Paradox of the weak young sun

from Wikipedia, the free encyclopedia
Development of luminosity (red), radius (blue) and effective temperature (green) of the sun during its existence as a main sequence star in units of today's values. Three to four billion years ago the luminosity was 20 to 25% less than it is now.
Reconstruction of the mean temperature and precipitation course of the earth from the Archean to the present

The paradox of the weak young sun is understood as the not yet fully clarified contradiction between the low radiation power of the young sun in the early history of the earth and the not correspondingly colder climate at that time. The astronomers Carl Sagan and George Mullen first pointed out this discrepancy in 1972.

Sagan suggested a comparatively high concentration of greenhouse gases as a possible overarching explanation, but this has not been confirmed for the period in question. On the contrary, the significant changes in the composition of the atmosphere that took place in the Archean Era and the relatively even climatic course compared to recent geological history after global glaciation 2.4 billion years ago ( see boring billion) tend to raise additional questions. Controversial discussions in geology , astrophysics , planetology , climatology and atmospheric sciences over the decades made the paradox one of "the great open questions in paleoclimatology ". Some authors claim a final interpretation, but it is by no means undisputed.

Extent of the problem

From the standard solar model, a 25 to 30% lower radiation power can be derived for the time 4.4 billion years ago. At the same time, the existence of liquid water on the earth's surface was proven in the earliest geological history by means of geochemical analyzes. Without relatively mild climatic conditions, water could only have existed as ice. The first traces of life, which also require liquid water, have already been identified at this early stage. The paradox begins at a time when an initial atmosphere was just formed and continues for billions of years, during which continents and oceans formed. This also applies when looking at the early Martian atmosphere.

overview

Pinatubo volcanic eruption

To explain the paradox, factors are taken into account that played a role in the entire earthly climate history . Initially, high greenhouse gas concentrations in the early atmosphere were assumed to solve the problem . Knowledge of the atmospheric composition at the time and the associated climatic conditions have increased considerably since the 1970s. An originally very high concentration of the greenhouse gases that are relevant today is questionable due to geochemical restrictions.

In 2009 sulfidic greenhouse gases were identified that could have been an effective climate factor in the early reducing atmosphere up to the Great Oxygen Disaster 2.4 billion years ago. A 2003 explanation of the paradox and the global warm and cold periods due to the influence of cosmic rays on the climate sparked a controversial debate and intensified research in this sector. A climate-determining influence of cosmic rays in the present could not be confirmed in follow-up studies.

Attempts are currently being made to simulate the archaic earth climate with comparatively simple climate models. Assuming a low albedo , a high nitrogen content and a sparse occurrence of condensation nuclei for cloud formation, the existence of liquid water in the tropical regions would have been possible even then. The same applies to the analysis of the early Martian atmosphere . Other ancillary theses deal with, among other things, possible deviations in the Earth's orbit parameters, a change in the physical constants and the solar radiation intensity beyond the standard model; some studies also discuss the emergence of life on earth and on other celestial bodies under comparatively cold conditions.

Earth and climate historical background

After the formation of the moon about 4.5 billion years ago, when the earth's mantle was deeply melted, it took about 2 million years for the geothermal energy to become negligible for the surface temperature. Delaying factors were an insulating atmosphere of water vapor (H 2 O) and the dissipation of rotational energy through tidal friction . When the water condensed, a galloping greenhouse effect ( runaway greenhouse effect ) started for at least 10 million years, based on initially around 100 bar carbon dioxide (CO 2 ), before the gas was largely subducted as carbonate (see also carbon cycle ).

According to current estimates, subject to new lunar rock samples , there was no major bombardment of the earth by asteroids and comets 4.1 to 3.8 billion years ago, but a gradual decrease in the impacts, which only locally melted the earth's mantle and between which relatively cool areas existed , with water in liquid and solid form. Back then, as now, volcanic outgassing mainly consisted of water vapor, carbon dioxide and hydrogen sulfide (H 2 S) as well as smaller proportions of nitrogen (N 2 ), hydrogen (H 2 ), carbon monoxide (CO), helium, methane and ammonia.

A presumably brief glacial phase in the form of the Pongola glaciation occurred about 2.9 billion years ago, which was followed 500 million years later by the Paleoproterozoic glaciation , probably caused by the Great Oxygen Catastrophe and with a duration of about 300 million years the longest ice age of the Geological history. This was followed by a longer warm period, jokingly called the boring billion (boring billion). Only after that, for about a billion years, did longer warm periods alternate with shorter cold periods until the most recent geological history.

The paradox is occasionally used in the environment of young earth creationists and supporters of so-called intelligent design as an argument against the consistent scientific dating, which fix the age of the earth at around 4.6 billion years.

Influence of the atmosphere

Overview of the greenhouse effect. Short-wave radiation from the sun hits the atmosphere and the earth's surface. Long-wave radiation is emitted from the earth's surface and almost completely absorbed in the atmosphere. The numbers indicate the current output in watts per square meter

The greenhouse effect is based on the different permeability for the short-wave (mainly incoming) part of solar radiation compared to the long-wave (mainly reflected) heat radiation . In the earth's atmosphere , greenhouse gases such as water vapor , carbon dioxide , methane and ozone have had a central influence on the climate since the beginning . The natural greenhouse effect raises the average temperature of the earth's surface is currently at about 33 ° C to +15  ° C on. Without this effect, the air layer close to the ground would only have a hostile -18 ° C on global mean. With the current composition of the atmosphere, the surface temperature at the beginning of the Earth's history would have been around 20 ° C colder globally, assuming otherwise the same conditions (land distribution, albedo).

A climate that is largely stable over billions of years requires effective control mechanisms. Water in its various aggregate states alone does not counteract a cooling due to a lower radiation output from the sun. The observed climatic changes must therefore be influenced by other factors such as B. the cloud formation can be explained. Low clouds cool the earth's surface through their reflection from the sun, whereas high clouds warm it. The cloud formation is u. a. influenced by condensation nuclei, suspended particles and trace gases. Volcanism plays an important role here due to the gases, dust particles and aerosols emitted into the atmosphere .

