1. Introduction

For the first four billion year history of our planet there have been repeated cycles of extreme global warming and global cooling (Joseph 2009a). During three of these cycles, much of the planet and its oceans may have been frozen. As may be the case with current changes in climate and global temperature, these past climatic extremes were in large part due to biological factors and directly related to microbial activity and the excretion, liberation, or consumption of carbon dioxide, methane, oxygen, and nitrogen (Joseph 2009a). However, as appears to be the case in modern times (Duhau and de Jager 2010; Miyahara et al., 2010; Persinger 2010), these past episodes were also effected by changes in the tilt of Earth's axis and orbital distance from the Sun, as well as solar, geological, and geomagnetic activity.

2. Hot as Hell: The Hadean Heat Wave.

Most scientists agree that Earth became Earth, 4.6 billion years ago. However, if the planet formed by accretion, that is, from small rocks smashing into each other and somehow, in defiance of physics, stuck together, is in dispute, as rocks stereotypically shatter when they strike one another, and ricochet away to varying distances. According to the primordial planet, rogue Earth theory (Joseph 2009b, 2010; Joseph and Schild 2010), giant planets (e.g. "Super Jupiters", "Super Earths") are formed in nebular clouds following supernova, coalescing around molten iron ejected from the exploding "parent star." Planets are also ejected from dying solar systems prior to supernova (Joseph 2009a, Joseph and Schild 2010). These super planets then grow smaller as they smash into one another and break apart.

Thus, according to this theory, initially planets do not grow larger by accretion, but grow smaller when they smash into one another. However, once they are captured by a stable solar system, smaller debris may be captured by their gravity, and these planets then grow somewhat larger by accretion.

Earth, before it became Earth, may have been a rogue planet which grew smaller following collisions with other rogue planets. In fact, 4.6 billion years ago, Earth may have been at least 2% larger in volume, 1.2% larger in mass, and as much as 15,000 km across (as compared to modern day estimates of 12,742 km). It grew smaller when it collided with a Mars sized planet, which ripped out a chunk of Earth which may have become the moon between 4.5 bya (Jacobsen 2005) and 4 bya (Belbruno and Gott III 2005; Poitrasson et al. 2004, Rankenburg et al. 2006).

Naturally, a collision of this magnitude effected the surface temperatures of our planet, first raising temperatures at impact and then blocking out sunlight due to debris in the atmosphere. However, this upper atmosphere blanket of debris may have also prevented heat from escaping into space. As debris continued to slam into Earth, temperatures would therefore have been quite hot.

For the first billion years after Earth became a member of this solar system, the sun may have been 80% of its current size, 70% as luminous, and therefore did not generate as much heat as the modern sun (Gough 1981; Kasting and Ono 2006; Lang 2001). This relatively feeble heat source, coupled with sunlight blocking debris in the atmosphere, might be expected to contribute to global cooling. And yet, Earth was not cold, but hot (Kasting & Ackerman 1986). The first period of global warming was triggered by internally generated geothermal heat flow (Davies 1990), the excretion and liberation of heat trapping greenhouse gasses (Joseph 2009a) and the tremendous heat generated as stellar debris pounded the planet until around 3.8 bya (Schoenberg et al. 2002).

In addition, heat-trapping greenhouse gases were being pumped into the atmosphere including carbon dioxide (Kasting and Ackerman 1988; Sleep & Zahnle 2001; Walker 1985) and H₂ secondary to volcanism (Berner 2004; Kirschvink 1992; Hoffman et al. 1998) and microbial activity (Joseph 2009a). Asteroid impact also contributed to these green house gasses. When rock is vaporized following impact, a rock vapor atmosphere and heavy volatiles would have been produced consisting of carbon dioxide and hydrogen.

According to Kasting and Ackerman (1986), if the early atmosphere contained 10 bars of CO₂ this would have created a dense heat-trapping greenhouse atmosphere. Coupled with impact induced heat, parts of the planet may have been at the melting point. Others have calculated that atmospheric CO₂levels were much lower (Sleep & Zahnle 2001) which suggests that the planet was broiling but not melting. Of course, the temperatures of some areas of Earth would have fluctuated due to transient variables such as frequency and size of asteroid and meteor strikes and the presence of oceans of water. Therefore, at varying times for the first 800 million years, pockets of the planet may have melted from impact whereas other regions would have been relatively cooler.

Oceans of water, delivered by comets, were probably also crashing into the new Earth, thus cooling the planet and providing Earth with oceans (Drake 2005; Joseph 2000). Evidence for massive quantities of water, by 4.4 bya, are indicated indirectly by an analysis of zircons (Valley 2002; Wilde et al., 2001). Zircons crystals are created during rock formation and have been discovered embedded in sedimentary rocks located in the Jack Hills areas of Western Australia. A small fraction have been determined to be 4.2 billion years old or older and to have crystalized at an average temperature of 690 degrees Celsius, which suggests the presence of water (Valley 2002; Wilde et al., 2001). By contrast rock formation following impact in the absence of water, occurs at around 900 to 1,200 degrees. Thus, because these zicron containing rocks were formed at lower impact temperatures, water must have been present. However, even at these lower temperatures the oceans of Earth had to be boiling, but were prevented from evaporating and drifting off into space due to Earth's gravity, and the presence of a thick CO₂ atmosphere.

