AGW Observer

Observations of anthropogenic global warming

Papers on aerosol forcing observations

Posted by Ari Jokimäki on October 20, 2009

This is a list of papers about aerosol forcing observations with an emphasis to global estimates. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Consistency Between Satellite-Derived and Modeled Estimates of the Direct Aerosol Effect – Myhre (2009) “This study demonstrates consistency between a global aerosol model and adjustment to an observation-based method, producing a global and annual mean radiative forcing that is weaker than –0.5 W m-2, with a best estimate of –0.3 W m-2. The physical explanation for the earlier discrepancy is that the relative increase in anthropogenic black carbon (absorbing aerosols) is much larger than the overall increase in the anthropogenic abundance of aerosols.” [Full text]

Global aerosol climatology from the MODIS satellite sensors – Remer et al. (2008) “The recently released Collection 5 Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol products provide a consistent record of the Earth’s aerosol system. Comparing with ground-based AERONET observations of aerosol optical depth (AOD) we find that Collection 5 MODIS aerosol products estimate AOD to within expected accuracy more than 60% of the time over ocean and more than 72% of the time over land. … However, the new collection introduces a 0.015 offset between the Terra and Aqua global mean AOD over ocean, where none existed previously. Aqua conforms to previous values and expectations while Terra is higher than what had been expected. The cause of the offset is unknown, but changes to calibration are a possible explanation.” [Full text]

Satellite-based estimate of the direct and indirect aerosol climate forcing – Quaas et al. (2008) “We develop a new methodology to derive a measurement-based estimate using almost exclusively information from an Earth radiation budget instrument (CERES) and a radiometer (MODIS). We derive a statistical relationship between planetary albedo and cloud properties, and, further, between the cloud properties and column aerosol concentration. Combining these relationships with a data set of satellite-derived anthropogenic aerosol fraction, we estimate an anthropogenic radiative forcing of −0.9 ± 0.4 Wm-2 for the aerosol direct effect and of −0.2 ± 0.1 Wm-2 for the cloud albedo effect.” [Full text]

Satellite-based assessment of top of atmosphere anthropogenic aerosol radiative forcing over cloud-free oceans – Christopher et al. (2006) “Here, by combining MODIS narrowband measurements with broadband radiative flux data sets from the Clouds and the Earth’s Radiant Energy System (CERES), we provide a measurement-based assessment of the global direct climate forcing (DCF) of anthropogenic aerosols at the top of atmosphere (TOA) only for cloud free oceans. The mean TOA DCF of anthropogenic aerosols over cloud-free oceans [60N–60S] is −1.4 ± 0.9 Wm-2, which is in excellent agreement (mean value of −1.4 Wm-2) with a recent observational study by Kaufman et al. [2005].” [Full text]

A review of measurement-based assessment of aerosol direct radiative effect and forcing – Yu et al. (2006) “In recent years, a great deal of effort has gone into improving measurements and datasets. It is thus feasible to shift the estimates of aerosol forcing from largely model-based to increasingly measurement-based. Here we assess the aerosol optical depth, direct radiative effect (DRE) by natural and anthropogenic aerosols, and direct climate forcing (DCF) by anthropogenic aerosols, focusing on satellite and ground-based measurements supplemented by global chemical transport model (CTM) simulations. … Despite these achievements, a number of issues remain open and more efforts are required to address them. Current estimates of the aerosol direct effect over land are poorly constrained.” [Full text]

Aerosol anthropogenic component estimated from satellite data – Kaufman et al. (2005) “Satellite instruments do not measure the aerosol chemical composition needed to discriminate anthropogenic from natural aerosol components. However the ability of new satellite instruments to distinguish fine (submicron) from coarse (supermicron) aerosols over the oceans, serves as a signature of the anthropogenic component and can be used to estimate the fraction of anthropogenic aerosols with an uncertainty of ±30%. Application to two years of global MODIS data shows that 21 ± 7% of the aerosol optical thickness over the oceans has an anthropogenic origin. We found that three chemical transport models, used for global estimates of the aerosol forcing of climate, calculate a global average anthropogenic optical thickness over the ocean between 0.030 and 0.036, in line with the present MODIS assessment of 0.033. This increases our confidence in model assessments of the aerosol direct forcing of climate. The MODIS estimated aerosol forcing over cloud free oceans is therefore −1.4 ± 0.4 W/m2.” [Full text]

