The Earth's Imbalanced Heat Budget and its Relationship to Past, Present and Future Climate Change Michel Vert IBMM, UMR CNRS 5247, University of Montpellier, France Corresponding author: [email protected] Abstract: Climate changes predicted by the International Panel on Climate Change are currently linked to the growth of an excess of carbon dioxide in the atmosphere, as successive reports have asserted. The forecasts are based on an unusual exploitation of greenhouse physics that results in ocean warming due to radiative forcing. In the absence of experimental support, the mechanism and predictions are universally adopted but only by consensus. Many scientists have opposed the consensus on the grounds that the bases do not respect the fundamentals of hard sciences. Recently, we proposed an alternative mechanism in which the radiative forcing due to carbon dioxide is replaced by heat, a fundamental phenomenon in physics and thermodynamics. According to this new mechanism briefly recalled, heat is managed on Earth by water and its interphase equilibria, whatever the sources. Previously developed for the present, it is used here to show that the Earth's heat balance, hitherto said to be balanced in terms of radiative flux inputs and outputs, has never been balanced in terms of heat. The thermal imbalance in the distant past was estimated from the energy necessary for the melting of the ice during the last deglaciation, during the current Holocene interglacial plateau, and between 1994 and 2017. The melting of the ice progressed almost linearly during the first 80% of the deglaciation period with a slow decline towards near-steady-state during the Holocene. Estimates of ice loss over the period 1994-2017 showed that the imbalance is increasing again, a feature that should lead to a proliferation of sun-obscuring clouds followed by the inversion of the imbalance required to initiate the next ice age. The confirmation of the disqualification of carbon dioxide as a source of global warming could put back in the saddle certain applications currently penalized due to the production of this gas. In any case, it is the fight against anthropogenic heat sources that should be promoted in the future. Keywords: global warming, paleoclimatology, heat management, thermal infrared radiations, glacial cycles, Key Points• The Earth budget is said to be balanced in terms of radiative input and output, but it is not balanced when thermal infrared waves present in solar irradiation are converted to heat.• The thermal imbalance on Earth, significant during past glaciation periods, was almost stable during the Holocene interglacial plateau but is currently increasing again en route to the reversal necessary to cause the next glaciation• Thermal imbalance provides credible justifications of glacial cycles and Holocene climate changes but leaves open the question of the responsibility for increased anthropogenic heat. I Introduction Climate change is a source of concern, as it is currently linked to an increase of atmospheric carbon dioxide (CO2) attributed to human activities. Excessive carbon dioxide in the atmosphere is believed to be the cause of global warming at the origin of dramatic climate forecasts for coming decades. Both the mechanism and the forecasts result from successive reports issued by the Intergovernmental Panel on Climate Change (IPCC), an organization created in 1988 with the mission of assessing and exploiting the climatology publications fund [1]. In the absence of experimental support, the forecasts come solely from hypothesis and models in which a greenhouse effect, different from that well known in physics, and the resulting radiative forcing stored in oceans play essential roles. There are many reasons to contest this mechanism [2], not least because it lacks scientific consistency and does not respect the fundamentals of hard sciences [2]. This may be due to the fact that climatology is a field where state of the art and advances are not discussed in a multidisciplinary and contradictory manner in national or international congresses and conferences, unlike what is usually done in science. Until now, protest arguments, generally considered to be signs of climate skepticism, were mainly limited to the “state of the art” in the absence of alternative mechanism. To fill this gap, an alternative mechanism has recently been proposed [3] in which heat is the physical phenomenon that warms the planet, while water and its interphase equilibria are the means by which heat is managed until radiative removal in space is possible. Water exists in solid, liquid and vapor physical forms in the environment and in the atmosphere, unlike CO2 and other greenhouse gases (GHGs), which are only gaseous. In the hard sciences, melting of ice and evaporation of liquid water are recognized as highly efficient heat absorbers and transmitters. Based on these undisputable facts, it has been demonstrated that the role of water in heat management on Earth is comparable to that of the volatile refrigerant operating in a refrigerator to absorb internal heat and release it to the outside through evaporation-condensation cycles [4]. This new vision had several important consequences. First, on Earth, the melting of ice in combination with evaporation and condensation phenomena absorb and manage the natural heat inputs (solar, volcanic, and from forest fires) since water and life exit on Earth. Today, the anthropogenic heat inputs are added that must be managed by the same mechanism. Second, while solar irradiance passes through space unchanged, some waves are more or less absorbed specifically as soon as they encounter molecules and matters present on Earth, including GHGs present in the air. Despite this undisputable fact, it is common strategy to consider the solar irradiance in its entirety when discussing the Earth’s Heat Budget. This means that visible light is capable of heating atmosphere and land, which is obviously not observed in the environment. Reflection and diffraction are taken into account, but the selection of waves by absorption and the