EOS has published another example of the diversity of human and natural climate forcings. In this instance it is dust which has both a natural (e.g. from desert dust storms such as haboobs) and human component (e.g. from dust from overgrazed landscapes in semi-arid regions). The new paper is
G. S. Okin et al., 2011: Dust: Small-Scale Processes With Global Consequences. EOS. volume 92 number 29 19 July 2011. pages 241-241.
The article starts with the text [highlight]
Desert dust, both modern and ancient, is a critical component of the Earth system. Atmospheric dust has important effects on climate by changing the atmospheric radiation budget, while deposited dust influences biogeochemical cycles in the oceans and on land. Dust deposited on snow and ice decreases its albedo, allowing more light to be trapped at the surface, thus increasing the rate of melt and influencing energy budgets and river discharge. In the human realm, dust contributes to the transport of allergens and pathogens and when inhaled can cause or aggravate respiratory diseases. Dust storms also represent a significant hazard to road and air travel.
Further excerpts include
“….a growing body of literature reveals that vegetated landscapes and dune fields can emit dust [Bullard et al., 2008; Rivera Rivera et al., 2009] (Figure 1). Recent advances using satellite data over northern Africa have also shown that dust sources may be more diverse than previously believed [Schepanski et al., 2007], and in the Mojave Desert of the southwestern United States, alluvial fans and plains may be larger overall contributors to total dust emission than dry lakes [Reheis and Kihl, 1995].”
Dust plumes are commonly observed originating from areas of localized human disturbance such as roads, agricultural fields, military installations, construction sites, and off-road vehicle areas. Grazing is a widespread, dust-producing disturbance, and grazed areas consistently produce more dust than areas never grazed. Grazing removes vegetation, breaks protective soil crusts, and promotes large-scale shrub encroachment on grassland, which itself can lead to order-of-magnitude increases in emissions by changing the unvegetated gap size distribution in a landscape. A clear understanding of the myriad ways in which human disturbance promotes dust emission and the magnitude of the effects of different land use types on dust production are both critical for predicting how changes in land usage (and thus changes in land use policies) will influence dust emission, loading, and deposition in the future.”
“…..dust emission is not so different from a variety of other phenomena in which small scale processes have global consequences, such as cloud formation, anthropogenic carbon dioxide emission, and land use change.”
This article provides further support for Hypothesis 2a in our paper
Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R. Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W. Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell, W. Rossow, J. Schaake, J. Smith, S. Sorooshian, and E. Wood, 2009: Climate change: The need to consider human forcings besides greenhouse gases. Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American Geophysical Union
“Although the natural causes of climate variations and changes are undoubtedly important, the human influences are significant and involve a diverse range of first-order climate forcings, including, but not limited to, the human input of carbon dioxide (CO2). Most, if not all, of these human influences on regional and global climate will continue to be of concern during the coming decades.”