The Story of Climate Change (Part 2)
"To everything turn, turn, turn - There is a season turn, turn, turn - And a time to every purpose under Heaven." - Pete Seeger
Climate Variability Loops
Carbon Dioxide Loop
In 1989, Caltech geologist Joe Kirschvink coined the term “Snowball Earth” merging ideas that some geologists, climate physicists and planetary chemists had been pondering at the time. Together, these ideas propose that our entire planet may have once been completely covered in ice. Building on earlier work, Kirschvink became the first to associate the runaway ice-albedo concept to a known geological event, the Marinoan glaciation during the Cryogenian period, 640 million years ago. He established three independent tests of his hypothesis: global glacial synchroneity, ocean anoxia since they would be ice covered, and ultra-greenhouse aftermaths. There is confirmatory geological evidence for all three. This extreme climate scenario is believed to be the result of a unique continental configuration during this period where a run-away ice-albedo cooled and glaciated nearly the entire planet including the oceans. A presumed follow-on, carbon dioxide fueled run-away Hothouse period would then break the cold ice-albedo feedback loop and quickly deglaciate the planet.
In this scenario, when carbon dioxide in the atmosphere becomes depleted through chemical weathering of the Earth’s crust the planet begins to cool. If CO2 gets too low the planet gets very cold. As ice and snow accumulate on the surface, a whiter, more reflective Earth would cool even more … ice-albedo feedback. The unstoppable ice then, at a minimum, could expand to cover the poles and the high latitude oceans and land masses with kilometers thick glacial ice sheets or at the extreme, the full snowball planet scenario could develop. Earth’s frozen hydrologic and carbon sequestration cycles would then be compromised leading to anoxia of the oceans. The dysfunctional carbon sequestration systems allow CO2 to build up to high levels in the atmosphere. The resulting run-away Hothouse process would initiate global warming and quickly melt the glaciers. The Hothouse would then be terminated by atmospheric carbon dioxide depletion through chemical weathering of the Earth’s crust, subsequent carbon burial, and ultimately, recycling back into the atmosphere via new volcanism. The pattern and periodicity of real paleoclimate change however, do not seem to be well explained by weathering, subduction, and volcanic activity cycles throughout Earth's geologic past.
Some evidence for catastrophic climate change associated with very large, protracted volcanic eruptions is present in the geological record. One of the most famous associations is that of the eruption of volcanoes that produced the Siberian Traps. This is a large region of volcanic rock sequences in eastern Russia. Rapid and extensive volcanic eruptions around 250 million years ago are thought to have released sufficient quantities of sulfate aerosols to trigger short-duration volcanic winters. The mass of CO2 released from individual volcanic eruptions has been estimated to be small compared with the total mass of carbon in the atmosphere-ocean system, but it is thought that significant accumulation could occur over periods of hundreds of thousands of years. These timescales however, seem much too short to account for the climate changes over geologic time.
The Siberian Trap eruptions have been implicated as a possible causal factor in the Earth’s largest mass extinction at the end of the Permian period when 80% of Earth’s marine and terrestrial life ceased to exist. The eruptions continued for roughly two million years possibly igniting underlying Pennsylvanian coal deposits adding to the already stressed global environmental conditions.
It seems clear from our 675-million-year paleoclimate model (Fig. 6) that the major driver of mass extinction periods of the geologic past was long-term global cooling. The pattern of climate change around 250 million years ago seems to conform to “usual” warming then cooling cycles - just out of the hot Permian and after a long-term cooling period that ended in a cold climate trough, global temperatures fell below those not seen in 50 million years during the Carboniferous Period. Most of those creatures that evolved through the hot Permian could not survive this new colder world. The cold environmental conditions may have been exacerbated by volcanism during this time driving the extinction toll even higher. Another mass extinction that appeared during the final period of the Proterozoic eon, the Ediacaran saw an 80% reduction in biodiversity around 550 Mya. The cause of this extinction is controversial but it appears conspicuously during a significant negative δ13C cooling excursion. After the Gaskiers glacial age about 580 Mya, a 15-million-year warming climate followed by a 15-million-year cooling climate ended in a cold climate trough 550 Mya – cold climate seems like a plausible culprit here as well.