The spread of vegetation , which varies over longer periods of time , in connection with erosion , weathering and soil structure, has an impact on the reflective properties of the earth's surface as well as on evaporation and thus on cloud formation and climate. Another significant factor is the orbit parameters ( eccentricity , precession and inclination of the earth's axis ). The distribution and fluctuation of solar radiation caused by the so-called Milanković cycles is relatively minor, but acts as a "stimulus" in the climate system and is considered to be the main cause of the alternation between warm and cold phases within the current Ice Age . According to more recent findings, some of the cycles can be traced back over several hundred million years as a stable influencing variable and classified chronologically.

Climate influence of plate tectonics

The plate tectonics as the driving of all large-scale processes in the outer earth sheath ( lithosphere ) is one of the most important environmental factors with a plurality of associated processes. These include the formation of fold mountains ( orogenesis ), the various forms of volcanism , the formation of mid-ocean ridges , the "submergence" of oceanic crust under continental lithospheric plates ( subduction ) and continental drift , each with direct consequences for the earth's climate . In contrast to these developments, which took millions of years, the biological and climatic effects of so-called Magmatic Large Provinces ( Large Igneous Provinces ) often came to bear within a relatively narrow time window according to geological standards. It was the large-volume outflow of igneous rocks from the earth's mantle , predominantly in the form of flood basalts , which occurred primarily at the "seams" of colliding or drifting tectonic plates and occasionally spread over millions of km 2 over the course of several hundred thousand years . Depending on the extent and duration of the flood basalt release, considerable amounts of greenhouse gases and pollutants were released into the atmosphere. In contrast to "normal" volcanism, the activities of a magmatic large province did not cause aerosol-related cooling, but instead led to a worldwide temperature increase, in extreme cases coupled with an additional warming spiral with the help of methane or methane hydrate from oceanic deposits. Most of the mass extinctions in the history of the earth are very likely to be directly connected to the large-scale effusion of flood basalts and the subsequent destabilization of terrestrial and marine biotopes.

course

A possible hypothetical reconstruction of the Rodinia supercontinent

The first continent Ur , probably comparable in size to today's Australia, could have existed around 3 billion years ago, but is largely hypothetical. The first supercontinent Kenorland is better documented , the formation of which corresponds to the beginning of the Paleoproterozoic Ice Age (also Huronian Ice Age ) about 2.4 billion years ago. The supercontinent Columbia emerged 1.8 billion years ago and , according to current research, completely or partially united the land masses of the large continent of Nuna, which was originally considered to be independent . In the course of the Wilson cycle , which was classified as likely, the supercontinents Rodinia (1,100 to 750 mya = million years ago ) and Pannotia (600 to 550 mya) formed, whereby various studies draw the conclusion that Columbia was only partially in its late phase was fragmented and - with correspondingly moderate plate tectonics - completed a "flowing" transition to the subsequent Rodinia towards the end of the Mesoproterozoic . This assumption corresponds to the relatively calm climatic and geological development during the boring billion. However, this long “standstill phase” also had an impact on biological evolution. There are indications that the marine oxygen and sulphate concentrations stagnated permanently at a low level and that the anoxic conditions, including the occurrence of hydrogen sulphide, created a rather hostile environment for aerobic life forms in the Central Proterozoic Oceans .

The gradual increase in oxygen levels during the Neoproterozoic changed the chemical composition of the oceans, and at the same time began a period of extensive plate tectonic processes and pronounced cold periods, presumably linked to several snowball-earth events . During the geological age , the Phanerozoic , which continues to this day , further cold and warm periods of varying duration occurred at irregular intervals. A significant cooling occurred from the second half of the Ordovician 460 to 430 million years ago, followed by the Permocarbon Ice Age , which comprised large parts of the Carboniferous and extended into the Middle Permian . The often very rapid climatic fluctuations in the Jura and Lower Cretaceous coincide with the advancing disintegration of the Pangea supercontinent, which formed in the late Carboniferous (310 mya) . An important paleogeographical factor was the location of the continents and larger continental areas in the vicinity of the polar regions , since land areas close to the polar ice more quickly and more strongly than open sea zones due to the ice-albedo feedback .

Interpretations of the paradox about greenhouse effects

overview

Sagan and Mullen initially proposed a climate-active role for ammonia (NH 3 ) in the early atmosphere as a solution to the paradox. However, ammonia only stays in the earth's atmosphere for a short period of time and is broken down by photochemical processes, among other things. Sagan and Chyba therefore postulated an organic protective layer, similar to the atmosphere of the Saturn moon Titan , which could have increased the stability of ammonia. An atmosphere with a high ammonia content is also assumed for some planets outside our solar system .

As an explanation for the paradox, the ammonia hypothesis was soon superseded in favor of a considerably higher (factor ten thousand) CO 2 proportion. This theory was prevalent until the early 1990s. Due to contradictions with geochemical findings, the search for alternative causes began. Other authors suggested an increased occurrence of other greenhouse gases, which are still present in volcanic emissions, among other things. These include laughing gas (N 2 O) and in particular methane , ethane and other hydrocarbons as well as various sulfur compounds. The question of photochemical stability also affects the climate-affecting hydrocarbons and sulphides. The retention time of most greenhouse gases was promoted by the almost oxygen-free atmosphere of the early Earth. Overall, the sometimes dramatic changes in the composition of the early atmosphere, primarily due to biotically formed oxygen, in view of the relatively evenly warm climate over several billion years and the pronounced temperature fluctuations after the boring billion 2.1 to 1.0 billion years ago leave further questions open.

