Sentences with phrase «aerosol forcing effect»

Likely no net aerosol forcing effect.

Some of these studies use the difference between Northern and Southern Hemisphere mean temperature to separate the greenhouse gas and aerosol forcing effects (e.g., Andronova and Schlesinger, 2001; Harvey and Kaufmann, 2002).

Not exact matches

The models, which factor in natural effects such as solar winds and volcanic eruptions, along with anthropogenic forcings like greenhouse gases and aerosols, match these precipitation variations accurately in trend and reasonably well in magnitude.

One just included the effective influence on temperatures from manmade forces (including greenhouse gases and aerosols, which tend to have a cooling effect), while the second included both manmade and natural ones (including volcanic activity and solar radiation).

My main problem with that study is that the weather models don't use any forcings at all — no changes in ozone, CO2, volcanos, aerosols, solar etc. — and so while some of the effects of the forcings might be captured (since the weather models assimilate satellite data etc.), there is no reason to think that they get all of the signal — particularly for near surface effects (tropospheric ozone for instance).

Now if this was the 1980s they might have had a point, but the fact that aerosols are an important climate forcing, have a net cooling effect on climate and, in part, arise from the same industrial activities that produce greenhouse gases, has been part of mainstream science for 30 years.

The forcing over the last 150 years is around 1.6 W / m2 (including cooling effects from aerosols and land use change) but the climate is not (yet) in equilibirum, and so the full temperature response has not been acheived.

The cooling effect from this aerosol forcing is thought to be about half that of greenhouse gases, but in the opposing (cooling) direction.

In addition, researchers calculated the changes in the shortwave and longwave and net radiation between the pre-industrial simulation and the present - day simulations to estimate the radiative forcing resulting from the aerosol effects on cirrus clouds.

The top priorities should be reducing uncertainties in climate sensitivity, getting a better understanding of the effect of climate change on atmospheric circulation (critical for understanding of regional climate change, changes in extremes) and reducing uncertainties in radiative forcing — particularly those associated with aerosols.

Only a few estimates account for uncertainty in forcings other than from aerosols (e.g., Gregory et al., 2002a; Knutti et al., 2002, 2003); some other studies perform some sensitivity testing to assess the effect of forcing uncertainty not accounted for, for example, in natural forcing (e.g., Forest et al., 2006; see Table 9.1 for an overview).

Most studies consider a range of anthropogenic forcing factors, including greenhouse gases and sulphate aerosol forcing, sometimes directly including the indirect forcing effect, such as Knutti et al. (2002, 2003), and sometimes indirectly accounting for the indirect effect by using a wide range of direct forcing (e.g., Andronova and Schlesinger, 2001; Forest et al., 2002, 2006).

We don't know the total forcing that well, primarily because we don't know the aerosol (direct or indirect) effects.

It is rather surprising that adding cloud lifetime effect forcing makes any difference, insofar as Aldrin is estimating indirect and direct aerosol forcings as part of his Bayesian procedure.

The total of -0.7 W / m ^ 2 is the same as the best observational (satellite) total aerosol adjusted forcing estimate given in the leaked Second Order Draft of AR5 WG1, which includes cloud lifetime (2nd indirect) and other effects.

When Aldrin adds a fixed cloud lifetime effect of -0.25 W / m ^ 2 forcing on top of his variable parameter direct and (1st) indirect aerosol forcing, the mode of the sensitivity PDF increases from 1.6 to 1.8.

Thus to provide the clearest picture of the CO2 effect, we approximate the net future change of human - made non-CO2 forcings as zero and we exclude future changes of natural climate forcings, such as solar irradiance and volcanic aerosols.

The indirect aerosol effect on clouds is non-linear [1], [76] such that it has been suggested that even the modest aerosol amounts added by pre-industrial humans to an otherwise pristine atmosphere may have caused a significant climate forcing [59].