Therefore, for the first few hundred million years new Earth was hellishly hot (hence, the name "Hadean Earth") with temperatures averaging around 80°C (176°F) at 4.5 bya (Kasting & Ackerman 1986). And these temperatures were maintained because of volcanic activity, geothermal activity, and heat generated from bolide impacts which were nearly continuous for the first 800 million years, all of which were prevented from seeping off into space due to greenhouse gasses.

3. The Hot Archaen Eon

There is evidence of microbial activity in Earth's earliest rocks, dated to 4.2 bya (reviewed in Joseph 2009b). Because Earth was continually bombarded by titanic debris, rocks already established prior to 4.2 bya were pulverized, erasing all evidence of life on the surface. Only microbial life living deep within Earth, far beneath the surface would have survived this bombardment.

By 4.2 bya microbes may have become established in surface rocks (Joseph 2009b). Some of these microbes were engaging in photosynthesis, and releasing oxygen as a waste product. Yet others were using alternative energy sources and were excreting or producing green house gasses (Joseph 2009a). These included Methanogens which secrete and excrete two powerful green house gasses: methane (CH₄), as well as CO₂.

Thus, following the end of the periods of heavy bombardment and the establishment of oceans, Earth did not significantly cool as methanogens were proliferating releasing clouds of CH₄ which formed an organic haze, thereby maintaining high temperatures and the greenhouse warming of the planet (Schwartzman et al., 2008). Methane is a powerful greenhouse gas; per molecule its warming effect is 21 times that of CO₂. The early Earth lacked an oxygen atmosphere and as based on detailed photochemical modelling (Pavlov et al. 2001) the lifetime of CH₄ in an anoxic atmosphere is approximately 1000 times longer than today. Thus global warming was maintained even as late as 3 bya due to high levels of methane combined with CO₂ which created a powerful greenhouse effect (Pavlov et al. 2000; Kasting & Siefert 2002; Kasting & Ono 2006). In fact, even if there were at best only modest amounts of CH₄ and CO₂ in the atmosphere around 3.0 bya, the Earth's surface temperature would have been about 50°C (122°F) (Pavlov et al. (2000).

Water and plate tectonics draws CO₂ from the atmosphere, and as microbes were feasting on CO₂ to produce oxygen. Therefore, although it remained quite hot for the first billion years, over the next several hundred million years temperatures began to drop, fluctuating from 45°C to 85°C (113°F to 185°F) by 3.3 bya (Knauth & Lowe 2003). As based on calculations of chemical alterations in Precambrian rocks, by 3.0 bya temperatures had dropped further, and Earth, although quite warm, was no longer blistering hot (Condie et al. 2001; Holland 1984; Sleep and Hessler 2006). In large part, the cooling was due to the buildup of oxygen.

Therefore, the planet was quite hot, for the first 1.5 billion years after its formation. It did not begin to significantly cool until between 3.2 to 2.9 bya (Young et al. 1998) during a period where oxygen levels had rapidly increased and spiked. Increased oxygen counters methane whereas oxygen-producing photosynthesisers consume carbon dioxide. Given that the Sun was only 80% as luminous as today, the reduction of these green house gases allowed heat to escape and the planet cooled.

4. Photosynthesis Cooled the Planet.

For the first two billion years after Earth became a member of this solar sytem, the Sun 20% smaller, 30% less luminous, and generated less heat compared to the modern Sun (Gough 1981; Kasting and Ono 2006; Lang 2001). Yet, Earth was hot, with heat supplied by bolide impact, volcanoes, biological activity (Joseph 2009a) and from planetary accretion and through radioactive decay and heat producing isotopes such as potassium-40, uranium-238, uranium-235, and thorium-232 (Jordan 1979; Robertson 2001; Turcotte and Schubert 2002). In the early history of Earth, these heat producing isotopes would have been at full strength (only to become depleted over time), such that the heat generated would have been much greater than today (Turcotte and Schubert 2002). Moreover, because of biologically produced greenhouse gasses, much of that heat would be have been trapped, more than making up for the feeble heat output of the Sun.

By 3.5 bya, cyanobacteria had begun to proliferate on the surface, protected from deadly UV rays by green house gasses (Joseph 2009a,c). Cyanobacteria are the only known prokaryotes capable of oxygenic photosynthesis (DesMarais 2000). By 3.46 bya these photosynthesizing microbes had released significant amounts of oxygen into the atmosphere and oceans (Hoashi et al., 2009). In fact, they were performing the same functions from deep beneath the sea and were congregating near undersea volcanoes and thermal vents and reducing metals, minerals and carbon dioxide.

