Trace gases and other potential perturbations to global climate

Abstract

We review the various natural and anthropogenic factors that may affect the climate. The purpose is to summarize our understanding of these factors and their potential future climatic effects so that CO2‐induced climate change can be viewed in a proper context. The factors we discuss include trace gases, anthropogenic and volcanic aerosols, variation of solar constant, change of surface characteristics, and releases of waste heat. We discuss the origins of the various natural and anthropogenic perturbations, the physical and chemical processes and their interactions, model sensitivity calculations, and model projections of their potential future climatic effects. The discussions center on trace gases because of their potentially large climatic effects. It appears that the increases of atmospheric trace gases of other kinds in addition to CO2 could have important climatic effects. The model calculations suggest that the combined effect of these other trace gases, and the associated change of atmospheric ozone and water vapor distributions, could potentially warm the climate by an amount comparable in magnitude to the effect of doubling the CO2. Aerosols of anthropogenic origins may have substantial effects on regional climate, while the volcanic aerosols may have an effect on large‐scale climate for up to a few years after injection. Changes of surface characteristics and releases of waste heat may also have substantial effects on the regional climate, but these effects are most likely to be small when compared with the effect of CO2 increase. Changes of solar constant could have an effect on the global scale, but the time scale is much longer. There is much more that needs to be learned with regard to the above mentioned natural and anthropogenic factors that may affect the climate. A brief summary of those needs is presented.

Linking local air pollution to global chemistry and climate

“…Urban air pollution can alter concentrations of greenhouse gases such as tropospheric ozone directly [e.g., Wang et al, 1986; Hauglustaine and Granier, 1995] …”

Atmospheric Methane: Trends and Impacts

“…Other modeling studies have included increasing methane concentrations in studies evaluating scenarios for potential future changes in radiative forcing and global temperatures (Wang and Molnar, 1985;Ramanathan et al, 1985Ramanathan et al, , 1987WMO, 1985;Dickinson and Cicerone, 1986;Wang et al, 1986;Wigley, 1987;Hansen et al, 1988Hansen et al, , 1989IPCC, 1990. ) Table 2 the change in radiative forcing (Wm -2 ) due to increasing methane compared to total change due to all greenhouse gases as derived by IPCC (1996) for their high (IS92e), medium (IS92a), and low (IS92c) scenarios.…”

Cloud Albedo, Greenhouse Effects, Atmospheric Chemistry, and Climate Change

“…Until recently, the role of atmospheric sulfur species in climate has been limited to the impact of sulfur emissions on stratospheric aerosols (e.g., Wang et al, 1986). 37 Since these have a long lifetime, and may spread globally, changes in stratospheric sulfur and aerosol concentrations may clearly impact climate.…”

“…37 Since these have a long lifetime, and may spread globally, changes in stratospheric sulfur and aerosol concentrations may clearly impact climate. More recently, however, it has been recognized that even short-lived reactive tropospheric sulfur species may have consequences for climate through their effects on cloud albedos.…”