Natural Disasters

Summary

• Natural disasters kill on average 60,000 people per year, globally.
• Globally, disasters were responsible for 0.1% of deaths over the past decade. This was highly variable, ranging from 0.01% to 0.4%.
• Deaths from natural disasters have seen a large decline over the past century – from, in some years, millions of deaths per year to an average of 60,000 over the past decade.
• Historically, droughts and floods were the most fatal disaster events. Deaths from these events are now very low – the most deadly events today tend to be earthquakes.
• Disasters affect those in poverty most heavily: high death tolls tend to be centred in low-to-middle income countries without the infrastructure to protect and respond to events.

All our charts on Natural Disasters

• Accumulated Cyclone Energy of North Atlantic hurricanes
• Annual Heat Wave Index in the United States
• Average acres burned per wildfire in the United States
• Death rate from natural disasters
• Death rates from natural disasters
• Deaths from natural disasters as a share of total deaths
• Direct disaster economic loss
• Direct disaster economic loss as a share of GDP
• Direct economic loss attributed to disasters
• Disaster risk reduction progress score (1-5 scale; 5=best)
• Drought Severity Index
• Economic damage by natural disaster type
• Fatality rates due to lightning in the US
• Fatality rates in the US due to weather events
• Frequency of North Atlantic hurricanes
• Global damage costs from natural disasters
• Global deaths from natural disasters
• Global disaster losses as a share of GDP
• Global economic losses from disasters as a share of GDP
• Global injuries from natural disasters
• Global natural disaster death rates
• The global number affected by natural disasters
• Global precipitation anomaly
• Global reported natural disasters by type
• Global weather disaster losses as a share of GDP
• How many deaths does it take for a disaster in different continents to receive news coverage?
• How many deaths does it take for a disaster to receive news coverage?
• Hurricane landfalls in the United States
• Intensity error
• Internally displaced persons from natural disasters
• Natural disaster deaths by country
• News coverage of disasters
• News coverage of disasters, by continent
• Number left homeless from natural disasters
• Number of deaths from earthquakes
• Number of deaths from natural disasters
• Number of deaths from natural disasters by type
• Number of deaths from volcanic eruptions
• Number of known significant earthquakes
• Number of local governments that adopt disaster risk reduction strategies
• Number of people affected by natural disasters
• Number of recorded natural disaster events
• Number of significant volcanic eruptions
• Number of wildfires in the United States
• Power Dissipation Index (PDI) of North Atlantic cyclones
• Precipitation anomaly in the United States
• Score of adoption and implementation of national strategies in line with Sendai framework
• Score of adoption of legislative and/or regulatory provisions for managing disaster risk
• Share of US land area with unusually high summer temperatures
• Share of US land area with unusually low winter temperatures
• Share of land area which experienced extreme one-day precipitation, USA
• Share of land area with unusually high annual precipitation
• Share of local governments that adopt and implement local disaster risk reduction strategies
• Track error
• Wildfire acres burned in the United States
• Wildfire acres burned in the United States (not comparable)

Natural disasters kill on average 60,000 people per year and are responsible for 0.1% of global deaths

The number of deaths from natural disasters can be highly variable from year to year; some years pass with very few deaths before a large disaster event claims many lives.

If we look at the average over the past decade, approximately 60,000 people globally died from natural disasters each year. This represents 0.1% of global deaths.

In the visualizations shown here, we see the annual variability in the number and share of deaths from natural disasters in recent decades.

What we see is that in many years, the number of deaths can be very low – often less than 10,000, and accounting for as low as 0.01% of total deaths. But we also see the devastating impact of shock events: the 1983-85 famine and drought in Ethiopia; the 2004 Indian Ocean earthquake and tsunami; Cyclone Nargis which struck Myanmar in 2008; and the 2010 Port-au-Prince earthquake in Haiti. All of these events pushed global disasters deaths to over 200,000 – more than 0.4% of deaths in these years.

Low-frequency, high-impact events such as earthquakes and tsunamis are not preventable, but such high losses of human life are. We know from historical data that the world has seen a significant reduction in disaster deaths through earlier prediction, more resilient infrastructure, emergency preparedness, and response systems.

