sea - ice the change in water vapour will be catastrophic, because it produces a positve feedback.

The climate sensitivity classically defined is the response of global mean temperature to a forcing once all the «fast feedbacks» have occurred (atmospheric temperatures, clouds, water vapour, winds, snow, sea ice etc.), but before any of the «slow» feedbacks have kicked in (ice sheets, vegetation, carbon cycle etc.).

[Response: CO2 / GHG changes add about 40 % to LGM cooling, water vapour feedback adds about 60 %, so they are comparable in size — and both large!

Both cause temperature change so both will play a role in any future water vapour feedback process that is dependent on temperature.

They got 10 pages in Science, which is a lot, but in it they cover radiation balance, 1D and 3D modelling, climate sensitivity, the main feedbacks (water vapour, lapse rate, clouds, ice - and vegetation albedo); solar and volcanic forcing; the uncertainties of aerosol forcings; and ocean heat uptake.

Recent observational and modelling evidence thus provides strong additional support for the combined water vapour - lapse rate feedback being around the strength found in AOGCMs.

On temperature dependence, water vapour feedback, once in place, will be self - sustaining (it will require a greater forcing to reverse compared with the initial forcing it started with)?

Lower obliquity should result in more water vapour in the tropics if the water vapour feedback holds true.

And that additional water vapour would in turn cause further warming - this being a positive feedback, in which carbon dioxide acts as a direct regulator of temperature, and is then joined in that role by more water vapour as temperatures increase.

The climate sensitivity classically defined is the response of global mean temperature to a forcing once all the «fast feedbacks» have occurred (atmospheric temperatures, clouds, water vapour, winds, snow, sea ice etc.), but before any of the «slow» feedbacks have kicked in (ice sheets, vegetation, carbon cycle etc.).

However, they can provide both positive and negative forcing» and Ray # 252 «we understand extremely well the way greenhouse gasses [sic] like CO2 warm the planet» So here we go — Assumptions from considerations of physics: Unless CO2 could enlist water vapour to amplify its forcing it would simply be an unremarkable trace gas in the atmosphere, but — CO2 + water (vapour) = + ve feedback implying warming CO2 + water (liquid) = - ve feedback implying cooling Facts: Clouds cover half the surface of the planet.

You can show quite easily that without water - vapour feedbacks (for instance), you can not get a good match to volcanic forcings and responses in the real world (Soden et al, 2005), or to ENSO, or to the long term trends.

If the enhanced atmospheric warming from a CO2 - induced temperature rise of 1 oC results in enhanced water vapour that gives an additional warming of say x oC, the overall warming (doubled CO2 + water vapour feedback; leaving out other feedbacks for now) will be something like 1.1 * (1 + x + x2 + x3...) or 1.1 / (1 - x)-RSB-.

The water vapour theory suggests that a small increase in CO2 will result in a large positive feedback loop from water vapour and this feedback loop will lead to dangerous warming.

Positive feedback caused by rise in water vapour (caused by warming) accounts for perhaps half of the estimated warming and this will be located most where the air is humid in contradiction to Dyson's «cold and dry».

gavin: You can show quite easily that without water - vapour feedbacks (for instance), you can not get a good match to volcanic forcings and responses in the real world (Soden et al, 2005)...

Tropospheric water vapour plays an important role in regulating the energy balance of the surface and TOA, provides a key feedback mechanism and is essential to the formation of clouds and precipitation.

However both do in fact force global temperature, therefore both could be called forcings and the greenhouse effect of water vapour would then be a positive feedback forcing.

What other things in the Earth system will change when it warms up that will affect how much SW radiation is reflected back into space [eg ice - albedo feedback, cloud changes] or affect what proportion of emitted LW radiation is allowed to escape to space [eg Water Vapour, cloud changes].

Observations of the humidity in the upper troposphere and its relation with sea surface temperature in areas of deep convection point to an overall positive climate feedback by water vapour in the upper troposphere, which is inconsistent with the Iris effect.

