Major natural disasters: what are the most likely threats?

Illustration of natural disasters — Natural disasters: The aftermath of a devastating tsunami on an inhabited coast.
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Scientific summary

This article examines major natural disasters according to their probability and potential impact. Threats are classified into regular events such as super hurricanes (5–10% per decade) and mega-fires, and into extremely rare but devastating phenomena: supervolcanic eruptions (<0.001% per century), asteroid impacts (<0.0001% per century) or nearby gamma-ray bursts. Intermediate risks include pandemics (0.1–1% per century), mega-earthquakes (0.1–0.2% per century) and abrupt climate collapses. Probabilistic analysis shows that high-frequency threats have a regional impact, while rare events can affect the entire biosphere, with human losses ranging from a few thousand to several billion.

What are the most likely and most devastating natural disasters?

The article draws up an inventory of natural threats by cross-referencing their frequency and their impact. The most likely events on a human scale are super hurricanes (5–10% per decade), mega-fires and major floods, whose damage is regional but significant (10,000 to 100,000 deaths). On a centennial scale, extreme pandemics (0.1–1% per century) and mega-earthquakes (0.1–0.2% per century) represent major risks, with potential losses reaching several million lives. Finally, cataclysmic phenomena such as supervolcanic eruptions (<0.001%), asteroid impacts larger than one kilometer (<0.0001%) or nearby gamma-ray bursts are extremely rare but capable of mass extinctions (several billion deaths). Between these extremes, abrupt climate collapse and the "Hothouse Earth" scenario present uncertain probabilities but potentially irreversible consequences for human societies.

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Natural disasters: between regularity and extreme rarity

Major natural disasters are high-impact events that can radically transform the environment and human societies. Some, such as 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.

Table of the worst potential 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 modification of the global climate, impact on agriculture, water resources, migrations	Millions to hundreds of millions (indirect)
Hothouse Earth	Probably millennial (very uncertain)	Cascading climate feedbacks, 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 failures	Indirect, potentially millions through infrastructure collapse
Mega-earthquake	~Every 500 to 1,000 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
Asteroid impact (>1 km)	~Every 500,000 years (<0.0001% per century)	Intense impact energy 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)

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 ocean conditions (>28°C) and complex atmospheric dynamics. The kinetic power dissipated 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 engulf several million hectares, temporarily modifying 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 timescales of decades to centuries depending on climate change 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 at between 0.1 and 1% per century.
Abrupt climate collapse: Abrupt climate collapse refers to a rapid and irreversible change in global climate regimes, often linked to disruption of water and carbon cycles and accelerated melting of polar ice. These modifications severely impact agricultural resources, water systems and cause massive human migrations. The probability remains uncertain but is estimated at around 0.1% per century, with indirect impacts on several hundred million individuals.
Hothouse Earth: This extreme scenario involves a cascading climate runaway where natural carbon sinks, such as the Amazon rainforest and permafrost, cease to store CO₂ or even become sources. This leads to an uncontrolled increase in global temperatures, transforming terrestrial and marine ecosystems, and destabilizing the biosphere. The probability is highly uncertain but is probably on a millennial scale, with a potential indirect impact on several hundred million to billion people.
Major solar storm: Intense solar flares release flows of energetic particles and electromagnetic pulses that can damage electrical and satellite infrastructure. 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 of magnitude greater than 9 result from the rupture of a very long portion of a major tectonic fault. The energy released is measured in hundreds of megatons of TNT. These events cause extensive regional destruction and massive human losses. Their frequency is about one per 500 to 1,000 years, i.e., 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, massive rapid melting of glaciers, or the sudden obstruction of river basins. These phenomena can generate colossal volumes of water submerging vast regions within hours to days, causing extensive destruction and very significant human losses. Their frequency is difficult to quantify but may be on the order of a few centuries to millennia depending on the geological and climatic context.
Detachment of an Antarctic block: The rupture and drift of a massive Antarctic ice block 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 it 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 luminosity. These events are extremely rare, about one every 100,000 years, but their consequences are catastrophic, with several million deaths and global environmental disruptions.
Asteroid impacts: An asteroid impact larger than one kilometer in diameter 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 deaths possible.
Nearby gamma-ray burst: Gamma-ray bursts are extremely energetic cosmic explosions, producing an intense beam of gamma rays. A burst located less than 6,000 light-years away could expose 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 timescales, but their effects would be cataclysmic.

References

FAQ: Everything you need to know about Major Natural Disasters

What is the most likely natural disaster in the coming decades?

According to the article, super hurricanes (winds >250 km/h) are the most frequent major threats, with a probability of 5 to 10% per decade. Mega-fires and extreme floods are also regular risks, whose probability increases with climate change. These events can cause massive destruction and human losses ranging from 10,000 to 100,000 people.

Which disasters are capable of affecting humanity on a planetary scale?

Several phenomena can have a global impact:
• Supervolcanic eruptions (every 100,000 years) cause a volcanic winter by projecting aerosols into the stratosphere, reducing solar luminosity.
• The impact of an asteroid larger than one kilometer (every 500,000 years) releases energy equivalent to several million megatons of TNT.
• Nearby gamma-ray bursts could partially destroy the ozone layer.
These events are extremely rare (probability <0.001% per century) but could lead to mass extinctions affecting several billion human beings.

What is the risk associated with abrupt climate change?

Abrupt climate collapse and the "Hothouse Earth" scenario represent long-term threats whose probabilities are uncertain (estimated at around 0.1% per century). These phenomena would involve cascading feedbacks: melting ice, release of permafrost methane, transformation of the Amazon rainforest into a CO₂ source. The impacts would be indirect but massive, affecting agriculture, water resources and forcing large-scale human migrations, with losses potentially reaching hundreds of millions to one billion people.

How are probabilities estimated for these rare events?

The probabilities presented in the article are derived from statistical models based on geological records (for eruptions and impacts), historical records (for hurricanes and earthquakes) and numerical simulations for future scenarios. For very rare events, uncertainties are large: a probability range is often indicated. For example, extreme pandemics are estimated at between 0.1 and 1% per century, while major impacts are described as "very low" due to the lack of historical data.

Which disasters are the deadliest in terms of potential victims?

The article's table ranks events according to their estimated human impact:
• Asteroid impact (>1 km): up to several billion deaths (mass extinction).
• Nearby gamma-ray burst: several million to billion (depending on distance).
• Extreme pandemic: from hundreds of thousands to several billion.
• Climate collapse / Hothouse Earth: hundreds of millions to billion (indirect impacts).
• Supervolcanic eruption: several million.
• Mega-tsunami or mega-earthquake: hundreds of thousands to millions.

Are there measures to prevent or mitigate these risks?

The article does not detail prevention measures, but it suggests that risk management relies on:
• Monitoring (seismic, meteorological, space networks).
• Early warning systems (for hurricanes, tsunamis, eruptions).
• Reducing vulnerabilities (earthquake-resistant construction, forest management).
• International cooperation for global threats (pandemics, climate).
Rare but cataclysmic events (asteroids, supervolcanoes) are the subject of detection programs and deflection strategies (for asteroids), although their implementation remains complex.