Extreme weather

thumb|A [[tornado is an example of an extreme weather event.]]

Extreme weather includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based on a location's recorded weather history. The main types of extreme weather include heat waves, cold waves, droughts, and heavy precipitation or storm events, such as tropical cyclones. Extreme weather can have various effects, from natural hazards such as floods and landslides to social costs on human health and the economy. Severe weather is a particular type of extreme weather which poses risks to life and property.

Weather patterns in a given region vary with time, and so extreme weather can be attributed, at least in part, to the natural climate variability that exists on Earth. For example, the El Niño-Southern Oscillation (ENSO) or the North Atlantic oscillation (NAO) are climate phenomena that impact weather patterns worldwide. Generally speaking, one event in extreme weather cannot be attributed to any one single cause. However, certain system wide changes to global weather systems can lead to increased frequency or intensity of extreme weather events.

Climate change might make some extreme weather events more frequent and more intense. This applies in particular to heat waves and cold waves. The extreme event attribution sector looks at possible explanations behind extreme events. Climate models indicate that rising temperatures might make extreme weather events worse worldwide.

Extreme weather has serious impacts on human society and on ecosystems. There is loss of human lives, damage to infrastructure and ecosystem destruction. Some human activities can exacerbate the effects, for example poor urban planning, wetland destruction, and building homes along floodplains.

Definition

thumb |upright=1.75 |One way of judging which weather events are extreme involves selecting events that exceed a certain threshold of intensity (or frequency, or impact, etc., not shown). This threshold might select events lying above a certain [[percentile or beyond a certain number of standard deviations above average. In the field of extreme event attribution, climate models then process the climate characteristics underlying the selected events for comparison to models of climates in which man-made climate drivers are excluded.]]

Extreme weather describes unusual weather events that are at the extremes of the historical distribution for a given area.Aside from being rare, extreme weather can also be determined by the severity, rate or effects of a specific weather episode. In fact, weather can be designated as extreme not only when it is statistically uncommon , but also when it causes substantial disruption to the impacted community or ecosystem.

In contrast, the World Meteorological Organization define severe weather as any aspect of the weather that poses risks to life, property or requires the intervention of authorities. Severe weather is thus a particular type of extreme weather.

Types

Definitions of extreme weather vary in different parts of the community, changing the outcomes of research from those fields. Types of extreme weather can include, but are not limited to, heavy precipitation, droughts, heat waves, cold waves, tornadoes, and hurricanes.

Heat waves

thumb|250px|[[2003 European heat wave]]

thumb |Analyzing >250 US cities, all but two experienced fewer freezing days in 2025 than in 1956. In 2025, on average, freezing days began 11 days later and ended 26 days earlier.

Some studies assert a connection between rapidly warming arctic temperatures and thus a vanishing cryosphere to extreme weather in mid-latitudes. In a study published in Nature in 2019, scientists used several simulations to determine that the melting of ice sheets in Greenland and Antarctica could affect overall sea level and sea temperature. Other models have shown that modern temperature rise and the subsequent addition of meltwater to the ocean could lead to a disruption of the thermohaline circulation, which is responsible for the movement of seawater and distribution of heat around the globe. A collapse of this circulation in the northern hemisphere could lead to an increase in extreme temperatures in Europe, as well as more frequent storms by throwing off natural climate variability and conditions. In this report, a 'climate-related event' refers to floods, storms, droughts, landslides, extreme temperatures (like heat waves or freezes), and wildfires; it excludes geophysical events such as volcanic eruptions, earthquakes, or mass movements.

The increasing probability of record week-long heat extremes occurrence depends on warming rate, rather than global warming level.

Some researchers attribute increases in extreme weather occurrences to more reliable reporting systems.

| image2= 1920- Category 5 Atlantic hurricanes.svg |caption2= Category 5 Atlantic hurricanes have become much more common in recent decades.

| image3= 1980- Cost of billion dollar hurricanes - US - variwide chart - NOAA data.svg |caption3= The number of $1 billion Atlantic hurricanes almost doubled since the 1980s, and costs have increased >elevenfold.

In 2020, the National Oceanic and Atmospheric Administration (NOAA) of the U.S. government predicted that, over the 21st Century, the frequency of tropical storms and Atlantic hurricanes would decline by 25 percent while their maximum intensity would rise by 5 percent.

Floods

alt=A reservoir with low water levels surrounded by dry, golden hills.|thumb|A California reservoir in 2015 with low water levels due to drought conditions. From [[2011–2017 California drought|2011 to 2017, California experienced one of its driest periods in recorded history.]]

Climate change has led to an increase in the frequency and/or intensity of certain types of extreme weather. Storms such as hurricanes or tropical cyclones may experience greater rainfall, causing major flooding events or landslides by saturating soil. This is because warmer air is able to 'hold' more moisture due to the water molecules having increased kinetic energy, and precipitation occurs at a greater rate because more molecules have the critical speed needed to fall as rain drops.