Cosmic Radiation Loop
We must look to another climate driver that looms much larger than the Earth’s internal cauldron. In 1913, Victor Hess, while measuring the background level of atmospheric ionization during balloon ascents, discovered that the Earth is continuously bathed in ionizing radiation from outer space. In the 1920s, physicist Robert Millikan coined the term “cosmic rays” insisting that the Hess radiation was electromagnetic in nature. In 1934, Walter Baade and Fritz Zwicky suggested that cosmic rays originate from supernovae, the explosive death of massive stars. It was not until 2013, using gamma-ray observations from the FERMI satellite, that it was directly proven that cosmic rays are indeed accelerated by supernovae. We now know that cosmic rays are made up of high-speed ions, mostly protons, with some heavier nuclei. Their equivalent energies range from their rest mass to a trillion times larger. In 1949, Enrico Fermi speculated that the galactic spiral arms might concentrate and direct this radiation out of the galaxy. Exo-galaxy radio observations reveal a galactic plane-polarized synchrotron radiation emission confined to spiral arm regions. Synchrotron radiation is a tell-tale signature for high energy ions like cosmic rays being redirected from their paths by very strong electromagnetic fields.
The idea that cosmic rays might affect climate through modulation of ionization in the atmosphere goes back to Edward Ney in 1959. It is known that our own solar wind modulates the flux of cosmic rays reaching Earth — high solar activity deflects more of the cosmic rays away from the inner solar system, thus reducing atmospheric ionization. Ney realized that this ionization could have climate effects and would link solar activity with shorter term climate variations like the 500-year Little Ice Age during the Maunder minimum, when sunspots disappeared from the sun, or the millennial-scale climate variability of the Dansgaard–Oeschger (DO) events in Greenland where the sedimentary record reveals that these DO events produced abrupt warming to near-interglacial conditions that occurred in a matter of decades followed by a gradual re-cooling.
In the 1990s, Danish physicist, Henrik Svensmark presented the first empirical evidence of this link in the form of a correlation between cloud cover and the cosmic ray flux variations over the solar cycle. This link was later supported with further evidence including climate correlations with cosmic ray variations that are independent of solar activity. Svensmark’s laboratory experiments (The SKY Experiment at the Danish National Space Institute) showed how ions play a key role in the nucleation of small aerosols and their growth to larger ones producing condensation nuclei for clouds. The CLOUD experiments performed at CERN (European Organization for Nuclear Research) seem to confirm the central mechanism for creation of cloud condensation nuclei via ionization but do cast some doubt on Svensmark’s thesis that cosmic rays play a central role in the lower atmosphere cloud modulation.
A Cosmoclimatology
This cosmic radiation/ionization concept might now be expanded, while accepting the centrality of cosmic ray ionization in cloud modulation, and with observational and mechanistic support, to propose that climate is sensitive to the amount of lower tropospheric ionization caused by Galactic Cosmic Rays (CR). More high energy radiation in the lower atmosphere means more ionization, more aerosols, more and whiter low-level clouds, thus cooler climate. Alternatively, less radiation in the lower atmosphere means fewer clouds driving warmer climates. We can call this the cloud-albedo effect.
Let’s propose the following ideas for consideration: The modulation of Earth's tropospheric cloud cover and global temperature are driven in a top-down process beginning with high energy galactic radiation variations originating in Earth's galactic orbit location within the Milky Way spiral structure producing low frequency climate responses (Fig. 8) over the hundreds-of-millions of years. Our solar system also experiences galactic orbital oscillatory out-of-plane perturbations. The plane polarized cosmic radiation intensity is further modulated by in-and-out-of-plane orbital motion. This acts as a secondary driver of higher frequency climate responses (Fig. 9) over tens-of-millions of years. Lesser, more granular, but not necessarily inconsequential climate influences might now show their influence through solar activity changes, planetary orbital dynamics, plate tectonics, volcanism, and variable proximate celestial events such as asteroids and supernovae. The radiation modulated, cloud cover driven, global temperature sets the baseline from which all other climate drivers vary. The timing and duration of deep time paleoclimate patterns seem to be tied directly to galactic orbital exposure of the Earth and it’s system to the Milky Way’s galactic spiral structure modulated high energy radiation initiating a uniquely periodic climate response signature.