“This time is by no means boring for a climatologist, it calls for an explanation, especially because the sun was much less bright than it is today. […] The question of why the middle Proterozoic was warm and why it cooled so dramatically around 750 million years before our time is fascinating, but goes beyond the subject of research discussed here. "

- Kasting and Ono 2006

Interpretation of extreme carbon dioxide greenhouse

Cloud cover of Venus
Thin atmosphere of Mars

If all of the CO 2 currently stored in the lithosphere were to escape into the atmosphere, this would result in a carbon dioxide concentration with a partial pressure of several bars that is more than ten thousand times higher than today's values . A gradual weakening of these extreme greenhouse conditions in parallel with the increase in solar radiation output should solve the paradox. In 1979 the astrophysicist Michael H. Hart suspected that the earth had taken this exact path. According to Hart's calculations, this gradual decrease between the formation of the primordial atmosphere 4.58 billion years ago and the current level of radiation is extremely unlikely and also unstable. If there were only a few percent deviations upwards or downwards, either a galloping greenhouse effect similar to that of Venus would occur, or the planet would have developed into a snowball earth or a Mars-like, hostile desert world with a thin atmosphere.

Hart coined the term Continuously Habitable Zone (CHZ). The emergence and continuation of life was therefore only possible because the earth was always in an optimal, but spatially very narrowly limited “life zone” throughout its entire history. Hart used this unlikely circumstance for the much-noticed thesis (see Fermi paradox ) that extraterrestrial life would occur extremely rarely in the galaxy and possibly also in the universe.

James F. Kasting and others pointed out that the thesis of an initially extremely high, only gradual decrease in CO 2 concentration is contrary to the Paleoproterozoic Ice Age , which began 2.4 billion years ago . After that, the relatively warm climate remained stable for over a billion years, according to geological evidence and climate proxy , before icing phases and warm periods began to alternate.

In 2011 in the journal Nature published study we find again the conclusion that the moderate climate of the Archean not with the assumed then CO 2 content of the atmosphere is consistent. The authors see a possible solution in a greenhouse effect caused by other substances.

Interpretations of mixtures of different greenhouse gases

Jacob D. Haqq-Misra and others (including Kasting) favored a mixture of methane (CH 4 ), water vapor and carbon dioxide instead of a pure carbon dioxide greenhouse in 2007 . In 2000, Kasting and Pavlov emphasized the role of CH 4 and in 2001 questioned the shielding of ammonia by organic trace gases in the primordial atmosphere.

Pavlov and Kasting mentioned a methane-rich atmosphere after 2.4 billion years in the discussion on the paradox in 2000 and 2003. This presupposes a sulphidic ocean, which was denied by Holland in 2006 with reference to the geochemical problem. Kasting mentioned this contradiction and summed up “ We leave this issue to be sorted out elsewhere ” ( Kasting and Ono 2006 , German: “ We leave this issue to be clarified elsewhere”).

Interpretation of the paradox about carbonyl sulfide

Yuichiro Ueno , Matthew S. Johnson, et al. a. published in August 2009 Studies on the ratio of sulfur isotopes in rocks of the Pilbara - Craton , which dates back to the early days of Earth. The group used spectral analysis to examine a number of greenhouse gases that occur in today's volcanic emissions, for their behavior in the ultraviolet range . According to this, carbonyl sulfide (COS) in particular could have accumulated in an early, reducing earth's atmosphere and thus compensated for the paradox. According to the authors, the distribution rates for different sulfur isotopes in rocks could be used as very good evidence for the different composition of the early atmosphere.

The photolytic decomposition of sulfur dioxide was previously believed to be a limiting factor. In contrast to others, COS as an effective and stable greenhouse gas is also able to prevent the decomposition of sulfur dioxide, which is also climate-affecting. The investigations on the sulphurous sediments were related to different scenarios for the shielding of ultraviolet light. According to the authors, the noticeable accumulation of the sulfur isotope 33 S found in the rocks can only be explained by the presence of COS in the atmosphere at that time and its specific shielding effect.

According to the authors, the paradox can be conclusively interpreted with carbonyl sulfide until the severe cooling in the late Archean 2.4 billion years ago. They linked this "Archaic Ice Age" with the free oxygen mainly produced by cyanobacteria , which began to accumulate both in the atmosphere and in the ocean after it had previously been converted into trivalent iron ions during the oxidation of organic compounds and divalent iron ions Fe 2+. Ions Fe 3+ had been largely consumed. In accordance with the COS hypothesis, the change from a reducing to an oxidizing atmosphere is assigned to this temporal environment. The reducing atmosphere necessary for COS is then no longer given.

In 2006 Kasting discussed differentiated geochemical findings on the role of sulfur compounds in the archaic atmosphere. He referred in particular to the barite deposits that were only temporarily deposited . Since barite is an extremely poorly soluble sulphate , the deposition of SO 2 would only have been prevented for a limited period between 3.2 and 2.4 billion years.

Proposed control mechanisms

The carbonate-silicate cycle is considered to be the central negative (in the sense of control engineering) and counteracting control mechanism for climate-active greenhouse gases. It links the weathering of silicates and the concentration of carbon dioxide in the oceans and the atmosphere with the deposition and reprocessing of carbonate rock on the continents and in the oceans. According to Walker, the initially high greenhouse gas concentration with the formation of continents was reduced by the deposition of large amounts of carbonates after about a billion years, especially in the early earth history. Subsequently, an interaction between warming through the greenhouse effect of carbon dioxide in the atmosphere, increased silicate weathering, then increased cooling through the formation of carbonates and warming after renewed outgassing of carbon dioxide through volcanic processes is assumed.

Changed cloud formation

Roberto Rondanelli and Richard S. Lindzen came to the conclusion in 2010 that even a moderate effect of cirrus clouds in the tropical regions of the early Earth could cause sufficient global warming. Their explanation is based on the iris hypothesis , which deals with the decrease in high tropical cirrus clouds with increasing global warming. However, there are considerable problems with this hypothesis. The iris effect cannot be detected in satellite data series at the present time. In addition, Rondanelli's and Lindzen's explanation for the Archean period implies an unrealistically dense covering of the entire earth with very cool clouds. As a partial explanation of the paradox, however, their hypothesis is still viewed as noteworthy.

