Last updated August 11, 2025

Major Natural Disasters: What Are the Most Likely Threats?

Natural disasters: between regularity and extreme rarity

Major natural disasters are high-impact events that can radically transform the environment and human societies. Some, like earthquakes or floods, occur regularly and are relatively well quantified. Others, such as supervolcanic eruptions or asteroid impacts, are extremely rare but potentially devastating on a planetary scale.

Main categories of threats and their probabilities

Super hurricanes: These extreme tropical cyclones have winds exceeding 250 km/h, generating destructive storm surges and torrential rainfall. Their formation depends on warm oceanic conditions (> 28 °C) and complex atmospheric dynamics. The dissipated kinetic energy reaches several terajoules, causing massive destruction in coastal areas. Their frequency is on the order of a few decades, with a probability of 5 to 10% per decade.
Mega fire: These large-scale fires result from the convergence of prolonged droughts, strong winds, and vast flammable biomass. They can burn several million hectares, temporarily altering the atmospheric composition through significant emissions of fine particles and CO₂, affecting air quality on a continental scale. Their occurrence is variable but can be expected on scales of decades to centuries depending on climate changes and ecosystem management.
Extreme global pandemic: The emergence or rapid mutation of a highly contagious and lethal pathogen can cause a global pandemic. Transmission is facilitated by population density, human mobility, and interactions with animal reservoirs. These biological events represent a threat with potentially massive human losses, ranging from hundreds of thousands to several billion. Their probability over a few centuries is estimated between 0.1 and 1% per century.
Abrupt climate collapse: Abrupt climate collapse refers to rapid and irreversible changes in global climate regimes, often linked to disruptions in water and carbon cycles and accelerated melting of polar ice. These changes severely impact agricultural resources, water systems, and cause massive human migrations. The probability remains uncertain but is estimated around 0.1% per century, with indirect impacts on several hundred million individuals.
Hothouse Earth: This extreme scenario involves cascading climate runaway where natural carbon sinks, such as the Amazon forest and permafrost, cease to store CO₂, or even become sources. This leads to uncontrolled increases in global temperatures, transforming terrestrial and marine ecosystems, and destabilizing the biosphere. The probability is very uncertain but is likely on a millennial scale, with a potential indirect impact of several hundred million to billions of people.
Major solar storm: Intense solar flares release fluxes of energetic particles and electromagnetic pulses that can damage electrical and satellite infrastructures. The Carrington Event of 1859 is a reference, but more powerful storms are possible. These phenomena have a probability of about 0.7% per century and could indirectly affect millions of people by causing widespread blackouts.
Mega-earthquake: Earthquakes with a magnitude greater than 9 result from the rupture of a very long portion of a major tectonic fault. The released energy is measured in hundreds of megatons of TNT. These events cause extensive regional destruction and massive human losses. Their frequency is about one every 500 to 1000 years, or 0.1–0.2% per century.
Mega-tsunami: Generated by very powerful earthquakes, underwater landslides, or the detachment of immense glacial masses, these tsunamis reach heights exceeding 30 meters, flooding coastal areas over hundreds of kilometers. Their occurrence is on the order of a few thousand years. Human losses can reach several million.
Mega-floods: Mega-floods are extreme events resulting from the rapid rupture of natural or artificial dams, the massive rapid melting of glaciers, or the sudden obstruction of river basins. These phenomena can lead to colossal volumes of water submerging vast regions in a few hours to days, causing extensive destruction and very significant human losses. Their frequency is difficult to quantify but can range from a few centuries to millennia depending on the geological and climatic context.
Detachment of an Antarctic block: The rupture and drift of a massive block of Antarctic ice accelerate sea-level rise on centennial to millennial scales. This phenomenon leads to the submersion of large coastal areas, affecting millions of people. The probability is difficult to estimate precisely but remains low to very low.
Supervolcanic eruptions: Supervolcanic eruptions eject thousands of cubic kilometers of pyroclastic materials and volcanic gases, causing a global volcanic winter with a drastic reduction in solar brightness. These events are extremely rare, about one every 100,000 years, but their consequences are catastrophic, with several million deaths and global environmental disruptions.
Asteriod impacts: An asteroid impact with a diameter greater than one kilometer releases colossal energy, comparable to several million megatons of TNT, causing global fires, giant tsunamis, atmospheric disturbances, and mass extinctions. The probability of this event is very low, about one every 500,000 years, but the consequences are planetary with several billion possible deaths.
Nearby gamma-ray burst: Gamma-ray bursts are extremely energetic cosmic explosions, producing an intense beam of gamma rays. A burst located less than 6000 light-years away could expose the Earth to lethal radiation, causing partial destruction of the ozone layer and sterilizing a significant part of the biosphere. These events are extremely rare, with an infinitesimal probability on human scales, but their effects would be cataclysmic.