The Signature
Assuming that during the Sun’s orbit around the gravitational center of the Milky Way, we transit the entire spiral arm structure of the galaxy. This structure includes a galactic core, four spiral arms and the four spaces between the arms. If it is true that passing through a spiral arm produces higher galactic radiation intensity than that encountered during an inter-arm crossing, then the radiation flux intensity will be modulated during our passage across the different galactic regions. Higher radiation flux during arm crossings should produce colder climates. Lower radiation flux during inter-arm space crossings should produce hotter climates. So, for an entire orbital transit through the full spiral structure of the Milky Way galaxy, the solar system would travel across all four spiral arms and the four inter-arm spaces. This passage would produce four alternating cold then hot periods (Fig. 7).
Low Frequency Climate Response: Spiral Arm Crossing
Israeli astrophysicist Nir Shaviv has published evidence linking the galactic environment and climate on Earth to the exposure ages of iron meteorites. Shaviv proposed that cosmic radiation intensity fluctuates across the galaxy and that meteorites might act as a cosmic ray intensity integrator for the time between the detachment of these meteorites from their parent bodies and their entry into Earth's atmosphere. The exposure ages of these meteorites can then be determined by analyzing the radioactive and stable isotopes accumulated through interactions with the high-energy cosmic radiation encountered during that long journey to our planet. Shaviv posits that the formation of meteorites occurs at a constant rate, while the cosmic radiation flux is subject to variations. Consequently, the history of cosmic ray flux can be reconstructed. This history exhibits seven clear low frequency cycles which coincide with the seven periods of ice age epochs that took place over the past billion years. Veizer’s extensive geochemical reconstruction of ocean temperatures over the past half billion years shows no correlation with CO2 over geological time scales but his reconstruction fits the meteorite cosmic radiation exposure reconstruction to a T.
The galactic orbital period of the Sun is generally thought to be about 225 million years or so. If the orbital motion of our solar system across the structure of the Milky Way produces a uniquely repeating pattern of climate change from galactic radiation flux variations, then we should see a repeated pattern in the proxy temperature record. We do not see a 225 million year pattern. Instead, we see a 675 million year pattern. Here, we will graphically remove the 30-million-year high frequency climate responses from the detrended baseline of “The Splice” to reveal the four cold arm crossings (blue) and five hot inter-arm space crossings (red). These are the low frequency climate responses imprinted on the Earth’s paleoclimate by galactic spiral arm structure transit (Fig. 8).
High Frequency Climate Response: Out-of-Plane Galactic Orbital Oscillations
What accounts for the high frequency climate responses in these paleoclimate reconstructions depicted as periodic warming-then-cooling periods about 30 million years long?
In 1987 Raup and Sepkoski published a study analyzing major extinction intensities over the last 250 million years. These events showed a significant periodicity of 26 million years between events. Two of the events coincide with extinctions that have been previously linked to meteorite impacts (late Cretaceous and Eocene) but the ultimate causes remain unknown. The authors proposed an extraterrestrial origin such as passage of our solar system through a Milky Way spiral arm with accompanying increased cosmic radiation.
In 2023, Slah Boulila and associates published evidence of cycles of tens of millions of years in marine animal fossil data over the same 250-million-year period as Raup. The authors proposed that periodic movement in the Earth's tectonic plates indirectly triggered bursts of biodiversity in 36-million-year cycles by forcing sea levels to rise and fall.
Besides the low frequency cosmic ray modulation during spiral arm passages, our galactic motion also gives rise to a higher frequency cosmic radiation flux modulation. In addition to the solar system’s circular orbit around the galaxy center, the solar system also oscillates perpendicular to the galactic plane. It should be colder every time our system crosses that plane. There is no measured cosmic radiation history for these shorter time scale oscillations but Veizer’s Phanerozoic temperature record bolstered by Halverson’s Neoproterozoic indicate that the 30-million-year high frequency signal is real and prominent. Even without direct evidence that cosmic radiation is the actual link to the 30-million-year oscillation, Shaviv infers that CR is the only link that can fully explain these long time scale observations. The periodic vertical oscillation of our solar system through the plane of the galaxy is superimposed on our circular orbital motion across the galactic structure (Fig. 9). If the high energy galactic radiation is plane polarized then the cosmic radiation flux intensity will increase as we proceed into the galactic plane and decrease as we proceed out-of-plane. This would give rise to a repeating warming then cooling climate cycle about 30 million years long superimposed on the low frequency spiral arm structure induced warming or cooling baseline periods.