Those at low incomes are often the most vulnerable to disaster events: improving living standards, infrastructure and response systems in these regions will be key to preventing deaths from natural disasters in the coming decades.

What share of deaths is from natural disasters?

Globally, over the past decade, natural disasters accounted for an average of 0.1% of total deaths. This was, however, highly variable to high-impact events and ranged from 0.01% to 0.4% of total deaths.

In the map shown here, you can explore these trends by country over the past few decades. Using the timeline on the chart you can observe changes across the world over time, or by clicking on a country you can see its individual trend.

What we observe is that for most countries the share of deaths from natural disasters is very low in most years. Often it can be zero – with no loss of life to disasters – or well below 0.01%. But we also see clearly the effects of low-frequency but high-impact events: in 2010, more than 70% of deaths in Haiti were the result of the Port-au-Prince earthquake.

Number of deaths from natural disasters

IN THIS SECTION

• Annual deaths from natural disasters
• Average number of deaths by decade
• Number of deaths by type of natural disaster

Annual deaths from natural disasters

In the visualization shown here, we see the long-term global trend in natural disaster deaths. This shows the estimated annual number of deaths from disasters from 1900 onwards from the EMDAT International Disaster Database.

What we see is that in the early-to-mid 20th century, the annual death toll from disasters was high, often reaching over one million per year. In recent decades we have seen a substantial decline in deaths. In most years fewer than 20,000 die (and in the most recent decade, this has often been less than 10,000). Even in peak years with high-impact events, the death toll has not exceeded 500,000 since the mid-1960s.

This decline is even more impressive when we consider the rate of population growth over this period. When we correct for population – showing this data in terms of death rates (measured per 100,000 people) – we see an even greater decline over the past century.

The annual number of deaths from natural disasters is also available by country since 1990. This can be explored in the interactive map.

Average number of deaths by decade

In the chart we show global deaths from natural disasters since 1900, but rather than reporting annual deaths, we show the annual average by decade.

As we see, over the course of the 20th century there was a significant decline in global deaths from natural disasters. In the early 1900s, the annual average was often in the range of 400,000 to 500,000 deaths. In the second half of the century and into the early 2000s, we have seen a significant decline to less than 100,000 – at least five times lower than these peaks.

This decline is even more impressive when we consider the rate of population growth over this period. When we correct for population – showing this data in terms of death rates (measured per 100,000 people) – then we see a more than 10-fold decline over the past century.

Number of deaths by type of natural disaster

In the visualization shown here, we see the number of deaths globally by type of disaster – earthquakes, volcanic activity, or extreme weather, for example. You can add additional ‘disaster categories’ on the interactive chart.

This data is shown from 1900 onwards. If we explore these categories we see that historically earthquakes, floods and droughts could result in a large number of deaths. Over the last few decades, most years with a high death toll tend to result from large earthquake events.

We have also visualized this data in a single chart, where the number of deaths from each disaster type is represented by the bubble size. Once again, the devastating impacts of drought, flood and earthquake events of the past become clear. But what we also observe is the significant decline in deaths from almost all types of disasters with the exception of earthquakes and extreme weather.

When we consider that the world population has also grown rapidly over this period, this reduction in deaths is even more impressive. Here we show this trend as death rates, which corrects for population growth over this period.

Injuries and displacement from disasters

Human impacts from natural disasters are not fully captured in mortality rates. Injury, homelessness, and displacement can all have a significant impact on populations.

The visualization below shows the number of people displaced internally (i.e. within a given country) from natural disasters. Note that these figures report on the basis of new cases of displaced persons: if someone is forced to flee their home from natural disasters more than once in any given year, they will be recorded only once within these statistics.

