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SOLAR RADIATION AND CLIMATE OF THE EARTH


BASIC RESULTS AND CONCLUSIONS

Solar climate of the Earth

1. In the modern era, the temporary variability of incoming solar radiation is marked by a secular trend for the annual reduction probably related to the increase of the distance between the Earth and the Sun as a result of Earth orbit eccentricity change. Annual reduction of incoming radiation for the whole period (3000 B.C. - 2999 A.D.) is 1.159Ĺ+09 J/m2 or 0.339% of the annual average value of radiation coming to the Earth (in the absence of atmosphere) for this period. Against the background of incoming solar radiation, interannual, 2-, 3-, 8-, 11- and 19-years periodicity develops.

2. In the spatial variability, with general reduction of radiation coming to the Earth in its polar areas, a trend for significant reduction is revealed, and in the equatorial area—to reduction of solar radiation incoming for the tropical year. This nature of solar radiation distribution is related to secular variations (reduction in the modern era) of the Earth's rotational axis inclination with a period of about 40,000 years(Milankovich, 1939). Thus, latitudinal contrasts in the modern era increase (seasonal ones are levelled). This effect may result in escalation of meridian heat transfer from the equatorial region to polar regions within total atmosphere circulation and changes of the Earth’s global climate. Reduction of radiation coming to solar regions for the whole period (3000 B.C. - 2999 A.D.) reaches 1.58Ĺ+08 J/m2, which amounts to 2.8% relative to the average (for the entire interval of 5,999 years) value of incoming radiation for zones of 85–90 degrees of latitude. Increase in the equatorial region (0–5 degrees of latitude) is 3.32Ĺ+07 J/m2 (0.25%).

3. The biggest contribution into the long-term variability is made by the 19-years periodicity. Regular changes are found in the spatial structure of incoming radiation in various phases of the 19-years nutation cycles. A single phase of the cycle is described by the reduction of radiation coming to polar regions and its increase in the equatorial area. The other phase shows an opposite situation—reduction of incoming radiation in the equatorial area and its increase in polar regions. One phase of the 19-years summer cycle intensifies the secular trend for the reduction of incoming solar radiation, and the other phase attenuates it.

4. With lower amplitude values in terms of radiation income, interannual, 2-, 3-, 8-, 11-years periodicity is expressed, with 2- and 3-years periodicity forming 8- (2+3+3) and 11-years (2+3+3+3) combinations synchronized with 8- and 11-years phases of the 19-years cycle. Thus, 8- and 11-years cycles represent a result of synchronization and superposition of 19-, 2- and 3-years variations.

5. The secular trend for changes in incoming solar radiation contains the following features.

ŕ). In winter six months for hemispheres, the income of solar radiation is increased, and in summer six months, it is reduced. Analysis of changes in radiation coming to the Earth within the considered interval for hemispheres shows that during summer six months for hemispheres, the reduction is 1,19Ĺ+09 J/m2, and during winter ones — 6.10Ĺ+08 J/m2. These changes can be probably related to changes in Earth's rotational axis orientation as a result of precession.

In winter six months for hemispheres, the most significant increase is found in the 3rd month (during the last 1/3 part) of the autumn astronomic season and the 1st month of the winter astronomic season in each hemisphere. Maximum increase of incoming radiation is found in latitudinal range 35-50 degrees of latitude in each hemisphere.

In summer six months for hemispheres, the most significant reduction is found in 2nd and 3rd month of the spring astronomic season in each hemisphere. The reduction during these seasons is sequentially increased along with the latitude increase.

b). Maximum reduction in secular variability occurs on equinoxes, and minimal ones—on solstices. In the annual radiation income, maximum radiation is found for solstices and minimal one for equinoxes. It means that the secular trend of solar radiation income in the annual course is opposed to the annual income.

c). Dead zones are distinguished, i.e. polar areas that are not supplied with solar radiation during individual seasons (for the whole period of 5,999 years). During the 2nd and 3rd autumn months (last 2/3 of the astronomic autumn) and two first winter months (two first thirds of the astronomic season), latitudinal zones 80-90 degrees of latitude are not supplied with radiation at all, in each hemisphere. In the last third of the astronomic autumn and the first third of the astronomic winter, the income of solar radiation equals zero in zones within 70-80 degrees of latitude in each hemisphere.

d). A subequatorial zone is distinguished within 5 degrees southern latitude to 5 degrees northern latitude, which is described by the increase of incoming radiation at the studied interval during the whole year. This zone is expanded to 10 degrees of latitude in 2nd and 3rd month of the astronomic spring and first two thirds of the astronomic season and the first third of the summer for each hemisphere, and 15 degrees in the last third of the spring astronomic season and the first third of the astronomic season in each hemisphere.