Human activities that exacerbate the effects

There are plenty of anthropogenic activities that can exacerbate the effects of extreme weather events. Urban planning often amplifies urban flooding impacts, especially in areas that are at increased risk of storms due to their location and climate variability. First, increasing the amount of impervious surfaces, such as sidewalks, roads, and roofs, means that less of the water from incoming storms is absorbed by the land. The destruction of wetlands, which act as a natural reservoir by absorbing water, can intensify the impact of floods and extreme precipitation. This can happen both inland and at the coast. However, wetland destruction along the coast can mean decreasing an area's natural 'cushion,' thus allowing storm surges and flood waters to reach farther inland during hurricanes or cyclones. Building homes below sea level or along a floodplain puts residents at increased risk of destruction or injury in an extreme precipitation event.

More urban areas can also contribute to the rise of extreme or unusual weather events. Tall structures can alter the way that wind moves throughout an urban area, pushing warmer air upwards and inducing convection, creating thunderstorms.

Effects

Extreme weather can also have serious consequences for public health. Heat waves, floods, cyclones and wildfires can all result in an increased number of cases of illness and death as well as mental health effects. Such disasters can also increase the demand on hospitals, emergency responders and public health agencies in response and recovery efforts.

Extreme weather can also have an impact on ecosystems. Temperature extremes and precipitation extremes may affect the survival of species, the condition of their habitats and ecological processes. These effects may matter outside the natural environment because ecosystems can support agriculture, regulate water flows and help shield humans against certain types of hazards.

Economic cost

In the face of record breaking extreme weather events, climate change adaptation efforts fall short while economists are confronted with inflation, the cost-of-living crisis, and economic uncertainty. In 2011 the IPCC estimated, that annual losses have ranged since 1980 from a few billion to above US$200 billion, with the highest economic losses occurring in 2005, the year of Hurricane Katrina. The global weather-related disaster losses, such as loss of human lives, cultural heritage, and ecosystem services, are difficult to value and monetize, and thus they are poorly reflected in estimates of losses. A 2023 study estimated that, the costs of extreme weather caused by climate change totaled about US$2.86 trillion between the years 2000 - 2019; this equates to approximately US$143 billion in losses each year.

The World Economic Forum Global Risks Perception Survey 2023–2024 (GRPS) found that 66 percent of respondents selected extreme weather as top risk. The survey was conducted after the 2023 heat waves. According to the GRPS results, the perception of necessary short and long-term risk management varies. Younger respondents prioritize environmental risks, including extreme weather, in the short-term. Respondents working in the private sector prioritize environmental risks as long-term.

Casualties

The death toll from natural disasters has declined over 90 percent since the 1920s, according to the International Disaster Database, even as the total human population on Earth quadrupled, and temperatures rose 1.3 °C. In the 1920s, 5.4 million people died from natural disasters while in the 2010s, just 400,000 did.

The most dramatic and rapid declines in deaths from extreme weather events have taken place in south Asia. Where a tropical cyclone in 1991 in Bangladesh killed 135,000 people, and a 1970 cyclone killed 300,000, the similarly-sized Cyclone Ampham, which struck India and Bangladesh in 2020, killed just 120 people in total.

On July 23, 2020, Munich Re announced that the 2,900 total global deaths from natural disasters for the first half of 2020 were a record-low, and "much lower than the average figures for both the last 30 years and the last 10 years."

A 2021 study found that 9.4% of global deaths between 2000 and 2019, ~5 million annually, can be attributed to extreme temperatures, with cold-related deaths making up 8.5% and decreasing, and heat-related deaths making up 0.9% and increasing.

A 2023 study published in The Lancet Planetary Health estimates that extreme cold events contributed to over 130,000 excess deaths annually and extreme heat events contributed to over 13,000 excess deaths annually in European urban areas between 2000 and 2019.

Agriculture

Extreme weather events destroy crops through multiple mechanisms, including physical damage from hail, wind and flooding, as well as physiological stress from temperature extremes and moisture deficits. One global study of cereal production between 1964 and 2007 found that a drought and extreme heat lowered national cereal production by 10%. The study also found that a drought impacted both the harvested area yields while extreme head by itself only reduced yield. These primary impacts often trigger secondary effects such as increased pest and disease pressure in weakened plants, creating cascading consequences that extend beyond the initial damage. For instance, increased humidity resulting from flooding can create favorable conditions for fungal pathogens, while stressed plants may exhibit compromised immune responses. Livestock systems experience similar multifaceted impacts, including direct mortality from extreme weather, heat stress.

Sources

References

External links

Statistics of Weather and Climate Extremes The University Corporation for Atmospheric Research (UCAR)
Research forecasts increased chances for stormy weather , Purdue University study
Severe world weather overview