Evolution of the Global Carbon Cycle and Climate Regulation on Earth

In the paper

“Silicate weathering rates decrease as a soil horizon matures given that primary phases become more depleted (Fig. 9).”

In the paper

“Unfortunately, flux estimates from these approaches are typically significantly different (see discussion in Zhang and Planavsky, 2019)”

What the sources say

• Not checked yetcites Zhang and Planavsky, 2019

In the paper

“The sedimentary record of zircon production was assessed in sediments ranging from the Cryogenian to the present (i.e., the past ~720 million years of Earth history) and demonstrated a correlation with icehousegreenhouse transitions.”

What the sources say

• Not checked yetcites McKenzie et al., 2016

In the paper

“The model outputs indicate that at pCO 2 levels of 280 ppm, 10m yr -1 of rainfall is required to neutralize volcanic CO 2 if here was no soil respiration.”

In the paper

“This is roughly an order of magnitude higher than modern average annual rainfall estimates.”

In the paper

“The remaining 7 Tmol yr -1 of CO 2 can be accounted for by acid generation in terrestrial porewaters through soil respiration.”

In the paper

“To achieve an annual rainfall estimate of ~1 m yr -1 , this requires that rain supplies only 3 Tmol yr -1 of CO 2 for silicate weathering (right panel).”

In the paper

“However, at high pCO 2 conditions the amount of rainfall needed to deliver enough CO 2 to the critical zone to ensure a balanced carbon cycle (silicate weathering equal to CO 2 outgassing) is significantly less (left panels).”

In the paper

“This simple model indicates that rainfall is not the dominant source of CO 2 for weathering today (red circle does not sit on the red line).”

In the paper

“Through the same Urey reaction pathway invoked for continental silicate weathering (equation 1), the generation of alkalinity and cations during the weathering of marine sediment plays a potentially large role in global carbon sequestration when coupled to carbonate formation.”

In the paper

“On the empirical side, terrestrial cyanobacterial biofilms have been found to significantly increase silicate weathering rates (Seiffert et al., 2014).”

What the sources say

• Not checked yetcites Seiffert et al., 2014

In the paper

“Silicate mineral availability varies depending on the local tectonic regime, bottom water temperature, and proximity to the shoreline.”

In the paper

“Further, there is evidence that groundwater plays a significant role in coastal ecosystem evolution (Moosdorf & Oehler, 2017;Paytan et al., 2006).”

What the sources say

• Not checked yetcites Moosdorf & Oehler, 2017
• Not checked yetcites Paytan et al., 2006

In the paper

“Silicate dissolution has been observed to take place throughout the sediment column within virtually all redox zones (oxic, suboxic, sulfidic and methanic).”

In the paper

“In areas with limited denudation, integrated or long-term weathering rates with and without land plants will be closer than the observed initial difference.”

In the paper

“Compared with river systems that are well gauged and monitored throughout the world, direct quantification of global SGD is extremely difficult since it mainly occurs as unseen diffusive flow on continental margins and varies significantly over temporal and spatial scales.”

In the paper

“However, there is mounting evidence that groundwater discharge is a critical component of the water and nutrient budget in the land-ocean system (e.g., Burnett et al., 2003;Kwon et al., 2014;Moore et al., 2008).”

What the sources say

• Not checked yetcites Burnett et al., 2003
• Not checked yetcites Kwon et al., 2014
• Not checked yetcites Moore et al., 2008

In the paper

“In terms of the global carbon cycle, continental groundwater discharge serves as a pathway for dissolved carbon fluxes to the ocean where carbonate eventually precipitates, and may therefore likely provide a significant but previously underappreciated carbon sink (Zhang and Planavsky, in press).”

What the sources say

• Not checked yetcites Zhang and Planavsky, in press

In the paper

“On the basis that methanogenesis is responsible for the generation of ~5-20 Tmol yr -1 of CO 2 (and an equal amount of CH 4 ) globally (Hinrichs and Boetius, 2002;Reeburgh, 1993;Wallmann et al., 2012)”

What the sources say

• Not checked yetcites Hinrichs and Boetius, 2002
• Not checked yetcites Reeburgh, 1993
• Not checked yetcites Wallmann et al., 2012

In the paper

“Given the fact that DIC concentration in groundwater is typically higher than rivers in the same region (Stewart et al., 2015;Szymczycha and Pempkowiak, 2015), even a relatively small magnitude of fresh SGD could potentially make a non-negligible contribution to the total dissolved carbon flux to the ocean.”

