"Extreme weather events (hurricanes, wildfires, floods) have become dramatically more frequent and intense solely because of climate change."

climate · generated 2026-03-28 · v1.0.0
DISPROVED 4 citations
Evidence assessed across 4 verified citations.
Verified by Proof Engine — an open-source tool that verifies claims using cited sources and executable code. Reasoning transparent and auditable.
methodology · github · re-run this proof · submit your own

Climate change is a real and significant driver of extreme weather — but the claim goes further than the science does, and that extra step is where it fails.

What Was Claimed?

The claim is that hurricanes, wildfires, and floods have all become dramatically more frequent and more intense, and that climate change is the only reason why. This kind of statement circulates widely in discussions about climate policy, and the core concern behind it — that our changing atmosphere is making weather more dangerous — is well-founded. But the word "solely" carries a heavy load, and it's worth asking whether any serious scientific source actually says that.

What Did We Find?

The short answer is that no major scientific institution uses "solely" when explaining extreme weather trends. Four independent authoritative sources — spanning federal agencies, peer-reviewed research, and the world's leading intergovernmental climate body — all explicitly name non-climate factors as contributing causes.

For hurricanes, NOAA's Geophysical Fluid Dynamics Laboratory, the leading U.S. center for hurricane-climate research, points out that the increase in Atlantic tropical storm frequency since the 1970s has been "at least partly driven by decreases in aerosols from human activity and volcanic forcing." In other words, clean air regulations that reduced pollution also changed how much sunlight reaches the ocean — a factor entirely separate from greenhouse gas warming.

For floods, the U.S. Geological Survey is direct: "Urbanization generally increases the size and frequency of floods." When cities replace forests and fields with pavement, rainwater that would have soaked into the ground instead runs off immediately. This happens regardless of whether precipitation is increasing. More people living in developed areas means more exposure to floods even with no change in rainfall at all.

For wildfires, a 2024 study in PNAS Nexus found that wildfire risk "lies in the confluence of climate change and development in the WUI" — the wildland-urban interface, where housing has expanded into fire-prone landscapes. Decades of fire suppression policy has also let fuel accumulate in forests. Neither of these factors is a consequence of greenhouse gas warming.

And then there is the IPCC itself — the scientific consensus document that climate advocates most often cite. Its Sixth Assessment Report attributes observed changes in extreme events to "human influence (including greenhouse gas and aerosol emissions and land-use changes)." That parenthetical matters: three distinct categories of human influence, not one.

There is a further wrinkle beyond the "solely" question. Global hurricane counts have not clearly increased at all. NOAA GFDL notes that global tropical cyclone frequency data "do not show evidence for significant rising trends." Heat extremes, heavy rainfall, and wildfire area have increased — but not all three event types named in the claim have become more frequent.

What Should You Keep In Mind?

None of this means climate change is not a serious problem or a major driver of extreme weather. The evidence strongly supports climate change as a significant contributor to more intense hurricanes, longer fire seasons, heavier precipitation events, and more severe heat. The scientific consensus on that is robust.

What the evidence does not support is exclusive causation. Aerosol chemistry, urban development, land use choices, and fire management policy all independently shape the trends we observe. Removing climate change from the equation would improve things considerably — but removing the other factors would too.

It is also worth noting that the four sources used here are among the most credible available: two U.S. federal agencies, a peer-reviewed journal published by Oxford University Press, and the IPCC. These are not contrarian or fringe sources. They are the same institutions that document climate change's real effects most carefully — and they all reject sole causation.

How Was This Verified?

This proof identified four independent authoritative sources that explicitly document non-climate drivers of the three event types named in the claim, exceeding the threshold of three required for disproof. Full methodological details are in the structured proof report and the full verification audit. To inspect or reproduce the evidence-gathering process, see re-run the proof yourself.

What could challenge this verdict?

Four adversarial searches were conducted:

  1. "Solely" in mainstream science: Searched IPCC AR6, NOAA, NASA, and WMO for language attributing extreme weather "solely" or "only" to climate change. No mainstream scientific body uses such language. All authoritative sources name multiple drivers.

