Increasing cloud in a warming world

Abstract

Cloud amount records for the U.S.A. have been analyzed in the context of the 'warming world' analogue model described by Lough et al. (1983). Cloud amount increases over practically the entire U.S.A. in all seasons. This result considerably strengthens the more tentative conclusion of HendersonSellers (1986) that clotid amount increases over Europe in the same warming world scenario. These results are in contrast to the few numerical model predictions of cloud changes in warming world experiments. A possible, rather tantalizing, conclusion is that current GCM cloud prediction schemes tend to enhance temperature increases through cloud-climate feedback whereas the historical data could suggest a negative feedback. Part, possibly all, of this difference may be the result of the fundamental distinction between the two experimental scenarios: the equilibrium change modelled by GCMs as compared to the smaller transient change represented by the historical analogue. On the other hand the current 'real-world' experiment is, itself, a transient change in boundary and atmospheric conditions. At the least, surface-observed cloudiness seems to offer a useful and complementary data source with which to examine one aspect of the performance of numerical climate models.

Global radiation climate changes: The world network

“…Neither have increases in cloud cover of the amount required to account for such decreases in K+ been observed. For example, the increase in the running mean annual cloud cover for the continental U.S.A. between 1900 and 1955 was from 0.49 to 0.56 (Henderson-Sellers, 1986b). Using the cloud cover insolation relationships reported by Neumann (1954) and Monteith (1966), this would result in a decrease of only 2.0% in K~; this is less than half the reduction reported herein for a period only half as long, 1958 to 1985. If the reduction in insolation reported is due to an increase in aerosol load its effect on surface air temperature will depend on the height and size distribution of the particles and surface reflectivity (Paltridge and Platt, 1976).…”

“…There is, however, considerable uncertainty concerning cloud feedbacks on global warming (Cess, 1989;Slingo, 1989). From historical records of cloud cover observations Henderson-Sellers (1986a, 1986b has shown for 1958, 1965, 1975 and 1985 59 1958 1965 1975 1985 area represented by each record of K~ of 0.613 M km 2 land surface in 1985 compared with 1.026 M km 2 in 1958. Despite this increase in density global distribution remained very uneven.…”

Hydrological effects of changes in levels of atmospheric carbon dioxide

“…see Manabe, 1983;US Environmental Protection Agency, 1984;Henderson-Sellers, 1987; Idso e t a / . , 1985).…”

Climate engineering a review of aerosol approaches to changing the global energy balance

“…Trends of increasing cloud cover have been reported by several authors (e.g. Henderson-Sellers, 1986). The intriguing possibility that this increasing cloudiness is tied to increasing tropospheric aerosol, along with indirect effects in general, needs further exploration.…”