What the sources say

• Not checked yetcites Stewart et al., 2015
• Not checked yetcites Szymczycha and Pempkowiak, 2015

In the paper

“Geochemical evidence for marine weathering deviates from the traditional framework, which specifies that silicate mineral dissolution is largely limited to terrestrial environments.”

In the paper

“Some of the most rapid rates of silicate weathering have been observed to occur within the methanogenic zone of the sediment pile (Wallmann et al., 2008).”

What the sources say

• Not checked yetcites Wallmann et al., 2008

In the paper

“Further, integrating these biologically enhanced weathering rates derived from short lived experiments ('instantaneous' relative to the time scale of soil formation) into long-term global biogeochemical cycle models that operate on the multi million-year time scales has the potential to drastically overestimate the integrated weathering rate.”

In the paper

“There have been extensive studies of river input to the ocean and its influence on global biogeochemical cycling (e.g.Berner & Berner, 2012;Gaillardet et al., 1999;Meybeck, 1987;Milliman & Farnsworth, 2011), but we still have a relatively nascent understanding of groundwater discharge and element fluxes to the ocean (Taniguchi et al., 2002).”

What the sources say

• Not checked yetcites Taniguchi et al., 2002

In the paper

“For instance, in situ weathering rates have been observed to vary by up to 4 orders in magnitude between the deep sea site ODP Site 984 in the North Atlantic, and slope sediments on the Sakhalin Slope, Sea of Okhotsk (Maher et al., 2006;Wallmann et al., 2008).”

What the sources say

• Not checked yetcites Maher et al., 2006
• Not checked yetcites Wallmann et al., 2008

In the paper

“Although both field and experimental data that highlight biotic enhancement of weathering (sometimes by several orders magnitude), rate enhancements at such high levels are likely not sustainable on longer time scales.”

In the paper

“However, it has become clear over the past decade that this flux is likely a significant part of the global carbon cycle.”

In the paper

“The difference between measured conductive heat flow at the seafloor and that predicted by thermal models of the cooling of the oceanic lithosphere-the”

What the sources say

• Not checked yetcites Hasterok, 2013
• Not checked yetcites Stein and Stein, 1994

In the paper

“Support for this argument typically involve calling upon both laboratory (e.g., Quirk et al., 2015) and field data (e.g., Bormann et al., 1998;Moulton and Berner, 1998) that indicate enhanced chemical weathering in systems with land plants as compared to barren surfaces or ones covered with moss/lichen (i.e., no significant root penetration) (Lenton, 2001).”

What the sources say

• Not checked yetcites Quirk et al., 2015
• Not checked yetcites Bormann et al., 1998
• Not checked yetcites Moulton and Berner, 1998

In the paper

“Here, recent work provides compelling geochemical evidence for potentially substantial rates of silicate dissolution in marine sediments (e.g., Kim et al., 2016;Maher et al., 2004;Maher et al., 2006;Scholz et al., 2013;Solomon et al., 2008;Wallmann et al., 2008).”

What the sources say

• Not checked yetcites Kim et al., 2016
• Not checked yetcites Maher et al., 2004
• Not checked yetcites Scholz et al., 2013

In the paper

“When weathering fluxes are integrated on time scales similar to or longer than that of soil formation (and maturation), the net weathering effect with or without vascular plants become significantly less or even indistinguishable (Fig. 9).”

In the paper

“The physical erosion of rocks in terrestrial environments delivers detrital silicate materials (e.g., feldspar, olivine, pyroxene, volcanic ash, clays) to the marine environment where they can make up a significant portion of marine sediments.”

In the paper

“It should be noted that a large portion of SGD is thought to belong to saline SGD (Kwon et al., 2014;Taniguchi et al., 2006).”

