Sentences with phrase «what aerosol forcings»

Neither is climate sensitivity one to one dependent on what the aerosol forcing is.

Not exact matches

They, too, assume an equivalence in radiative forcing between GHG and aerosol, What they do is add different estimates of the aerosol radiative forcing to the GHG forcing, while keeping the temperature response fixed at the observed recent warming.

The uncertainty in aerosol forcing looks unsettling, but this is a good example of the case where one needs to ask: What are the consequences of this uncertainty for our predictions of future climate?

To better understand what Kilimanjaro and other tropical glaciers are telling us about climate change, one ultimately ought to drive a set of tropical glacier models with GCM simulations conducted with and without anthropogenic forcing (greenhouse gases and sulfate aerosol).

Depending on what you are looking at, it could have a bottom up estimate of aerosol forcing or aerosol forcings from a residual calculation — neither of which really have the range of uncertainty.

Therefore in a fingerprint study that doesn't distinguish between aerosols and GHGs, what the exact value of the aerosol forcing right is basically irrelevant.

What is clear is that although the net aerosol forcing is indeed an important determinant of the uncertainty, it is not overwhelming.

They, too, assume an equivalence in radiative forcing between GHG and aerosol, What they do is add different estimates of the aerosol radiative forcing to the GHG forcing, while keeping the temperature response fixed at the observed recent warming.

In terms of the aerosols: If you want to argue really simplistic, you could still explain what is seen in Dave's NH - SH time series: due to the larger thermal inertia of the SH, you would expect slower warming there with greenhouse gas forcing, so an increase in NH - SH early on, which would then be reduced as aerosol forcing becomes stronger in the NH.

-- Or is this simply a parallel set of shifts to what happened with aerosols through that period, in a way that could point the finger to one (or both) as driving forces?

A lot of assumptions need to be made to interpret what these satellite measurements are actually seeing — hence the big uncertainty in the radiative forcing by aerosols.

What is being done to address the considerable uncertainty associated with cloud and aerosol forcings?

However, I can't follow what Lewis is doing to get such a low aerosol forcing, which is the central reason for his low sensitivity.

The method that Nic is using, and what Forest et al used previously, has aerosol forcing as one of the three free parameters.

In trying to sort out which models use what for aerosol forcing, I ran into a dead end (rather dead link) referenced to in Table S9.1.

Taking out ENSO from a climate regression is different from taking out volcanic aerosols, because we don't know if ENSO is itself a forcing, an endogenous response to forcings, a temporally varying exogenous shift in the response of the climate to forcings, or what.

This would appear to be an error, as even the ISPM itself states: «Studies have concentrated on what are believed to be the most important forcings: greenhouse gases, direct solar effects, some aerosols and volcanism.»

One is that the IPCC forcing central estimate is 40 % larger than that from CO2 alone since 1950 (due to other GHGs and possibly reduced aerosol impacts relative to previous reports), so if you are going to use CO2 alone, you should really add this other 40 % to match what has happened since 1950 and that is what they did.

So not hugely different from what has gone before, though the increased confidence in aerosol forcing is clearly cutting down the upper end gradually.

I may have to re-read the Wild paper and again look exactly for what I failed to find the first time: local temperature observations on the surface matching the expected effects of the aerosol radiative forcings the paper does talk a lot about.

My question woiuld be: What happens when human related forcing such as aerosols, sulfur emission, etc. act in opposition to other human related forcing such as greenhouse gas emissions?

By the way, what is the basis for claiming that the negative aerosol forcing estimate has been reduced?

Irrespective of what one thinks about aerosol forcing, it would be hard to argue that the rate of net forcing increase and / or over-all radiative imbalance has actually dropped markedly in recent years, so any change in net heat uptake can only be reasonably attributed to a bit of natural variability or observational uncertainty.

But this information is not easily translated into aerosol radiative forcing, partly because we do not know what the pre-industrial concentrations were though direct observations, and because of the complexity of cloud - aerosol interactions (see Ch.

What I meant was that if the flattening is caused by «Chinese» aerosols then the temperatures will stay depressed until China stops generating them + however long it takes for the additional forcing to manifest.

Hegerl: [IPCC AR5 models] So using the 20th c for tuning is just doing what some people have long suspected us of doing -LSB-...] and what the nonpublished diagram from NCAR showing correlation between aerosol forcing and sensitivity also suggested.

