Concerning the Breadbasket Collapse post, Reddit user Metalt_ asked the following:

Pretty good write up. A big question of mine is.. We are definitely going to try to start geo engineering at some point. Pending its effectiveness, I wonder whether or not it delays the timeline specifically for heating.

Maybe existing feedback loops and failures of carbon sinks overwhelm whatever reflectivity atmospheric injections can provide, but I haven’t seen much of that included into peoples analyses/predictions of the future.

Their question cuts to the heart of one of the most contentious debates in climate science: Can geoengineering buy humanity time to avoid breadbasket collapse, or would it merely mask—or even accelerate—the systemic unraveling of food systems?

The Geoengineering Gamble: Types and Timelines

Most climate models assume linear warming trajectories, but geoengineering proposals like solar radiation management (SRM)—stratospheric aerosol injections, marine cloud brightening—aim to artificially cool the planet by reflecting sunlight. These are distinct from carbon dioxide removal (CDR), which targets emissions. SRM could theoretically delay temperature rise, but with critical caveats:

1. Masking vs. Solving: SRM treats the symptom (heat) but not the disease (CO₂). Even if global temperatures stabilize, ocean acidification, soil degradation, and carbon sink failures (e.g., dying Amazon rainforests, thawing permafrost) would continue unabated.
2. Regional Trade-offs: Cooling the U.S. Midwest might worsen droughts in the Sahel or disrupt India’s monsoons. A 2022 Nature study found that stratospheric aerosols over the Northern Hemisphere could shift tropical rainfall patterns, collapsing rice production in Southeast Asia.
3. Termination Shock: If SRM is deployed and later halted (due to cost, political shifts, or unintended consequences), temperatures would spike rapidly, overwhelming agricultural systems already weakened by delayed adaptation.

Feedback Loops vs. Geoengineering: Who Wins?

The Breadbasket Collapse analysis underplays three feedback loops that could overwhelm SRM’s cooling effects:

1. Permafrost Thaw and Methane Bombs

By 2035, even at 2°C, Siberia’s permafrost emits 1.5–2 gigatons of methane annually—equivalent to 500 coal plants. Methane’s short-term warming potential is 80× CO₂, and SRM does nothing to curb it. A 2023 PNAS paper modeled that permafrost emissions alone could add 0.3°C to global temps by 2040, negating much of SRM’s cooling.

2. Forest Dieback and Carbon Sink Collapse

The Amazon, now a net carbon emitter, could lose 40% of its biomass by 2035 due to drought and fires. This would release 120 billion tons of CO₂—equal to 12 years of current U.S. emissions. SRM cannot re-grow forests or restore their moisture recycling, which is critical for rainfall in breadbaskets like the U.S. Midwest.

3. Albedo Loss and Arctic Amplification

Melting Arctic ice reduces Earth’s reflectivity (albedo), adding 0.5°C of warming by 2040 (Hansen et al., 2024). SRM might offset this locally, but ice loss is irreversible past tipping points. Meanwhile, darker oceans absorb more heat, accelerating marine heatwaves that disrupt fisheries—a key protein source for 3 billion people.

Could SRM Delay Breadbasket Collapse? A Scenario Analysis

Let’s model two scenarios:

Scenario A: Moderate SRM Deployment (2030–2050)

• Action: Aerosols injected annually to limit warming to 1.8°C by 2050 (instead of 3°C under SSP2-4.5).
• Outcomes:
  • Short-Term Relief: Midwest heatwaves reduce by 20%, buying 5–10 years for drought-resistant crop R&D.
  • Hidden Damage: Ocean pH drops to 7.8 (from 8.1 today), collapsing plankton populations that underpin marine food chains.
  • Political Fragmentation: India and Brazil weaponize SRM by unilaterally altering regional climates, sparking conflicts over “whose crops get saved.”
  • Collapse Delay: Breadbasket failures shift from 2035–2040 to 2045–2050, but with higher systemic fragility (soils depleted, aquifers drained).

