"We can expect the onset of a deep bicentennial minimum of total solar irradiance (TSI) in approximately 2042±11 and the 19th deep minimum of global temperature in the past 7500 years – in 2055±11. After the maximum of solar cycle 24, from approximately 2014 we can expect the start of deep cooling with a Little Ice Age in 2055±11."
--Habibullo I. Abdussamatov, Russian Academy of Science, 1 February 2012
Temporal changes in the power of the longwave radiation of the system Earth-atmosphere emitted to space always lag behind changes in the power of absorbed solar radiation due to slow change of its enthalpy.
That is why the debit and credit parts of the average annual energy budget of the terrestrial globe with its air and water envelope are practically always in an unbalanced state. Average annual balance of the thermal budget of the system Earth-atmosphere during long time period will reliably determine the course and value of both an energy excess accumulated by the Earth or the energy deficit in the thermal budget which, with account for data of the TSI forecast, can define and predict well in advance the direction and amplitude of the forthcoming climate changes.
From early 90s we observe bicentennial decrease in both the TSI and the portion of its energy absorbed by the Earth. The Earth as a planet will henceforward have negative balance in the energy budget which will result in the temperature drop in approximately 2014.
Due to increase of albedo and decrease of the greenhouse gases atmospheric concentration the absorbed portion of solar energy and the influence of the greenhouse effect will additionally decline. The influence of the consecutive chain of feedback effects which can lead to additional drop of temperature will surpass the influence of the TSI decrease. The onset of the deep bicentennial minimum of TSI is expected in 2042±11, that of the 19th Little Ice Age in the past 7500 years – in 2055±11.
William Herschel (1801) was the first to report correlation between a level of sunspot activity and the climate after his discovery of inverse interrelation between a wheat price and a level of cyclic variations of solar activity before and during Dalton minimum. When the Sun’s surface was covered with sunspots, the wheat prices were going down. When the number of sunspots dropped the prices went up. He supposed that variations of wheat prices are the consequence of the corresponding climate changes. However, he could not explain the physical nature of this phenomenon. Later Eddy (1976) was discovered interconnection between clearly determined periods of significant variations of the sunspot activity level during the last millennium and corresponding deep climatic changes in both phase and amplitude. During each of the eighteen deep minima of solar activity (of Maunder type) with a bicentennial cycle found in the preceding 7.5 millennia, deep cooling was observed, while during the periods of high maxima – global warming (Borisenkov, 1988). Recent studies (Bal, et al. 2011; McPhaden, et al. 2011) confirm our results (Abdussamatov, 2009a, b) concerning a common action of eleven-year and bicentennial cyclic variations of the total solar irradiance (TSI) (with some time-lag) on the change of state of the surface and subsurface layers (with the depth of tens and hundreds of meters) in the tropical part of the Pacific Ocean accompanied with appearance of warm or cold water (the cycles of La Niña or El Niño phenomena) which affects the climate change as well. Observed characteristics of El Niño during the last 31 years have been changing in the opposite direction with regard to predictions of the climatic models assuming predominant influence of the greenhouse gases.
4. Bicentennial Decrease of the TSI Leads to the Little Ice Age
From early 1990s the values of both eleven-year and bicentennial components of TSI variations are decreasing at accelerating (at present) rate (Fig. 2), and hence a fraction of TSI absorbed by the Earth is declining at practically the same rate (e.g., Fröhlich, 2011; Abdussamatov, 2007b, 2009a, b). Average value of TSI in the 23rd cycle was by 0.17 W/m2 less than in the 22nd cycle. Smoothed value of TSI in the minimum between the cycles 23/24 (1365.24 ± 0.02 W/m2) was by 0.26 W/m2 and by 0.33 W/m2 less than in the minima between cycles 22/23 and 21/22, respectively. However, forming from early 1990s long-term deficit of TSI (see Fig. 2) was not compensated by decrease in the emission of the Earth intrinsic thermal energy into space which practically remains on the same high level during 14±6 years due to thermal inertia of the World Ocean. Since the Sun is now entering a bicentennial long-term phase of low luminosity (e.g., Abdussamatov, 2004, 2005, 2007b; Penn and Livingston, 2010; American Astronomical Society, 2011) such energy imbalance of the system (E<0) will continue further for the next few 11-year cycles. As a result, the Earth as a planet will henceforward have negative balance (E<0) in the energy budget. This gradual consumption of solar energy accumulated by the World Ocean during the whole XX century will result in decrease of global temperature after 14±6 years because of a negative balance in the energy budget of the Earth. This, in its turn, will lead to the rise of Earth albedo, the drop of atmospheric concentration of the most important greenhouse gas – water vapor, as well as of carbon dioxide and other gases.
Let us note that water vapor absorbs ~68% of the integral power of the intrinsic long-wave emission of the Earth, while carbon dioxide – only ~12%. As a consequence, a portion of solar radiation absorbed by the Earth will gradually go down together with manifestations of the greenhouse effect caused by the secondary feedback effects. The influence of the growing consecutive chain of such changes will cause additional decrease of the global temperature exceeding the effect of a bicentennial TSI decrease.
Since the Sun is now approaching the phase of decrease of bicentennial luminosity on the basis of observed accelerating drop in both the 11-year and bicentennial components of TSI from early 90s, we can forecast its further decline similar to a so called Maunder minimum down to 1363.4±0.8 W/m2, 1361.0±1.6 W/m2 and down to a deep minimal level 1359.5±2.4 W/m2 in the minima between the cycles 24/25, 25/26 and 26/27, respectively (Fig. 3).
Assuming an expected increase in the duration of the eleven-year cycles during the phase of decline of a bicentennial cycle (Abdussamatov, 2006, 2009a,b), we can expect the approximate moment of minimum between the cycles 24/25, 25/26 and 26/27 in 2020.3±0.6, 2031.6±1.2 and 2042.9±1.8, respectively. Under these circumstances the maximal smoothed for 13 months level of sunspot number in the cycles 24, 25 and 26 can reach 65±15, 45±20 and 30±20, respectively (Abdussamatov, 2007b, 2009a,b). Hence, we can expect the onset of a deep bicentennial minimum of TSI in approximately 2042±11 and of the 19th deep minimum of global temperature in the past 7500 years – in 2055±11 (Fig. 4).
In the nearest future we will observe a transition (between global warming and global cooling) period of unstable climate changes with the global temperature fluctuating around its maximum value reached in 1998-2005. After the maximum of solar cycle 24, from approximately 2014 we can expect the start of the next bicentennial cycle of deep cooling with a Little Ice Age in 2055±11. Thus, long-term variations of TSI (with account for their direct and secondary, based on feedback effects, influence) are the main fundamental cause of climate changes since variations of the Earth climate is mainly determined by a long-term imbalance between the energy of solar radiation entering the upper layers of the Earth's atmosphere and the total energy emitted from the Earth back to space.
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