Interactive charts on the following global impacts are available using the links below:

• Injuries: number of people injured is defined as “People suffering from physical injuries, trauma or an illness requiring immediate medical assistance as a direct result of a disaster.”
• Homelessness: number of people homeless is defined as the “Number of people whose house is destroyed or heavily damaged and therefore need shelter after an event.”
• Affected: number of people affected is defined as “People requiring immediate assistance during a period of emergency, i.e. requiring basic survival needs such as food, water, shelter, sanitation and immediate medical assistance.”
• Total number affected: total number of people affected is defined as “the sum of the injured, affected and left homeless after a disaster.”

Natural disasters by type

IN THIS SECTION

• Earthquakes
• Volcanoes
• Landslides
• Famines & Droughts
• Hurricanes, Tornados, and Cyclones
• Extreme precipitation and flooding
• Extreme Temperature (Heat & Cold)
• Wildfires
• Lightning

Earthquakes

Earthquake events

Earthquake events occur across the world every day. The US Geological Survey (USGS) tracks and reports global earthquakes, with (close to) real-time updates.

However, the earthquakes which occur most frequently are often too small to cause significant damage (whether to human life or in economic terms).

In the chart below we show the long history of known earthquakes classified by the National Geophysical Data Center (NGDC) of the NOAA as ‘significant’ earthquakes. Significant earthquakes are those which are large enough to cause notable damage. They must meet at least one of the following criteria: caused deaths, moderate damage ($1 million or more), magnitude 7.5 or greater, Modified Mercalli Intensity (MMI) X or greater or generated a tsunami.

Available data — which you can explore in the chart below — extends back to 2150 BC. But we should be aware that the most recent records will be much more complete than our long-run historic estimates. An increase in the number of recorded earthquakes doesn’t necessarily mean this was the true trend over time. By clicking on a country in the map below, you can view its full series of known significant earthquakes.

Deaths from earthquakes

Alongside estimates of the number of earthquake events, the National Geophysical Data Center (NGDC) of the NOAA also publishes estimates of the number of deaths over this long-term series. In the chart below we see the estimated mortality numbers from 2000 BC through to 2017.

These figures can be found for specific countries using the “change country” function in the bottom-left of the chart, or by selecting the “map” on the bottom right.

At the global level, we see that earthquake deaths have been a persistent human risk through time.

What were the world’s deadliest earthquakes?

The number of people dying in natural disasters is lower today than it was in the past, the world has become more resilient.

Earthquakes, however, can still claim a large number of lives. Whilst historically floods, droughts and epidemics dominated disaster deaths, a high annual death toll now often results from a major earthquake and possibly a tsunami caused by them. Since 2000, the two peak years in annual death tolls (reaching 100s of thousands) were 2004 and 2010. Earthquake deaths accounted for 93 percent and 69 percent of such deaths, respectively. In fact, both events (the Sumatra earthquake and tsunami of 2004, and Port-au-Prince earthquake in 2010) are in the deadliest earthquake rankings below.

What have been the most deadly earthquakes in human history? In the visualization below we have mapped the top 10 rankings of known earthquakes which resulted in the largest number of deaths. This ranking is based on mortality estimates from the NOAA’s National Geophysical Data Center (NGDC).

This ranking is also summarized in table form.

The most deadly earthquake in history was in Shaanxi, China in 1556. It’s estimated to have killed 830,000 people. This is more than twice that of the second most fatal: the recent Port-au-Prince earthquake in Haiti in 2010. It’s reported that 316,000 people died as a result.

Two very recent earthquakes — the Sumatra earthquake and tsunami of 2004, and the 2010 Port-au-Prince earthquake — feature amongst the most deadly in human history. But equally, some of the most fatal occurred in the very distant past. Making the top three was the earthquake in Antakya (Turkey) in the year 115. Both old and very recent features are near the top of the list. The deadly nature of earthquakes has been a persistent threat throughout our history.

Volcanoes

Number of significant volcanic eruptions

There are a large number of volcanoes across the world that are volcanically active but display little or only very low-level activity.

On the map, we see the number of significant volcanic eruptions which occur in each country in a given year. A significant eruption is classified as one that meets at least one of the following criteria: caused fatalities, caused moderate damage (approximately $1 million or more), with a Volcanic Explosivity Index of 6 or larger, caused a tsunami, or was associated with a major earthquake.