Scenario B: Aggressive SRM + CDR (2030–2070)

• Action: Large-scale SRM combined with direct air capture (DAC) to remove 10 gigatons of CO₂/year by 2050.
• Outcomes:
  • Temperature Stabilization: Warming held at 1.5°C, but only if DAC scales miraculously (current capacity: 0.001 gigatons/year).
  • False Security: Governments slow emissions cuts, assuming tech will save them. Result: CO₂ levels still hit 550 ppm by 2060, ensuring long-term breadbasket decline.
  • Resource Wars: Lithium and cobalt shortages (needed for DAC machines) trigger mining conflicts in Congo and Chile, diverting funds from food resilience.

The Agricultural Wildcards SRM Ignores

Even if SRM delays heating, these unaddressed threats would still ravage food systems:

1. Soil Carbon Loss: At 2°C, extreme heat accelerates microbial activity, burning through soil organic matter. The FAO estimates 40% of global cropland becomes low-nutrient “dirt” by 2040, reducing yields irrespective of SRM.
2. Pollinator Collapse: Wild bees—critical for 75% of crops—decline by 60% at 2°C due to pesticide use and habitat loss. SRM doesn’t regrow wildflowers.
3. Groundwater Exhaustion: The Ogallala Aquifer and North India’s groundwater reserves are already on pace to hit 90% depletion by 2040. No geoengineering fix exists for empty wells.

The Verdict: A Dangerous Distraction?

Geoengineering might delay specific thresholds (e.g., pushing 2°C to 2038 instead of 2035), but it cannot resolve the root causes of breadbasket collapse. Worse, it risks:

• Complacency: Slowing emissions cuts because “SRM will handle it.”
• Weaponization: Climate interventions becoming tools of geopolitical coercion.
• Termination Chaos: If funding or political will lapses, abrupt warming could trigger simultaneous global breadbasket failures.

A Better Path: “Adaptation First”

Instead of betting on unproven tech, prioritizing region-specific resilience could buy meaningful time:

• Mexico: Reviving ancient chinampa systems (floating gardens) to cope with erratic rainfall.
• Sahel: Farmer-managed natural regeneration (FMNR) of trees boosts soil moisture and crop yields.
• Global North: Shift from water-intensive corn/soy to perennial crops like Kernza (deep-rooted wheatgrass).

These solutions lack SRM’s sci-fi allure but address the core vulnerabilities the Breadbasket Collapse analysis outlines. The clock is ticking, but the tools exist—if we ditch silver bullets for systemic change.

A reader of this blog asked for the references used in “Agriculture in the Crosshairs: Breadbasket Collapse at 2°C and 3°C”. Here are the references:

Scientific Sources

1. 1. Leng et al. (2024) – Nonlinear Impacts of Compound Heat-Drought Events on U.S. Corn Yields(EarthArXiv).
   2. Global Water Security Institute (2023) – Peak Water: The Ogallala Aquifer’s Point of No Return(Nature Water).
   3. EPA (2021) – Aflatoxin Contamination Risk Under Climate Change.
   4. Entomology Society of America (2024) – Insect Pest Adaptation to CRISPR Crops (preprint).
   5. Turetsky et al. (2019) – Permafrost Collapse is Accelerating Carbon Release (Nature).
   6. EU Joint Research Centre (2024) – Desertification and Olive Cultivation: A Tipping Point Analysis.
   7. World Resources Institute (2024) – Climate-Driven Water Wars in the Mediterranean.
   8. Chatham House (2024) – Climate Nationalism: Food Export Bans in a 2°C World.
   9. International Food Policy Research Institute (2023) – AI-Driven Speculation in Climate-Stressed Grain Markets (Science).
   10. World Bank (2012) – Turn Down the Heat: Why a 4°C Warmer World Must Be Avoided.
   11. Schewe et al. (2014) – Multimodel Assessment of Water Scarcity Under Climate Change (PNAS).
   12. FAO (2023) – Global Soil Health Report.

Also, Reddit user spectrumanalyze doubted some of the scenarios in the Breadbasket Collapse analysis:

“The scenarios presented are not credible in most cases (methane requiring people to be using masks, 30% declines from smoke induced photosynthesis losses, etc).

I don’t know why people like talking that way about things they know nothing about and are clearly making it up. Is there a thing where they like to edge people with fantasy?