What the sources say

• Not checked yetcites Kwon et al., 2014
• Not checked yetcites Taniguchi et al., 2006

In the paper

“It was recently estimated that between 20%-250% of chemical silicate weathering globally occurred in groundwaters (Zhang and Planavsky, in press).”

What the sources say

• Not checked yetcites Zhang and Planavsky, in press

In the paper

“Largely based on extrapolations from work carried out in the proximal Amazon delta (Michalopoulos and Aller, 2004), dissolved silica sequestration as authigenic clay phases globally was initially estimated at ~1 to 1.5 Tmol yr -1 (Holland, 2005;Laruelle et al., 2009;Tréguer and De La Rocha, 2013).”

What the sources say

• Not checked yetcites Holland, 2005
• Not checked yetcites Laruelle et al., 2009
• Not checked yetcites Tréguer and De La Rocha, 2013

In the paper

“Similarly, the global export of Si does not translate directly to a flux of carbon being recycled through reverse weathering.”

In the paper

“At modern seawater DIC levels of ~2.3 mmol kg -1 , this equates to ~1.5-4x10 13 moles of C passing through off-axis hydrothermal systems annually.”

In the paper

“Detrital zircon U-Pb ages extracted from clastic sedimentary rocks provide a means to assess regional continental magmatism in deep geologic time.”

In the paper

“Zircons can remain in upper crustal rocks for extended intervals of time because of the mineral's resilience to physical and chemical degradation (e.g., Gehrels, 2014).”

What the sources say

• Not checked yetcites Gehrels, 2014

In the paper

“An exception to this rule is continental arc systems, which have the potential to contribute large fluxes of CO 2 to the atmosphere due to recycling of carbon preserved in the upper plate (Lee and Lackey, 2015;Lee et al., 2013;Mason et al., 2017).”

What the sources say

• Not checked yetcites Lee and Lackey, 2015
• Not checked yetcites Lee et al., 2013
• Not checked yetcites Mason et al., 2017

In the paper

“Similar to marine weathering, reverse weathering has been observed to take place in both marine sediments (e.g., Ehlert et al., 2016) and oceanic crust (e.g., Chan et al., 1992;Chan et al., 2002;Chan and Kastner, 2000).”

What the sources say

• Not checked yetcites Ehlert et al., 2016
• Not checked yetcites Chan et al., 1992
• Not checked yetcites Chan and Kastner, 2000

In the paper

“Reverse weathering can involve a variety of different dissolved cation species (e.g., Li + , K + , Mg 2+ , Fe 2+ ), and so keeping track of this process through any of these individual cycles will provide an incomplete view of its impact on the global carbon and alkalinity budgets.”

In the paper

“These observations lead to a simple model for the role of seafloor weathering of basalts in the long-term carbon cycle in which increased atmospheric CO 2 gives rise to an increased global mean surface temperatures, and in turn increase in bottom water temperature of the same magnitude (Krissansen-Totton and Catling, 2017).”

What the sources say

• Not checked yetcites Krissansen-Totton and Catling, 2017

In the paper

“Fluid-rock reactions within the uppermost crust lead to dissolution of basaltic phases (e.g.glass, feldspar, pyroxene) and precipitation of secondary minerals such clays, zeolites and calcite (or aragonite), providing a sink for ocean DIC (carbon from the ocean-atmosphere system).”

In the paper

“Thus, zircon can survive multiple episodes of sedimentary recycling (i.e., burial, exhumation, erosion and reburial).”

In the paper

“Fluid temperatures within the upper oceanic crust are typically 5-10°C higher than that of bottom water during the first 10-20 Myr after crustal accretion when most fluid-rock reaction occurs (Coogan and Gillis, 2018).”

What the sources say

• Not checked yetcites Coogan and Gillis, 2018

In the paper

“A clay mineral species/assemblage with a higher Alk:Si ratio will have a larger impact on global carbon recycling (e.g., Isson and Planavsky, 2018).”

What the sources say

• Not checked yetcites Isson and Planavsky, 2018

In the paper

“These enhanced rates of continental crustal recycling would have driven enhanced CO 2 outgassing in the Precambrian, providing part of the solution to the faint young Sun paradox.”