Global anthropogenic aerosol direct forcing derived from satellite and ground-based observations – Chung et al. (2005) “A global estimate of the direct effects of anthropogenic aerosols on solar radiation in cloudy skies is obtained by integrating satellite and ground-based observations with models of aerosol chemistry, transport, and radiative transfer. The models adopt global distribution of aerosol optical depths (from MODIS), clouds, water vapor, ozone, and surface albedo from various satellite climatology. … The global annual mean direct forcing is −0.35 Wm-2 (range of −0.6 to −0.1 Wm-2) at the top-of-the atmosphere (TOA), +3.0 Wm-2 (range of +2.7 to +3.3Wm-2) in the atmosphere, and −3.4 Wm-2 (range of −3.5 to −3.3 Wm-2) at the surface. … Another major finding of this study is that the reduction in the surface solar radiation is a factor of 10 larger than the reduction in net solar (down minus up) radiation at TOA.” [Full text]

Global estimate of aerosol direct radiative forcing from satellite measurements – Bellouin et al. (2005) “Here we use state-of-the-art satellite-based measurements of aerosols and surface wind speed to estimate the clear-sky direct radiative forcing for 2002, incorporating measurements over land and ocean. … Probability density functions obtained for the direct radiative forcing at the top of the atmosphere give a clear-sky, global, annual average of -1.9 W m-2 with standard deviation, ± 0.3 W m-2. These results suggest that present-day direct radiative forcing is stronger than present model estimates, implying future atmospheric warming greater than is presently predicted, as aerosol emissions continue to decline10.” [Full text]

Climate Forcing by Aerosols–a Hazy Picture – Anderson et al. (2003) “Anthropogenic aerosol emissions are believed to have counteracted the global-warming effect of greenhouse gases over the past century. However, the magnitude of this cooling effect is highly uncertain. In their Perspective, Anderson et al. argue that the magnitude and uncertainty of aerosol forcing may be larger than is usually considered in models.” [Full text]

Large differences in tropical aerosol forcing at the top of the atmosphere and Earth’s surface – Satheesh & Ramanathan (2000) “Here we present an observational method for quantifying aerosol forcing to within ± 5 per cent. We use calibrated satellite radiation measurements and five independent surface radiometers to quantify the aerosol forcing simultaneously at the Earth’s surface and the top of the atmosphere over the tropical northern Indian Ocean. … Accordingly, mean clear-sky solar radiative heating for the winters of 1998 and 1999 decreased at the ocean surface by 12 to 30 W m-2, but only by 4 to 10 W m-2 at the top of the atmosphere. This threefold difference (due largely to solar absorption by soot) and the large magnitude of the observed surface forcing both imply that tropical aerosols might slow down the hydrological cycle.”

Direct radiative forcing by anthropogenic airborne mineral aerosols – Sokolik & Toon (1996) “The effects of mineral aerosols on the radiation budget are important relative to those of other types of aerosols—such as sulphate and smoke particles—due to the widespread distribution and large optical depth of mineral dust. … Here we use estimates of anthropogenic dust inputs and observations of dust optical properties to show that although the key quantities contributing to the evaluation of the direct solar radiative forcing by dust generated through human activities have a wide range of uncertainty, the forcing by anthropogenically generated mineral aerosols may be comparable to the forcing by other anthropogenic aerosols.”

Atmospheric transmission at Davos, Switzerland 1909–1979 – Hoyt & Fröhlich (1983) “Pyrheliometric measurements at Davos, Switzerland from 1909 to 1979 are used to reconstruct the time history of atmospheric transmission. Measurements were numerous enough to allow yearly and seasonal values of atmospheric transmission to be determined. Other than the eruptions of Katmai in 1912 and Agung in 1963, there are no significant long-term changes in atmospheric transmission observed at this central European site.”


2 Responses to “Papers on aerosol forcing observations”

  1. skagedal said

    This page misses a closing tag for italics.

    Regards, Simon

  2. Ari Jokimäki said

    Corrected, thank you! 🙂

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