The real consequences are horrific enough, and they will arrive soon enough. People will deny it of they are expecting absurd and hilarious scenarios like what are presented here. you don’t need this purported level of impacts to initiate a rapid global bottleneck event.

Smoke from megafires can reduce photosynthesis significantly. For example:

Megafires have lingering effects on tree health

“Photosynthesis produces carbohydrates, which are critical elements for tree survival,” said Orozco. “Trees need carbohydrates not just to grow but to store energy for when they’re under stress or when photosynthesis isn’t happening.”

The team found that megafire smoke not only reduced the amount of carbohydrates in trees but also caused losses that continued even after the fires were out. This led to nut yield decreases of 15% to as much as 50% in some orchards. The most active time for wildfires also coincides with the time trees start storing carbohydrates to sustain them through winter dormancy and spring growth.

https://caes.ucdavis.edu/news/smoke-megafires-puts-orchard-trees-risk

Other studies:

• • California (2020 Wildfires): A study in Nature Food (2021) found smoke from record wildfires reduced solar irradiance in California’s Central Valley by 15–30%, causing:
    • 27% decline in photosynthesis in wine grapes.
    • 10–15% yield losses in tomatoes and almonds.
• • Australia (2019–2020 Bushfires): Research in Global Change Biology (2021) showed smoke reduced PAR by 40% in southeastern Australia, lowering wheat yields by 5–10% during critical growth stages.

Megafire smoke consistently reduces crop photosynthesis by 5–30%, depending on smoke intensity, crop type, and growth stage. With climate change increasing wildfire frequency and severity, these impacts threaten global food security, particularly in fire-prone regions like the western U.S., Australia, and the Amazon.

A large methane burst from thawing permafrost poses the following health risks:

1. Oxygen Depletion

• • • • Methane Displacement: Methane (CH₄) is not toxic, but in high concentrations, it can displace oxygen in the air, reducing oxygen levels below safe thresholds (19.5% O₂). This can lead to dizziness, headaches, asphyxiation, or loss of consciousness, especially in enclosed or low-lying areas.

2. Toxic Co-Released Gases

• • • • Hydrogen Sulfide (H₂S): Thawing permafrost often releases hydrogen sulfide, a byproduct of anaerobic decomposition of organic matter. H₂S is highly toxic, causing respiratory distress, eye irritation, and even death at concentrations as low as 500 ppm. Its “rotten egg” smell becomes undetectable at dangerous levels, increasing the risk of exposure.
      • Volatile Organic Compounds (VOCs): Decomposing organic material may emit harmful VOCs like benzene or formaldehyde, which are carcinogenic and can cause chronic health issues with prolonged exposure.

3. Particulate Matter and Airborne Pollutants

• • • • Dust and Soot: Thawing permafrost destabilizes soil, releasing dust and particulate matter. When combined with methane plumes, these particles can irritate the lungs and exacerbate respiratory conditions like asthma.
      • Microbial Pathogens: Thawed permafrost may expose ancient bacteria or viruses, posing unknown health risks if inhaled.

A clarification on James Hansen’s latest study:

Under the section titled “The Next Decade or Two”, James Hansen writes:

“Global warming in the next two decades is likely to be about 0.2–0.3°C per decade, leading to global temperature +2°C by 2045.”

While James Hansen’s paper does not explicitly predict crossing 2°C of global warming by 2035, his analysis suggests this timeline is plausible under accelerating conditions. The 2023 temperature spike to +1.6°C (relative to 1880–1920) demonstrated the rapid warming influence of reduced aerosol cooling and greenhouse gas forcing. Post-2024, temperatures are unlikely to fall significantly below +1.5°C due to Earth’s persistent energy imbalance (~1.4 W/m²). Hansen projects a post-2020 warming rate of 0.2–0.3°C per decade, which, if sustained at the higher end, could push global temperatures to 2°C by the mid-2030s. This acceleration could be driven by further reductions in cooling aerosols (e.g., stricter pollution controls in Asia), surging methane emissions, and amplifying feedbacks like Arctic sea ice loss and permafrost thaw. Natural variability, such as prolonged El Niño conditions, could also temporarily boost temperatures. Critically, Hansen argues that IPCC models underestimate both aerosol cooling (masking past warming) and climate sensitivity (revised to 4.5–6°C for doubled CO₂), meaning real-world warming could outpace current projections. While his central estimate for 2°C remains closer to 2040–2045, the 2035 threshold cannot be ruled out if aerosol unmasking, methane growth, and feedback dynamics intensify faster than anticipated.

