A mental picture of the greenhouse effect

Abstract

The popular picture of the greenhouse effect emphasises the radiation transfer but fails to explain the observed climate change. An old conceptual model for the greenhouse effect is revisited and presented as a useful resource in climate change communication. It is validated against state-of-the-art data, and nontraditional diagnostics show a physically consistent picture. The earth's climate is constrained by well-known and elementary physical principles, such as energy balance, flow, and conservation. Greenhouse gases affect the atmospheric optical depth for infrared radiation, and increased opacity implies higher altitude from which earth's equivalent bulk heat loss takes place. Such an increase is seen in the reanalyses, and the outgoing longwave radiation has become more diffuse over time, consistent with an increased influence of greenhouse gases on the vertical energy flow from the surface to the top of the atmosphere. The reanalyses further imply increases in the overturning in the troposphere, consistent with a constant and continuous vertical energy flow. The increased overturning can explain a slowdown in the global warming, and the association between these aspects can be interpreted as an entanglement between the greenhouse effect and the hydrological cycle, where reduced energy transfer associated Electronic supplementary material The online version of this article

Implications of a decrease in the precipitation area for the past and the future

“…Total global precipitation estimated for the CMIP5 simulations exhibited a scatter over the range 1386-1640 giga-ton per day, but all models indicated an increase over 2000-2100 in the range of 14-90 giga-ton/day. Precipitation can be considered as a byproduct of moist convection and connected to the greenhouse effect [7], and an increase in the total precipitation implies a shift in the relative contribution of the forms of heat transport from Earth's surface to higher levels where it is free to escape to space. If the energy input is balanced by the heat loss [7], then the total energy flux is defined by the incoming portion 2 (1 − ) 0 , where r is Earth's radius, the planetary albedo, and S 0 the solar constant (SM).…”

“…Precipitation can be considered as a byproduct of moist convection and connected to the greenhouse effect [7], and an increase in the total precipitation implies a shift in the relative contribution of the forms of heat transport from Earth's surface to higher levels where it is free to escape to space. If the energy input is balanced by the heat loss [7], then the total energy flux is defined by the incoming portion 2 (1 − ) 0 , where r is Earth's radius, the planetary albedo, and S 0 the solar constant (SM). Based on this crude and simplistic calculation, the total precipitation estimated from ERA-Interim implies that moist convection accounted for 32.8% of the vertical energy flow in 1979 and 33.0% in 2016.…”

“…The precipitation between 50 • S-50 • N dominates the water budget of the global hydrological cycle both because it represents 77% of the surface area and because the precipitation is most intense in the tropics (table 2). One plausible physical explanation for the observed decline may be that an increased rate of atmospheric overturning [7] may have resulted in more convection and precipitation from cumulonimbus type clouds rather than more spatially extensive stratonimbus clouds. Such changes will have consequences even ERAINT day −0.5%/decade (p−val=0) Figure 3.…”

“…Contrasting trends between wet and dry regions complicate the estimation of a simple aggregated index such as the global mean temperature or sea level, although an indicator referred to as the hydroclimatic intensity has been suggested [5] that accounts for the differences between dry and wet regions. The movement of water is related to the flow of energy [6] and the greenhouse effect is entangled with the hydrological cycle [7] where the energy flow involves both radiative transfer as well as a chain of processes that includes evaporation, convection, condensation of water vapour to form clouds, and precipitation (e.g. the Hadley cell and the Walker circulation [8]).…”

A simple equation to study changes in rainfall statistics

“…Higher surface temperatures lead to higher rates of evaporation and a more rapid turnover in the hydrological cycle. A change in the hydrological cycle is expected to affect the vertical energy flow and the atmospheric overturning [37], and more intense rainfall is also often associated with higher cloud tops [38]. In addition, a decrease in the global area with daily rainfall implies a general decrease in f w and increase in μ [39].…”