  2. Hurricane frequency: Reviewed NOAA GFDL's assessment of global tropical cyclone frequency. Their explicit finding is that global frequency timeseries show no significant rising trend. This contradicts the "more frequent" component of the claim for hurricanes.

  3. Linguistic interpretation of "solely": Analyzed whether "solely" could be charitably read as "primarily." Standard English meaning (Merriam-Webster: "without another; only") does not support this re-interpretation. The disproof holds under any standard reading.

  4. Indirect causation argument: Examined whether aerosol changes and urbanization could be considered indirect effects of climate change (which would preserve the "solely" claim). Both are driven by independent human policy and demographic choices — not by greenhouse gas warming — and NOAA GFDL lists them as distinct forcings.

None of these adversarial searches identified evidence that would restore the "solely" qualifier.


Sources

SourceIDTypeVerified
NOAA Geophysical Fluid Dynamics Laboratory (GFDL) — Global Warming and Hurricanes B1 Government Yes
U.S. Geological Survey (USGS) Fact Sheet FS-076-03 — Effects of Urban Development on Floods B2 Government Yes
PNAS Nexus — Wildfire risk management in the era of climate change (2024) B3 Academic Yes
IPCC Sixth Assessment Report (AR6) Working Group I — Chapter 11: Weather and Climate Extreme Events B4 Government Yes
Count of independent sources confirming non-climate drivers of extreme weather A1 Computed

detailed evidence

Detailed Evidence

Evidence Summary

ID Fact Verified
B1 NOAA GFDL: Atlantic hurricane frequency partly driven by aerosol changes, not solely greenhouse gases Yes
B2 USGS: urbanization independently increases the size and frequency of floods Yes
B3 PNAS Nexus: wildfire risk is a confluence of climate change AND development (WUI expansion) Yes
B4 IPCC AR6 Ch.11: attribution cites greenhouse gases, aerosol emissions, AND land-use changes as separate human influences Yes
A1 Count of independent sources confirming non-climate drivers of extreme weather Computed: 4 independent sources confirmed (threshold: 3)

Proof Logic

The claim's compound structure means all four sub-claims must hold simultaneously. SC4 — "solely because of climate change" — is the most precisely testable.

SC4 Disproof (Hurricanes — B1): NOAA's Geophysical Fluid Dynamics Laboratory, the leading U.S. center for hurricane-climate research, states: "the increase in tropical storm frequency in the Atlantic basin since the 1970s has been at least partly driven by decreases in aerosols from human activity and volcanic forcing." Aerosol reductions (from clean air regulations) and natural volcanic cycles are distinct from greenhouse gas warming — confirming non-climate factors in hurricane trends (B1).

SC4 Disproof (Floods — B2): The U.S. Geological Survey concludes: "Urbanization generally increases the size and frequency of floods and may expose communities to increasing flood hazards." Urbanization — driven by population growth and economic development — operates independently of climate change (B2). Replacing permeable soil with impervious surfaces increases flood frequency regardless of precipitation changes.

SC4 Disproof (Wildfires — B3): Peer-reviewed research in PNAS Nexus (2024) states: "Wildfire risk lies in the confluence of climate change and development in the WUI." The wildland-urban interface (WUI) has expanded by 50% in the United States in the past 50 years, driven by land use decisions independent of climate. Decades of fire suppression policy has also accumulated fuels. Neither WUI expansion nor fire suppression is caused by greenhouse gas warming (B3).

SC4 Disproof (General attribution — B4): The IPCC Sixth Assessment Report (AR6) itself — the definitive scientific consensus document — attributes observed changes in extremes to "human influence (including greenhouse gas and aerosol emissions and land-use changes)." The parenthetical lists three distinct categories of human influence: greenhouse gases, aerosols, and land-use changes. This is not "solely climate change" (B4).

SC1 Partial falsification: Beyond SC4, the "more frequent" component (SC1) is also only partially true. NOAA GFDL states that global tropical cyclone frequency timeseries "do not show evidence for significant rising trends." After correcting for pre-satellite observation gaps, there is "essentially no long-term trend in hurricane counts." For heat extremes and heavy precipitation, frequency has increased — but not for all three named event types.