Do the math
The climate responses from our model produce a visualization of galactic radiation driven climate change during a complete solar orbital transit of the Milky Way structure. If the proxy temperature record for the Earth’s oceans over hundreds of millions of years also acts as a proxy indicator for a rotating galactic structure within the Solar reference frame, and transiting this structure of unique pattern-stable galactic cosmic radiation takes 675 million years, then, it must take three orbits of our solar system around the gravitational center of the galaxy to accomplish this astronomical feat.
Carved in Stone
If the Milky Way is a 4-arm spiral galaxy and if the galactic structure and our orbital location derived radiation exposure drives the global climate, then the 675 million year climate response pattern above represents one full orbital transit of the Milky Way spiral structure. Would these unique alternating sequences of warming and cooling periods, driven by modulated cosmic radiation, persist during subsequent or previous orbital transits? Would this radiation pattern then be imprinted on the Earth's climate to be preserved in sedimentary carbonates for billions of years?
The Milky Way galaxy may be nearly as old as the universe itself. In 2023, the Webb space telescope using its near-infrared camera captured images of fully formed spiral galaxies. The light from some of these ancient galaxies originated a mere 320 million years after the Big Bang. If our own galaxy is amongst the oldest and largest in the universe then its spiral structure has probably been stable for many billions of years as manifested in the rotating gravity waves that we call spiral arms. The repeated climate signature derived from paleoclimate proxies, driven by galactic structural radiation, galactic orbital dynamics, and imprinted on the geologic record for at least 930 million years should not be expected to change for past or future climates.
We can probably agree that the repeating “pattern” of paleoclimate change will produce Hothouses and Ice Houses punctuated by out-of-plane orbital oscillation driven warmer periods. We might disagree however, about the repeatability of the intensity of the radiation flux driving these changes. Long term local star formation rate changes might influence intensity over geological time. Here, we will assume, for at least the last 4 billion years, an aggregate steady-state star formation rate within the galactic spiral arm structure. Each arm produces its own unique radiation flux intensity gradient depending on the mass and density of the individual arm. The galaxy core itself might even be a source of cosmic rays where our own supermassive black hole at the center of the Milky Way might interact with stellar objects to produce mega-mass ejections containing high energy protons – cosmic rays to be added to the background radiation flux. Here, we will conjecture that the dual confinement processes of spiral arm magnetic fields and gravitational density wave shepherding within the arms provide for a consistent and repeatable CR flux density variation during each of our galactic orbital transits.
Archean-Mesoproterozoic Isotope Data (1000 to 3500 Mya)
If the climate/cosmic radiation hypothesis is true and that the ancient Earth retained liquid water and life almost from the beginning, a deep time geological record laid down in the sediments should reflect a unique proxy climate signature imprinted on early Earth oceans. The 930-million-year climate reconstruction above (“The Splice”, Fig. 4) reflects temperature, time and galactic orbit location and can be used to construct a template for predicting and locating deep time climate changes as indicated by the isotope record in the literature.
From “The Geologic Time Scale”, Gradstein et al, 2012 (Fig 10), for the Archean and Mesoproterozoic data (1000 to 3500 Mya), positive carbon isotope values above the green “0” line indicate warmer climates while negative values below the green line indicate cooler.
Three complete climate cycles (2 billion years), have been graphically flipped, spliced and scaled to provide a concurrent roadmap to the Archean-Mesoproterozoic data. The variability of hot and cold climate periods of the template should coincide with similar climate variability implied by the isotope excursions in the “The Geologic Time Scale” data.
As our climate template contains three full climate cycles, with significant Archean and Mesoproterozoic data coincidence, it seems convincing that a unique repeating pattern of climate change driven by galactic orbit with accompanying galactic radiation variability has been imprinted on the Earth’s climate from the beginning – for more than three billion years.
end part 2