According to a study published in 2010, the paradox for the young earth can be explained without greatly increased greenhouse gas concentrations. In the early stages of the earth, the oceans were around 20% larger than they are today. However, since there were neither plants nor animals on land at that time, the condensation nuclei that are important for cloud formation were missing. The cloud cover of the earth was consequently considerably less than originally assumed. Both the absence of condensation nuclei and the smaller extent of continental land masses would have contributed to temperatures above freezing point via a lower albedo . This reasoning assumes that condensation nuclei should have consisted primarily of biogenic dimethyl sulfide (DMS) and that DMS was only produced by eukaryotes . Both assumptions are controversial.

Astrophysical interpretations

Possible climatic influence of galactic cosmic rays

Spiral arms of the Milky Way
Cosmic radiation (red) and global temperature (black) assumed from geochemical findings up to 500 million years before our era, according to Shaviv (2003), not confirmed in later work

The geochemist Jan Veizer and the Israeli astrophysicist Nir Shaviv interpret the paradox through the inclusion of solar wind and galactic cosmic rays on the early earth's climate. According to Henrik Svensmark , reduced cosmic radiation via fewer condensation nuclei could lead to weaker cloud formation and thus to warming. Shaviv postulated that the stronger solar wind had initially shielded the earth more strongly from cosmic rays and made the early long warm phase possible. The icing phase that began 2.4 million years ago should therefore coincide with the increased star formation rates in the galaxy and the corresponding increased radiation at the same time. After this model, the radiation intensity gradually rose to today's level.

Shaviv found four peaks in cosmic ray flux (CRF) during the past 500 million years by analyzing meteorite material. These peaks would have occurred at a distance of 143 ± 10 million years and correlated with spiral arm passages of the sun. Shaviv worked on this topic together with Jan Veizer and was able to compare his geochemical records, which he had collected over decades, with his meterorite data. In their common interpretation of the paradox, times of increased star formation rates and correspondingly increased cosmic radiation correlate with global cold times, which would explain the climatic course both in the Precambrian and in the entire Phanerozoic (see figure on the right). However, the peaks from Shaviv's analysis could not be confirmed by later work.

Some work on the connection postulated by Svensmark, for example in the Danish SKY experiment, specifically examined the interaction of sulfur-containing aerosols with cosmic rays in higher layers of the atmosphere. Something similar happens with the CLOUD experiment at CERN . However, the current impact of this effect on the climate cannot be demonstrated: the cloud cover measured with satellites does not correlate with Forbush events . According to the current state of science , periodically occurring cosmic influences on biological and climatic development are only poorly documented with the exception of the Milanković cycles and apparently only play a subordinate role in terms of their significance .

Orbital parameters and earth rotation

The inclination of the earth's axis to the ecliptic from 22.1 to 24.5 °, which changes over thousands of years , has a significant influence on the climate. A further inclination of the earth's axis during the Archean is discussed by some studies as a possible explanation for higher temperatures in the early days of the earth.

Another possible influencing factor is a formerly faster earth rotation, as a day length of 14 hours would lead to a temperature increase of 1.5 ° C. For the paradox itself as well as for the course of the first three billion years and to explain the subsequent cold and warm periods, this approach is not sufficient.

Gravitational constant

The luminosity of a star is related to the gravitational constant due to the Eddington limit . The luminosity L is extremely by the gravitation constant dependent on G, and the mass of the star M: . Smaller fluctuations in the constant in the beginning would explain the phenomenon. The corresponding interpretations also give indications of the so-called dark energy and are still very speculative.

Assumption of a strong, young sun

In connection with the paradox - in contrast to the astrophysical standard model - a higher radiation power of the sun in the early period was discussed. A moderately (10%) heavier sun compared to the standard model is sufficient to compensate for the paradox. According to Thomas Graedel, the noticeable depletion of trace elements such as beryllium in the sun and other stars speaks in favor of this hypothesis , against the assumption of the relatively uniform climate over several billion years. A higher mass of the central star would have had a considerably increased radiant power over only a few hundred million years due to the standard assumptions about seismics of the sun; indirectly estimated mass losses of the early sun are too small for this according to other studies. An increased mass could not be confirmed by the comparison with today's young suns in the cosmic neighborhood. A young sun evenly strong over billions of years is also in contradiction to established knowledge of climatic history, especially about the cold periods and snowball earth stages occurring in the Precambrian, and also collides with the astrophysical finding that the mass loss with nearby suns of different ages takes place continuously.

Biological interpretations

Gaia hypothesis and the self-regulating role of life

The Gaia hypothesis of James Lovelock , according to the life on Earth even the essential control mechanism, without which the earth might have experienced the fate of Mars or Venus. According to the hypothesis, the earth, and in particular the biosphere, can be viewed as a self-similar macroscopic living organism with properties of life such as autopoiesis and homeostasis , which creates, maintains and develops its own conditions. The name is derived from Gaia , the earth goddess of Greek mythology. This includes the feedback between vegetation, its water storage capacity and precipitation as well as the albedo changed by vegetation cover and land use . Another feedback effect mentioned in this context is the uptake of carbon dioxide by calcareous marine plankton and corals, as is the release of carbon dioxide in the course of the rock cycle . These functions are largely taken over by "lower" life forms such as single cells or algae .

Extinction events mainly affect higher and highly specialized forms of life and do not contradict this. Important forms of biological control loops such as reef-building corals and a large number of other organisms only appeared after the Cambrian explosion more than 500 million years ago. For the proven stability and the almost continuously livable climate during the billions of years before, which was central to the paradox, other organisms would have to have performed this function before they were ousted by evolutionary "newcomers".

Jim Kasting agrees that life plays an important role in the carbon cycle, such as its influence on weathering and oxygen content, but the main influencing factors remain both physical and abiotic.

