Schematic representation of the volume of water equivalent to the volume of water generated during the pre-Holocene deglaciation.
II.2 Thermal Energy necessary to melt 28,000 Gt of ice
The heat energy absorbed to melt the 28,000 Gt of ice or 28 x 1015 kg lost between 1994 and 2017 was about 9.34 x 1021 or 9.34 ZJ. The rise in ocean level due to the melting of the ground ice was about 35 mm, i.e. 1.5 mm/year [15].
III Discussion
III.1 The distant past
During the last deglaciation, melting was very active and formed liquid water which caused the ocean level to rise. The available data differ slightly from one source to another but we have retained respectively + 120 m of ocean level rise and +10°C of temperature rise [9,18]. These increases were rather rapid since they spread over around ten kyrs. Basically, the melting of ice indicates the presence of excess of heat mainly due to solar radiation and more precisely to the conversion of incoming solar infrared radiation into heat after absorption mainly by water vapor molecules [7]. In terms of ocean level change, the melt of floating ice has almost no effect. Only the land ice contributes. In contrast, in terms of heat absorption, the floating ice contributes significantly but its contribution was not included in our assessment because of inaccessibility. This drawback affected the consistency of the heat imbalance derived from the ocean level change but left the possibility of exploiting the trends for comparison purposes. According to our assessment, deglaciation involved 4.24 x 1019 kg of land ice, an estimate close to the 52 x 106 km3 (about 4.7 x 1019 kg) determined by a more complex method applied to - 134 m ocean level at the maximum glaciation [18]. The melt of 4.24 x 1019 kg of ice required at least 14,141 ZJ of heat energy. During the first -20 and -12 Kyrs BP, atmospheric humidity was very low and the solar heating was thus very efficient over the icy areas. The ocean levels rose rapidly and almost linearly despite minor intermediate variations [18]. Between –20 and –12 Kyrs BP the annual thermal imbalance and the ocean rise were approximately 1.6 ZJ and 12.5 mm, respectively. Today the stock of ice on Earth is estimated at about 2.6 x 1019 kg [19-20]. Therefore, the amount of land ice lost during deglaciation was almost twice as large as the current stock. After a transition period of about 4 kyrs, the changes levelled off and the Holocene interglacial plateau was established with rather small ocean level and global temperature variations. Over the last 6 kyrs BP, the annual rise of the oceans was about 0.2 - 0.5 mm [21]. Meanwhile, temperature fluctuations were limited to a rather narrow ± 1°C range [22] even if the occurrence of minor intermediate warming has been reported [23-24]. In the case of archaeological studies cited in the AR4 IPCC report, Roman ruins built near sea level in Israel and the west coast of Italy suggest a mean eustatic component of 0.07 mm per year over the last 2000 years [25]. Taking 0.3 mm as the annual average ocean rise between - 6 and - 2 kyrs BP and 0.1mm for the next 1.8 kyrs before the start of the industrial era, annual heat imbalances were respectively approximately 4 x 10-3 ZJ and 1.4 x 10-3 ZJ, which means almost three orders of magnitude lower than during deglaciation. The relative steady state observed during the Holocene agrees well with the control by ice loss, evaporation and humidity taught by the water-based heat management mechanism. This mechanism complements the fund of possible origins emitted so far to account for glacial cycles [26].
II.2 The present and the future
Today, the heat budget includes anthropogenic heat input. Anthropogenic heat is generally discussed in terms of waste heat from energy consumptions [2, 27-30], and loacal and urban contributions [31-32]. However, we recently expanded the list to include inputs due the artificial enclosed spaces like cars, buildings, photovoltaic and thermal panels, etc., which are all greenhouse-like systems as defined in physics [6].
Ice melt and evaporation that limited the increases of global temperature and ocean level during Holocene millennia appeared to have increased over the past two centuries, as evidenced by the ice imbalance between 1994 and 2017 reported in [15]. During these 23 years, the loss of ice was 28,000 Gt that absorbed 9.34 ZJ, with approximately half absorbed by the melt of sea ice [15]. The imbalance due to land ice was thus approximately 4.15 ZJ, the average annual imbalance being 0.18 ZJ. However, in reality, the annual imbalance ranged from an average of 800 Gt in the 1990’s to an average of 1,300 Gt in the 2000’s [15]. During the study period, the ocean level rise was 35 mm with an annual rate of 1,5 mm significantly higher than in the mid Holocene [15].