6. Maximum values of amplitude with interannual variability of incoming radiation are typical of equatorial and polar regions. Minimal values are typical of latitudinal zones 60–65 degrees in each hemisphere.

During summer six months for the northern hemisphere, maximum amplitudes of interannual variability are typical of the equatorial region, and minimal for the zone 60–65 degrees of southern latitude. During winter six months for the northern hemisphere, maximum values of amplitudes of interannual variability are found in the southern polar region, and minimal ones in the northern polar region and the latitudinal zone 25–30 degrees of northern latitude.

 

Geophysical studies

 

Atmosphere

1. Solar radiation coming to the atmosphere upper boundary and features of planetary circulation (PC) are spatially interconnected and are described by definite latitudinal correspondence. Reasons for this correspondence may consist in the fact that distribution of incoming radiation is defined by the Earth shape (zoning) and the inclination of its axes of rotation (changes in solar radiation income to various latitudes during various seasons). Revealed spatial consistencies depend (to a lesser extent) on disturbed orbital movement of the Earth (related to interannual variability of incoming radiation due to change in the distance to the Sun and tropical year duration). As the incoming solar radiation is a basic source of PC energy, PC features can be defined by the nature of incoming solar radiation distribution, its space and time non-uniformity (along with change of the Earth rotational speed, the Coriolis force and other factors). This is reflected in some latitudinal consistencies of parameters of incoming radiation and localization of PC peculiarities.

2. A connection is found between the incoming solar radiation and difference of solar radiation coming to the equatorial and polar region of the Earth’s northern hemisphere (in the absence of atmosphere) with duration of some circulation groups (meridian southern group and zoning disturbances), as well as zonal (Z+NZ) and meridian (MN+MS) circulation, which ratio is a profiling attribute in classification by B. L. Dzerdzeyevskiy. The nature of response of duration of zonal and meridian circulation to changes of incoming solar radiation is positive and negative, respectively. Response to changes of variations of radiation coming to the equatorial and polar region has an opposite sign. A connection between the duration of circulation groups (NZ and MS), as well as zonal (Z+NZ) and meridian (MN+MS) circulation with accumulated incoming solar radiation was determined. Increase of values R (between the accumulated solar radiation and circulation duration) for NZ group is 7.4%, for MS group – 13.2%, for zonal circulation (Z+NZ) – 10.8%, for meridian (MN+MS) circulation – 16.9%. Discrepancy between calculated (second-degree polynomial quadric) and actual values of duration on average for all groups is reduced by 3.5 days or 1.7%. Increase of R values between the duration of circulation groups and accumulated incoming radiation, as well as the reduction of discrepancy between actual values of duration with calculated values indicate heat accumulation related to incoming solar radiation in the atmosphere, e.g., the augmentation of the greenhouse effect. The trend for increasing the duration of meridian circulation is a result and indication of increased inter-latitude heat exchange.

3. For the modern era, a close negative connection is revealed for the abnormal solar radiation coming to the atmosphere upper boundary and the abnormal near-surface temperature. An effect of inter-latitude heat exchange augmentation in the atmosphere is found (first type thermal machine) related to the reduction of incoming polar radiation into polar regions and increase of income to the Earth equatorial region. More intensive augmentation of inter-latitude heat exchange is found in summer six months, and less extensive are typical of winter six months. In the southern hemisphere, the mechanism of inter-latitude heat exchange is expressed more clearly than in the northern hemisphere. The effect of inter-latitude heat exchange augmentation is related to secular change in the Earth's rotational axis inclination (Milankovich, 1939).

The connection of abnormal near-surface temperature and accumulated solar radiation is described by the highest values of evaluation characteristics: correlation and discrepancy ratio. The values of the correlation ratio between the accumulated solar radiation and the abnormal temperature are increased in relation to the values calculated without respect to the solar radiation accumulation (by 3.9% for the Earth, by 4.0% for the northern hemisphere, by 4.3% for the southern hemisphere). The discrepancy of calculated (with respect to the accumulated solar radiation) values of abnormal near-surface temperature with actual values is reduced (by 6.7% for the Earth, by 4.6% for the northern hemisphere, by 4.8% for the southern hemisphere). These results indicate the accumulation of heat in the atmosphere related to the incoming solar radiation (greenhouse effect augmentation) and the influence of this accumulation on the change of the Earth’s temperature profile.