The assumption of earthly life as a highly organized regulating mechanism contradicts the Medea hypothesis formulated by the paleontologist Peter Ward , according to which multicellular life has no system-preserving properties but a tendency towards self-destruction.

Life on a young, cold earth

In recent decades, life forms have been discovered on earth under very cold environmental conditions, such as the Vostok Sea, which lies under the Antarctic ice sheet . According to John Priscu , this could also be the case on Mars. Contrary to Hart's assumption, the Continuously Habitable Zone in the solar system has meanwhile been extended to close to Mars.

However, an interpretation of the paradox on this basis has little relevance. The Earth's archaic climate appears to have been warmer than it is today, and geological traces with regard to liquid water, unlike icing processes, have been widespread since earliest times. To put it more pointedly, there have been indications of water-based life on earth "since there were stones". Priscus' finding is central to the continuation of earthly life during global glaciations (as well as the probability of life on other planets and moons).

Influence of measurement errors on the paradox

Older paleoclimatological studies described a hot climate with temperatures of up to 70 ° C for the Archean and partly for the entire Precambrian. This assumption is doubted by most geoscientists because of the cold periods that have occurred in the meantime. Currently, a moderately higher average temperature than today is considered likely.

According to various analyzes, the basic elements of the carbon cycle were established 4 billion years ago. A maximum one hundred times higher value of the CO 2 concentration and other greenhouse gases compared to the present is not further disputed, but according to the overwhelming opinion it cannot resolve the paradox. With a significantly increased proportion of carbon dioxide in the atmosphere, the iron carbonate mineral siderite should have formed in considerable quantities, which has not yet been proven. In contrast, Haqq-Misra and others do not see the lack of siderite as the sole exclusion criterion. According to a study published in 2008, a comparison with more recent absorption data required a lower carbon dioxide concentration of an order of magnitude for the late Archean and early Proterozoic. For the late Archean, only 1.5 to 5.5 mbar (compared to pre-industrial 0.28 mbar) partial pressure of carbon dioxide would be required for a moderately warm climate.

Methodological challenges

Rock from the period of the Paleoproterozoic glaciation with traces of early life
Fine-layer structure of stromatolites from the Cretaceous period ( Maastrichtian )

Even the reconstruction of recent climate history, based on a large number of indirect climate indicators , has occasionally been accompanied by controversy. However, paleoclimatological methods of determination are necessary to interpret the paradox. Regardless of the rapid progress of the various analytical techniques such as isotope research , statements about ancient epochs are always fraught with certain uncertainties, although the fossil record can also show larger gaps with increasing time.

Early life

Indirect evidence of early life can be found in chemofossils and fossils, in which biogenic structures such as stromatolites are found. The detection of traces of life and the assessment of the material cycle in the atmosphere in different geological periods is done through the high resolution investigation of the finest graphite and gas inclusions as well as microfossils in minerals.

Formation of the ocean and the earth's crust

Evidence for the existence of an ocean and a solid earth's crust for 3.8 billion years ago is relatively common. The oldest known mineral, at 4.4 billion years old, are zircon crystals from the Pilbara Craton in Western Australia . In addition, there are indications that the crust and ocean were separated at that time. Zircons can run through the cycle of rocks several times . Due to their stable lattice structure, they are resistant to influences such as weathering and rock metamorphosis and, thanks to the nuclides enclosed in the crystals, allow isotope-geochemical information on their formation conditions in addition to radiometric age determination . This requires complex sampling and preparation as well as high-resolution analysis methods such as mass spectrometry .

Reconstruction of the temperature curve

Evaluations of the temperature profile in the geological past are similarly complex. In the measurements of the earliest average temperatures, systematic shifts in the underlying oxygen isotope measurements are possible; an influence on the measured values ​​determined today by interim influences must also be taken into account.

Role of the Paradox in Mars and Saturn's Moon Titan

Panoramic view of the 4000 km long Valles Marineris

The paradox also affects the planet Mars , on whose surface liquid water should therefore not have appeared. In contrast, according to more recent findings, the Martian atmosphere in the early days of the solar system was much denser than it is today. In addition, there were probably extensive water resources on the Red Planet, possibly even in the form of relatively extensive oceans and river systems . Evidence of this is provided by water-based erosion structures or the dry valleys of former rivers.

On Saturn's moon Titan , an orange-colored nebula made up of organic compounds of as yet unknown composition was observed. The astrophysicist Carl Sagan coined the term Tholine for this and suspected an essential factor for the origin of life in such a layer of the early earth. Because of this property, Saturn's moon has become one of the most interesting objects in the solar system. Sagan had also assumed a warming effect from this fog. Other authors contradicted this view and postulated an "anti-greenhouse effect".

According to current research results, an aerosol of branched hydrocarbons (instead of spherical droplets as previously assumed) could have had a major influence on the absorption behavior of the atmosphere. Such an aerosol absorbs UV light, but is largely transparent to visible light.