According to the water-based heat management, a rise of heat imbalance can be related to a natural loss of efficiency of ice melt and evaporation after 10 kyrs of interglacial glacial plateau, or to an increase of anthropogenic heat, or both. In other words, the question remains open as to whether the acceleration of temperature currently emphasized by climatologists is natural or is the signal of an acceleration due to an increase in anthropogenic heat. Anyhow, the future should be characterized by more and more evaporation and more and more clouds leading to Sun masking and therefore to a reversal of imbalance that will pave the way for a new glaciation. Data by hemisphere are missing. However, ice loss appears to occur more in the Northern hemisphere [33] where a majority of the humanity is located and where an excess temperature is observed [34]. This imbalance between the hemispheres can be seen as an argument in favor of the existence of a relation between anthropogenic heat and an acceleration of climate changes. In particular, the loss of grounded ice is often regarded the main source of ocean level rise. However, such rise is, actually, more or less mitigated by evaporation which leads to more humidity, more clouds in the air and more rains in return, and likely more floods offset by droughts elsewhere. Although minor with respect to the volume of liquid water present on Earth, it is interesting to note that, when burning, hydrocarbons release hot liquid water stored in fossils fuels long ago, or as biomass [4].
IV Conclusions
The large variation in ocean level reported by paleoclimatologists has been used to estimate the thermal imbalance that caused the melting of ice during the pre-Holocene deglaciation period. The imbalance was shown to still be active though largely reduced during the last 8 Kyrs of the Holocene interglacial plateau that includes the 21th century. Once the Holocene was well underway, ocean level and global temperature remained fairly constant, consistent with a control by ice melt and evaporation. Currently, the imbalance is increasing again but, so far, current climate changes perceived as abnormal can hardly be considered a serious threat because they are still within preindustrial limits. However, and independently of its origin, the acceleration in annual ice loss observed today is in favor of a future drift in temperature exceeding the upper limit observed in the Holocene. If so, the result will likely be greater ice loss, more evaporation and ultimately more clouds partly obscuring solar heating, but enough to cause a reverse thermal imbalance, a necessary condition for the occurrence of a new glaciation. In the future, the average global ice imbalance, the humidity of the atmosphere, and the extent and the density of cloudy zones are the markers of climate evolution to follow. Given the stock of ice still present on Earth, the next glaciation is not expected for several centuries unless the release of anthropogenic heat diverges as one might fear if the growth of humanity and the race for better living standard continue.
Last but not least, appealing to excess of CO2 was not necessary to account for climate fluctuations like warming, floods and droughts perceived today as abnormal. The role given to heat and the management by water and its different physical forms, applicable before the industrial era provides a credible origin as soon as today instead for several decades as the IPCC claims in the case of CO2. This finding suggests reconsidering certain beliefs and strategies in terms of life cycle assessment. For instance, heat generated by aircrafts burning fossil fuel high in the dry skies should be rapidly eliminated radiatively in space, unlike the heat from surface vehicles moving in a humid air. Therefore, aircrafts may not be as bad as they are made out to be because of CO2 emissions. On another hand, making hydrogen from oil could arouse interest despite the production of carbon dioxide that is one of the reasons to currently limit the development of this source of energy issued from water and restituting water after exploitation.
Acknowledgements
MV is indebted to the University of Montpellier for providing an access to peer-reviewed and on-line free archive literatures and blogs.
Remark
Failing to respect the consensus on CO
2, I faced reject of some previous papers by journals specialized in Climatology (and I am not the only one (see
https://youtu.be/zmfRG8-RHEI?si=Qp1Dlm8XptIdQ-Re). These papers are available in free access archives or published in journals specializing in energy (see the reference list). The present work has again been placed as preprint in open archives and is left to the appreciation and the fair exploitation by readers with citation. Today, publishing is too expensive for a scientist on pension.
References
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https://doi.org/10.34343/ijpest.2023.17.e020034) Vert, M., (2021) Refrigerator as Model of How Earth's Water Manages Solar and Anthropogenic Heats and Controls Global Warming,
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