Estimates of volcanic eruptions are available dating back as early as 1750 BCE, however, the data completeness for long historic events will be much lower than in the recent past.

Deaths from volcanic eruptions

In the visualization, we see the number of deaths from significant volcanic eruptions across the world. Using the timeline on the map we can see the frequency of volcanic activity deaths over time.

If we look at deaths over the past century we see several high-impact events: the Nevado del Ruiz eruption in Colombia in 1985; the Mount Pelée eruption in Martinique in 1902; and the 1883 eruption of Krakatoa in Indonesia.

Landslides

This visualization – sourced from the NASA Socioeconomic Data And Applications Center (SEDAC) – shows the distribution of mortality risk from landslides across the world.

As we would expect, the risks of landslides are much greater close to high mountainous regions with dense neighbouring populations. This makes the mortality risk highest across the Andes region in South America and the Himalayas across Asia.

Famines & Droughts

We cover the history of Famines in detail in our dedicated entry here. For this research, we assembled a new global dataset on famines from the 1860s until 2016.

In the visualization shown here, we see trends in drought severity in the United States. Given is the annual data of drought severity, plus the 9-year average.

This is measured by The Palmer Drought Severity Index: the average moisture conditions observed between 1931 and 1990 at a given location is given an index value of zero. A positive value means conditions are wetter than average, while a negative value is drier than average. A value between -2 and -3 indicates moderate drought, -3 to -4 is severe drought, and -4 or below indicates extreme drought.

Hurricanes, Tornados, and Cyclones

Long-term trends in deaths from US weather events

Trends in the US provide some of the most complete data on impacts and deaths from weather events over time.

This chart shows death rates from lightning and other weather events in the United States over time. Death rates are given as the number of deaths per million individuals. Over this period, we see that on average each has seen a significant decline in death rates. This is primarily the result of improved infrastructure, predicted and response systems to disaster events.

Frequency of North Atlantic Hurricanes

The visualization here shows the frequency of North Atlantic Hurricanes – given as the total number, and a number of ‘major’ hurricanes in any given year. A ‘major’ hurricane is defined as category 3, 4 or 5 on the Saffir–Simpson hurricane wind scale (SSHWS).

This data is also available specifically for the United States, shown as the number of hurricanes that reach landfall in the US. In this visualization, you can add or remove ‘categories’ of hurricanes to focus on the trend in a particular category (e.g. major hurricanes) over time.

If we focus on the most powerful hurricanes – categories 4 and 5 – for example, we do not see a clear trend in the frequency of events over time.

The intensity of North Atlantic Hurricanes

The frequency of hurricanes is important, but so too is the intensity and power that they carry.

The visualizations here use two metrics to define this: the accumulated cyclone energy (ACE), an index that measures the activity of a cyclone season; and the power dissipation index of cyclones.

Extreme precipitation and flooding

Precipitation anomalies

In the visualization shown we see the global precipitation anomaly each year; trends in the US-specific anomaly can be found here.

This precipitation anomaly is measured relative to the century average from 1901 to 2000. Positive values indicate a wetter year than normal; negative values indicate a drier year.

Also shown is US-specific data on the share of land area which experiences unusually high precipitation in any given year.

Precipitation extremes

We can look at precipitation anomalies over the course of a year, however, flooding events are often caused by intense rainfall over much shorter periods. Flooding events tend to occur when there is extremely high rainfall over the course of hours or days.

The visualization here shows the extent of extreme one-day precipitation in the US. What we see is a general upwards trend in the extent of extreme rainfall in recent decades.

Extreme Temperature (Heat & Cold)

Extreme temperature risks to human health and mortality can result from both exposures to extreme heat and cold.

Heatwaves and high temperatures

In the visualizations shown here, we see long-term data on heatwaves and unusually high temperatures in the United States.

Overall we see there is significant year-to-year variability in the extent of heatwave events. What stands out over the past century of data was the 1936 North American heatwave – one of the most extreme heatwave events in modern history, which coincided with the Great Depression and Dust Bowl of the 1930s.