In addressing the question of the effects of greenhouse gases on Atlantic tropical storms, it might clarify (and even partially defuse) the controversy to lump internal variability together with other forced responses (particularly aerosols), rather than to focus on internal variability vs the total forced response.

Earth's measured energy imbalance has been used to infer the climate forcing by aerosols, with two independent analyses yielding a forcing in the past decade of about − 1.5 W / m2 [64], [72], including the direct aerosol forcing and indirect effects via induced cloud changes.

al., Earth's Energy Imbalance and Implications suggests that many climate models underestimate the effect of positive climate forcings but also underestimate the effects of negative forcings due to aerosols.

In addition, since the global surface temperature records are a measure that responds to albedo changes (volcanic aerosols, cloud cover, land use, snow and ice cover) solar output, and differences in partition of various forcings into the oceans / atmosphere / land / cryosphere, teasing out just the effect of CO2 + water vapor over the short term is difficult to impossible.

From the Physical Science Basis: «Shindell et al. (2009) estimated the impact of reactive species emissions on both gaseous and aerosol forcing species and found that ozone precursors, including methane, had an additional substantial climate effect because they increased or decreased the rate of oxidation of SO2 to sulphate aerosol.

There are indeed uncertainties in aerosol forcing (not just the indirect effects) and, especially in the earlier part of the 20th Century, uncertainties in solar trends and impacts.

It is my understanding that the uncertainties regarding climate sensitivity to a nominal 2XCO2 forcing is primarily a function of the uncertainties in (1) future atmospheric aerosol concentrations; both sulfate - type (cooling) and black carbon - type (warming), (2) feedbacks associated with aerosol effects on the properties of clouds (e.g. will cloud droplets become more reflective?)

Can any of the experts lurking here refer me to any updates to the anthropogenic direct effect aerosol radiative forcing digram — Figure 6.8 -(Figure 401) in the TAR?

Greenhouse gases are well mixed and have an effect globally, other forcings may be more regional (aerosols, land use) but they can still have far field affects due to the nature of the atmospheric circulation.

Also, due to the multiplicity of anthropogenic and natural effects on the climate over this time (i.e. aerosols, land - use change, greenhouse gases, ozone changes, solar, volcanic etc.) it is difficult to accurately define the forcings.

As an aside, the radiative forcing by aerosols (in both long wave and solar radiation at the tropopause) is not the same as global dimming (which is a solar radiation effect at the surface) though they are related.

While there is good data over the last century, there were many different changes to planet's radiation balance (greenhouse gases, aerosols, solar forcing, volcanoes, land use changes etc.), some of which are difficult to quantify (for instance the indirect aerosol effects) and whose history is not well known.

Unfortunately they also have to apply figures for forcing whose values and effects are not known and have ongoing debate about them, reflective aerosols, land use, black carbon etc etc..

This is a peer reviewed paper by respected scientists who are saying that aerosol forcing means that the majority of the warming caused by existing co2 emission has effectively been masked thus far, and that as aerosols remain in the atmosphere for far shorter a duration of time than co2, we will have already most likely crossed the 2 degree threshold that the G8 politicians have been discussing this week once the cooling effect of aerosols dissipate.

But more generally, something I've wondered is: while in the global annual average, aerosols could be said to partly cancel (net effect) the warming from anthropogenic greenhouse forcing, the circulatory, latitudinal, regional, seasonal, diurnal, and internal variability changes would be some combination of reduced changes from reduced AGW + some other changes related to aerosol forcing.

... and all by itself... woops... a possible isolated, independent temperature rise of 3 - 5 degrees C average world surface temperatures by 2100, not even including any other positive forcings, because the forcing is already there waiting for the cancelling aerosol cooling effect to be removed...

Inclusion of calculated indirect effects from aerosols for instance or if unknown / un-included forcings are significant this may lead to more model - obs disagreements.

The top panel shows the direct effects of the individual components, while the second panel attributes various indirect factors (associated with atmospheric chemistry, aerosol cloud interactions and albedo effects) and includes a model estimate of the «efficacy» of the forcing that depends on its spatial distribution.