Conclusion

Verdict: DISPROVED

The claim fails on two independent grounds:

  1. SC4 (sole causation) is false. Four independently verified authoritative sources — NOAA GFDL (B1), USGS (B2), PNAS Nexus (B3), and IPCC AR6 (B4) — explicitly document non-climate drivers of extreme weather events. This directly contradicts "solely because of climate change." No adverse citations are unverified; all four reached full-quote verified status.

  2. SC1 (frequency increase) is only partially true. Global hurricane frequency has not clearly increased (NOAA GFDL). This is an independent additional ground for disproof.

What the evidence does support: Climate change is a significant, documented contributor to more intense hurricanes, increased heavy precipitation, longer fire seasons, and more severe heat extremes. The scientific consensus strongly supports climate change as a major driver — but explicitly rejects "sole" causation.

All citations are fully verified (no "with unverified citations" qualifier needed). The disproof does not depend on any single source; it is independently established by at least three institutional sources from different sectors (federal agencies, peer-reviewed research, intergovernmental body).

audit trail

Citation Verification 3/4 unflagged 1 flagged

3/4 citations unflagged. 1 flagged for review:

  • fetched from Wayback Machine
Original audit log

B1 — NOAA GFDL - Status: verified - Method: full_quote - Fetch mode: live - Coverage: N/A (full match)

B2 — USGS - Status: verified - Method: full_quote - Fetch mode: live - Coverage: N/A (full match)

B3 — PNAS Nexus - Status: verified - Method: full_quote - Fetch mode: wayback (live Oxford Academic page returned access restrictions; Wayback Machine copy retrieved and verified) - Coverage: N/A (full match)

B4 — IPCC AR6 - Status: verified - Method: full_quote - Fetch mode: live - Coverage: N/A (full match)

All four citations are fully verified. No citations require "with unverified citations" qualifier in the verdict.


Claim Specification
Field Value
Subject Extreme weather events (hurricanes, wildfires, floods)
Property Causal attribution of increased frequency and intensity
Operator >=
Threshold 3 (independent sources confirming non-climate drivers)
Proof direction disprove
Operator note The claim is a conjunction of SC1 (frequency increased), SC2 (intensity increased), SC3 (change is dramatic), SC4 (climate change is the sole cause). A conjunction is false when any conjunct is false. SC4 is the decisive falsifier. "Solely" is interpreted as "exclusively" per standard English (Merriam-Webster). Threshold 3 means 3 independent authoritative sources documenting non-climate drivers suffice to disprove SC4. SC1 is also only partially true: global hurricane frequency has not clearly increased (NOAA GFDL).

Claim Interpretation

Natural language claim: "Extreme weather events (hurricanes, wildfires, floods) have become dramatically more frequent and intense solely because of climate change."

Formal interpretation: The claim is a conjunction of four sub-claims: - (SC1) Extreme weather events have increased in frequency - (SC2) They have increased in intensity - (SC3) The change is "dramatic" - (SC4) Climate change is the sole cause

A conjunction is false when any one conjunct is false. SC4 is the decisive falsifier: if any non-climate factor contributes to the observed changes, the "solely" qualifier fails. The proof collects 4 independent authoritative sources documenting non-climate drivers. The threshold for disproof is 3 verified sources — met here at 4.

SC1 is also only partially true: global hurricane frequency has not clearly increased (NOAA GFDL). SC2 and SC3 have stronger evidence for heat extremes and precipitation but are not uniformly "dramatic" across all event types.

Operator note: "Solely" is interpreted as "exclusively" (the standard English meaning: Merriam-Webster: "without another; only"). Even under the most charitable reading, a single independently documented non-climate driver falsifies this qualifier.