The values of the abnormal near-surface temperature (in relation to the average value for 1961–1990) in 2050 calculated (with respect to the solar radiation accumulation) on the basis of the linear regression equation are 0.393 °Ń for Earth, the northern hemisphere – 0.458 °Ń, for the southern hemisphere – 0.328 °Ń. The abnormality growth relative to the values calculated for 2014 is 0.166 °Ń, 0.171 °Ń and 0.161 °Ń, for Earth, northern and southern hemisphere, respectively. When calculating temperature abnormality using the polynomial regression equation (second-degree polynomial) for 2050, the following values were obtained: 0.992 °Ń for Earth, 1.106 °Ń for the northern hemisphere, 0.878 °Ń for the southern hemisphere. Increase of the temperature abnormality in 2050 relative to the values of 2014 is 0.533 °Ń for Earth, 0.568 °Ń for the northern hemisphere, 0.498 °Ń for the southern hemisphere.

Abnormalities of seasonal temperature in 2050 calculated on the basis of the linear regression equation with respect to solar radiation accumulation are: 0.411 °Ń for the northern hemisphere during summer six months; 0.500 °Ń – for the northern hemisphere during winter six months; 0.351°Ń for the southern hemisphere during summer six months; 0.302 °Ń – for the southern hemisphere during winter six months. Increase in the temperature abnormality in relation to 2014 is 0.145 °Ń, 0.196 °Ń, 0.169 °Ń and 0.152 °Ń, respectively.

 

World Ocean

For the modern era, an effect of intensified inter-latitude heat exchange is defined (first type thermal machine) in the World Ocean surface layer, related to the decrease of incoming solar radiation (in the absence of atmosphere) in polar regions and increase of incoming solar radiation to the equatorial region (increase of the difference in solar radiation coming to the equatorial region and polar regions). In polar stratospheric clouds (PSC) of the southern hemisphere, the mechanism of inter-latitude heat exchange is expressed more intensely than in the northern hemisphere PSC. The increase of the inter-latitude heat exchange is related to secular change of the Earth's rotational axis inclination. Close connections between the sea surface temperature abnormality and the incoming solar radiation are found. Close connections are also typical of variability of the temperature abnormality and difference of the solar radiation coming to the equatorial region and polar regions of the Earth, which proves that the increase of the inter-latitude heat exchange participates in formation of secular trends of the sea surface temperature abnormality.

Higher values of the correlation ratio were obtained, along with lower values of discrepancy between actual values of PSC temperature abnormality with calculated values of PSC abnormalities, with respect to accumulation of incoming solar radiation. Values of the correlation ratio between accumulated solar radiation and PSC temperature abnormality exceed the correlation ratio values obtained for the connection of solar radiation with no respect to accumulation or abnormality, by 5.3% for the Earth, by 4.6% for the northern hemisphere and by 5.0% for the southern hemisphere. The discrepancy of temperature abnormality values calculated with respect to solar radiation accumulation with actual values for the World Ocean are reduced by 6.8%, by 1.1% for the northern hemisphere and by 7.7% for the southern hemisphere. The results obtained testify the intensification of the greenhouse effect due to accumulation of heat from incoming solar radiation and impact of this intensification for secular trends of changes in the sea surface temperature abnormality.

The values of PSC temperature abnormality in 2050 (relative to the average value for 1961–1990) calculated on the basis of the linear regression values are 0.351 °Ń for the World Ocean, 0.410 °Ń for the northern hemisphere and 0.382 °Ń for the southern hemisphere. Abnormality increase in 2050 relative to respective values calculated in 2014 are expected to be 0.143 °Ń, 0.124 °Ń and 0.155 °Ń. Temperature abnormalities calculated for 2050 using the polynomial regression equation (second-degree polynomial) are described by values equal to 0.827 °Ń for the World Ocean, 0.843 °Ń for northern hemisphere SPC, 0.843 °Ń for southern hemisphere SPC. Increase in the temperature abnormality in 2050 relative to respective values of 2014 is 0.435 °Ń for the World Ocean, 0.433 °Ń for the northern hemisphere, 0.461° Ń for the southern hemisphere.

Abnormalities of seasonal temperature in 2050 calculated using the linear regression equation are described by 0.363 °Ń for northern hemisphere SPC during summer six months; 0.326 °Ń for northern hemisphere SPC during winter six months; 0.371 °Ń for southern hemisphere SPC during summer six months; 0.327 °Ń for southern hemisphere SPC during winter six months. Increase of temperature abnormality relative to 2014 is 0.126 °Ń, 0.127 °Ń, 0.165 °Ń and 0.148 °Ń, respectively.