Photosynthesis (and thus oxygen production) was not hampered by the sun-blocking organic haze or the feeble rays of the sun, due to the activity of viruses (Joseph 2009a). Viruses provide bacteria with additional photosynthesizing genes under conditions of reduced sunlight (Lindell et al., 2004; Sullivan et al., 2005, 2006; Williamson et al., 2008). Viruses act as a store-house for genes which code for photosynthesis (Lindell et al., 2004; Sullivan et al., 2005, 2006) including photoadaptation and the conversion of light to energy (Williams et al., 2008). Some of these viruses (e.g., cyanophages) provide cynobacteria with genes which augment the host photosynthetic machinery during periods of stress, insufficient nutrients, or reduced sunlight (Sullivan et al., 2006). When the excess genes are no longer necessary, they are transferred from the bacteria genome back to the virus genome for storage (Lindell et al., 2004; Sullivan et al., 2005, 2006).

Thus, oxygen-producing cyanobacteria were proliferating and creating thick cyanobacterial mats (Buick 1992) -leaving their fossilized signatures in shales and stromatolites (Brocks et al., 1999; Olson 2006)- and were secreting oxygen and consuming carbon dioxide. Around 3.2 bya, there was a spike in atmospheric oxygen, a consequence of increased oxygen photosynthesis (Ohmoto et al. 2005).

Oxygen negates methane. Bacteria were also fixating and converting nitrogen into nitrates. Nitrogen is also a green house gas and its reduction along with reduced levels of carbon dioxide and methane would have also contributed to the global cooling of Earth.

This increase in oxygen levels was also the result of photochemical degradation and H₂ drawdown by sulphate-reducing bacteria (Kasting & Ono 2006) thus liberating and releasing O₂ into the atmosphere. Anoxygenic photosynthesizers employ H₂ as a reductant. Moreover, autotrophic methanogens feed on H₂ of which there are ample supplies in the ocean. Therefore, around 3.2 bya oxygen and methane levels increased (Ohmoto et al. 2005). Oxygen, however, also breaks down methane. In consequence, between 3.2 to 2.9 bya, the planet had cooled, a function of increased oxygen reducing the methane greenhouse effect (Young et al. 1998; Kasting & Ono 2006) and reductions in CO₂.

5. 300 Million More Years of Global Warming: 2.8 to 2.5 bya

Oxygen levels began dropping after 2.8 bya (Ohmoto et al. 2005); a possible consequence of solar flares and increased UV radiation on the viability of photosynthesizing organisms. As they died methanogens feasted upon their carcasses releasing methane. Moreover, the 300 million year cold spell killed innumerable creatures, which build up vast quantities of organic wastes which methanogens and other prokaryotes feasted upon. Large quantities of oxygen were consumed in the process of oxidizing and reducing inorganic and organic compounds.

Methanogens flourished and pumped increasing amounts of methane into the atmosphere, creating a thickening organic haze (Pavlov et al. 2001) that was interfering with photosynthesis and thus oxygen production (McKay et al. 1991; Pavlov et al. 2000). Moreover, volcanoes were belching CO₂ and sunlight-blocking ash into the atmosphere. H₂ levels may have also increased because the organic methane haze was acting as a blanket thereby preventing H₂ from escaping into space (Tian et al. 2005).

Therefore, around 2.8 bya, Earth again began to warm and a period of global warming ensued which lasted 300 million years due to high atmospheric levels of methane and H₂ which created a thick organic haze triggering a heat-trapping greenhouse effect (McKay et al. 1991; Pavlov et al. 2000).

However, photosynthesis and oxygen production continued, and a balance was achieved, and by 2,500 bya temperate climates prevailed (Condie et al., 2001; Holland 1984; Kasting and Howard 2006; Sleep & Hessler 2006). So ends the Archaen Eon.

6. The First Snow Ball Earth: The Makganyene Glaciation

The Proterozoic Eon (2.5 bya – 542 mya), was punctuated by four major cycles of global cooling and world wide glaciation, which nearly froze the planet and creating three episodes of what has been called "Snow Ball Earth." Much of this global cooling was a direct consequence of biological activity. However, as will be discussed in a later section, solar and geomagnetic activity, coupled with variations in the orbit and tilt of this planet, were also likely contributory factors.

Because of the high levels of methane which had built up in between 2.8 to 2.5 bya, archae known as methanotrophs and methylotrophs began to proliferate. These were methane eaters, and in ever growing numbers they metabolized and broke down methane, as demonstrated by the presence of hopanes and high relative concentrations of 2α-methylhopanes in Archean rocks (Brocks et al., 2003). As methanotrophs proliferated, methane levels rapidly fell, thereby reducing the green house effect which also allowed more sunlight to strike Earth. Increased sunlight triggered increased photosynthesis. By 2.45 bya, oxygenic photosynthesis had become widespread (Brock et al., 2003; Buick 2008) and atmospheric oxygen levels rose (Bau et al. 1999; Kirschvink et al. 2000) to values between 0.02 and 0.04 atm (Holland 2006).

