Sentences with phrase «atmospheric aerosol forcing»

Surely after decades of satellite measurements, countless field experiments, and numerous finescale modeling studies that have repeatedly highlighted basic deficiencies in the ability of comprehensive climate models to represent processes contributing to atmospheric aerosol forcing, it is time to give up on the fantasy that somehow their output can be accepted at face value.»

Not exact matches

Professor Sybren said: «It can be excluded, however, that this hiatus period was solely caused by changes in atmospheric forcing, either due to volcanic eruptions, more aerosols emissions in Asia, or reduced greenhouse gas emissions.

Areas of expertise: Satellite remote sensing, atmospheric aerosols, climatology, radiative forcing

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.

This method tries to maximize using pure observations to find the temperature change and the forcing (you might need a model to constrain some of the forcings, but there's a lot of uncertainty about how the surface and atmospheric albedo changed during glacial times... a lot of studies only look at dust and not other aerosols, there is a lot of uncertainty about vegetation change, etc).

The measured energy imbalance accounts for all natural and human - made climate forcings, including changes of atmospheric aerosols and Earth's surface albedo.

Ice sheet albedo forcing is estimated to have caused a global mean forcing of about — 3.2 W m — 2 (based on a range of several LGM simulations) and radiative forcing from increased atmospheric aerosols (primarily dust and vegetation) is estimated to have been about — 1 W m — 2 each.

Reduction of the amount of atmospheric CH4 and related gases is needed to counterbalance expected forcing from increasing N2O and decreasing sulfate aerosols.

However, calculation of the radiative forcing is again a job for the line - by - line codes that take into account atmospheric profiles of temperature, water vapour and aerosols.

The important point here is that a small external forcing (orbital for ice - ages, or GHG plus aerosols & land use changes in the modern context) can be strongly amplified by the positive feedback mechanism (the strongest and quickest is atmospheric water vapor - a strong GHG, and has already been observed to increase.

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?)

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.

Based on NASA's CMIP5 forcing model, year 2012 has a greenhouse forcing of 3.54 Wm2, ozone has 0.45 Wm2, atmospheric aerosols have -0.89 Wm2 combined direct / indirect, and land use has -0.19 Wm2, all based on iRF.

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.

«Climate models consider anthropogenic forcings like greenhouse gases and tiny atmospheric particles known as aerosols, but they can not study a specific climate event like the current hiatus,» said Yu Kosaka, co-author of the Nature paper.

This is in contrast to externally forced variability in global mean surface temperature which arises due to changes in atmospheric greenhouse gasses, aerosols, solar irradiance, ect.

Forcing however is dependent upon the climate model, and in the case of aerosols distribution due to atmospheric circulation is estimated independently of the main model itself.

Differences in future atmospheric burdens and radiative forcing for aerosols are dominated by divergent assumptions about emissions from South and East Asia.

«The second largest human - made forcing is probably atmospheric aerosols, although the aerosol forcing is extremely uncertain3, 4.

via changes in cloud cover, ice cover, atmospheric aerosols concentrations and distributions) is incomplete and contains uncertainties on the order of the estimates of the forcing changes themselves. . .

Research published in 2008 by Arizona State University professor Peter Crozier suggests that this nanoscale atmospheric aerosol species is abundant in the atmosphere over East Asian countries and should be explicitly included in models of radiative forcing (the gap between energy radiation reaching the Earth and that leaving through the upper atmosphere).

The impact of the meteorite that wiped out the dinosaurs released vast amounts of CO2 from vaporising carbonate - rich rocks, pushing atmospheric CO2 levels up to approx 2,300 ppm resulting in a climatic forcing of +12 W - m -LRB--) 2 that would have been sufficient to warm the Earth's surface by 7.5 °C, in the absence of counter forcing by sulfate aerosols.