Source Credibility Assessment
Fact ID Domain Type Tier Note
B1 noaa.gov government 5 NOAA Geophysical Fluid Dynamics Laboratory — leading U.S. hurricane-climate research center
B2 usgs.gov government 5 U.S. Geological Survey — authoritative federal source for hydrological data
B3 oup.com academic 4 Oxford University Press / PNAS Nexus — peer-reviewed scientific journal
B4 ipcc.ch government/intergovernmental 5 IPCC — the definitive intergovernmental scientific consensus body on climate

All citations are Tier 4 or higher. No low-credibility sources were used.


Computation Traces
[✓] source_gfdl: Full quote verified for source_gfdl (source: tier 5/government)
[✓] source_usgs: Full quote verified for source_usgs (source: tier 5/government)
[✓] source_pnasnexus [wayback]: Full quote verified for source_pnasnexus (source: tier 4/academic)
[✓] source_ipcc: Full quote verified for source_ipcc (source: tier 5/government)
  Confirmed sources (non-climate drivers documented): 4 / 4
  SC4 disproof: verified sources confirming non-climate drivers >= 3: 4 >= 3 = True

Independent Source Agreement
Check Details
Sources consulted 4
Sources verified 4
Independence basis Four distinct institutions: NOAA (federal agency), USGS (federal agency), PNAS Nexus (peer-reviewed journal, Oxford University Press), IPCC (intergovernmental scientific body). Each addresses a different event type (hurricanes, floods, wildfires, general attribution). The finding is not institution-specific.
source_gfdl verified
source_usgs verified
source_pnasnexus verified
source_ipcc verified

Independence note: Two sources are US federal agencies (NOAA, USGS), which trace to the same government but are distinct agencies covering different domains. PNAS Nexus and IPCC are independent of both and of each other. The convergence across these four institutions is robust.


Adversarial Checks

Check 1: Does any mainstream scientific organization claim climate change is the sole cause? - Searched: IPCC AR6 Chapter 11, NOAA, NASA, WMO statements for "solely", "only", "exclusively" attributing extreme weather to climate change - Finding: No. All authoritative sources identify multiple drivers. IPCC AR6 explicitly lists greenhouse gases, aerosol emissions, AND land-use changes. No "solely" language found. - Breaks proof: No

Check 2: Is SC1 (frequency increase) fully true for all three event types? - Searched: NOAA GFDL global tropical cyclone frequency data - Finding: Global hurricane COUNT has NOT clearly increased. NOAA GFDL: "global tropical cyclone frequency timeseries do not show evidence for significant rising trends." This is an additional independent reason the claim fails. - Breaks proof: No (it further supports disproof, not the original claim)

Check 3: Could "solely" be charitably interpreted as "primarily"? - Analysis: Merriam-Webster defines "solely" as "without another; only". Standard English gives no room for reinterpretation. "Primarily because of X" is a different and weaker claim. - Finding: No charitable interpretation rescues the "solely" qualifier. - Breaks proof: No

Check 4: Could aerosol forcing and land-use changes be indirect effects of climate change? - Analysis: Aerosol reductions result from clean air legislation (independent policy choice). Urbanization is driven by population growth and economic development. WUI expansion results from residential development decisions. NOAA GFDL lists "aerosols from human activity" as a separate forcing category distinct from greenhouse gases. - Finding: These are genuinely independent causal factors, not downstream consequences of greenhouse gas warming. - Breaks proof: No


Quality Checks
Rule Status Notes
Rule 1: Values parsed from quotes, not hand-typed ✓ Pass Qualitative proof — no numeric values extracted; citation verification status is computed, not hand-typed
Rule 2: Citations verified by fetching ✓ Pass All 4 citations verified via verify_all_citations() with wayback_fallback=True
Rule 3: System time anchored ✓ Pass date.today() used
Rule 4: Claim interpretation explicit ✓ Pass CLAIM_FORMAL with operator_note documents the conjunction structure and "solely" interpretation
Rule 5: Adversarial checks are independent ✓ Pass 4 adversarial checks covering: institutional language search, hurricane frequency data, linguistic analysis, indirect-causation argument
Rule 6: Cross-checks use independent inputs ✓ Pass 4 sources from 3 distinct institutional types (federal agency ×2, peer-reviewed journal, intergovernmental body), each covering a different event type
Rule 7: No hard-coded constants or formulas ✓ Pass compare() from computations.py used; no inline formulas
validate_proof.py PASS 15/15 checks passed, 0 issues, 0 warnings
Source Data

For qualitative proofs, extractions record citation verification status rather than numeric values.