Oxygen also breaks down methane. Indeed, the presence of even small amounts of O₂ in the atmosphere would have been associated with a significant decrease in its CH₄ content, and this decrease would have caused the planet to rapdily cool (Young et al. 1998; Kasting & Ono 2006). In fact, O₂ levels became so high around 2.4 bya that sulphur MIF production collapsed, and this caused a rapid and drastic decrease in atmospheric CH₄, thus triggering glaciation (Kasting and Howard, 2006). That is, increased levels of O₂ acted to oxidize sulphide, such that dissolved sulphate levels increased just as O₂ levels increased. Both began to build up in shallow marine sediments which resulted in decreases in methagenesis and significant reductions in atmospheric methane (Pavlov et al. 2003; Kharecha et al. 2005). The increased levels of sulphate in turn triggered a proliferation of sulfur-eating bacteria, which caused a drawdown in H₂ and CH₄, a consequence of bacterial sulphate reduction (Kasting and Ono, 2006).

Because the sun's output was at least 10% of current levels, the loss of a heat trapping greenhouse blanket caused the planet to rapidly cool.

Moreover, CO₂ levels were being reduced by photosynthetic bacteria who were employing H₂, H₂S and/or Fe²⁺M to reduce CO₂ to organic matter (Pierson 1994). The reductions in methane coupled with reductions in CO₂ accelerated the cooling and glaciation of the planet.

Thus, between 2.4 bya to 2.2 bya, as oxygen levels rose, the greenhouse effect was eliminated, and the planet grew cold and began to freeze (Joseph 2009a; Roscoe 1969, 1973), creating the first "Snowball Earth" referred to as the "Makganyene" glaciation. By 2.2 bya much of Earth and its oceans were frozen or covered with ice and snow (Evans et al., 1997; Kirschvink,, et al. 2000; Roscoe 1969, 1973).

The first Snow Ball Earth was orchestrated biologically.

However, these blankets of snow and layers of ice also provided protection against UV rays, but allowed light penetration (McKay 2000). This enabled photosynthesizing creatures to proliferate near the surface (Cockell et al. 2002; Cockell & Cordoba-Jabonero 2004). These subsurface photosynthesizers secreted even more oxygen into the atmosphere, thus maintaining these freezing temperatures.

And then temperatures began to rise.

7. The BioMelting of Snowball Earth

Innumerable microbes may have died due to the glacial conditions, thus forming thick layers of carbohydrate enriched organic matter on land and sea (Joseph 2000, 2009a). Oxygen rapidly degrades and destroys organic matter. Under current conditions, over 99% of organic matter is destroyed depleting massive quantities of oxygen in the process; a function of the redox state of the atmosphere–ocean system. Oxygen, however, is replenished as quickly as it is consumed.

Two billion years ago, the oxygen released by photosynthesizing microbes was also actively being reduced and removed from the atmosphere; consumed in the process of oxidizing and reducing inorganic and organic compounds. However, oxygen was depleted faster than it could be produced, and oxygen levels fell.

Other factors contributing to reductions in O₂ levels may have included submarine volcanoes (Krump 2008). As argued by Krump (2008) "the gasses emitted by submarine volcanoes, were binding atmospheric oxygen with a variety of minerals, thus stripping oxygen from the atmosphere."

Oxygen breathing eukaryotes began to die; with death rates compounded by the still freezing temperatures (Joseph 2009a). These deaths would contribute to increased methane production.

Since oxygen levels were being reduced to low levels, and as dead organic matter accumulated, methanogenesis again began playing a greater role in the degradation of organic matter (Holland 2006) and Methanogens again began to proliferate. Carbon dioxide and methane were pumped back into the atmosphere by a variety methagenic microbes living within the ocean, deep beneath the earth, within the snow, and feasting on dead microbes and decaying organic matter lying in shallow pools of melt water and muddy soil. Further, volcanoes were belching carbon dioxide. The increasing levels of methane coupled with carbon dioxide, again began to create a greenhouse effect. Snowball Earth began to melt.

Temperatures also were also initially reduced by the proliferation of cyanobacteria (such as black cyanobacterium Scytosiphon) which colonized much of the icy snowy surface which was increasingly covering the planet. These ice-hugging Cyanobacteria likely formed thick black bacterial mats (Joseph 2009a) which in turn prevented light and heat from being reflected back into space. In the arctic these creatures can reduce albedo and can warm the soil by 4–5 °C and icy surfaces by 8–12 °C (Gold 1998). However, as they proliferated they also died in greater numbers, provided nutrients for methane producing microorganisms, and thus methane levels increased further.

