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According to our calculations for the active industrialization period (1959-2021), the content of anthropogenic CO2 (excluding volcanic activity) was no more than 4.1% of its total content in the atmosphere. The carbon dioxide associated with human activity during this period determines an increase in the Earth global temperature by no more than 0.0004°C, against the total temperature increase of 0.81°С. At the same time, the global temperature increase is assumed to be completely determined by the greenhouse effect of our planet only. In connection with results obtained, the conclusions of IPCC on the leading role of the anthropogenic factor in climate warming do not seem convincing. The possibility of realistic forecasting of changes in the CO2 content in the atmosphere based on a simple regression model and a multiblock (linear and non-linear) of the global carbon cycles was assessed. Annual insolation contrast (AIC) was used as a predictor in the regression model. Generally, AIC (according to the areas of heat source and sink) reflects changes in the meridional insolation gradient, which regulates the meridional transfer of radiative heat in the ocean--atmosphere system. Our eight-block model of global circulation included the following blocks: the atmosphere, land biota, humus, inorganic ocean carbon, phytoplankton, dissolved organic matter in the ocean, sedimentary carbonate rocks of the continents, and sedimentary carbonate rocks in the ocean. Linear and non-linear relationships were used to describe global CO2 fluxes from the atmosphere to biota due to net photosynthesis and from the active layer of the ocean to the atmosphere. Carbon penetration into the deep ocean was described by a diffusion equation, and the other fluxes were described by linear relations. The discrepancy between the two independent model (regression and block) forecasts was 1.2% and 0.93% for 2020 and 2030, respectively. The discrepancy between our calculated data and the actual values of CO2 content for 2020 was 0.24% and 0.97% for the block model and the regression model, respectively. The results obtained indicate no need to use any scenario forecasts proposed by IPCC and leading to uncertainty when forecasting global climate changes.

A brief overview of reliably established global climate events in the Holocene is provided. On the basis of high-precision astronomical ephemeris with high spatial and temporal resolution, the annual and seasonal insolation of the Earth and hemispheres was calculated for the period 3000 BC-AD 2999. According to the results of calculations, the values of insolation contrast were obtained in a generalized manner (for the regions of the heat source and sink), reflecting the changes in the meridional insolation gradient that controls the meridional heat transfer in the hemispheres. The character of long-term variations of both the annual and seasonal arrival, and the annual and seasonal meridional transport of radiation heat in the hemispheres was obtained. The long-term distribution of insolation characteristics of the Earth and hemispheres (annual and seasonal insolation and insolation contrast in the hemispheres) is analyzed. The synchronicity of the extrema of the irradiation characteristics with the global climatic event in the history of the Earth (the Medieval Warm Period of the Holocene) was revealed. On the basis of the revealed synchronicity, the maximum insolation contrast in the winter half of the year in the Northern Hemisphere (the maximum of meridional heat transfer in the winter half of the year), as well as the maximum of interhemispheric heat transfer may be determined to be the reasons for the Medieval Warm Period.

This article discusses the possibility of using an unconventional method of heat treatment of a wall structure in winter. The methods of introducing concrete work at a negative outside temperature are analyzed. The basis of the article is the derivation of systems of differential equations characterizing thermal processes during concreting of a wall fragment to previously constructed sections and floor slabs. A mathematical model has been developed that describes heat transfer processes based on the differential heat equation. In compiling the mathematical model, the classical equations of thermophysics are used, which do not require proof of reliability. The article also discusses the classical boundary conditions of the first, second, third, and fourth genera. The reliability of the calculation results was estimated by the experimental method on a fragment of a concrete wall with a given shape thickness. Processing of experimental data was performed using standard methods of mathematical statistics.

One of the promising means of foamed concrete quality improvement is micro-reinforcement by adding synthetic and mineral fibers to the base mix. This research is the first to investigate peculiarities of using recycled cellulose fiber extracted from waste paper for obtaining fiber reinforced foam concrete. The paper presents results of experimental research on the influence of cellulose fibers on structure and properties of fiber reinforced foam concrete by using methods of chemical analysis and scanning electron microscopy. The research determines peculiarities of new formations appearance and densification of binder hydration products in the contact zone between fiber and cement matrix, which boost mechanical strength of fiber reinforced foam concrete. Physico-mechanical properties of fiber reinforced foam concrete were defined depending on the amount of recycled cellulose fiber added to the base mix. It was found that the use of recycled cellulose fibers allows obtaining structural thermal insulating fiber reinforced foam concretes of non-autoclaved hardening of brand D600 with regard to mean density with the following improved properties: compressive strength increased by 35% compared to basic samples, higher stability of foamed concrete mix and decreased shrinkage deformation.

The article discusses the development of a mathematical model of the thermodynamic system during winter concreting of bored piles. The processes of heat transfer based on the differential heat equation and the Stefan problem are described. A method for calculating the rationale for the parameters of the energy-saving and gentle thermal treatment of concrete using non-traditional sources of thermal energy is proposed. The solutions for using two-phase thermosyphons as heating elements are considered.

In this paper we present a mathematical model of a three-dimensional non-stationary temperature field for concrete that hardens in winter conditions. The developed mathematical model describes heat transfer processes basing on the differential heat equation. We also consider the classical boundary conditions of the I, II, III and IV kinds. We compiled a computer interpolation of the family of nomograms in the second order regression equation in order to calculate the relative theoretical strength of concrete after heat treatment.