Web links

Individual evidence

  • TE Graedel et al .: Early solar mass loss - A potential solution to the weak sun paradox. In: Geophys. Res. Lett. 18, 1991, pp. 1881-1884.
  1. ↑ a b Graedel et al., 1991.
  • Jacob D. Haqq-Misra, Shawn D. Domagal-Goldman, Patrick J. Kasting, James F. Kasting: A Revised, Hazy Methane Greenhouse for the Archean Earth. In: Astrobiology. Volume 8, Number 6, 2008. doi: 10.1089 / ast.2007.0197
  1. ↑ a b c d Haqq-Misra et al
  • E. Jansen, J. Overpeck, KR Briffa, J.-C. Duplessy, F. Joos, V. Masson-Delmotte, D. Olago, B. Otto-Bliesner, WR Peltier, S. Rahmstorf, R. Ramesh, D. Raynaud, D. Rind, O. Solomina , R. Villalba, D Zhang: Frequently Asked Question 6.1, What Caused the Ice Ages and Other Important Climate Changes Before the Industrial Era? (PDF; 8.1 MB). In: SD Qin, M. Manning, Z. Chen, M. Marquis, KB Averyt, M. Tignor, HL Miller (eds.): Palaeoclimate in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Solomon. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  1. ↑ a b Climate Change 2007: The Physical Science Basis, p. 448.
  1. ↑ a b c d e quoted in Kasting 1988.
  1. ↑ a b after HD Holland: The oxygenation of the atmosphere and oceans. In: Phil. Trans. R. Soc. Volume 361, 2006, pp. 903-915. doi: 10.1098 / rstb.2006.1838 , quoted in Kasting and Ono 2006.
  2. ↑ a b c d e f g h Kasting and Ono 2006.
  3. ↑ A detailed discussion of the stratigraphic sequence is given in Section 5 Triggering of the Palaeoproterozoic glaciations .
  4. ↑ a b Kasting and Ono 2006, 1. Introduction: the early climate record
  • Vanessa Killops, Stephen Killops: An Introduction to Organic Geochemistry. John Wiley & Sons, 2005, ISBN 1-4051-3692-8 .
  1. ↑ Overview illustration, p. 16.
  2. ↑ Compare the overview on p. 262.
  3. ↑ Detailed presentation of the carbon cycle and the interaction with other factors, pp. 246–248.
  1. ↑ a b c Sagan and Mullen 1972.
  1. ↑ Fig. 2. The history of the star formation rate (SFR), in Shaviv 2003, p. 50.
  1. ↑ a b c d e f g h Shaviv 2003.
  • Y. Ueno, MS Johnson, SO Danielache, C. Eskebjerg, A. Pandey, N. Yoshida: Geological sulfur isotopes indicate elevated OCS in the Archean atmosphere, solving faint young sun paradox. In: Proceedings of the National Academy of Sciences. online pre-publication August 17, 2009. doi: 10.1073 / pnas.0903518106
  1. ↑ a b c d Ueno et al. 2009.
  1. ↑ a b c Veizer 2005.
  • Other:
  1. ↑ Why the early earth was not a snowball: the "paradox of the weak young sun". Press release from the Potsdam Institute for Climate Impact Research (December 17, 2012). Quote: "The paradox of the weak young sun has been one of the great open questions in paleoclimatology since its discovery four decades ago".
  2. ↑ Minik T. Rosing, Dennis K. Bird, Norman H. Sleep, Christian J. Bjerrum: No climate paradox under the faint early sun. In: Nature. Volume 464, April 1, 2010, doi: 10.1038 / nature08955 , abstract online , pp. 744-747.
  3. ↑ a b c d Georg Feulner: The Faint Young Sun Problem. Reviews of Geophysics 50, June 2012, doi: 10.1029 / 2011RG000375 (free full text).
  4. ^ DO Gough: Solar Interior Structure and Luminosity Variations. In: Solar Physics. 74, 1981, pp. 21-34, bibcode : 1981SoPh ... 74 ... 21G , doi: 10.1007 / BF00151270 .
  5. ↑ a b Simon A. Wilde et al .: Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago. In: Nature. 409, 2001, pp. 175-178. doi: 10.1038 / 35051550
  6. ^ A b The Ancient Martian Climate System . Toronto, Canada May 14, 2014 ( nasa.gov [accessed May 14, 2015]).
  7. ↑ a b J. F. Kasting: Earth's early atmosphere. (Abstract online) In: Science. Vol 259, Issue 5097, 1993, pp. 920-926.
  8. ↑ a b c d Vivien Gornitz: Encyclopedia of paleoclimatology and ancient environments . (= Encyclopedia of earth sciences ). Springer, 2009, ISBN 978-1-4020-4551-6 , p. 63 limited preview in the Google book search.
  9. ↑ Eric Theodore Wolf: Solutions to the faint young Sun paradox simulated by a general circulation model . Thesis . 2014, ISBN 978-1-303-92513-9 , pp. 20 , bibcode : 2014PhDT ........ 20W .
  10. ↑ Kevin J. Zahnle et al .: The Tethered Moon. Earth and Planetary Science Letters 427, 2015, doi: 10.1016 / j.epsl.2015.06.058 , arxiv: 1508.01467 .
  11. ↑ a b Kevin J. Zahnle et al .: Emergence of a Habitable Planet. Space Science Reviews 129, 2007, doi: 10.1007 / s11214-007-9225-z
  12. ^ Adam Mann: Bashing holes in the tale of Earth's troubled youth. Nature 553, 2018, doi: 10.1038 / d41586-018-01074-6 .
  13. ↑ Elizabeth B. Watson, Theresa M. Harrison: Zircon thermometer reveals minimum melting conditions on earliest Earth. Science 308, 2005, doi: 10.1126 / science.1110873 .
  14. ↑ Detailed consideration in Usenet under Talk.origins Counter arguments to solar creationism Counter arguments to Faint young sun creationism .
  15. ↑ S. Rahmstorf, HJ Schellnhuber: Der Klimawandel. 6th edition. CH Beck, 2007, p. 14.