1936 North American heat wave - Wikipedia

Wikimedia Foundation, Inc.Contributors to Wikimedia projects

When we look at the trajectory of unusually high summer temperatures over time (defined as ‘unusually high’ in the context of historical records) we see an upward trend in recent decades.

Cold temperatures

Whilst we often focus on the heatwave and warm temperatures in relation to weather extremes, extremely low temperatures can often have a high toll on human health and mortality.

In the visualization here we show trends in the share of US land areas experiencing unusually low winter temperatures. In recent years there appears to have been a declining trend in the extent of the US experiencing particularly cold winters.

Wildfires

US Wildfires

How are the frequency and extent of wildfires in the United States changing over time?

In the charts below we provide three overviews: the number of wildfires, the total acres burned, and the average acres burned per wildfire. This data is shown from 1983 onwards when comparable data recording began.

Over the past 30-35 years we notice three general trends in the charts below (although there is significant year-to-year variability):

• on average, the annual number of wildfires has not changed much;
• on average, the total acres burned has increased from the 1980s and 1990s into the 21st century;
• the combination of these two factors suggests that the average number of acres burned per wildfire has increased.

There has been significant media coverage of the long-run statistics of US wildfires reported by the National Interagency Fire Center (NIFC). The original statistics are available back to the year 1926. When we look at this long-term series (our chart is here) it suggests there has been a significant decline in acres burned over the past century. However, the NIFC explicitly states:

Prior to 1983, sources of these figures are not known, or cannot be confirmed, and were not derived from the current situation reporting process. As a result the figures prior to 1983 should not be compared to later data.

Representatives from the NIFC have again confirmed (see the Carbon Brief’s coverage here) that these historic statistics are not comparable to those since 1983. The lack of reliable methods of measurement and reporting means some historic statistics may in fact be double or triple-counted in national statistics.

This means we cannot compare the recent data below with old, historic records. But it also doesn’t confirm that acres burned today are higher than in the first half of the 20th century. Historically, fires were an often-used method of clearing land for agriculture, for example. It’s not implausible to expect that wildfires of the past may have been larger than today but the available data is not reliable enough to confirm this.

Lightning

Long-term trends in US lightning strikes

This chart shows the declining death rate due to lightning strikes in the US.

In the first decade of the 20th century, the average annual rate of deaths was 4.5 per million people in the US. In the first 15 years of the 21st century, the death rate had declined to an average of 0.12 deaths per million. This is a 37-fold reduction in the likelihood of being killed by lightning in the US.

Lightning strikes across the world

The map here shows the distribution of lightning strikes across the world. This is given as the lightning strike density – the average strikes per square kilometre each year.

In particular, we see the high frequency of strikes across the Equatorial regions, especially across central Africa.

Economic costs

IN THIS SECTION

• Global disaster costs
• Disaster costs by country

Global disaster costs

Natural disasters not only have devastating impacts in terms of the loss of human life but can also cause severe destruction with economic costs.

When we look at global economic costs over time in absolute terms we tend to see rising costs. But, importantly, the world – and most countries – have also gotten richer. Global gross domestic product has increased more than four-fold since 1970. We might therefore expect that for any given disaster, the absolute economic costs could be higher than in the past.

A more appropriate metric to compare economic costs over time is to look at them in relation to GDP. This is the indicator adopted by all countries as part of the UN Sustainable Development Goals to monitor progress on resilience to disaster costs.

In the chart shown here, we see global direct disaster losses given as a share of GDP. There is notable year-to-year variability in costs – ranging from 0.15% to 0.5% of global GDP. In recent decades there has been no clear trending increase in damages when we take account of economic growth over this period.

This is also true when we look at damages specifically for weather-related disasters. This trend in damages relative to global GDP is also shown in the interactive chart.

Disaster costs by country

Since economic losses from disasters in relation to GDP is the indicator adopted by all countries within the UN Sustainable Development Goals, this data is also now reported for each country.