conversion of thermal infrared ones in heat are not. Physics teaches us that a thermal infrared radiation with a wavelength in the range of about 4 to 30 µm is absorbed (its intensity decreases proportionally to the concentration in absorber and to the path length) to generate heat. The process reflects an energetic harmony between the radiative energy of such a wave and the discrete interatomic vibrational energy of an asymmetric transition forming an electric dipole. Therefore, water vapor that absorbs strongly thermal infrared waves is an absorber (greenhouse gas) in reality much more efficient to generate heat than CO2. Despite this essential property, water vapor is neglected in climatology [1] and by NASA as well [5] because its residence time in the atmosphere is too small, particularly relative to the long-lived CO2. This is not correct because in chemistry and physics, it is the concentration that must be considered when it comes to interaction with and absorption by electromagnetic waves moving at the speed of light. Therefore, in addition to ice that cools the environment on melting, we have attributed to water vapor a major role in the water-based mechanism because when the temperature of the liquid water at the surface increases, evaporation tends to absorb the heat by generating warm vapor rising to a cooler zone to form clouds when local conditions are favorable. The result is a transfer of the heat from the surface to a cool zone from where it can be directly eliminated to space, notably through the 8-14 µm spectral transparency window specific of the atmospheric water vapor [6], or indirectly from clouds above which the concentration in water vapor is very small and favorable to radiative elimination of heat, as well schematized in a video [7]. Transparency above clouds or when the humidity is low has an unexpected advantage in the case of aircrafts flying high in the sky. Indeed, the heat due to hot CO2 and hot water vapor ejected by the engines can be easily removed in space radiatively, a property that can mitigate the negative role attributed to aircraft in terms of radiative forcing of CO2 and of carbon footprint. In other words, in terms of anthropogenic heat releases, an airplane at altitude could be more acceptable than a car on the surface, which remains to be proven quantitatively. Third, whatever its origin, if the heat input into the environment increases, the ice stock decreases and gradually evaporation increases, as does cloud formation. In addition to being a source of heavier rainfall, or even flooding, a dense cloud layer can block thermal infrared radiation on the way in and out, a process that must first lead to a rise in temperature under the clouds followed by a rapid inversion towards cooling, as is easily felt in cloudy weather. If the cooling is severe, as in winter when solar heat gain is minimized by longer nights and a longer Sun-Earth distance, or when the night-time atmosphere is dry, icing occurs. The process is well illustrated by a dark, stormy sky under which a fairly high temperature suddenly drops, while ice stones form and eventually fall to the surface. Environmental events such as winds, hurricanes, tornadoes, air and ocean streams are the means by which heat is distributed and tend to average out local temperatures and meteorological differences. In reality, the average is largely limited by the size of the planet, the heterogeneity of its components and the involvement of chaotic phenomena affecting the air, seas and oceans. It remains to be seen whether the various recently identified anthropogenic heat sources are sufficiently large to worsen natural climate change [8]. The balance between the input and output of radiative fluxes is a fundamental basis of climatology. This is no longer the case when thermal infrared radiation is converted into heat. A good reason for this is kinetic. In space and in a transparent medium, electromagnetic waves travel at and near light speed, respectively. Conversely, heat exchanges and balancing occur through slow convection and conduction phenomena. Currently, the small variations in global temperature and sea level occurring during the Holocene are in favor of balance, but if we consider ice loss and glacial ups and downs in distant past, they point to time-dependence of thermal imbalance. Indeed, glacial cycles are characterized by changes in temperature and sea level of up to around 10°C and 120 m, respectively [9]. A complete cycle lasts between 120 and 150 thousand years (kyrs), according to the last four glaciations reported by paleoclimatologists [9]. A cycle is made up of a period of fairly rapid deglaciation lasting 10 to 20 kyrs, followed by an interglacial plateau lasting 10 to 20 kyrs and a period of very slow glaciation lasting at least 100 kyrs. The case of the pre-Holocene deglaciation that covered the period from -20 to -10 kyrs before the present (BP) is schematized in Figure 1. The preceding glaciation period was about 10 times longer, a difference attributed in part to the involvement of several interphase transitions not involved in the deglaciation process [2]. Monitoring climate change is difficult, if not impossible, because it depends on many factors, most of which are time- and location-dependent, such as solar heating, temperature, evaporation and cloud formation. The corresponding data vary from one source to another and, unlike in many other scientific fields, the extent of errors and uncertainties is difficult to quantify. Although far from perfect, solid ice is a better indicator of change. Although rare, in situ glacier mass balance surveys date back to the 1890s [11]. It was not until the 1970s that substantial records of changes in the cryosphere became available through satellite observations. The extent of ice shelves has been monitored by satellite imagery since the 1940s [12]. The extent of sea ice has been monitored by satellite since the late 1970s [13]. Changes in ice cap, ice shelf, sea ice and glacier thickness have been systematically recorded by satellite altimetry since the 1990s [14].