Table of Potential Major Natural Disasters

Extreme phenomena and estimated impacts according to their frequency
Phenomenon	Estimated Frequency	Physical Impact	Estimated Number of Deaths
Super hurricane	A few decades (5–10% per decade)	Winds > 250 km/h, massive coastal destruction	10,000 – 100,000
Mega fire	Decades to centuries (variable depending on climatic conditions)	Extreme forest fires destroying millions of hectares, massive pollution	Thousands to tens of thousands
Extreme global pandemic	A few centuries (0.1–1% per century)	Rapid spread of a highly lethal and contagious pathogen	Hundreds of thousands to several billion
Abrupt climate collapse	A few centuries to millennia (uncertain, potentially 0.1% per century)	Rapid change in global climate, impact on agriculture, water resources, migrations	Millions to hundreds of millions (indirect)
Hothouse Earth	Probably millennial (very uncertain)	Cascading climate runaway, ecosystem transformation, high CO₂ emissions	Hundreds of millions to billions (indirect)
Major solar storm	~Every 150 years (~0.7% per century)	Global electromagnetic disturbances, power grid failure	Indirect, potentially millions due to infrastructure collapse
Mega-earthquake	~Every 500 to 1000 years (0.1–0.2% per century)	Magnitude > 9, extensive regional destruction	Hundreds of thousands
Mega-tsunami	A few thousand years (~0.01% per century)	Waves > 30 m, massive coastal destruction	Millions
Detachment of an Antarctic block	Unknown, probably millennial (≤ 0.01% per century)	Rapid sea-level rise, submersion of coastal areas	Millions
Supervolcano	~Every 100,000 years (≪ 0.001% per century)	Massive eruption causing a global volcanic winter	Millions
Asteriod impact (>1 km)	~Every 500,000 years (≪ 0.0001% per century)	Intense energetic impact causing mass extinction	Billions
Nearby gamma-ray burst	Very rare event (< 0.0001% per century)	Intense cosmic explosion in gamma rays, partial sterilization of the biosphere	Millions to billions (depending on proximity)

Bibliographic References: Scenarios Beyond Fiction

IPCC, 2023: Climate Change 2023: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the IPCC.
Peterson, T.C., et al., 2013: Explosive volcanic eruptions and global climate change. Earth-Science Reviews, 129, 1-18.
Gehrels, N., et al., 2003: Ozone Depletion from Nearby Supernovae. Astrophysical Journal, 585(2), 1169–1176.
Rocca, M., et al., 2020: Superstorms and their socio-economic impacts: an interdisciplinary review. Environmental Research Letters, 15(4), 043001.
Smith, A.B., et al., 2016: Global Risk of Megafires in a Changing Climate. Nature Climate Change, 6, 839–844.
World Health Organization, 2020: Managing Epidemics: Key Facts About Major Deadly Diseases.
Melott, A.L., Thomas, B.C., 2011: Astrophysical ionizing radiation and Earth: a brief review and census of intermittent intense sources. Astrobiology, 11(4).