The map shows direct disaster costs for each country as a share of its GDP. Here we see large variations by country – a 100-fold difference ranging from less than 0.05% to 5%.

Not all deaths are equal: How many deaths make a natural disaster newsworthy?

How many deaths does it take for a natural disaster to be newsworthy?

This is a question researchers Thomas Eisensee and David Strömberg asked in a 2007 study.

The two authors found that for every person killed by a volcano, nearly 40,000 people have to die of a food shortage to get the same probability of coverage in US televised news.

The type of disaster matters

In other words, the type of disaster matters to how newsworthy networks find it to be. The visualizations show the extent of this observed “news effect”. The chart shows the proportion of each type of disaster that receives news coverage, and the second shows the “casualties ratio”, which tells us—all else equal—how many casualties would make media coverage equally likely for each type of disaster.

The study, which primarily set out to examine mass media’s influence on US natural disaster response, considered over 5,000 natural disasters and 700,000 news stories from the major US national broadcast networks (ABC, CBS, NBC, and CNN) between 1968 and 2002.

The findings tell us, among other important things, that networks tend to be selective in their coverage and attention is not reflecting the severity and number of people killed or affected by a natural disaster.

Instead of considering the objective damage caused by natural disasters, networks tend to look for disasters that are “rife with drama”, as one New York Times article put it¹²—hurricanes, tornadoes, forest fires, earthquakes all make for splashy headlines and captivating visuals.

Thanks to this selectivity, less “spectacular” but oftentimes more deadly natural disasters tend to get passed over. Food shortages, for example, result in the most casualties and affect the most people per incident but their onset is more gradual than that of a volcanic explosion or sudden earthquake. As a result, food shortages are covered only 3% of the time while a comparatively indulgent 30% of earthquakes and volcanic events get their time in the spotlight.

Additionally, when the researchers “hold all else equal” by controlling for factors such as yearly trends in news intensity and the number of people killed and affected, the difference in coverage is even more pronounced.

This bias for the spectacular is not only unfair and misleading but also has the potential to misallocate attention and aid. Disasters that happen in an instant leave little time for preventative intervention. On the other hand, the gradual disasters that tend to affect more lives build up slowly, allowing more time for preventative measures to be taken. However, in a Catch-22 situation, the gradual nature of these calamities is also what prevents them from garnering the media attention they deserve.

And the location of the disaster matters too

There are other biases, too. Eisensee and Strömberg found that while television networks cover more than 15% of the disasters in Europe and South Central America, they show less than 5% of the disasters in Africa and the Pacific. Disasters in Africa tend to get less coverage than ones in Asia because they are less “spectacular”, with more droughts and food shortages occurring there relative to Asia.

However, after controlling for disaster type, along with other factors such as the number killed and the timing of the news, there is no significant difference between the coverage of African and Asian disasters. Instead, a huge difference emerges between coverage of Africa, Asia, and the Pacific on the one hand, and Europe and South and Central America, on the other.

According to the researchers’ estimates, 45 times as many people would have to die in an African disaster for it to garner the same media attention as a European one. The two visualizations show the extent of this bias.

ABC News’s slogan is “See the whole picture” and CNN’s is “Go there”, but good follow-up questions might be: what exactly, and where?

The link between poverty and deaths from natural disasters

One of the major successes over the past century has been the dramatic decline in global deaths from natural disasters – this is despite the fact that the human population has increased rapidly over this period.

Behind this improvement has been the improvement in living standards; access to and development of resilient infrastructure; and effective response systems. These factors have been driven by an increase in incomes across the world.

What remains true today is that populations in low-income countries – those where a large percentage of the population still live in extreme poverty or score low on the Human Development Index – are more vulnerable to the effects of natural disasters.

We see this effect in the visualization shown. This chart shows the death rates from natural disasters – the number of deaths per 100,000 population – of countries grouped by their socio-demographic index (SDI). SDI is a metric of development, where low-SDI denotes countries with low standards of living.

What we see is that the large spikes in death rates occur almost exclusively for countries with a low or low-middle SDI. Highly developed countries are much more resilient to disaster events and therefore have a consistently low death rate from natural disasters.