ID Extracted Value Found in Quote Quote Snippet
B1 verified Yes "the increase in tropical storm frequency in the Atlantic basin since the 1970s h..."
B2 verified Yes "Urbanization generally increases the size and frequency of floods and may expose..."
B3 verified Yes "Wildfire risk lies in the confluence of climate change and development in the WU..."
B4 verified Yes "Evidence of observed changes in extremes and their attribution to human influenc..."

Cite this proof
Proof Engine. (2026). Claim Verification: “Extreme weather events (hurricanes, wildfires, floods) have become dramatically more frequent and intense solely because of climate change.” — Disproved. https://doi.org/10.5281/zenodo.19489838
Proof Engine. "Claim Verification: “Extreme weather events (hurricanes, wildfires, floods) have become dramatically more frequent and intense solely because of climate change.” — Disproved." 2026. https://doi.org/10.5281/zenodo.19489838.
@misc{proofengine_extreme_weather_events_hurricanes_wildfires_floods,
  title   = {Claim Verification: “Extreme weather events (hurricanes, wildfires, floods) have become dramatically more frequent and intense solely because of climate change.” — Disproved},
  author  = {{Proof Engine}},
  year    = {2026},
  url     = {https://proofengine.info/proofs/extreme-weather-events-hurricanes-wildfires-floods/},
  note    = {Verdict: DISPROVED. Generated by proof-engine v1.0.0},
  doi     = {10.5281/zenodo.19489838},
}
TY  - DATA
TI  - Claim Verification: “Extreme weather events (hurricanes, wildfires, floods) have become dramatically more frequent and intense solely because of climate change.” — Disproved
AU  - Proof Engine
PY  - 2026
UR  - https://proofengine.info/proofs/extreme-weather-events-hurricanes-wildfires-floods/
N1  - Verdict: DISPROVED. Generated by proof-engine v1.0.0
DO  - 10.5281/zenodo.19489838
ER  -
View proof source 287 lines · 14.2 KB

This is the exact proof.py that was deposited to Zenodo and runs when you re-execute via Binder. Every fact in the verdict above traces to code below.

"""
Proof: Extreme weather events (hurricanes, wildfires, floods) have become dramatically
more frequent and intense solely because of climate change.
Generated: 2026-03-28

Claim structure: This is a conjunction of four sub-claims:
  SC1: Extreme weather events have become more frequent
  SC2: Extreme weather events have become more intense
  SC3: The change is "dramatic"
  SC4: Climate change is the *sole* cause

A conjunction is false if any conjunct is false. This proof focuses on falsifying SC4,
which is the most clearly contradicted by scientific literature. SC1 is also only
partially true (global hurricane frequency has not clearly increased).
"""
import json
import os
import sys

PROOF_ENGINE_ROOT = os.environ.get("PROOF_ENGINE_ROOT")
if not PROOF_ENGINE_ROOT:
    _d = os.path.dirname(os.path.abspath(__file__))
    while _d != os.path.dirname(_d):
        if os.path.isdir(os.path.join(_d, "proof-engine", "skills", "proof-engine", "scripts")):
            PROOF_ENGINE_ROOT = os.path.join(_d, "proof-engine", "skills", "proof-engine")
            break
        _d = os.path.dirname(_d)
    if not PROOF_ENGINE_ROOT:
        raise RuntimeError("PROOF_ENGINE_ROOT not set and skill dir not found via walk-up from proof.py")
sys.path.insert(0, PROOF_ENGINE_ROOT)
from datetime import date

from scripts.verify_citations import verify_all_citations, build_citation_detail
from scripts.computations import compare

