6. Water released from fossil hydrocarbons
In the previous section, the discussion was based on a constant mass of water on Earth dispatched as solid, liquid, vapor and clouds since matter cannot escape to space. However, the combustion of all hydrocarbons (oil, natural gas, and biomass) that generates hot CO2 from the carbon content generates also water as hot vapor from the atoms of hydrogen included in molecules. Once the heat stored in these hot gases is transferred to the environment; the cooled and condensed hot water constitutes a surplus that joins the existing pool of liquid water. It is important to note that heat produced by biomass burning is not compensated at the stage of biomass formation because this renewal requires solar light at ambient and not heat.
Quantifying the amount of extra water from hydrocarbons is as difficult as quantifying heats of e and rAHR-types. Nevertheless, estimates of the overall consumptions (close but slightly less than productions when heat release is concerned) of fossil oil and natural gas are available in oil equivalents and provide means to estimate the surplus of water. Between 1870 and 2018, about 180 Gt of oil and 30 GToe of natural gas have been extracted (Martin-Amouroux, 2015; BP, 2019) i.e. about 210 Gt of hydrocarbons. To compensate the complex composition of oil and natural gas, one can assume these fossil hydrocarbons, including methane (CH4), composed of alkanes only, the general chemical formula of which is CnH2n+2 reasonably simplified to nCH2. Accordingly, 210 Gt of oil equivalent contain c.a. 180 Gt of carbon and 30 Gt of hydrogen. From the general equation CH2 + 3 O2 → CO2 + H2O + heat, 14 g of hydrocarbon (12 + 2) generates 44 g of CO2 (12 + 32) and 18 g of water (16 + 2), both compounds being hot. One can deduced that 210 Gt of hydrocarbons produced about 270 Gt of hot water in about 150 years. In 2018, 8 GT of oil equivalent of the hydrocarbon-type generated about 11.3 GT of hot water, an amount negligible compared with the heat absorption capacity of 1,500 GT of disappeared ices and of surface water evaporation.
According to section 5 and 6, the waste heat derived from the production and the consumption of energy on Earth seems negligible today relative to the radiative forcing estimate. However, this may change in the future if the production of energy continues to grow while the production of anthropogenic CO2 and the corresponding radiative forcing are decreased as recommended to politicians by IPCC.