Sentences with phrase «feedback sensitivity estimates»

Note also that the Earth System Sensitivity is deduced from various past climate change events like the Paleocene — Eocene Thermal Maximum (PETM), but the qualitative estimates of longer - term climate sensitivity are less precise than the HS12 fast feedback sensitivity estimates.

Not exact matches

New paper mixing «climate feedback parameter» with climate sensitivity... «climate feedback parameter was estimated to 5.5 ± 0.6 W m − 2 K − 1» «Another issue to be considered in future work should be that the large value of the climate feedback parameter according to this work disagrees with much of the literature on climate sensitivity (Knutti and Hegerl, 2008; Randall et al., 2007; Huber et al., 2011).

It seems that current sensitivity estimates ignore feedback CO2 for the modern era.

I'm increasingly thinking that what we really need is an estimate of the sensitivity of the system to an injection of carbon dioxide including the feedback from the carbon cycle etc..

Climate model studies and empirical analyses of paleoclimate data can provide estimates of the amplification of climate sensitivity caused by slow feedbacks, excluding the singular mechanisms that caused the hyperthermal events.

On sensitivity positive and negative feedbacks: Since the temps are pushing the upper bounds of the estimated ranges, one could say reasonably that what we don't know has more in common with the speed of the feedbacks, not the question of CO2 sensitivity as you infer.

Dan has yet to acknowledged is that the fossil record clearly shows that the best value of the known feedbacks, whatever their «exact» values may be, are included in the IPCC's approximate estimate of the climate sensitivity, and that this is strongly supported by the GCMs.

The «slow feedback» sensitivity is likely to be higher (since carbon cycle, methane and ice sheet feedbacks are very likely positive), however, estimating that from paleo is tricky since we are moving into a new regime which hasn't ever happened before.

This sensitivity estimate is not the last word on the subject, because of uncertainties in the approximate formulae used to compute the terms in the energy balance, and neglect of possible effects of water vapor feedback on the surface budget.

Thus if this tells us that sensitivity is near 3 degrees, and that is close to the model estimates, we can have some confidence that we have captured the main feedbacks.

Climate models provide sensitivity estimates that may not fully incorporate slow, long - term feedbacks such as those involving ice sheets and vegetation.

Just to follow - up on John Finn's question (# 10), if one puts in a rough value for the emissivity of the earth (whatever that might be), so one is no longer assuming it is a perfect blackbody, then does the resulting estimate for climate sensitivity correspond to what one would expect in the absence of any feedback effects?

This is enough to matter, but it's no more scary than the uncertainty in cloud feedbacks for example, and whether they could put us on the high end of typical climate sensitivity estimates.

As we discussed at the time, those results were used to conclude that the Earth System Sensitivity (the total response to a doubling of CO2 after the short and long - term feedbacks have kicked in) was around 9ºC — much larger than any previous estimate (which is ~ 4.5 ºC)-- and inferred that the committed climate change with constant concentrations was 3 - 7ºC (again much larger than any other estimate — most are around 0.5 - 1ºC).

Even the conventional notion of ECS involving the short - term (Charney) feedbacks doesn't represent an equilibrium result, which is better represented by «Earth System Sensitivity» estimates.

So how cool is it then that the recent paper by Fasullo and Trenberth estimates the net climate sensitivity without getting into the details of the cloud feedback then?

But 3,2 °C is the best estimate for equilibrium climate sensitivity (that is when the runs of models consider all the feedbacks).

They do cite a study by Lindzen and Choi, which has shown, based on ERBE satellite observations, that the net impact of a doubling of CO2 including all feedbacks is likely to be significantly lower than the model - based estimates by Myhre for sensitivity without feedbacks.

The reports for which you provided links are interesting, but do not provide any empirical evidence in support of the Myhre et al. model - based estimate of CO2 climate sensitivity (clear sky, no feedbacks).

Further to earlier post, the attached curve shows various estimates of (2xCO2) climate sensitivity plotted against the feedback parameter.

To translate this into 2xCO2 temperature impact (equilibrium climate sensitivity) means that this would be around 0.6 deg C including all feedbacks, compared to the Myhre et al. estimate before feedbacks of around 1.0 degC and the IPCC mid-range estimate including all feedbacks of 3.2 degC.

Nevertheless, an estimate of total climate sensitivity that considers all feedbacks is crucial for checking these model results.

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.

Traditionally, only fast feedbacks have been considered (with the other feedbacks either ignored or treated as forcing), which has led to estimates of the climate sensitivity for doubled CO2 concentrations of about 3 ◦ C.

Based on the principles of radiative physics and reasonable estimates of feedbacks and climate sensitivity, I would say that any current oscillations beyond those we already know can't be strong so strong that they leave little or no room for what anthropogenic emissions are contributing to the temperature trend.

Steve: Archer and Rahnstorf, Climate Crisis, reported that Callendar's sensitivity estimate was 2 deg C and that he had supported water vapor feedbacks.