In the paper

“Most importantly, there is compelling evidence from modeling the 142 Nd isotope and zircon records that crustal recycling rates have declined through Earth's history-with the most precipitous decline in the Archean (Korenaga, 2018;Rosas and Korenaga, 2018).”

What the sources say

• Not checked yetcites Korenaga, 2018
• Not checked yetcites Rosas and Korenaga, 2018

In the paper

“Organic matter remineralization reactions have the potential to alter marine porewater chemistry and pH levels and their evolution with depth in the sediment pile, that have the potential to influence rates of reverse weathering (and forward marine weathering).”

In the paper

“The activities of dissolved cations, silica, H + and temperature all play a role in regulating the saturation state and thus rate of formation of an authigenic clay mineral phase.”

In the paper

“There is no debate that outgassing fluxes likely varied through Earth history, but it is difficult to provide constraints on outgassing evolution.This is not surprising, given that there are large uncertainties even in modern outgassing fluxes (see section 3.1).”

In the paper

“At these temperatures, fluid fluxes of ~0.6-1.7x1016 kg yr -1 (roughly 10-50 % of the river flux) are required to transport the”

In the paper

“Subsequently, both field (e.g., Baldermann et al., 2015;Baldermann et al., 2013;Ehlert et al., 2016;Ku and Walter, 2003;Mackenzie et al., 1981;Mackin andAller, 1984, 1986;März et al., 2015;Michalopoulos andAller, 1995, 2004;Michalopoulos et al., 2000;Presti and Michalopoulos, 2008;Rahman et al., 2016Rahman et al., , 2017;;Ristvet, 1978;Solomon et al., 2008;Tatzel et al., 2015;Wallmann et al., 2008”

What the sources say

• Not checked yetcites Baldermann et al., 2015
• Not checked yetcites Ehlert et al., 2016
• Not checked yetcites Wallmann et al., 2008

In the paper

“Because finding and sampling fluids exiting off-axis hydrothermal systems is technically challenging, most observational constraints on the role of seafloor weathering in the long-term carbon cycle come from studies of rocks altered in such systems.”

In the paper

“Clastic sediments deposited along continental margins with arc systems, however, tend to contain large abundances of zircon with crystallization ages close to the depositional age of the sediment (Cawood et al., 2012), which are likely firstcycle zircons sourced from volcanic or rapidly exhumed plutonic rocks produced by the arc system.”

What the sources say

• Not checked yetcites Cawood et al., 2012

In the paper

“However, with knowledge of the alkalinity (Alk) : silica (Si) consumption ratio associated with clay authigenesis, that is determined by the composition (clay species) of the globally integrated clay mineral assemblage, the reverse weathering flux of CO 2 can be estimated.”

In the paper

“However, most recent work adopting the use of cosmogenic 32 Si suggest that this flux could be significantly higher at ~4.5 to 4.9 Tmol yr -1 globally in coastal and deltaic systems (Rahman et al., 2017).”

What the sources say

• Not checked yetcites Rahman et al., 2017

In the paper

“The only way to have such a large C-uptake by the crust (~10% of the C that passes through the crustal aquifer) appears to be through alkalinity generation during seafloor weathering reactions (Coogan and Gillis, 2013;Spivack and Staudigel, 1994).”

What the sources say

• Not checked yetcites Coogan and Gillis, 2013
• Not checked yetcites Spivack and Staudigel, 1994

In the paper

“Specifically, this would increase the chances that a subducting slab was rich in carbonates, which (in the standard view) should increase the amount of carbonate recycled and degassed as CO 2 in arc systems (e.g., Edmond and Huh, 2003).”

What the sources say

• Not checked yetcites Edmond and Huh, 2003

In the paper

“Hydrogen ion and alkalinity budgets evolve with depth in marine sediments.”

In the paper

“Note that the latter should not be confused with cation exchange between fluids and primary mineral phases in oceanic crust (Berner and Berner, 2012), which have no direct effect on the global marine alkalinity balance.”

What the sources say

• Not checked yetcites Berner and Berner, 2012

In the paper

“All of the major carbon dioxide outgassing sources can potentially vary dramatically through time.”

