Sentences with phrase «for water vapour feedback»
Allowing for changes to outgoing longwave radiation (OLR) but without allowing for water vapour feedback, detailed calculations show that the greenhouse sensitivity to doubling CO2 is about 0.24 Celsius.
https://friendsofscience.org/ Not exact matches
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.
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-.
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)...
We can wait for the post on Water Vapour and feedback effect for a response to this.
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....
On the real planet, there are multitudes of feedbacks that affect other greenhouse components (ice alebdo, water vapour, clouds etc.) and so the true issue for climate sensitivity is what these feedbacks amount to.
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).»
With regards to «climate modelling», an assumed (positive water vapour feedback) warming mechanism that can not be observed, that there is no experimental evidence for, combined with after the fact, admitted as invented cooling factors....
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.
If you want, you can compare the absorption rates of the whole atmosphere, or parts (poles, mid-latitudes and tropics), winter or summer, clear sky or cloudy,... for different CO2, O3 and CH4 levels and feedbacks of water vapour at the Archers page: http://geoflop.uchicago.edu/forecast/docs/Projects/modtran.orig.html
They had built the first completely correct radiative - convective implementation of the standard model applied to Earth, and used it to calculate a +2 C equilibrium warming for doubling CO2, including the water vapour feedback, assuming constant relative humidity.
The so - called water vapour feedback, caused by an increase in atmospheric water vapour due to a temperature increase, is the most important feedback responsible for the amplification of the temperature increase.
«As for alleged past water vapour feedback, this warming was not due to water vapour, as the feedbacks would have multiplied and fed back on themselves and led to the end of life on earth.
They discuss the part played by water vapour and cloud cover and summarise their conclusions as follows» Moreover it is not yet clear which tests are critical for constraining future projections.Consequently a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed.»
As I've demonstrated, some warming has to be attributed to the positive feedback effect of water vapour, however, you are right in saying that the trigger for past warming was (almost always) solar activity (or Milankovitch cycles).
(a) only CO2 + water vapour feedback effects can account for the majority of this rise (and that it can be separated from noise and natural processes like ENSO, PDO, cloud cover etc);
For instance if a 1 degree increase in T leads to lets say a further 3 degree increase through positive feedback with water vapour then shouldn't this 3 degree increase lead to a further 9 degree increase and then a 27 degree increase etc..
Also interesting that they don't understand that water vapour feedback, no matter what it's magnitude, applies equally to anything that causes a change in radiative forcing for the planet — more GH gases, Albedo change, any GCR induced changes in clouds.
[The paper was] the first to assess the magnitude of the water vapour feedback, and was frequently cited for a good 20 years after it was published.
As for Andrew Dessler's critique of my remarks about feedback by water vapour and clouds, his actual words confirm that I am right that these issues are still in doubt, as confirmed by the latest report from the IPCC.
Most of your readers are probably unaware of the fact that doubling carbon dioxide in itself only produces a modest warming effect of about 1.2 C and that to get dangerous warming requires feedbacks from water vapour, clouds and other phenomena for which the evidence is far more doubtful.
The modification of all feedback parameters results in changes of the sum of all feedbacks (water vapour, cloud, lapse rate and albedo), spanning a minimum — maximum range of 71 % (63 %) of the mean value for the correlated (uncorrelated) ensemble.
If water vapour feedback was positive then due to the increased evaporation spurred on by the original warming in the MWP there should have ensued a period of elevated temperatures for thousands of years until the cooling of the Holocene as we dip into the next glacial period overwhelmed the positive water vapour forcing.
In addition, although the post 60s warming period is over, it has allowed the principal green house gas, water vapour, to kick in with humidity, clouds, rain and snow depending on where you live to provide the negative feedback that scientists use to explain the existence of complex life on Earth for 550 million years.
Water vapour feedback adjusted for the fact that stratocumulus cloud cover will increase in a more humid atmosphere, all things being equal...
P. M. de F. Forster and M. Collins, «Quantifying the water vapour feedback associated with post-Pinatubo global cooling»: http://www.springerlink.com/content/37eb1l5mfl20mb7k/ Using J. Annan's figure of 3.7 W / m2 forcing for a 1ºC tmp rise, http://www.climateaudit.org/?p=2528#comment-188894, yields a 0.4 (±) ºC for H2O forcing, or a 1.4 ºC sensitivity (CS) figure for the Pinatubo natural experiment.