To obtain a likelihood function by estimating the climate feedback parameter and then to present it as a likelihood function in climate sensitivity, a reciprocal parameter, alongside other likelihoods that may have been derived in the sensitivity parameter space, seems to me misleading.

However, the structural uncertain with cloud feedbacks runs far deeper than intermodel variability in estimating climate sensitivity.

As I interpret the evidence, the observational data tend to confirm the modeling for these individual feedbacks at least semiquantitatively, and this suggests to me that the climate sensitivity estimates are probably not grossly in error, even if precise quantitation still eludes us.

Yeah, they're keeping that a huge secret: Section 8.6.3.2 of AR4 is called «Clouds,» and contains the statement «cloud feedbacks remain the largest source of uncertainty in climate sensitivity estimates.»

On the other hand the projected positive feedbacks you support, which are COMPLETELY theoretical, depend on the LEAST understood aspects of the affect of water vapor and cloud formation, so the strong feedbacks PROJECTED are the least dependable, while the «OBSERVATIONS» used by Lindzen, Spencer, and others, support the lower estimates of climate sensitivity.

The assumption used in A&H (following F&G) is that p (O S) has the same Gaussian form as function of O for each value of S when O is not an estimate of climate sensitivity but of feedback strength or L.

[Lorius et al., 1990] concluded from their analysis that climate sensitivity to a doubling of CO2 is 3 - 4ºC, in good agreement with independent estimates based on the physical understanding of CO2 forcing and relevant feedbacks as coded in models.

Climate model studies and empirical analyses of paleoclimate data can provide estimates of the amplification of climate sensitivity caused by slow feedbacks, excluding the singular mechanisms that caused the hyperthermal events.

This bias may be explained by a misrepresentation of mixed - phase extratropical clouds, often pinpointed as playing a key role in driving global - cloud feedback and uncertainties in climate sensitivity estimates (e.g., Tan et.

«Feedbacks» argument: Here Bart argues against low climate sensitivity estimates cited by NIPCC by simply stating that they are much lower than the estimates, which are» accepted» by IPCC or that can «satisfactorily» be modeled by the IPCC models.

Therefore, estimating equilibrium climate sensitivity based on measurements of a climate that's out of equilibrium requires making some significant assumptions, for example that feedbacks will remain constant over time.

Merging realistic estimates of low - cloud amount, high - cloud amount, and extratropical optical depth feedbacks would likely increase our confidence in constraints on climate sensitivity from climate models.

Some people may prefer to say that no - feedback climate sensitivity is estimated, I used calculated, as that fits well with the fact that it's a value defined true some formulas rather than by specifying a real physical parameter to be estimated.

Within a reasonable but not completely defined range, TCR estimates sensitivity because of its substantial dependence on the feedbacks.

The low estimates of climate sensitivity by Chylek and Lohmann (2008) and Schmittner et al. (2011), ~ 2 °C for doubled CO2, are due in part to their inclusion of natural aerosol change as a climate forcing rather than as a fast feedback (as well as the small LGM - Holocene temperature change employed by Schmittner et al., 2011).»

Changes in cloudiness in a warmer climate can be either a negative or positive feedback and the uncertainty in this feedback is the major source of uncertainty in the IPCC's estimate of climate sensitivity.

Second, you can not directly compare the IPCC estimates of Charney sensitivity (which excludes slow feedbacks like ice sheets and vegetation) and earth system sensitivity (which includes slow feedbacks).

28 Estimated Strength of Water Vapor Feedback Earliest studies suggest that if the absolute humidity increases in proportion to the saturation vapor pressure (constant relative humidity), this will give rise to a water vapor feedback that will double the sensitivity of climate compared to an assumption of fixed absolute hFeedback Earliest studies suggest that if the absolute humidity increases in proportion to the saturation vapor pressure (constant relative humidity), this will give rise to a water vapor feedback that will double the sensitivity of climate compared to an assumption of fixed absolute hfeedback that will double the sensitivity of climate compared to an assumption of fixed absolute humidity.

The average fast - feedback climate sensitivity over the LGM — Holocene range of climate states can be assessed by comparing estimated global temperature change and climate forcing change between those two climate states [3,86].

The wide range of estimates of climate sensitivity is attributable to uncertainties about the magnitude of climate feedbacks (e.g., water vapor, clouds, and albedo).

Prather et al. (2001) estimated the feedback of CH4 to tropospheric OH and its lifetime and determined a sensitivity coefficient f = 0.28, giving a ratio τpert / τglobal of 1.4.

Our initial assessment is a fast - feedback sensitivity of 3 ± 1 °C for 2 × CO2, corresponding to an LGM cooling of 4.5 °C, similar to the 2.2 — 4.8 °C estimate of PALAEOSENS [99].

Estimates of climate sensitivity, which should be high if positive feedbacks are strong, are instead getting lower and lower.

The official climate Team says that water vapor feedback has a net positive effect, which is why they estimate the sensitivity of doubling CO2 as high as they do, +2 ºC to +5 ºC.