In the paper

“But collectively, multiple lines of data from recent studies are demonstrating a consistent relationship between outgassing estimates and major shifts in climate (Cao et al., 2017;McKenzie et al., 2016;McKenzie et al., 2014;Mills et al., 2017;Van Der Meer et al., 2014).”

What the sources say

• Not checked yetcites Cao et al., 2017
• Not checked yetcites McKenzie et al., 2016
• Not checked yetcites Mills et al., 2017

In the paper

“Therefore, atmospheric oxygenation may not lead to a jump in ferric/ferrous ratio of marine sediments.”

In the paper

“This transient, sulfur driven CO 2 source likely played an important role in shaping Cenozoic climate, where there was a marked and progressive increase in marine sulfate concentrations (e.g., Wortmann and Paytan, 2012).”

What the sources say

• Not checked yetcites Wortmann and Paytan, 2012

In the paper

“The subsequent radiation of siliceous organisms (sponges, radiolarians, and most recently diatoms) through the Phanerozoic forced a drop in dissolved marine Si levels, and thus the extent of reverse weathering and baseline pCO 2 levels.”

In the paper

“Large igneous provinces have been linked to short term climate shifts (foremost the end Permian mass extinction and temperature spike; Burgess and Bowring (2015)), but cannot be linked to longer-term climate swings and shifts given their limited active lifespan.”

In the paper

“In this case, the arc systems before and after the onset of extensive deep sea carbon burial may have, on average, had roughly similar ratios of CO 2 outgassed to new zircons produced.”

In the paper

“In sum, there are still major uncertainties in the sources and sinks of all major cations even in the modern oceans, and the evolution of cation budgets through Earth's history are even more poorly understood.”

In the paper

“The iron and sulfur cycles both have the potential to drive significant variations in atmospheric carbon dioxide levels.”

In the paper

“In sum, there are still major uncertainties in the sources and sinks of all major cations even in the modern oceans, and the evolution of cation budgets through Earth's history are even more poorly understood.”

In the paper

“At steady state, the cycling of these elements does not impact the global carbon cycle.”

In the paper

“Sulfide and ferrous iron oxidation produce acidity while ferric iron and sulfate reduction produce alkalinity-potentially altering the ocean-atmosphere carbonic acid system balance and thus the ocean's capacity to hold inorganic carbon.”

In the paper

“Foremost, oxidation of continental crust rich in siderite and the deposition of sediments rich in ferric iron can result in a net CO 2 release.”

In the paper

“Indeed, work over the last few decades suggests the presence of a terrestrial silicate weathering feedback (e.g., Von Strandmann et al., 2013).”

What the sources say

• Not checked yetcites Von Strandmann et al., 2013

In the paper

“There is increasing evidence for CO 2 degassing from metacarbonate rock in the overriding plate when there is fluid infiltration (Stewart and Ague, 2018).”

What the sources say

• Not checked yetcites Stewart and Ague, 2018

In the paper

“An increase in pyrite weathering coupled to carbonate weathering can drive a jump in atmospheric carbon dioxide levels as long as the resulting sulfate accumulates in the ocean or is deposited as evaporite (Torres et al., 2014).”

What the sources say

• Not checked yetcites Torres et al., 2014

In the paper

“However, the current sedimentary zircon record points towards carbon outgassing history playing a critical role in shaping Earth's climate.”

In the paper

“The extent of silicate weathering in groundwater has likely been underappreciated.”

In the paper

“Large igneous provinces have been linked to short term climate shifts (foremost the end Permian mass extinction and temperature spike; Burgess and Bowring (2015)), but cannot be linked to longer-term climate swings and shifts given their limited active lifespan.”

What the sources say

• Not checked yetcites Burgess and Bowring (2015)

In the paper

“The drop in atmospheric pCO 2 levels since the Precambrian (Kasting, 1987) can, to a significant degree be explained by this evolution of clay mineral assemblage and Alk:Si.”

What the sources say

• Not checked yetcites Kasting, 1987

In the paper

“Earth has been a habitable planet for over 4 billion years because of the persistence of stabilizing feedbacks in the global carbon and silicon cycles.”

