1. Introduction
So far, the predictions of climate changes are those reported in successive Intergovernmental Panel on Climate Change (IPCC) reports (IPCC, 2014; IPCC, 2022) issued from an international consensual exploitation of the available literature to predict climate changes in distant future. The trends are still small but nevertheless detectable today. The consensus is adopted almost universally although controversies exist, the dispatching of which is limited to articles in open access archives, blogs and magazine outlets [Dunlap & Jacques, 2013].
Until recently, global climate changes were assigned to imbalanced inputs and outputs of electromagnetic infrared radiations and to anthropogenic greenhouse gas, especially CO2, considered as sources of radiative anthropogenic heat release at the top of the troposphere (rAHR) (IPCC, 2014; NASA, 2009; Mackenzie & Lerman, 2006) without consideration to heat in the low atmosphere, notably anthropogenic heat release (eAHR), also known as waste heat energy, generated by the sources of energy produced and exploited by humanity for works. In the past, only rAHR related to greenhouse gas was taken into account and considered as absorbed predominantly by oceans (Hansen, et al., 2011; Trenberth et al., 2014; IPCC, 2014). rAHR is said resulting from electromagnetic radiative flux that amounted annually from 0.5 to 1 W/m2 in the early 2000s (Trenberth et al., 2014; IPCC, 2014), i.e. between about 8 and 16 x 1021 Joules (8 and 16 Zeta Joules (ZJ)). The AR6 IPCC reports an observed annual average rate of heating of the climate system at 0.79 [0.52 to 1.06] W m–2 (12.7 ZJ) for the period 2006–2018 (IPCC, 2022). Regardless of its origin, heat energy released or generated in the atmosphere has to be evacuated to space otherwise it is absorbed and causes warming as it is proposed in the case of residual radiative forcing assigned to greenhouse gas. According to (IPCC, 2022), “ocean warming accounted for 91% of the heating in the climate system, with land warming, ice loss and atmospheric warming accounting for about 5%, 3% and 1%, respectively (high confidence) ”.
In general, global ice was considered a negligible heat absorber relative to oceans (Hansen et al., 2011; IPCC 2022). Based on outstanding facilities including satellites, NASA is the reference body to quantify ice imbalance and its role on the polar environment (Scott & Hansen, 2016). The occurrence of dramatic global ice loss is now certain, especially over the recent years, and concerns different ices, namely ice caps, sea ice, glaciers and permafrost (Rignot et all, 2019; Slater et all, 2021). Ices melting is generally considered as a source of ocean rise (Allan & Liepert; 2010) on top of temperature-dependent dilatation. Long considered negligible, eAHR is now more and more regarded as a contributing factor to climate changes. The context and the history are well introduced in a recent publication (Yang et al, 2017) in which the authors proposed an algorithm to evaluate global eAHR. This approach consisted in calculations based on heat energy estimates derived from urban zones. Although there were limitations, the algorithm provided multi-scale anthropogenic heat information said reliable and useable for further research on regional or global climate changes and on urban ecosystems despite difficulties to establish ratios for converting energy consumption to anthropogenic heat.
Earth, as living systems, is too complex to be represented experimentally so that exploitations using climate models is necessarily based on local measurements or on global averaged data like radiative forcing in term of flux in W/m2. We recently attempted a different approach (Vert, 2021) based on ice loss, fundamentals of chemistry and physics and annual global energy consumptions derived from various sources (fossil ones, biomass, nuclear electricity, etc.) found converted in oil-equivalents (Martin-Amouroux, 2015; BP, 2019). According to (Manowska, & Nowrot (2019), eAHR corresponds to c.a. 60 % of the global energy consumption, the rest being consumed to provide work. On the basis of this estimate, it was deduced that eAHR released from all the energy sources in the low atmosphere between 1994 and 2017 provided enough thermal energy (7.2 ZJ) to melt 77% (Vert, 2021) of the 28 trillion tonnes of disappeared ice reported recently for the same long period (Slater et all, 2021). The corresponding 0.31 ZJ annual average eAHR estimate was effectively negligible when compared with the 12.7 ZJ estimate of annual average rAHR deduced from the 0.79 W/m2 annual average rate of heating of the climate system applied to the surface of the planet (IPCC AR6, 2022). As ices imbalance is a partial signature of heat energy supply regardless of its origin, the large dominance of rAHr, a source of energy assigned to CO2-based radiative forcing, raises a question: why rAHR that is said warming the environment does not cause much greater ices imbalance than presently observed since, in physics, any source of heat tend to transfer part of it to its environment up to equilibrium?
In attempt to answer this question, , let us consider that solar radiations have been heating the global environment over billions of years without dramatic heat accumulation despite occurrence of short and long and more or less important local ups (high temperature) and downs (glaciation) periods. The relative stability included natural greenhouse effect assumed the origin of a 15°C excess of average temperature relative to an atmosphere-free Earth. eAHR, rAHR and any other sources of heat on Earth have to be managed similarly and simultaneously to solar heat to keep Earth’s environment and climate under relative control and compatible with Life. Indeed, the Earth can be schematically considered as a huge globe with land, solid matters, surface water and atmosphere heated locally since no matter or molecule can escape in intersidereal space. Only the energy stored in molecules can escape to space through radiation phenomena.
A few thousand years ago, humans began to use biomass as sources of heat and light. The generated eAHR remained very small compared with solar inputs until about 150 years ago when humans began to exploit fossil sources and, more recently, nuclear energy and renewable resources for the production of electricity in order to satisfy work, heat and comfort needs. The side effect was the appearance of increasing eAHR in the low atmosphere in addition to rAHR in the high troposphere (Yang et al.; 2017). Therefore, Earth can be compared to a mammalian body which has its metabolism generating heat in a closed space, the body. This body which burns foods has to be cooled to keep its temperature constant. Cooling is provided by the evaporation of sweat. If water cycle has been recognized for years as an important factor in climate control (Allan & Liepert; 2010), water evaporation and condensation have not been considered as important to limit the storage of radiative forcing in oceans.
The present article aims to compare Earth’s water with the refrigerant that controls the temperature inside a refrigerator, a simpler example than human body, where inner heat has to be eliminated. Results are discussed relative to global warming and climate changes.