# 1. CLAIM INTERPRETATION (Rule 4)
CLAIM_NATURAL = (
    "Extreme weather events (hurricanes, wildfires, floods) have become dramatically "
    "more frequent and intense solely because of climate change."
)
CLAIM_FORMAL = {
    "subject": "Extreme weather events (hurricanes, wildfires, floods)",
    "property": "causal attribution of increased frequency and intensity",
    "operator": ">=",
    "operator_note": (
        "The claim is a conjunction of four sub-claims: "
        "(SC1) extreme weather events have increased in frequency; "
        "(SC2) they have increased in intensity; "
        "(SC3) the change is 'dramatic'; "
        "(SC4) climate change is the *sole* cause. "
        "A conjunction is false when any conjunct is false. SC4 is the clearest falsifier: "
        "if scientific literature identifies ANY non-climate factor as a contributing cause, "
        "the claim is disproved. "
        "This proof tests SC4 by counting independent authoritative sources that explicitly "
        "document non-climate drivers of extreme weather (aerosol forcing, urbanization, "
        "land use change, fire suppression history). "
        "Threshold: 3 independent sources confirming non-climate drivers suffices to disprove SC4. "
        "SC1 is also only partially true: global hurricane frequency has not clearly increased "
        "(NOAA GFDL). SC2 and SC3 have stronger support for some event types."
    ),
    "threshold": 3,
    "proof_direction": "disprove",
}

# 2. FACT REGISTRY
FACT_REGISTRY = {
    "B1": {"key": "source_gfdl",     "label": "NOAA GFDL: Atlantic hurricane frequency partly driven by aerosol changes, not solely greenhouse gases"},
    "B2": {"key": "source_usgs",     "label": "USGS: urbanization independently increases the size and frequency of floods"},
    "B3": {"key": "source_pnasnexus","label": "PNAS Nexus: wildfire risk is a confluence of climate change AND development (WUI expansion)"},
    "B4": {"key": "source_ipcc",     "label": "IPCC AR6 Ch.11: attribution cites greenhouse gases, aerosol emissions, AND land-use changes as separate human influences"},
    "A1": {"label": "Count of independent sources confirming non-climate drivers of extreme weather", "method": None, "result": None},
}

# 3. EMPIRICAL FACTS — sources confirming the claim is FALSE (non-climate drivers documented)
# proof_direction = "disprove": these sources confirm that non-climate factors exist,
# thereby falsifying the "solely because of climate change" qualifier in SC4.
empirical_facts = {
    "source_gfdl": {
        "quote": (
            "the increase in tropical storm frequency in the Atlantic basin since the 1970s "
            "has been at least partly driven by decreases in aerosols from human activity "
            "and volcanic forcing."
        ),
        "url": "https://www.gfdl.noaa.gov/global-warming-and-hurricanes/",
        "source_name": "NOAA Geophysical Fluid Dynamics Laboratory (GFDL) — Global Warming and Hurricanes",
    },
    "source_usgs": {
        "quote": (
            "Urbanization generally increases the size and frequency of floods and may "
            "expose communities to increasing flood hazards."
        ),
        "url": "https://pubs.usgs.gov/fs/fs07603/",
        "source_name": "U.S. Geological Survey (USGS) Fact Sheet FS-076-03 — Effects of Urban Development on Floods",
    },
    "source_pnasnexus": {
        "quote": (
            "Wildfire risk lies in the confluence of climate change and development in the WUI"
        ),
        "url": "https://academic.oup.com/pnasnexus/article/3/5/pgae151/7665998",
        "source_name": "PNAS Nexus — Wildfire risk management in the era of climate change (2024)",
    },
    "source_ipcc": {
        "quote": (
            "Evidence of observed changes in extremes and their attribution to human influence "
            "(including greenhouse gas and aerosol emissions and land-use changes) has strengthened "
            "since AR5"
        ),
        "url": "https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-11/",
        "source_name": "IPCC Sixth Assessment Report (AR6) Working Group I — Chapter 11: Weather and Climate Extreme Events",
    },
}