In the paper

“In contrast, enhanced sulfide oxidation directly coupled to enhanced pyrite burial does not have a direct effect on the global carbon cycle.”

In the paper

“However, there are two scenarios that have been the most thoroughly explored and are most likely to have impacted Earth's climate on a several million-year time scale (Bachan and Kump, 2015;Torres et al., 2014).”

What the sources say

• Not checked yetcites Bachan and Kump, 2015
• Not checked yetcites Torres et al., 2014

In the paper

“The progressive oxidation of iron in the upper continental crust can also result in a net release of carbon dioxide.”

In the paper

“On the other hand, shifts in the iron and sulfur weathering and burial terms can drive transient yet geologically meaningful shifts in pCO 2 tied to longterm imbalances in the global marine alkalinity budget.”

In the paper

“Reverse weathering could have evolved dramatically through time (Fig. 10).”

In the paper

“Therefore, empirical records support the idea that carbon sources have played a major role in controlling Earth's climate and provide a simple explanation for why Earth has toggled between icehouse-greenhouse intervals.”

In the paper

“Similarly, marine weathering-both within the sediment pile and during oceanic crust alteration-is also likely a more important part of the global carbon cycle than was traditionally envisioned (Coogan and Gillis, 2018;e.g., Gillis and Coogan, 2011;Wallmann et al., 2008).”

What the sources say

• Not checked yetcites Coogan and Gillis, 2018
• Not checked yetcites Gillis and Coogan, 2011
• Not checked yetcites Wallmann et al., 2008

In the paper

“Nonetheless, recent attempts to use paleogeographic maps to estimate arc length and outgassing have demonstrated similar results to that of the zircon record (Cao et al., 2017;Mills et al., 2017;Van Der Meer et al., 2014).”

What the sources say

• Not checked yetcites Cao et al., 2017
• Not checked yetcites Mills et al., 2017
• Not checked yetcites Van Der Meer et al., 2014

In the paper

“For instance, Fe-rich clays with higher Alk:Si consumption ratios (e.g., greenalite, berthierine, chamosite) appear to be more abundant in anoxic Precambrian marine sediments than observed in the modern oceans characterized by lower Alk:Si consumption ratios such as montmorillonite.”

In the paper

“This transient, sulfur driven CO 2 source likely played an important role in shaping Cenozoic climate, where there was a marked and progressive increase in marine sulfate concentrations (e.g., Wortmann and Paytan, 2012).”

What the sources say

• Not checked yetcites Wortmann and Paytan, 2012

In the paper

“This idea builds on the same principles introduced for silicate weathering and reverse weathering-numerous iron and sulfur reactions either produce acidity or alkalinity.”

In the paper

“A general problem in studies utilizing zircon age compilations is the unevenness of data available, which biases composite global age distributions from being truly”

What the sources say

• Not checked yetcites Campbell and Allen, 2008
• Not checked yetcites Voice et al., 2011

In the paper

“Foremost, the diffuse outgassing flux is poorly constrained (Kelemen and Manning, 2015).”

What the sources say

• Not checked yetcites Kelemen and Manning, 2015

In the paper

“Therefore, empirical records support the idea that carbon sources have played a major role in controlling Earth's climate and provide a simple explanation for why Earth has toggled between icehouse-greenhouse intervals.”

In the paper

“Estimating the areal extent of regions undergoing low-, mid-, and high-grade metamorphic alteration, which can also be a major CO 2 source (e.g., Stewart and Ague, 2018;Stewart et al., 2019;Zhang et al., 2018), is similarly hindered by inconsistent geologic reconstructions.”

In the paper

“In other words, terrestrial silicate weathering in the critical zone only accounts for part of the carbon removal from the oceanatmosphere system and global silicate weathering fluxes are much higher than those reconstructed from riverine alkalinity budgets.”

In the paper

“It is important to note that the observed weathering rates are not likely sustainable over the time scale of soil formation (on a time scale of typically thousands of years).”