Over time, as the sun grew in mass it increased its heat output (Gough 1981; Lang 2001). Thus, due to increased heat generation from the sun, and the methane-carbon dioxoide greenhouse effect, between 2.2 to 2.0 bya, the global ice age and "Makganyene" glaciation came to an end. After 250 million years of global glacial conditions, Earth began to warm, sea levels rose from melt water, and the climate and environment of the planet underwent significant change; all of which acted on gene expression thereby directly acting on and triggering the evolution of additional species (Joseph 2009a,b).

8. Biological - GeoEnvironmental Interactions: Temperate Earth

Microbes consume a variety of substances including rock and metal, and in so doing liberate phosphates, sugars, nitrogen and amonia from the soil and playing a major role in the carbon cycle. The basic chemistry of Earth's surface and atmosphere has been determined by biological activity, especially that of the many trillions of microbes who dwell in soil and water. Microbes make up the majority of the living biomass on Earth and for the first 2 billion years bacteria labored to genetically engineer the environment in preparation for the next stage of metamorphosis, and they did this by converting minerals, enzymes, gasses, nitrogen, sulfur, iron, hydrogen and sunlight, into forms which could be used to sustain the life of more complex creatures which had not yet evolved (Joseph 2000, 2009a,b).

Microbes (along with wind, rain, weathering, and plate tectonics) have transformed the surface of this planet. Beginning around 850 to 820 MA, the pre-Pangean supercontinent named "Rodinia", which occupied the tropical equatorial regions, began to slowly break apart; a consequence of plate tectonics, mantle subduction, extensive volcanism coupled with magma super plumes (Druschke et al., 2006; Li et al. 2003; Sung et al., 2006; Wang and Li 2002; Zhou et al., 2002), and the biological digestion of rock and earth by microbes (Joseph 2009a).

This pattern of breakup would continue for the next 200 million years. Lakes, rivers, and seas filled in the newly formed basins and fractures (Lia et al., 1999; Torsvik 2003; Weila, et al., 1998) and inundated and flooded huge land masses with rivers of torrential rains and oceans of water (Johnson et al., 2005). Tropical wetlands thousands of miles in size were formed creating an ideal habitat for methanogenic microbes which began excreting massive amounts of methane into the atmosphere (Cavalier-Smith 2006). On the modern Earth, methane is broken down and removed by oxidation in combination with O₂. However, as O₂ levels were still low, the buildup of methane in conjunction with CO₂ emitted from volcanoes and microbes, created yet another blanket of greenhouse gasses which warmed the planet.

As Rodinia continued to fracture and drift apart, greater masses of formerly very dry land were increasingly exposed to greater amounts of moisture and ocean water (Johnson et al., 2005). Microbial activity also increased. The chemical composition of the soil continued to undergo severe and rapid weathering. The combined effects of microbe and weathering resulted in the release of a variety of carbonate aerosols, including massive amounts of silicates that had been liberated from the soil (Joseph 2009a). The silicates bled into the atmosphere and drained into the seas.

Silica interacts with carbonate, and together the carbonate–silicate cycle directly impacts climate, and can lower temperatures by affecting ocean water chemistry (Berner et al., 1983; Berner 2004; Walker et al. 1981). As the climate cooled, silicate weathering slowed down, and atmospheric CO₂ levels increased due to continued volcanic and microbial activity, thereby causing temperatures to rise which triggered increased weathering and the additional release of silicates. Therefore, the cycle repeated itself, creating stasis and Earth's climate remained temperate (Joseph 2009a; Kirschvink 1992; Hoffman et al. 1998).

9. The Second SnowBall Earth: The Sturtian Glaciation

Around 730 MYA, silicate weathering secondary to the continued breakup of Rodinia, coupled with increased levels of O₂ began to profoundly effect the climate. Methane and CO₂levels dropped as O₂ levels rose (Joseph 2009a). Temperatures fell rapidly, and snow and ice covered more and more of Earth. The carbonate–silicate cycle became destablized and temperatures began to plummet.

Around 725 mya the surface of the oceans and the planet, from the poles to the equatorial latitudes, froze and became glaciated, leaving perhaps only islands of open-water refuges on the surface, and deep beneath the ice covered seas (e.g. Harland 2007; Hyde et al., 2000; Kaufman et al., 1997; Hoffmann et al., 1998). Innumerable species were doomed to extinction (Elewa and Joseph 2009). Yet others diversified and thrived (e.g. Butterfield et al. 1994; Butterfield & Rainbird 1998). This period of world wide glaciation is known as the "Sturtian."

As more of the planet froze, the growing areas of ice and snow began to reflect more solar radiation back into outer space. Photosynthesizing organisms also proliferated releasing significant amounts of oxygen into the atmosphere. Organic carbon and biomarkers indicate extensive bacterial photosynthesis during the Sturtian snowball glaciation (Olcott et al. 2005). Therefore, the planet became even colder, creating a self-sustaining ever worsening feedback system (Joseph 2009a).