Other feedbacks include forests, and most importantly, water vapour, which as the temperature of the atmosphere rises increases in the atmosphere (think tropical rain forest), and water vapour is a potent greenhouse gas (but it is not the «controller» of our climate because it does not accumulate in the atmosphere, only gases like CO2, methane and nitrous oxide do this) See Skeptical Science https://skepticalscience.com/co2-lags-temperature.htm

The 4 W / m2 TOA forcing is the consequence of an imposed change in CO2 — all changes to LW absorption in the atmosphere as a consequence of that initial change (through water vapour, cloud or temperature profile responses) are feedbacks.

You really need to account for the vertical structure of temperature (the lapse rate), and if you want your model to get a number of basic things right you need to include spectrally grey absorbers — plus the additional mixing in the troposphere (which depends on convection, and hence affects water vapour feedbacks) etc....

The chemical feedbacks due to photolytic reactions in both the stratosphere and troposphere involving ozone, NOx, and water vapour, can have significant impacts.

This of course implies relatively constant relative humidity is therefore a big part in the water - vapour feedback.

It is standard practice to include only the fast feedback processes, including changes in water vapour, in the calculation of climate sensitivity, but to exclude possible induced changes in the concentrations of other greenhouse gases (as well as other slow feedback processes).

They got 10 pages in Science, which is a lot, but in it they cover radiation balance, 1D and 3D modelling, climate sensitivity, the main feedbacks (water vapour, lapse rate, clouds, ice - and vegetation albedo); solar and volcanic forcing; the uncertainties of aerosol forcings; and ocean heat uptake.

Thus when you ask «where is the convective feedback in GCMs», the answer is in the water vapour feedback.

[10] All of the models used by the IPCC assume that this increase in water vapour will result in a positive feedback in the order of 3 - 4 times the increase in temperature that would be caused by the increase in CO2 alone.

Water vapour is also the dominant positive feedback in our climate system and amplifies any warming caused by changes in atmospheric CO2.

After all, the theory is that CO2 is a well mixed gas, and subject differences in humidity (water vapour feedback), the effect of CO2 should be similar wherever it is measured.

The strength of the combined feedback is found to be robust across GCMs, despite significant inter-model differences, for example, in the mean climatology of water vapour (see Section 8.6.2.3).»

This leaves all other feedbacks including changes in ocean circulation, water vapour, clouds, and snow as the undetermined factors in past climate changes.

July 17, 2013 at 1:39 pm The lapse rate feedback is only a negative feedback (in the general circulation model) if the long wave radiation that is released when the water vapour condenses is emitted to space rather than trapped by increased water vapour.

Based on evidence from Earth's history, we suggest here that the relevant form of climate sensitivity in the Anthropocene (e.g. from which to base future greenhouse gas (GHG) stabilization targets) is the Earth system sensitivity including fast feedbacks from changes in water vapour, natural aerosols, clouds and sea ice, slower surface albedo feedbacks from changes in continental ice sheets and vegetation, and climate — GHG feedbacks from changes in natural (land and ocean) carbon sinks.

The most credible of the contrarians, Richard Lindzen, has relied primarily on arguments that the feedback from water vapour, which plays a central role in climate models, might actually be zero or even negative.

If the water vapour feedback didn't, in the end, change to negative, the Earth would eons ago have lost its oceans.

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

The identified atmospheric feedbacks including changes in planetary albedo, in water vapour distribution and in meridional latent heat transport are all poorly represented in zonal energy balance model as the one used in [7] whereas they appear to be of primary importance when focusing on ancient greenhouse climates.

Of course Ferdinand is right not to project catastrophism onto anthropogenic CO2 levels for as you likely know there is a inverse logarithmic relationship between changes in temperature and CO2 levels such that without the assumed positive feedback from water vapour there is no chance of runaway global warming, tipping points or whatever.