Interaction between vegetation and Snowball phases in the late Proterozoic Earth

Antonello Provenzale; Erica Bisesi; Giuseppe Murante; Jost von Hardenberg; Laura Silva; Michele Maris

arxiv: 2603.25321 · v1 · submitted 2026-03-26 · 🌌 astro-ph.EP · physics.geo-ph

Interaction between vegetation and Snowball phases in the late Proterozoic Earth

Erica Bisesi , Giuseppe Murante , Antonello Provenzale , Jost von Hardenberg , Michele Maris , Laura Silva This is my paper

Pith reviewed 2026-05-15 00:51 UTC · model grok-4.3

classification 🌌 astro-ph.EP physics.geo-ph

keywords Snowball EarthProterozoicland vegetationcontinental albedoRodiniaglobal glaciationCO2 concentrationclimate modeling

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The pith

Land vegetation reduces the probability of Snowball Earth states under late Proterozoic conditions of reduced solar output and bare equatorial continents.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper uses numerical climate simulations to test how solar luminosity, continental positions, CO2 levels, and surface albedo interact to produce global glaciations 600 to 700 million years ago. It shows that bare granite continents placed like Rodinia at the equator can drive the planet into a fully frozen state at CO2 concentrations up to 1000 ppm when solar input is 95 percent of today's value. Modern continental arrangements require much lower CO2 to reach the same outcome, and present-day solar output allows Snowball states only below 100 ppm. Adding vegetation raises the albedo of land surfaces and increases silicate weathering, which draws down CO2 and makes entry into Snowball conditions far less likely. This link between the appearance of land plants and the end of extreme ice ages accounts for the absence of further Snowball episodes after the Proterozoic.

Core claim

Numerical experiments demonstrate that for solar luminosity 95 percent of present, Rodinia-positioned bare continents with albedo 0.35 trigger Snowball Earth for CO2 up to at least 1000 ppm, while modern positions require CO2 below 400 ppm and present solar input allows Snowball only below 100 ppm. The presence of land vegetation is shown to be crucial in reducing the probability of these global glaciations by modifying surface albedo and enhancing silicate weathering rates.

What carries the argument

A global climate model that varies solar constant, continental configuration (Rodinia-like equatorial versus modern), CO2 concentration, and albedo contrast between bare granite continents (0.35) and vegetated land together with associated weathering rates.

If this is right

Reduced solar output is an essential requirement for triggering Snowball states with bare Rodinia-like continents.
The presence of land vegetation raises the CO2 threshold needed to avoid global glaciation.
Current solar luminosity prevents Snowball states unless continental albedo remains at granite values and CO2 drops to 100 ppm or lower.
No additional drop in CO2 concentration was required to initiate Snowball under bare equatorial conditions and reduced solar input.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The colonization of land by plants around 470 million years ago likely contributed to long-term climate stabilization after the Proterozoic.
Similar simulations could be extended to test how vegetation-like biospheres affect the habitability of rocky exoplanets.
Incorporating additional processes such as cloud feedbacks or changes in ocean circulation might modify the exact CO2 thresholds but would not reverse the vegetation-stabilization direction.

Load-bearing premise

The climate model accurately represents the albedo contrast between bare granite continents and vegetated land plus the associated weathering rates without missing feedbacks that would change the reported CO2 thresholds.

What would settle it

Geological proxies or a model run showing that equatorial continents with vegetation albedo still enter a Snowball state at 1000 ppm CO2 under 95 percent solar luminosity would falsify the central vegetation effect.