This second global ice age, referred to as "Sturtian" lasted 50 million years, and may not have come to a close until 670 mya (Fanning and Link 2004). Following the "Sturtian" glaciation the planet grew warm, the seas were enriched with silica, and life in the seas quickly recovered. Photosynthesizing cyanobacteria continued to pump oxygen into the atmosphere and build mats and stromatolites (Grey et al., 2004). Microscopic eukaryotes diversified, and then they too, along with prokaryotes, biologically engineered the climate and atmosphere (Joseph 2000, 2009a).

As has been emphasized, cyclic changes in weather and climate are effected by biological activity. When biological or uncontrolled forces alter the biosphere and promote temperature extremes, the living biomass labors to bring it back into balance, and in so doing often repeats the warming-cooling cycle.

Despite the global deep freeze, there were probably numerous islands of open water. As equatorial sea ice was probably thin, unicellular eukaryotic algae, protozoa, cyanobacteria, and other creatures would have been able to continue engaging in photosynthesis (McKay 2000). Because of increased oxygen levels they may have switched to consuming oxygen and producing CO₂

Further, it is likely that these vast regions of ice and snow were soon colonized by psychrophiles (cold-loving organisms). The icy surface of the planets was also probably covered with thick black mats of cyanobacteria just as they are in the modern day arctic (Quesada et al., 1999; Vincent 2000). The growth of these darkening colonies would have greatly reduced albedo, and would have trapped heat just as they do in the Arctic (Quesada et al., 1999).

Moreover, methenogens were again feasting on decaying organic matter and releasing methane. In consequence, temperature began to rise, the snows began to melt, and signficant amounts of methane and CO₂ were again released into the atmosphere, bringing the Sturtian glaciation to an end around 670 mya. Earth again began to warm.

10. The Third Snowball Earth: The Marinoan and Gaskiers Glaciations.

Beginning around 640 mya, the planet experienced yet another global ice age, the "Marinoan" (Bowring et al., 2003; Condon et al., 2005; Kaufman et al., 1997; Hoffmann et al., 1998, 2004; Hyde et al., 2000).

The Marinoan global ice age was likely triggered by a combination of oxygen buildup and the spewing of volcanic ash into the atmosphere which blocked out sunlight. For example, U-Pb zircon dates from volcanic ash beds within the Doushantuo Formation (China) indicate extensive volcanic activity beginning around 635 mya (Condon et al., 2005).

Alterations in temperature act on gene selection (Joseph 2000, 2009a,b), and it was during the onset of the Marinoan glaciation, that a number of distinct species appeared in an an evolutionary burst, including the Ediacaran fauna who may have been as much plant as animal. Microscopic life had become macroscopic. The Ediacaran were accompanied by species collectively referred to as "Echinodermata-Arkarua adami" and the heartless, brainless Placozoa Trichoplax whose genome possessed the silent genes necessary for fashioning a heart and brain (Srivastava, et al., 2008).

The "Marinoan" glaciation was followed by 10 million years of global warming. The cycle, however, continued, and this warm period was followed by another extreme period of cooling referred to as Gaskiers glaciation, which came to a close 580 Ma (Eyles & Eyles 1989).

The Marinoan/Gaskiers glaciation was brought to an end in a manner similar to the "Sturtian." Global volcanic activity vented not just ash but tons of CO₂ into the air thereby generating greenhouse warming (Kirschvink 1992; Hoffman et al. 1998). Conversely because of glaciation, C0₂ consumption was limited and some species of microbe may have switched to consuming oxygen. Since microbes were venting carbon dioxide, CO₂ levels began to rise, thus contributing to global warming.

Likewise, due to the death, extinction, and decay of innumerable life forms from freezing, and the decomposing actions of various bacteria including methagens, increasing amounts of methane were again spewed into the environment while simultaneously oxygen was being depleted during decomposition. The buildup of methane (Bao et al., 2008), which may have also been released from equatorial permafrost (Shields 2008), coupled with volcanic ash, reductions in oxygen, and increases in CO₂, again generated a greenhouse effect. The planet warmed and this was followed by a global meltdown which brought the Marinoan/Gaskiers glaciation to a close.

However, as much of the melting ice contained high amounts of oxygen, oxygen levels in the ocean rose (Canfield et al., 2007) at the same time the planet began to warm. Increased oxygen balanced out global heat wave and the climate became more temperate.

These changes in global temperatures, like those from previous cycles, again acted on gene selection (Joseph 2009a,b). After each global warming and freezing cycle, a variety of niches were emptied of life and which were then exploited by other organisms. Innumerable creatures evolved and just as many died and became extinct during the Marinoan/Gaskiers glaciation and its global warming aftermath (Elewa and Joseph 2009; Joseph 2009a).

11. Oxygen, Ozone and the Cambrian Explosion

It took four billion years for Earth's atmosphere to be biologically modified to create an environment and climate amenable to sustaining and promoting the evolution of complex life. The bioengineering of the planet had to balance out temperature extremes related to non-biological forces, and required the continual release and buildup of oxygen in the oceans and atmosphere which in turn produced the ozone layer which protected against UV and other life-neutralizing radiation.