# 4. CITATION VERIFICATION (Rule 2)
citation_results = verify_all_citations(empirical_facts, wayback_fallback=True)

# 5. COUNT SOURCES WITH VERIFIED CITATIONS (supporting the disproof)
COUNTABLE_STATUSES = ("verified", "partial")
n_confirmed = sum(
    1 for key in empirical_facts
    if citation_results[key]["status"] in COUNTABLE_STATUSES
)
print(f"  Confirmed sources (non-climate drivers documented): {n_confirmed} / {len(empirical_facts)}")

# 6. CLAIM EVALUATION — MUST use compare()
# claim_holds=True means we have confirmed enough sources documenting non-climate drivers,
# which (combined with proof_direction="disprove") yields a DISPROVED verdict.
claim_holds = compare(n_confirmed, CLAIM_FORMAL["operator"], CLAIM_FORMAL["threshold"],
                      label="SC4 disproof: verified sources confirming non-climate drivers >= 3")

# 7. ADVERSARIAL CHECKS (Rule 5)
# For a disproof proof: adversarial checks search for sources *supporting* the original claim
# (i.e., claiming climate change is the sole cause). Finding strong support would weaken the disproof.
adversarial_checks = [
    {
        "question": "Does any mainstream scientific organization claim climate change is the *sole* cause of extreme weather?",
        "verification_performed": (
            "Searched IPCC AR6 Chapter 11, NOAA, NASA, and WMO statements for language claiming "
            "'solely', 'only', or 'exclusively' climate change drives extreme weather. "
            "IPCC AR6 consistently lists 'greenhouse gas and aerosol emissions and land-use changes' "
            "as separate contributing human influences. NOAA GFDL explicitly names aerosol changes "
            "and natural variability as distinct factors. No mainstream scientific body uses the "
            "word 'solely' in attributing extreme weather to climate change alone."
        ),
        "finding": (
            "No major scientific organization claims climate change is the sole cause. "
            "All authoritative sources identify multiple drivers. This confirms SC4 is false "
            "and strengthens the disproof."
        ),
        "breaks_proof": False,
    },
    {
        "question": "Is SC1 (frequency increase) fully true for all three event types?",
        "verification_performed": (
            "Reviewed NOAA GFDL on global hurricane frequency: "
            "'global tropical cyclone frequency timeseries do not show evidence for significant "
            "rising trends.' Also: 'after adjusting for a likely under-count of hurricanes in the "
            "pre-satellite era there is essentially no long-term trend in hurricane counts.' "
            "IPCC AR6 confirms heavy precipitation and heat extremes have increased globally. "
            "Wildfire burned area has increased in western US and globally. "
            "Flood frequency shows regional variation with urbanization as a major driver."
        ),
        "finding": (
            "SC1 is only partially true. Global hurricane COUNT has NOT clearly increased — "
            "a direct contradiction of 'more frequent' for that event type. "
            "Heat extremes, heavy precipitation, and wildfire area have increased. "
            "This is an additional reason the claim fails beyond SC4."
        ),
        "breaks_proof": False,
    },
    {
        "question": "Could 'solely' be charitably interpreted as 'primarily' rather than 'exclusively'?",
        "verification_performed": (
            "Linguistic analysis: 'solely' in standard English means 'only' or 'exclusively'. "
            "Example: 'I did this solely for you' means no other motive exists. "
            "Merriam-Webster: 'solely' = 'without another; only'. "
            "The claim says events became more frequent/intense 'solely because of climate change', "
            "leaving no room for other causes under any standard reading."
        ),
        "finding": (
            "Even the most charitable reading of 'solely' means 'exclusively.' "
            "Reinterpreting it as 'primarily' would change the claim's content, not clarify it. "
            "The disproof stands under any standard linguistic interpretation."
        ),
        "breaks_proof": False,
    },
    {
        "question": "Could aerosol forcing and land-use changes themselves be caused by climate change, making them indirect effects rather than separate causes?",
        "verification_performed": (
            "Examined the logical structure: aerosol reductions (clean air regulations), "
            "urbanization, and WUI expansion are human socioeconomic and policy choices independent "
            "of greenhouse gas warming. NOAA GFDL explicitly lists 'aerosols from human activity' "
            "as a separate forcing distinct from greenhouse gas warming. Urbanization is driven by "
            "population growth and economic development. These are not consequences of climate change."
        ),
        "finding": (
            "Aerosol policy changes, urbanization, and WUI development are independent human "
            "activities not caused by greenhouse gas warming. They are genuinely separate causal "
            "factors, not indirect effects of climate change. The 'solely' qualifier remains falsified."
        ),
        "breaks_proof": False,
    },
]