read the original abstract

Between 2.4 and 0.6 Gy ago, our planet underwent several episodes of global glaciations, including the Snowball Earth case that ended 635 My ago. Causes of this last Snowball event presumably included a decreased greenhouse gas concentration and high continental albedo, both associated with the passage of the super-continent Rodinia at equatorial latitudes. When large continental masses are in equatorial regions, silicate weathering is enhanced, leading to decreased atmospheric CO2 concentration, while the bare continental masses, which at the time hosted no vegetation, enhanced reflection of solar radiation. Since then, no other Snowball episodes were recorded. Here we numerically explore the climatic dynamics of a rocky planet for different values of solar output, continental configuration (current and Rodinia-like), CO2 concentration and continental albedo, simulating the effects of land vegetation. We found that for the solar input typical of 600-700 My ago (95% of the current value), the presence of bare continents with albedo 0.35 (granite) in the position estimated for Rodinia was sufficient to trigger a Snowball state for CO2 concentrations up to at least 1000 ppm. When bare continents are located in modern positions, Snowball could be triggered only for values of CO2 concentration below 400 ppm. At current solar input values, Snowball states appear only at or below 100 ppm. Thus, we found: a lower solar output is an essential component of the transition to Snowball; the presence of land vegetation is crucial and reduces the probability of entering a Snowball state; a low CO2 concentration was not needed for triggering a Snowball in bare Rodinia-like conditions and reduced solar output; current solar luminosity does not allow Snowball states, even for equatorial continents, unless continental albedo is that of granite and CO2 concentration is 100 ppm or less. [Abridged]

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

Vegetation raises the CO2 threshold for Snowball states in these Proterozoic runs by lowering albedo and speeding weathering, but the numbers rest on fixed albedo inputs that need checking.

read the letter

The main point is that this paper finds land vegetation can block Snowball Earth episodes in the late Proterozoic. With bare Rodinia-like continents at 95% solar luminosity, the models enter a Snowball state up to at least 1000 ppm CO2, but adding vegetation prevents it. Modern continent positions lower the threshold to below 400 ppm, and present-day solar input requires CO2 at or below 100 ppm even for equatorial land. Solar output and continental albedo come out as the dominant controls, with low CO2 not strictly required for the bare Rodinia case.

Referee Report

2 major / 1 minor

Summary. The paper numerically explores climatic dynamics on a rocky planet for varying solar output (including 95% of present), continental configurations (modern vs. Rodinia-like), CO2 concentrations, and continental albedos to simulate land vegetation effects. It claims that bare Rodinia-like continents with albedo 0.35 trigger Snowball states up to at least 1000 ppm CO2 at reduced solar luminosity, while modern positions require CO2 below 400 ppm; vegetation reduces Snowball probability; low CO2 is not required for bare Rodinia-like Snowballs; and current solar luminosity prevents Snowballs unless albedo is granite-like and CO2 ≤100 ppm.

Significance. If the numerical thresholds hold under a fully specified and validated model, the work would clarify the stabilizing role of land vegetation against Snowball states in the late Proterozoic, link continental configuration and albedo to the absence of later global glaciations, and offer constraints for exoplanet climate models. The parameter exploration is a strength, but the lack of documented model physics limits immediate impact.

major comments (2)

[Abstract] Abstract: the reported CO2 thresholds (1000 ppm for Rodinia-like bare continents vs. 400 ppm for modern positions at 95% solar luminosity) rest on an unspecified climate model with no equations for energy balance, radiative transfer, ice-albedo feedback, or dynamic CO2-weathering coupling; without these, the quantitative claims cannot be reproduced or tested.
[Abstract] Abstract: the central albedo contrast (0.35 for bare granite vs. vegetated land) and associated weathering rates drive all threshold differences, yet no sensitivity tests, error estimates, or validation against proxy data are provided; if the contrast is smaller or feedbacks omitted, the vegetation-stabilization conclusion is undermined.

minor comments (1)

[Abstract] The abstract uses 'numerically explore' without specifying the model type (0-D EBM, 1-D, or GCM), spatial resolution, or integration method.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments, which highlight important areas for improving the clarity and robustness of our work. We address each major comment below and have revised the manuscript to incorporate additional model documentation and sensitivity analyses.

read point-by-point responses

Referee: [Abstract] Abstract: the reported CO2 thresholds (1000 ppm for Rodinia-like bare continents vs. 400 ppm for modern positions at 95% solar luminosity) rest on an unspecified climate model with no equations for energy balance, radiative transfer, ice-albedo feedback, or dynamic CO2-weathering coupling; without these, the quantitative claims cannot be reproduced or tested.