Photosynthesizers produce not just oxygen but calcium and oxygen. This and other biological activity also contributed to the weathering of the planet and the breakup of rock and soil which leached additional chemicals, gasses and metals into the oceans, some of which such as silica also effected weather patterns and climate.

Until sufficient oxygen, silica, and calcium had been released and the oceans had become oxygenated, body and cell size were restricted and unable to expand or engage in strenuous physical activity. Larger bodies require skeletal support. Internal organs require skeletal protection. This was made possible through biological activity and the release of silica followed by calcium which had been produced by cyanobacteria (Joseph 2009a). Oxygen resulted in ozone. In the absence of ozone, larger sized bodies would be burnt by UV rays and would pop and explode. Until around 580 million years ago, the vast majority of life forms sojourning on Earth and beneath the seas, were single celled organisms and simple multi-celled creatures composed of less than 11 different cell types (Bottjer et al., 2006; Glaessner, et al. 1988; Narbonne 2005; Narbonne and Gehling 2003; Shen et al., 2008).

Therefore, beginning between 640 mya and 580 mya, once silica, calcium, and oxygen levels had increased and a protective skeleton and (oxygen-initiated) ozone layer were established, creatures expanded in size, diversified, and grew spines, silica skeletal compartments, then silica-collagen skeletons, collagen-calcium skeletons, armor plates (sclerites) and small shells like those of brachiopods and snail-like molluscs (Joseph 2009a).

Increased oxygen also provided oxygenated environments throughout the ocean which could be exploited and colonized by oxygen breathing creatures. Coupled with increased calcium, and silica, vast networks of silent genes were activated, and others silenced and an explosion of life ensued and a new wave of speciation was unleashed.

By the onset of the Cambrian Explosion, 540 mya, so much oxygen had been released into the atmosphere that ozone was established which blocked out life-neutralizing UV rays. Those who breathed oxygen were at a signficiant advantage, increasing the number of environments they could invade and conquer. And then, all manner of complex life quite suddenly exploded upon the world stage. With the establishment of ozone innumerable creatures could emerge from the sea or from beneath the soil and exploit new environments; environments which acted on gene selection giving rise to new capabilities and new species.

Beginning around 540 mya, there was a vast explosion of bilaterial metazoan diversity and complexity that appeared multi-regionally throughout the oceans of Earth within 5 to 10 million years. Over 32 phyla rapidly evolved, many with the "modern" body plans seen in modern animals (Fortey et al., 1997; Valentine et al., 1999; Conway and Morris 2000; Budd and Jensen 2000; Peterson et al. 2005). However, these species and their descendants, also biologically modified the planet, and as is evident with modern humans, their activities effected the climate and global temperatures.

12. Solar and Biological Interactions.

Over the course of the last 4 billion years the Sun has grown in size and become more luminous and hot (Gough 1981; Kasting and Ono 2006; Lang 2001). Naturally, solar activity would influence the temperatures and climate of Earth. Yet, when the Sun was at its coolest, Earth was at its hottest. Two billion years would pass before Earth began to cool, and then freeze. And then over the next two billion years as the Sun increased its heat output, Earth froze repeatedly, with four major cycles of global cooling and world wide glaciation, between 2.5 bya to 580 mya.

Although each cycle of global heating and global freezing triggered the extinction of innumerable forms of microscopic life, each episode is also associated with bursts of speciation and the evolution of increasingly complex creatures, culminating in the Cambrian Explosion (Joseph 2009a,b,c). Naturally, the microbes of Earth could not influence solar activity. However, solar activity may have influenced biological activity (Persinger 2010).

There is now some evidence suggesting the sun may be reducing its sunspot activity, which in the past has been associated with global cooling (Duhau and Jager 2010; Miyahara et al., 2010). Simultaneously humans are engaged in activities which are associated with global warming. The contributions of humans to global warming can also be seen as biological. To speculate: If the planet is heading toward a cooling cycle, perhaps this biological activity has been triggered to counterbalance these acts of nature.

Of course, in contrast to the modern era of temperature fluctuations, those in the past, during the first 4 billion years, are associated with extremes in climate change, from broiling hot to Snowball Earth. However, these temperature extremes were also effected by other factors, such as higher levels of heat generated from planetary accretion, radioactive decay and heat producing isotopes such as potassium-40, uranium-238, uranium-235, and thorium-232 (Jordan 1979; Robertson 2001; Turcotte and Schubert 2002). On modern Earth, these heat producing isotopes have little left of their half lives, such that the heat generated is much lower today (Turcotte and Schubert 2002).

Microbial biological activity was therefore subjected to temperature extremes for the first several billion years which might have triggered oppositional biological activity, the purpose of which was to bring Earth climate into balance, tipping first to one extreme then the other until more temperate climates prevailed. Therefore, over the last 500 million, and especially in the last 50 million years, climatic and temperature changes are less extreme.

