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

- **Generated:** 2026-03-28
- **Verdict:** DISPROVED
- **Audit trail:** [proof_audit.md](proof_audit.md) | [proof.py](proof.py)

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## Key Findings

- **4 of 4 sources verified** (all full-quote matches): NOAA, USGS, PNAS Nexus, and IPCC all explicitly document non-climate drivers of extreme weather — directly falsifying the "solely" qualifier.
- **SC4 (sole causation) is DISPROVED**: Hurricane frequency trends are partly driven by aerosol forcing changes (NOAA GFDL, B1); flood frequency independently increases with urbanization (USGS, B2); wildfire risk is "the confluence of climate change and development" (PNAS Nexus, B3); IPCC AR6 itself lists greenhouse gases, aerosol emissions, and land-use changes as separate human influences (IPCC, B4).
- **SC1 (frequency increase) is only partially true**: NOAA GFDL states that global tropical cyclone frequency timeseries "do not show evidence for significant rising trends." Heat extremes, heavy precipitation, and wildfire area have increased — but global hurricane counts have not clearly risen.
- **No mainstream scientific body uses the word "solely"** when attributing extreme weather to climate change — all authoritative sources name multiple factors.

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## 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.

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## 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) |

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## 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.

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## Counter-Evidence Search

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.

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## 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).

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*Generated by [proof-engine](https://github.com/yaniv-golan/proof-engine) v1.0.0 on 2026-03-28.*