Anomalies in the volcanic - aerosol induced global radiative heating distribution can force significant changes in atmospheric circulation, for example, perturbing the equator - to - pole heating gradient (Stenchikov et al., 2002; Ramaswamy et al., 2006a; see Section 9.2) and forcing a positive phase of the Arctic Oscillation that in turn causes a counterintuitive boreal winter warming at middle and high latitudes over Eurasia and North America (Perlwitz and Graf, 2001; Stenchikov et al., 2002, 2004, 2006; Shindell et al., 2003b, 2004; Perlwitz and Harnik, 2003; Rind et al., 2005; Miller et al., 2006).

Overall forcing at the TOA is negative averaged over all aerosols, but significant atmospheric heating and a net positive TOA forcing is possible for aerosols with a strong black carbon component, and some of this will eventually be transmitted to the surface despite the reduction in surface insolation from the light scattering and absorptive properties of the aerosols.

In particular, I think it would be interesting to use a complex atmospheric chemistry component to allow for spatial variation in the forcing reduction through sulphate aerosols: increase the aerosol optical depth over one source country, for example, and let it disperse over time.

The measured energy imbalance accounts for all natural and human - made climate forcings, including changes of atmospheric aerosols and Earth's surface albedo.

Reduction of the amount of atmospheric CH4 and related gases is needed to counterbalance expected forcing from increasing N2O and decreasing sulfate aerosols.

Sulfate aerosols wash out pretty quickly, so their current atmospheric concentration (and the resulting negative forcing) is mainly determined by the current emissions levels.

They found that changes in atmospheric ionization during the 11 - year solar cycle, and the resulting variations in aerosol formation, produced a globally asymmetric radiative forcing with a net cloud albedo effect of − 0.05 W m − 2.

Zonal mean atmospheric temperature change from 1890 to 1999 (°C per century) as simulated by the PCM model from (a) solar forcing, (b) volcanoes, (c) wellmixed greenhouse gases, (d) tropospheric and stratospheric ozone changes, (e) direct sulphate aerosol forcing and (f) the sum of all forcings.

I think it is really important to make that distinction - that there are a number of factors that influence the extent of Arctic sea ice, some of them of course associated with changes in the radiative forcing from the atmosphere, as a result of anthropogenic greenhouse gases and aerosols, but also changes in the atmospheric circulation and also the advection of heat into or out of the Arctic by the ocean circulation.

Further, within my field, atmospheric chemistry, we are very much focused on the other forcings; aerosol and tropospheric ozone, for instance.

Combined, the total amount, and type, of aerosols affect the amount of atmospheric forcing imposed inside the climate system.

By 1994, with work on SAR progressing, the Special Report on Radiative Forcing (IPCC, 1995) reported significant breakthroughs in a set of chapters limited to assessment of the carbon cycle, atmospheric chemistry, aerosols and RF.

The SAR, under Bert Bolin (IPCC Chair) and John Houghton and Gylvan Meira Filho (WGI Co-chairs), was planned with and coupled to a preliminary Special Report (IPCC, 1995) that contained intensive chapters on the carbon cycle, atmospheric chemistry, aerosols and radiative forcing.

Anomalies in the volcanic - aerosol induced global radiative heating distribution can force signifi cant changes in atmospheric circulation, for example, perturbing the equator - to - pole heating gradient (Stenchikov et al., 2002; Ramaswamy et al., 2006a; see Section 9.2) and forcing a positive phase of the Arctic Oscillation that in turn causes a counterintuitive boreal winter warming at middle and high latitudes over Eurasia and North America (Perlwitz and Graf, 2001; Stenchikov et al., 2002,2004, 2006; Shindell et al., 2003b, 2004; Perlwitz and Harnik, 2003; Rind et al., 2005; Miller et al., 2006).

Compute the surface radiative forcing and its amplification by the atmospheric warming in a manner following Myhre and Stordal 1997, using gridded global fields of of the input variables obtained from observations (e.g. the ECMWF reanalysis, ISCCP clouds, satellite ozone, some sort of aerosol optical depth from satellite.

Emissions scenarios were converted to projections of atmospheric GHG and aerosol concentrations, radiative forcing of the climate, effects on regional climate, and climatic effects on global sea level (IPCC, 2001a).