In the paper

“The switch to a biologically controlled Si cycle-where the majority of SiO 2 fluxes in the oceans are biogenic-caused a dramatic drop in dissolved marine Si concentrations (Siever, 1992).”

What the sources say

• Not checked yetcites Siever, 1992

In the paper

“Laboratory and field work both indicate that vascular plants accelerate chemical weathering of bedrock over the short time scales in which these experiments are conducted (<1 year).”

In the paper

“There is a strong correlation between outgassing tracers and climate records over the last 800 million years (e.g., McKenzie et al., 2016;Mills et al., 2017), tentatively suggesting that carbon sources were the main drivers of climate oscillations.”

What the sources say

• Not checked yetcites McKenzie et al., 2016
• Not checked yetcites Mills et al., 2017

In the paper

“Therefore, a biotic innovation (Si biomineralization) destabilized the climate system, adding to one of the central dogmas of the original Gaia hypothesis, that life as a part of a global Earth system can give rise to both positive and negative climate feedbacks (Lovelock and Kump, 1994;Lovelock and Margulis, 1974).”

What the sources say

• Not checked yetcites Lovelock and Kump, 1994
• Not checked yetcites Lovelock and Margulis, 1974

In the paper

“There is a strong correlation between outgassing tracers and climate records over the last 800 million years (e.g., McKenzie et al., 2016;Mills et al., 2017), tentatively suggesting that carbon sources were the main drivers of climate oscillations.”

In the paper

“New evidence for higher modern weathering rates than traditionally envisioned does not imply that the carbon cycle is dramatically out of steady state; carbon source terms have likely also been underestimated.”

In the paper

“Authigenic clay formation in the oceans-reverse weathering-is a relatively minor part of the modern global carbon cycle, but it is likely to have been more important earlier in Earth's history (Isson and Planavsky, 2018).”

In the paper

“By this framework, it follows that the ratio of terrestrial to marine silicate weathering rates would have been higher in the Precambrian.”

In the paper

“Therefore, a biotic innovation (Si biomineralization) destabilized the climate system, adding to one of the central dogmas of the original Gaia hypothesis, that life as a part of a global Earth system can give rise to both positive and negative climate feedbacks (Lovelock and Kump, 1994;Lovelock and Margulis, 1974).”

In the paper

“Global carbon cycle box model demonstrating that carbon input must equal output (steady-state) on geologic time scales (adapted from Berner and Caldeira, 1997).”

What the sources say

• Not checked yetcites Berner and Caldeira, 1997

In the paper

“Foremost, carbon dioxide fluxes from diffuse metamorphic outgassing are almost certainly higher than in traditional balanced long-term carbon cycles budgets (e.g., Berner, 2004).”

What the sources say

• Not checked yetcites Berner, 2004

In the paper

“New evidence for higher modern weathering rates than traditionally envisioned does not imply that the carbon cycle is dramatically out of steady state; carbon source terms have likely also been underestimated.”

In the paper

“Three main stabilizing feedbacks associated with the global carbon cycle: (A) terrestrial silicate weathering (blue); (B) marine silicate weathering (red); (C) reverse weathering (green).”

In the paper

“In other words, terrestrial silicate weathering in the critical zone only accounts for part of the carbon removal from the oceanatmosphere system and global silicate weathering fluxes are much higher than those reconstructed from riverine alkalinity budgets.”

In the paper

“In the absence of a stabilizing feedback, sustained imbalances (excess input or output) will very rapidly lead to either runaway icehouse or greenhouse conditions.”

In the paper

“However, shifts in weatherability (carbon sinks) have also been linked to major climate shifts (e.g., Cenozoic cooling; Caves et al., 2016;Jagoutz et al., 2016;Zhang and Planavsky, 2019).”

What the sources say

• Not checked yetcites Caves et al., 2016
• Not checked yetcites Jagoutz et al., 2016
• Not checked yetcites Zhang and Planavsky, 2019

In the paper

“Authigenic clay formation in the oceans-reverse weathering-is a relatively minor part of the modern global carbon cycle, but it is likely to have been more important earlier in Earth's history (Isson and Planavsky, 2018).”

What the sources say

• Not checked yetcites Isson and Planavsky, 2018