  16. ↑ Dennis V. Kent, Paul E. Olsen, Cornelia Rasmussen, Christopher Lepre, Roland Mundil, Randall B. Irmis, George E. Gehrels, Dominique Giesler, John W. Geissman, William G. Parker: Empirical evidence for stability of the 405 -kiloyear Jupiter – Venus eccentricity cycle over hundreds of millions of years . In: PNAS . 115, No. 24, June 2018, pp. 6153–6158. doi : 10.1073 / pnas.1800891115 .
  17. ^ David PG Bond, Paul B. Wignall: Large igneous provinces and mass extinctions: An update . (PDF) In: The Geological Society of America (GSA) Special Paper . 505, September 2014, pp. 29-55. doi : 10.1130 / 2014.2505 (02) .
  18. ^ Nick MW Roberts: The boring billion? - Lid tectonics, continental growth and environmental change associated with the Columbia supercontinent . In: Geoscience Frontiers . 4, No. 6, November 2013, pp. 681-691. doi : 10.1016 / j.gsf.2013.05.004 .
  19. ^ Grant M. Young: Precambrian supercontinents, glaciations, atmospheric oxygenation, metazoan evolution and an impact that may have changed the second half of Earth history . In: Geoscience Frontiers . 4, No. 3, May 2013, pp. 247-261. doi : 10.1016 / j.gsf.2012.07.003 .
  20. ↑ Jochen J. Brocks, Gordon D. Love, Roger E. Summons, Andrew H. Knoll, Graham A. Logan, Stephen A. Bowden: Biomarker evidence for green and purple Sulfur bacteria in a stratified Palaeoproterozoic sea . (PDF) In: Nature . 437, October 2005, pp. 866-870. doi : 10.1038 / nature04068 .
  21. ↑ P. Porada, TM Lenton, A. Pohl, B. Weber, L. Mander, Y. Donnadieu, C. Beer, U. Pöschl, A. Kleidon: High potential for weathering and climate effects of non-vascular vegetation in the Late Ordovician . (PDF) In: Nature Communications . August 7, 2016. doi : 10.1038 / ncomms12 .
  22. ↑ John L. Isbell, Lindsey C. Henry, Erik L. Gulbranson, Carlos O. Limarino, Margaret L. Fraiser, Zelenda J. Koch, Patricia L. Ciccioli, Ashley A. Dineen: Glacial paradoxes during the late Paleozoic ice age: Evaluating the equilibrium line altitude as a control on glaciation . (PDF) In: Gondwana Research . 22, No. 1, July 2012, pp. 1-19. doi : 10.1016 / j.gr.2011.11.005 .
  23. ↑ Guillaume Dera, Benjamin Brigaud, Fabrice Monna, Rémi Laffont, Emmanuelle Pucéat, Jean-François Deconinck, Pierre Pellenard, Michael M. Joachimski, Christophe Durlet: Climatic ups and downs in a disturbed Jurassic world . (PDF) In: Geology . 53, No. 3, March 2011, pp. 215-218. doi : 10.1130 / G31579.1 .
  24. ↑ Vivien Gornitz (Ed.): Encyclopedia of Paleoclimatology and Ancient Environments. Springer, 2009, ISBN 978-1-4020-4551-6 , pp. 334-335.
  25. ↑ Carl Sagan Christopher Chyba: The Early Faint Sun Paradox: Organic Shielding of Ultraviolet-labile Greenhouse gas. In: Science. Volume 276, No. 5316, May 23, 1997, pp. 1217-1221. doi: 10.1126 / science.276.5316.1217
  26. ^ R. Rye, PH Kuo, HD Holland: Atmospheric carbondioxide concentrations before 2.2 billion years ago. In: Nature. 378, 1995, pp. 603-605.
  27. ↑ Michael H. Hart: An explanation for the absence of extraterrestrials on Earth. In: Quarterly Journal of the Royal Astronomical Society. 16, 1975, pp. 128-135, reprint as Michael H. Hart: Atmospheric evolution, the Drake equation, and DNA: Sparse life in an infinite universe. In: Michael H. Hart, Ben Zuckerman (Eds.): Extraterrestrials, Where are They? Pergamon Press, Elmsford 1982, pp. 154-165.
  28. ↑ JF Kasting: Runaway and Moist Greenhouse Atmospheres and the Evolution of Earth and Venus. In: Icarus. Volume 74, 1988, pp. 472-494. bibcode : 1988Icar ... 74..472K doi: 10.1016 / 0019-1035 (88) 90116-9
  29. ↑ Christine Bounama, Werner von Bloh, Siegfried Franck: Where can there be twins on earth? The habitability concept and its applications. In: Stars and Space. 1/2004, pp. 30–36, summary of the status of the subsequent research on CHZ on the web server of the Potsdam Institute for Climate Impact Research.
  30. ^ Colin Goldblatt, Kevin J. Zahnle: Faint young Sun paradox remains. In: Nature. 474, E1 (June 2, 2011) doi: 10.1038 / nature09961
  31. ^ AA Pavlov, JF Kasting, LL Brown, KA Rages, R. Freedman: Greenhouse warming by CH4 in the atmosphere of early Earth. In: J. Geophys. Res. 105, 2000, pp. 11981-11990.
  32. ^ AA Pavlov, LL Brown, JF Kasting: UV shielding of NH3 and O2 by organic hazes in the Archean atmosphere. In: J. Geophys. Res. 106, 2001, pp. 23267-23287.
  33. ↑ AA Pavlov, MT Hurtgen, JF Kasting, MA Arthur: Methane-rich Proterozoic atmosphere? In: Geology. 31, 2003, pp. 87-90. doi : 10.1130 / 0091-7613 (2003) 031 <0087: MRPA> 2.0.CO; 2
  34. ↑ JCG Walker: Carbon Dioxide on the Early Earth. (PDF; 774 kB). In: Origins of Life. Volume 16, 1985, pp. 117-127.
  35. ↑ JCG Walker, PB Hays, JF Kasting: A negative feedback mechanism for the long-term stabilization of the earth's surface temperature. (PDF, 182 kB) ( Memento from September 20, 2008 in the Internet Archive ) In: Journal of Geophysical Research. Volume 86, 1981, pp. 9776-9782.
  36. ^ J. Veizer in BF Windley (ed.): The Early History of the Earth. John Wiley and Sons, London 1976, p. 569.