I was thinking that the ~ 1913 to 1940 period could provide some information on what factor would be reasonable, if more accurate solar and aerosol forcing could be teased out from that period.

Answer the question: If you had to use words to describe the relationship between the reported ECS and aerosol forcing what you see would you call it

Then you have what the abstract says except you put -(mainly from aerosols)- instead of - from other anthropogenic forcings.

I may as well say «Yes lets ignore climate changes in the past and what we can learn from them and only go with the tremendously uncertain aerosol forcing, and also lets forget that feedbacks aren't necessarily constant in time.»

They correctly identified the various forces acting in the various directions (greenhouse gases = > warming, aerosols = > cooling, on longer time scales expect natural cooling from interglacial into an ice age); however, they said more research was needed to reliably say what path the climate would take.

Matthew — I think it's still conjectural to what extent the hiatus has resulted from internal cooling vs negative forcing influences of volcanic aerosols and changes in solar irradiance — it may well be a mixture of both.

However, if one converts the total effects of all greenhouse gases, aerosols, etc. into an equivalent increase in CO2 concentration (by reference to their effective radiative forcing RF, that from a doubling of CO2 being F2xCO2), then what you suggest would be pretty much in line with the generic definition of TCR in Section 10.8.1 of AR5 WGI:

This is surely what is happening in hindcasts where aerosol forcing appears to me to be fine tuned to fit the data.

In the rest of this analysis I deal with the question of to what extent the model simulations used by Shindell can be regarded as providing reliable information about how the real climate system responds to forcing from aerosols, ozone and other forcing components.

While it is impossible to know what decisions are made in the development process of each model, it seems plausible that choices are made based on agreement with observations as to what parameterizations are used, what forcing datasets are selected, or whether an uncertain forcing (e.g. mineral dust, land use) or feedback (indirect aerosol effect) is incorporated or not.

And the following, related to aerosol forcing of climate: «In 1991, he predicted that, owing to the eruption of Mt. Pinatubo, in the Philippines, average global temperatures would drop, and then, a few years later, recommence their upward climb, which was precisely what happened.»

Lewis has also adjusted the aerosol forcing according to his opinion of which values are preferred» I'm not sure that «adjusted» is the best description of what I did regarding aerosol forcing.

Take GISS instead of HadCRUT4, take a more objective aerosol forcing and you get closer to where the mainstream is... @David Young: No worries, I am fully aware of what the papers are saying.

The critique of Shindell & Faluvegi 2009 is also without merit, where it states: A second does not estimate aerosol forcing over 90S — 28S, and concludes that over 1976 — 2007 it has been large and negative over 28S — 28N and large and positive over 28N — 60N, the opposite of what is generally believed.

I decided to check what GCMs say about the relationship between aerosol forcing and response by comparing latitudinal temperature change difference between HistoricalGHG and Historical all - forcing runs.

Paul S «I'm fully aware what it says in the text» In that case, why did you deny that the SOD text gave a best estimate of -0.73 W / m ^ 2 for total aerosol forcing based on satellite observations?

What about internal variability from an internal forcing like GHG, aerosols, landuse changes, etc..

Gregory 02 provides a good explanation for the basis of what I have done, although its observational data (and its model derived aerosol forcing change) has now been superceded.

A second does not estimate aerosol forcing over 90S — 28S, and concludes that over 1976 — 2007 it has been large and negative over 28S — 28N and large and positive over 28N — 60N, the opposite of what is generally believed.

and it means that when we're looking at relatively short - term trends... the variance in that and the inability to really constrain those aerosol forcings really kind of make it hard for us to say what we should have expected over that time period.

The study didn't explore anything like full ranges of key climate parameters: equilibrium climate sensitivities below 2 K were not included in the ensemble, only a limited range of ocean heat uptake levels appears to have been considered, and it is unclear to me to what extent the possibility of aerosol forcing being small was represented.

A much better critique would examine questions of the net forcing used in the 1981 paper versus what really happened — but that gets complicated quickly because of the uncertain changes in aerosol.

Looking at the last decade, it is clear that the observed rate of change of upper ocean heat content is a little slower than previously (and below linear extrapolations of the pre-2003 model output), and it remains unclear to what extent that is related to a reduction in net radiative forcing growth (due to the solar cycle, or perhaps larger than expected aerosol forcing growth), or internal variability, model errors, or data processing — arguments have been made for all four, singly and together.

The results differ based on what is assumed for climate sensitivity and aerosol forcing.