# 8. VERDICT AND STRUCTURED OUTPUT
if __name__ == "__main__":
    any_unverified = any(
        cr["status"] != "verified" for cr in citation_results.values()
    )
    is_disproof = CLAIM_FORMAL.get("proof_direction") == "disprove"
    any_breaks = any(ac.get("breaks_proof") for ac in adversarial_checks)

    if any_breaks:
        verdict = "UNDETERMINED"
    elif claim_holds and not any_unverified and is_disproof:
        verdict = "DISPROVED"
    elif claim_holds and any_unverified and is_disproof:
        verdict = "DISPROVED (with unverified citations)"
    elif not claim_holds:
        verdict = "UNDETERMINED"
    else:
        verdict = "UNDETERMINED"

    FACT_REGISTRY["A1"]["method"] = f"count(citations with status in {COUNTABLE_STATUSES}) = {n_confirmed}"
    FACT_REGISTRY["A1"]["result"] = str(n_confirmed)

    citation_detail = build_citation_detail(FACT_REGISTRY, citation_results, empirical_facts)

    # Extractions: for qualitative proofs, record citation verification status per source
    extractions = {}
    for fid, info in FACT_REGISTRY.items():
        if not fid.startswith("B"):
            continue
        ef_key = info["key"]
        cr = citation_results.get(ef_key, {})
        extractions[fid] = {
            "value": cr.get("status", "unknown"),
            "value_in_quote": cr.get("status") in COUNTABLE_STATUSES,
            "quote_snippet": empirical_facts[ef_key]["quote"][:80],
        }

    summary = {
        "fact_registry": {
            fid: {k: v for k, v in info.items()}
            for fid, info in FACT_REGISTRY.items()
        },
        "claim_formal": CLAIM_FORMAL,
        "claim_natural": CLAIM_NATURAL,
        "citations": citation_detail,
        "extractions": extractions,
        "cross_checks": [
            {
                "description": "Multiple independent institutions consulted (NOAA, USGS, PNAS Nexus, IPCC)",
                "n_sources_consulted": len(empirical_facts),
                "n_sources_verified": n_confirmed,
                "sources": {k: citation_results[k]["status"] for k in empirical_facts},
                "independence_note": (
                    "Sources are from four distinct institutions: NOAA (federal agency), "
                    "USGS (federal agency), PNAS Nexus (peer-reviewed journal), and "
                    "IPCC (intergovernmental scientific body). Each addresses a different "
                    "event type (hurricanes, floods, wildfires, general attribution), "
                    "confirming the finding is not institution-specific."
                ),
            }
        ],
        "adversarial_checks": adversarial_checks,
        "verdict": verdict,
        "key_results": {
            "n_confirmed_non_climate_sources": n_confirmed,
            "threshold": CLAIM_FORMAL["threshold"],
            "operator": CLAIM_FORMAL["operator"],
            "claim_holds": claim_holds,
            "sc4_falsified": claim_holds,
            "sc1_frequency_fully_true": False,
            "sc1_note": "Global hurricane frequency has not clearly increased (NOAA GFDL)",
            "proof_direction": "disprove",
        },
        "generator": {
            "name": "proof-engine",
            "version": open(os.path.join(PROOF_ENGINE_ROOT, "VERSION")).read().strip(),
            "repo": "https://github.com/yaniv-golan/proof-engine",
            "generated_at": date.today().isoformat(),
        },
    }

    print("\n=== PROOF SUMMARY (JSON) ===")
    print(json.dumps(summary, indent=2, default=str))

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