  37. ↑ Roberto Rondanelli, Richard S. Lindzen : Can thin cirrus clouds in the tropics provide a solution to the faint young Sun paradox? Journal of geophysical research. Vol. 115, 2010. doi: 10.1029 / 2009JD012050
  38. ↑ Minik T. Rosing, Dennis K. Bird, Norman H. Sleep, Christian J. Bjerrum: No climate paradox under the faint early sun. In: Nature. Volume 464, April 1, 2010, pp. 744-747. doi: 10.1038 / nature08955 (abstract online)
  39. ↑ Thomas Smith, David L. Cook, Silke Merchel, Stefan Pavetich, Georg Rugel, Andreas Scharf, Ingo Leya: The constancy of galactic cosmic rays as recorded by cosmogenic nuclides in iron meteorites . In: Meteoritics and Planetary Science . December 2019, doi : 10.1111 / maps.13417 .
  40. ↑ Hendrik Svensmark et al: Experimental evidence for the role of ions in particle nucleation under atmospheric conditions. In: Proceedings of the Royal Society. A 2007 463, 2007, pp. 385-396. doi: 10.1098 / rspa.2006.1773
  41. ^ New Experiment to Investigate the Effect of Galactic Cosmic Rays on Clouds and Climate. ( Memento from July 16, 2012 in the web archive archive.today ) Press release from CERN. PR14.06, October 19, 2006.
  42. Jump up ↑ J. Calogovic, C. Albert, F. Arnold, J. Beer, L. Desorgher, EO Flueckiger: Sudden cosmic ray decreases: No change of global cloud cover. In: Geophysical Research Letters. 37, 2010, L03802. doi: 10.1029 / 2009GL041327 (free full text). See also: Cloud cover unaffected by cosmic rays. In: Information Service Science . March 9, 2010 and Cosmic rays don't make clouds. In: Spektrumdirekt . March 10, 2010.
  43. ↑ Anatoly D. Erlykin, David AT Harper, Terry Sloan, Arnold W. Wolfendale: Mass extinctions over the last 500 myr: an astronomical cause? . In: Palaeontology . 60, No. 2, March 2017, pp. 159–167. doi : 10.1111 / pala.12283 .
  44. ^ Dana L. Royer, Robert A. Berner, Isabel P. Montañez, Neil J. Tabor, David J. Beerling: CO 2 as a primary driver of Phanerozoic climate . (PDF) In: GSA Today (American Geophysical Union) . 14, No. 3, March 2004, pp. 4-10. doi : 10.1130 / 1052-5173 (2004) 014 <4: CAAPDO> 2.0.CO; 2 .
  45. ^ A b Variations in the Gravitational Constant in General Theories of Gravitation . In: Measurement Techniques . tape 57 , no. 11 , February 15, 2015, p. 1255-1261 , doi : 10.1007 / s11018-015-0615-4 .
  46. ↑ a b Can a variable gravitational constant resolve the faint young Sun paradox? In: International Journal of Modern Physics D . tape 23 , no. 12 , October 1, 2014, p. 1442018 , doi : 10.1142 / S0218271814420188 .
  47. ^ DA Minton, R. Malhotra: Assessing the massive young Sun hypothesis to solve the warm young Earth puzzle. In: Astrophysical Journal. Volume 660, 2007, pp. 1700-1706.
  48. ↑ EJ Gaidos, M. Güdel, GA Blake: The Faint Young Sun Paradox: An observational test of an alternative solar model. In: Geophysical Research Letters. Volume 27, 2000, pp. 501-503.
  49. ↑ BE Wood, H.-R. Müller, GP Zank, JL Linsky: Measured mass-loss rates of solar-like stars as a function of age and activity. In: The Astrophysical Journal. Volume 574, 2002, pp. 412-425.
  50. ↑ James Lovelock, "Gaia"
  51. ^ JC Priscu, CM Foreman: Lakes of Antarctica. Encyclopedia of Inland Waters. Elsevier Press, 2007.
  52. ↑ SM Jepsen, JC Priscu, RE Grimm, MA Bullock: The Potential for Lithoautotrophic Life on Mars: Application to Shallow Interfacial-Water Environments. In: Astrobiology. 7, 2007, pp. 342-354.
  53. ↑ so in an overview presentation of the University of Montana 2008 (PDF; 1.6 MB).
  54. ^ Philip Paris et al: Warming the early earth — CO2 reconsidered. In: Planetary and Space Science. Vol. 56, 2008, pp. 1244-1259. doi: 10.1016 / j.pss.2008.04.008
  55. ↑ J. Schopf: Earth's Earliest Biosphere: Its Origin and Evolution. Princeton University Press, Princeton, NJ 1983.
  56. ↑ SJ Mojzsis, G. Arrhenius, KD McKeegan, TM Harrison, AP Nutman, CRL Friend: Evidence for life on Earth before 3,800 million years ago. In: Nature. 384, 1996, pp. 55-59. doi: 10.1038 / 384055a0
  57. ↑ Research activities of Yuichiro Ueno ( Memento from August 15, 2004 in the web archive archive.today )
  58. ↑ SJ Mojzsis, TM Harrison, RT Pidgeon: Oxygen-isotope evidence from ancient zircons for liquid water at the Earth's surface 4300 Myr ago. In: Nature. Volume 409, 2001, pp. 178-181, doi: 10.1038 / 35051557 .
  59. ^ Ján Veizer, Jochen Hoefs: The nature of O18 / O16 and C13 / C12 secular trends in sedimentary carbonate rocks. In: Geochimica et Cosmochimica Acta. 40, No. 11, November 1976, pp. 1387-1395. doi: 10.1016 / 0016-7037 (76) 90129-0
  60. ↑ Christopher P. McKaya, Ralph D. Lorenz, Jonathan I. Lunine: Analytic Solutions for the Antigreenhouse Effect: Titan and the Early Earth. In: Icarus. Volume 137, Issue 1, Jan. 1, 1999, pp. 56-61. doi: 10.1006 / icar.1998.6039
  61. ^ ET Wolf, OB Toon: Fractal Organic Hazes Provided an Ultraviolet Shield for Early Earth. In: Science. June 2010, Vol. 328, No. 5983, pp. 1266-1268. doi: 10.1126 / science.1189196