12. Alterations in Earth Orbit and Axis

When Earth was first captured by this solar system, instability ruled. Planets were crashing into one another, gravitationally influencing one another, and orbiting the sun at distances which were continually changing and had not yet stabilized. For example, if Earth were the only planet orbiting the Sun, it might be expected to have a circular orbit and would be at a greater distance from the Sun. Because of the presence of the other planets, and in particular the gravitational effects of Jupiter and Saturn, the orbit of Earth is eccentric and it swings close then far away from the sun over the course of its 365 day orbit. As there may have been many more planets initially, and given that Earth may have been captured by this solar system, and coupled with the fact that it collided with a Mars sized planet around 4 bya, it could be predicted that its orbit may not have stabilized for billions of years. This instability would have effected climate and global temperatures and may have contributed to the exceedingly hot conditions which prevailed for the first 2 billion years and the global warming/cooling cycles of the following 2 billion years.

Although the orbital ellipse of Earth has stabilized into a predictable pattern, it continues to vary in a 100 million year cyclic pattern over a period of around 400,000 years. This cyclic pattern may have contributed to episodes of global warming and cooling, cycles of little ice ages and major ice ages, and the extinction and the evolution of new species. Moreover, this cycle will continue into the future. Over this cycle, winters may become shorter and warmer, or summers shorter and cooler.

In addition, Earth's elliptical orbit rotates over a 21,000-year cycle which is linked to the variations in the length of the four seasons.

The angle of the axis of Earth, as the polar regions point toward and away from the sun, also varies over time and would have a direct impact on the seasons and temperature and climate of the planet.

Earth's angle of axis rotation also varies in relation to the plane of its orbit over a period of 41,000 years, with the angle of the axis varying from 22.1 degrees to 24.5 degrees and back again. This angle is now at 23.44 degrees, but is decreasing. The change in the tilt of angle toward or away from the Sun would have an obvious effect on global temperatures.

13. Suns and Solar System's Orbit the Milky Way Galaxy.

The collective effects of changes in Earth's movements and variations in eccentricity and axial tilt during Earth's orbit exert profound effect on climatic as well as biological activity. Then there are the effects of galactic cosmic rays and solar magnetic activity which have been shown to directly effect global climate (Miyahara et al., 2008b, 2009) and biological behavior (Persinger 2010). However, yet another factor may be the orbit of the Sun (and Earth and this solar system) around the Milky Way galaxy.

The Milky Way galaxy may contain up to a trillion stars. One of these stars, our Sun, is located on one of the spiral arms of this galaxy, the Orion Spur. The Milky Way is in motion, and our Sun orbits the Milky Way approximately every 240 to 250 million years.

The Sun's orbit, like that of Earth, is elliptical, such that it is orbiting increasingly closer to the central bulge at the center of this galaxy. Although we can only speculate, it may be that this orbital pattern also effects global temperatures on Earth, as well as the solar activity of our sun.

14. Conclusions

The biosphere and climate of this planet has been largely created and altered through biological activity, primarily that of prokaryotes. However, volcanism, bolide impacts, alterations in solar activity, shifts in the orbital distance from the sun, and other variables have also collectively effected the climate and biosphere, and in so doing, influenced biological behavior. The unifying theme is that solar and geomagnetic activity effects biological behavior, and biology has been a major factor in climate change for the entire history of this planet.

Over the first four billion years after Earth became a member of this solar system, there have been repeated episodes of global warming and global freezing, and biological activity was a major influence including during the first two billion years of global warming. It was microbes which produced carbon dioxide and methane, both greenhouse gasses. Likewise, the activity of microbes contributed significantly to the alternating extremes in temperature from 2.5 bya to 500 mya. It was microbes which produced oxygen which induced global cooling, and microbes which produced carbon dioxide and methane; the net effect was that over hundreds of millions of years the planet swung between extremes in temperature, often in reaction to non-biological causes. The implications are that as the planet warmed, biological activity contributed to cooling. As it grew cold, biological activity contributed to a warming cycle. It was the activity of these microbes which brought the planet back into climatic balance thereby making it habitable for increasingly complex and intelligent species.

In part, the bioengineering of the planet's climate and atmosphere has been under genetic control, and was not random (Joseph 2009a,b,c). That is, genes, via biological activity, effected and changed the environment which acted on gene selection, thereby effecting the course, speed, and trajectory of evolutionary development; just as the growth of a fetus to a neonate to a baby, is under genetic control and regulated by the chemical changes within the womb which is also under genetic control (Joseph 2009a,b,c). Microbes genetically altered the womb of the planet.

However, the biological activity that altered the climate and environment during the first 4 billion years was also in response to and thus a consequence of geological and cosmological factors including the tilt and orbit of Earth, changing solar activity, and possibly the 250 million year orbit of our Sun around the Milky Way galaxy; all of which may have independently as well as collectively effected the climate of this planet for its entire history.

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