Note that this does not mean low-income countries have high death tolls from disasters year to year: the data here shows that in most years they also have very low death rates. But when low-frequency, high-impact events do occur they are particularly vulnerable to its effects.

Overall development, poverty alleviation, and knowledge-sharing of how to increase resilience to natural disasters will therefore be key to reducing the toll of disasters in the decades to come.

Definitions & Metrics

Hurricanes, cyclones & typhoons

There are multiple terms used to describe extreme weather events: hurricanes, typhoons, cyclones and tornadoes. What is the difference between these terms, and how are they defined?

The terms hurricane, cyclone and typhoon all refer to the same thing; they can be used interchangeably. Hurricanes and typhoons are both described as the weather phenomenon ‘tropical cyclone’. A tropical cyclone is a weather event that originates over tropical or subtropical waters and results in a rotating, organized system of clouds and thunderstorms. Its circulation patterns should be closed and low-level.

The choice of terminology is location-specific and depends on where the storm originates. The term hurricane is used to describe a tropical cyclone that originates in the North Atlantic, central North Pacific, and eastern North Pacific. When it originates in the Northwest Pacific, we call it a typhoon. In the South Pacific and the Indian Ocean, the general term tropical cyclone is used.

In other words, the only difference between a hurricane and a typhoon is where it occurs.

When does a storm become a hurricane?

The characteristics of a hurricane are described in detail on the NASA website.

What Are Hurricanes?

Hurricanes are large swirling storms that form over warm ocean waters.

NASA

A hurricane evolves from a tropical disturbance or storm based on a threshold of wind speed.

A tropical disturbance arises over warm ocean waters. It can grow into a tropical depression which is an area of rotating thunderstorms with winds up to 62 kilometres (38 miles) per hour. From there, a depression evolves into a tropical storm if its wind speed reaches 63 km/hr (39 mph).

Finally, a hurricane is formed when a tropical storm reaches a wind speed of 119 km/hr (74 mph).

Difference between hurricanes and tornadoes

But, hurricanes/typhoons/cyclones are distinctly different from tornadoes.

What is the difference between a tornado and a hurricane? | NASA Global Precipitation Measurement Mission

Tornadoes and hurricanes appear to be similar in their general structure. Both are characterized by extremely strong horizontal winds swirling around the center, strong upward motion dominating the circulation with some downward motion in the center. The tangential winds far exceed the radial inflow…

NASA Global Precipitation Measurement Mission

Whilst hurricanes and tornadoes have a characteristic circulatory wind pattern, they are very different weather systems. The main difference between the systems is scale (tornadoes are small-scale circulatory systems; hurricanes are large-scale). These differences are highlighted in the table below:

Volcanic Explosivity Index (VEI)

The intensity or size of volcanic eruptions are most commonly defined by a metric termed the ‘volcanic explosivity index (VEI)’. The VEI is derived based on the erupted mass or deposit of an eruption. The scale for VEI was outlined by Newhall & Self (1982) but is now commonly adopted in geophysical reporting.

The table below provides a summary (from the NOAA’s National Geophysical Data Center) of the characteristics of eruptions of different VEI values. A ‘Significant Volcanic Eruption’ is often defined as an eruption with a VEI value of 6 or greater. Historic eruptions that were definitely explosive, but carry no other descriptive information is assigned a default VEI of 2.

Data Quality

Number of reported disaster events

A key issue of data quality is the consistency of even reporting over time. For long-term trends in natural disaster events, we know that reporting and recording of events today is much more advanced and complete than in the past. This can lead to significant underreporting or uncertainty of events in the distant past.

In the chart here we show data on the number of reported natural disasters over time.

This change over time can be influenced by a number of factors, namely the increased coverage of reporting over time. The increase over time is therefore not directly reflective of the actual trend in disaster events.

Number of reported disasters by type

This same data is shown here as the number of reported disaster events by type. Again, the incompleteness of historical data can lead to significant underreporting in the past. The increase over time is therefore not directly reflective of the actual trend in disaster events.