 

Seawater ice

For the modern era, an effect of intensified inter-latitude heat exchange is defined in the atmosphere, related to the reduction of solar radiation income into polar regions and increased income into equatorial regions of the Earth. Intensification of inter-latitude heat exchange is explained by secular changes of the Earth's rotational axis inclination. The inter-latitude heat exchange intensification is related to secular trends for increased abnormalities of near-surface temperature in Earth’s polar regions and reduction of the sea ice area in Artic in the modern era.

The values of the correlation ratio between the accumulated solar radiation coming per year (and summer six months) into the northern hemisphere and the values (1870–2007) of the sea ice area are -0.715 for annual average area, -0.776 for minimal area, 0.802 for seasonal amplitude. These values exceed those obtained in correlation analysis of seawater ice area with incoming solar radiation without respect to accumulation (0.689, 0.762 and -0.791, respectively). These values of the correlation ratio are increased by 3.6% for annular average values of area, by 1.8% for the minimal (summer) seawater area and by 1.4% for the seasonal amplitude. Values of the correlation ratio between the values calculated (using the regression equation – second-degree polynomial) with respect to accumulation of solar radiation and actual values of seawater ice area are also increased (by 13.4% for annular average values, by 7.0% for minimal area and by 8.2% for seasonal amplitude). Discrepancy of calculated seawater ice area values and actual values is reduced in this case by 30.5%, 31.3% and 19.8%, respectively. Increase of the correlation ratio values and reduction of discrepancy indicate heat accumulation related to incoming solar radiation in the atmosphere and the World Ocean surface layer. Higher evaluative characteristics obtained to relate the changes in the seawater ice area with the accumulated solar radiation prove the impact of greenhouse effect intensification on the formation of the secular trend to change the area of seawater ice. Calculations made on the basis of the linear regression equation upon the values of the continuous row of J. Walsh and W. Chapman show that the value of the average annual area of seawater ice in 2050 equals 12.02 mln. km2, minimal area – 7.95 mln. km2, seasonal amplitude – 7.24 mln. km2. The average annual area reduction in relation to 2014 is 3.0%, minimal – 8.8%. The seasonal amplitude is increased by 10.4%. Calculations based on polynomial form of connection show that the average annual area in 2050 is described by 9.78 mln. km2, the minimal area – 4.16 mln. km2, and the seasonal amplitude is increased by 10.05 mln. km2. Thus, the reduction of the average annual area relative to 2014 is 15.3%, the minimal area – by 42.9%. The seasonal amplitude is increased by 31.7%.

Calculations (based on the linear regression equation) for a less continuous number of satellite observations show that the maximum area of seawater ice in 2050 is 13.33 mln. km2, the minimal area – 1.60 mln. km2. In this case, the reduction in relation to the values calculated for 2014 is defined by 9.8% and 66.7%, respectively.

Thus, the results obtained indicate a new trend in studying cryosphere processes, which most important issue is determination of the form of connection of cryosphere indicators and values of the incoming solar radiation. Such studies can have an important practical value in surveying and mining of mineral deposits, oil and gas extraction on the arctic shield, for the development of fishery, navigation and construction of hydrotechnic and other structures on frozen soils. New fundamental studies of cryosphere processes seem to be necessary in development of strategic plan within a new phase of exploring the Russian Arctic.

 

 

Reasons for changes in the modern global climate of the Earth

On the basis of the results obtained, the following conclusions can be made regarding the reasons and mechanism for changes in the modern global climate.

In the studies, we revealed an effect of inter-latitude heat exchange intensification that is defined by the increased difference of the solar radiation coming to the equatorial region and polar regions of the Earth, related to secular change of the Earth's rotational axis inclination (Milankovich, 1939). Inter-latitude heat exchange intensification is more intensely expressed in summer six months and less intensively in winter six months. In the southern hemisphere, the heat exchange mechanism is expressed more actively than in the northern hemisphere. The effect of inter-latitude heat exchange intensification in the formation of the Earth thermal profile is proved by close positive relations of the solar radiation difference (coming to equatorial and polar regions) with the abnormality of annual and seasonal near-surface temperature and the near-surface ocean temperature, with the change (average annual and minimal) of seawater ice area in the northern hemisphere. The inter-latitude heat exchange intensification is also proved by the trend for intensification of the meridian circulation duration in the modern era. The inter-latitude heat exchange intensification is related to increased heat transfer from area being heat sources (from tropic latitudes) to heat outlet areas (polar latitudes), e.g., temperature increase in heat outlet areas.