Based on the understanding of both the physical processes that control key climate feedbacks (see Section 8.6.3), and also the origin of inter-model differences in the simulation of feedbacks (see Section 8.6.2), the following climate characteristics appear to be particularly important: (i) for the water vapour and lapse rate feedbacks, the response of upper - tropospheric RH and lapse rate to interannual or decadal changes in climate; (ii) for cloud feedbacks, the response of boundary - layer clouds and anvil clouds to a change in surface or atmospheric conditions and the change in cloud radiative properties associated with a change in extratropical synoptic weather systems; (iii) for snow albedo feedbacks, the relationship between surface air temperature and snow melt over northern land areas during spring and (iv) for sea ice feedbacks, the simulation of sea ice thickness.
It's noticeable that warmists don't know what natural climate forcings have managed to overcome the alleged power of co2 and his imaginary friend water vapour feedback for the last ten years.
In AOGCMs, the water vapour feedback constitutes by far the strongest feedback, with a multi-model mean and standard deviation for the MMD at PCMDI of 1.80 ± 0.18 W m — 2 °C — 1, followed by the (negative) lapse rate feedback -LRB--- 0.84 ± 0.26 W m — 2 °C — 1) and the surface albedo feedback (0.26 ± 0.08 W m — 2 °C — 1).
With water vapour feedback (quite sure for the lower troposphere, but absent where it matters: at the tropopause) it is 1.3 °C.
Under such a response, for uniform warming, the largest fractional change in water vapour, and thus the largest contribution to the feedback, occurs in the upper troposphere.
One of the biggest uncertainties for the science relate to the feedback mechanisms, from water vapour and cloud changes in particular, that arise when the atmosphere warms.
Crosses represent the water vapour feedback computed for each model from Soden and Held (2006) assuming no change in relative humidity.
Comparison of GCM climate feedback parameters for water vapour (WV), cloud (C), surface albedo (A), lapse rate (LR) and the combined water vapour plus lapse rate (WV + LR) in units of W m — 2 °C — 1.
Corrections: Del Genio et al. (1991); Raval and Ramanathan (1989) found that satellite infrared measurements gave «compelling evidence for the positive feedback between surface temperature, water vapour and the greenhouse effect; the magnitude of the feedback is consistent with that predicted by climate models;» similarly, Rind et al. (1991), p. 500; Sun and Held (1996); and the final nail in the coffin, Soden et.
Much of the time these «outsider» critiques are not based on anything other than a desire to confuse (claims that IPCC doesn't mention water vapour feedbacks for instance, or that there is a deliberate attempt to downplay solar effects on climate or that the number of vineyards in England a thousand years ago implies that CO2 has no radiative effect) and have no traction in the scientific community.
NO trend in global water vapour - a bit of a problem for the «positive feedback» found in GCMs.
Figure 9.43 (a) Strengths of individual feedbacks for CMIP3 and CMIP5 models (left and right columns of symbols) for Planck (P), water vapour (WV), clouds (C), albedo (A), lapse rate (LR), combination of water vapour and lapse rate (WV+LR) and sum of all feedbacks except Planck (ALL), from Soden and Held (2006) and Vial et al. (2013), following Soden et al. (2008).
As I read for example Bony et al. 2006, Soden and Held 2006, there are in the IPCC dogma four «feedbacks»: increased atmospheric optical thickness due to increased water vapour column amount due to sustained relative humidity; cloud radiative effects; albedo effects; lapse rate effects.
1) CO2 is not rising significantly compared to earlier in the 20th century (Beck, Segalstad, Jaworowski) 2) OK, so CO2 is rising, but human sources are but a minor player (Howard Hayden, Spencer on WUWT) 3) OK, so human CO2 is significant, but its temperature effect is nonexistant (Heinz Hug) 4) OK, so CO2 has a temperature effect, but it is dwarfed by water vapour (Lindzen, Reid Bryson, Tim Ball 5) OK, so the CO2 temperature effect is not completely dwarfed by water vapour, but the sun is much more important (Svensmark, Shaviv, many others) 6) OK, so the solar output has been flat since the 50ies, but there are no net positive feedback (Lindzen again, Spencer again) 7) Actually, there has been no significant global warming (Watts, Singer + more), 8) Hey, all this warming is a) unstoppable anyway (Singer again) b) good for humanity (Michaels).
Now there were two papers put out by a Swiss team (you should know who) on consideration of European warming where they argued that natural effects could be ruled out; the first paper argued for strong water vapour feedback causing the 1980 to 1998 temperature rise and the later paper, using exactly the same data, argued for a reduction in aerosols causing a recovery in temperatures over the same period.
For a challenge to the current view of water vapour feedback to succeed, relevant processes would have to be incorporated into a GCM, and it would have to be shown that the resulting GCM accounted for observations at least as well as the current generatiFor a challenge to the current view of water vapour feedback to succeed, relevant processes would have to be incorporated into a GCM, and it would have to be shown that the resulting GCM accounted for observations at least as well as the current generatifor observations at least as well as the current generation.