To recap:

While IPCC central estimates and Hansen place 2°C in the 2040s, converging evidence from aerosol reductions, methane growth, and feedback dynamics suggests 2035 is plausible under a high-risk scenario. This would require:

• Continued aerosol unmasking (e.g., Asia’s air quality laws).
• Methane acceleration (e.g., permafrost feedbacks).
• Policy inertia on fossil fuels.

The 2023–2024 temperature surge (1.6–1.7°C) highlights that even modest overshoots of 1.5°C could trigger feedbacks making 2°C unavoidable by 2035.

There is a new study out that adds to warming and which was not considered by Hansen:

Climate warming and heatwaves accelerate global lake deoxygenation

1. Key Omissions in Hansen’s Analysis

• Lake Deoxygenation Feedback Loops: The study on global lake deoxygenation highlights that low-oxygen conditions in lakes increase emissions of methane (CH₄) and nitrous oxide (N₂O), potent GHGs. Hansen’s paper does not incorporate these freshwater emissions into its climate forcing calculations.
• Methane Sources: While Hansen emphasizes permafrost thaw and oceanic methane hydrates, he omits lakes, which contribute ~20% of global freshwater methane emissions. Tropical lakes (e.g., Lake Victoria) are already significant CH₄ sources, and deoxygenation could amplify this.
• Nitrous Oxide Dynamics: N₂O production in oxygen-depleted lake sediments is absent from Hansen’s feedback analysis, despite its global warming potential (300× CO₂).

2. Why This Matters

• Underestimated Forcings: Excluding lake-derived GHGs likely understates total radiative forcing. For example:
  • Methane: Freshwater systems emit ~200 Mt CH₄/year, comparable to Arctic permafrost.
  • N₂O: Lakes under heatwaves can double N₂O fluxes, adding ~0.1 W/m² forcing by 2040 under SSP5-8.5.
• Accelerated Warming: These emissions could add 0.1–0.2°C to Hansen’s projected 2–3°C warming by 2040, hastening AMOC collapse and ice sheet instability.

---

3. Overlap with Hansen’s Broader Themes

• Nonlinear Feedbacks: Hansen stresses underestimated climate sensitivity due to aerosol forcing and ice-albedo feedbacks. Lake GHG emissions represent another nonlinear feedback loop that exacerbates warming.
• Policy Implications: Hansen advocates for rapid decarbonization and solar radiation management (SRM). Unaccounted lake emissions strengthen the case for SRM as a temporary buffer, but also highlight risks of complacency if models omit key feedbacks.

---

4. Why Hansen Might Have Excluded Lakes

• Data Gaps: Global lake GHG flux measurements are sparse and rarely integrated into Earth System Models (ESMs). Hansen relies on CMIP6 models, which poorly represent freshwater systems.
• Focus on Aerosols: The paper prioritizes aerosol-forcing revisions as the immediate driver of recent warming acceleration, sidelining slower feedbacks like lake emissions.

---

5. Consequences for Climate Projections

• Higher Sensitivity: If lake GHG emissions scale with warming (as deoxygenation accelerates), Hansen’s climate sensitivity estimate (4.5°C for 2×CO₂) might still be too low.
• Tipping Points: Lake emissions could push critical thresholds (e.g., AMOC shutdown, permafrost collapse) earlier than Hansen’s mid-century projection.

---

Conclusion: A Critical Blind Spot

Hansen’s analysis underscores the urgency of aerosol reductions and high climate sensitivity but misses a critical feedback: GHG bombs from stressed lakes. This omission suggests that:

1. Actual warming could exceed Hansen’s projections, particularly post-2040 as lake emissions intensify.
2. IPCC and UN assessments must prioritize freshwater GHG monitoring and modeling to avoid systemic underestimation.

Have a nice day!