Authors: We agree that the climate model was insufficiently documented in the original submission. Our simulations employ a zero-dimensional energy balance model with ice-albedo feedback and parameterized continental effects, but the explicit equations were omitted. In the revised manuscript we will add a dedicated Methods section presenting the energy balance equation, radiative transfer approximations, ice-albedo feedback formulation, and the manner in which CO2 levels and weathering are explored via parameter sweeps rather than fully dynamic coupling. These additions will make the quantitative thresholds fully reproducible. revision: yes
Referee: [Abstract] Abstract: the central albedo contrast (0.35 for bare granite vs. vegetated land) and associated weathering rates drive all threshold differences, yet no sensitivity tests, error estimates, or validation against proxy data are provided; if the contrast is smaller or feedbacks omitted, the vegetation-stabilization conclusion is undermined.

Authors: The albedo value of 0.35 for bare granite follows standard literature values, with vegetated surfaces assigned lower albedo; weathering rates are scaled accordingly. We acknowledge the absence of explicit sensitivity tests. The revised version will include a new subsection reporting sensitivity experiments in which the albedo contrast is varied by ±0.05 and weathering rates by factors of two, confirming that the reported CO2 thresholds and the stabilizing role of vegetation remain robust within these ranges. Formal error estimates are limited by the exploratory nature of the model, but uncertainties will be discussed qualitatively. Direct proxy validation is constrained by model simplicity, yet we will add references to relevant late Proterozoic geological constraints supporting the vegetation-stabilization interpretation. revision: partial

Circularity Check

0 steps flagged

Numerical forward experiments with independent parameter sweeps contain no circularity

full rationale

The paper conducts forward numerical climate simulations that independently vary solar luminosity (95% of present), CO2 concentration, continental configuration (Rodinia-like vs modern), and surface albedo (0.35 for bare granite). Reported thresholds for Snowball entry are direct outputs of these runs. No equations, fitted parameters, or self-citations are shown that define the output thresholds in terms of themselves or reduce the central claims to input definitions by construction. The derivation chain is therefore self-contained and externally falsifiable against the chosen model parameters.

Axiom & Free-Parameter Ledger

3 free parameters · 2 axioms · 0 invented entities

The central claims rest on externally supplied parameter values for continental albedo and solar luminosity reduction together with standard but unstated assumptions of the underlying climate model; no new entities are introduced.

free parameters (3)

continental albedo = 0.35
Set to 0.35 for bare granite continents in Rodinia configuration
solar output fraction = 0.95
Set to 95% of modern value for 600-700 My ago
CO2 concentration thresholds = discrete test values
Tested discrete values (1000 ppm, 400 ppm, 100 ppm) to determine Snowball onset

axioms (2)

standard math Energy-balance climate model equations govern temperature and ice-albedo feedback
Invoked implicitly to produce the reported global glaciation thresholds
domain assumption Bare continents during the Proterozoic have no vegetation and albedo 0.35
Used to contrast with vegetated cases and to set the high-albedo trigger

pith-pipeline@v0.9.0 · 5667 in / 1580 out tokens · 59753 ms · 2026-05-15T00:51:55.972580+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear

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unclear
Relation between the paper passage and the cited Recognition theorem.

We employed the Earth-like Surface Temperature Model (ESTM v3.5... solving a modified diffusion equation: C ∂T/∂t − ∂/∂x [D(1−x²)∂T/∂x] = [S(1−A)]−I ... coupled with pre-computed radiative transfer look-up tables... albedo from 0.35 (granite) to 0.10 (woods-like)
IndisputableMonolith/Foundation/RealityFromDistinction.lean reality_from_one_distinction unclear

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unclear
Relation between the paper passage and the cited Recognition theorem.

for the solar input typical of 600-700 My ago (95% of the current value), the presence of bare continents with albedo 0.35 (granite) in the position estimated for Rodinia was sufficient to trigger a Snowball state for CO2 concentrations up to at least 1000 ppm

What do these tags mean?

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supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.