A result of increased near-surface temperature in heat outlet areas related to inter-latitude heat exchange intensification is the formation of positive feedbacks in heat outlet areas in the Earth climatic system, for example, water vapor—solar radiation. The inter-latitude heat exchange intensification results in the increase of near-surface temperature and PSC temperature in heat outlet areas. This increase is possibly related to the fact that the heat coming from a large area of the heat source is distributed over a less area of heat outlet (2.66 times less), as well as due to condensation (with advection of warm air masses to cold areas). Temperature increase results in the increased concentration of water vapor in the atmosphere. Since water vapor detain IR radiation, further increase of near-surface temperature occurs (positive feedback). Moreover, the increase of water vapor concentration also increases air heat conductivity (constantly acting heat transfer from equatorial areas to polar regions). It is possible that the ice-albedo feedback participate in temperature increase. Ice and snow on the surface reflect almost all incoming solar radiation, which leads to further surface cool down. When some part of ice and snow covering melts, the albedo shrinks, which leads to the growth of solar radiation absorption by Earth and water surface, which contributes to near-surface temperature increase and melting of seawater ice and glaciers.

Positive feedbacks in heat outlet areas result in greenhouse effect intensification (R increase and reduction of discrepancy with radiation accumulated) by accumulating solar heat in the result of positive feedbacks. Greenhouse effect intensification is proved by close positive correlation links (R increase) between the accumulated solar radiation and abnormality of near-surface temperature, as well as the abnormality of the near-surface ocean temperature, and is verified by close positive links with seawater ice area changes in the northern hemisphere. The greenhouse effect intensification is also proved by the decrease of discrepancy between the actual and calculated (with respect to radiation accumulation) values of the abnormality of near-surface temperature and PSC temperature, the area of seawater ice and duration of various-type circulation processes.

Increase of annual near-surface temperature and PSC temperature is a result of greenhouse effect intensification (that, in its turn, results from inter-latitude heat exchange intensification). Greenhouse effect intensification is related to solar heat accumulation (caused by changes in atmosphere composition due to increased water vapor content). In polar regions, the temperature is increased more intensively due to two factors: heat transfer as a result of inter-latitude heat exchange and greenhouse effect intensification. But there are differences in the response of polar regions to inter-latitude heat exchange and greenhouse effect intensification, related to the fact that in the northern hemisphere, the response is defined by interaction with the “ocean-seawater ice – atmosphere” system, whereas in the southern hemisphere this system looks like “ice continent (average height 2,000m) – ocean – seawater ice – atmosphere”.

Thus, global warming is related to inter-latitude heat exchange intensification, which is conditioned by secular change of the Earth's rotational axis inclination and greenhouse effect intensification related to expression of feedback links in heat outlet areas. Consequently, modern global warming is a natural response of the Earth climatic system to the secular change of the Earth's rotational axis inclination. The trend for global climate change in the modern era is a result of the mechanism, which is based on the following sequence of cause-and-effect relationships: decrease of Earth's rotational axis inclination inter-latitude heat exchange intensification formation of positive feedback links (increase of water vapor content in the atmosphere) greenhouse effect intensification increase of near-surface temperature and sea surface temperature (Fig. 1).

 

Decrease of Earth's rotational axis inclination
Inter-latitude heat exchange intensification
Formation of positive feedback links
(increase of water vapor content in the atmosphere)
Greenhouse effect intensification
Increase of near-surface temperature and sea surface temperature

 

Fig.1. Physical mechanism of trend formation for Earth global climate change in the modern era.

 

It shall be noted that only particular solution of the climate change problem for the modern era is given. Probably, sometime in the future the determinant factor in climate formation will be the reduction of solar radiation coming to the Earth with respective feedback links. It is also possible that a result of polar region warming will be the formation of a positive link in relation to the inter-latitude heat exchange (reduction of temperature gradient in equatorial and polar regions). Besides, the form of relation of incoming solar radiation with the near-surface temperature (and other environment characteristics) is still ambiguous. This creates difficulties in developing prognostic scenarios. The climate predictability is also limited by space and time limits. These limits are defined by the fact that relations of solar radiation with environment characteristics found for rather large space and time dimensions start to disintegrate (with the increase of time and space dimensions). Study of the form and stability of solar radiation relation with environment and biosphere characteristics, as well as time and space limits of predictability of these characteristics are nowadays seen as the most important tasks in studying the Earth climate and forecasting its changes.

 


 

SOLAR RADIATION AND CLIMATE
OF THE EARTH

 
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