Given the total irrelevance of volcanic aerosols during the period in question, the only very modest effect of fossil fuel emissions and the many inconsistencies governing the data pertaining to solar irradiance, it seems clear that climate science has no meaningful explanation for the considerable warming trend we see in the earlier part of the 20th century — and if that's the case, then there is no reason to assume that the warming we see in the latter part of that century could not also be due to either some as yet unknown natural force, or perhaps simply random drift.

The details of the physics of different forcings (i.e. ozone effects due to solar, snow albedo and cloud effects due to aerosols etc.) do vary the feedbacks slightly differently though.

the only thing that scares me with those climate forcing charts is if policy makers look at the negative effect from particulates and aerosols... will this make some want to release more aerosols to abate the changes?

You can even go one better — if you ignore the fact that there are negative forcings in the system as well (cheifly aerosols and land use changes), the forcing from all the warming effects is larger still (~ 2.6 W / m2), and so the implied sensitivity even smaller!

First, for changing just CO2 forcing (or CH4, etc, or for a non-GHE forcing, such as a change in incident solar radiation, volcanic aerosols, etc.), there will be other GHE radiative «forcings» (feedbacks, though in the context of measuring their radiative effect, they can be described as having radiative forcings of x W / m2 per change in surface T), such as water vapor feedback, LW cloud feedback, and also, because GHE depends on the vertical temperature distribution, the lapse rate feedback (this generally refers to the tropospheric lapse rate, though changes in the position of the tropopause and changes in the stratospheric temperature could also be considered lapse - rate feedbacks for forcing at TOA; forcing at the tropopause with stratospheric adjustment takes some of that into account; sensitivity to forcing at the tropopause with stratospheric adjustment will generally be different from sensitivity to forcing without stratospheric adjustment and both will generally be different from forcing at TOA before stratospheric adjustment; forcing at TOA after stratospehric adjustment is identical to forcing at the tropopause after stratospheric adjustment).

Some of these forcings are well known and understood (such as the well - mixed greenhouse gases, or recent volcanic effects), while others have an uncertain magnitude (solar), and / or uncertain distributions in space and time (aerosols, tropospheric ozone etc.), or uncertain physics (land use change, aerosol indirect effects etc.).

The bottom two panels demonstrate that this weakening is due entirely to the anthropogenic forcings — greenhouse gas increases offset by sulfate aerosol effects.

These forcings are spatially heterogeneous and include the effect of aerosols on clouds and associated precipitation [e.g., Rosenfeld et al., 2008], the influence of aerosol deposition (e.g., black carbon (soot)[Flanner et al. 2007] and reactive nitrogen [Galloway et al., 2004]-RRB-, and the role of changes in land use / land cover [e.g., Takata et al., 2009].

In addition there is still clear evidence in my view for aerosols having played a significant role in holding back that warming, which acts on top of the effects of internal variability which play an important role in fluctuations about the forced changes.

Steve 440 says: «A recent paper by Douglas and Christy seems to claim that either 2C02 would lead to less than 1C or if 2C02 leads to greater than 1C then some forcing other than aerosols must be «masking» CO2's effect....»

Multi-signal detection and attribution analyses, which quantify the contributions of different natural and anthropogenic forcings to observed changes, show that greenhouse gas forcing alone during the past half century would likely have resulted in greater than the observed warming if there had not been an offsetting cooling effect from aerosol and other forcings.

While this does not invalidate the aerosol indirect effect at all, it underlines the limitations in using satellite observed changes in droplet size to compute the aerosol indirect forcing.

Hansen and colleagues have used two alternative approaches to characterise and quantify any missing climate forcing besides that due to greenhouse gases, solar constant, O3, and aerosol direct effect.

Assuming a Northern Hemisphere to Southern Hemisphere ratio of 2:1 for the aerosol indirect effect, this would imply a globally - averaged forcing of -1.5 Wm - 2.