|Part of the nature series|
Extreme weather includes unexpected, unusual, unpredictable, severe or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past.Often, extreme events are based on a location’s recorded weather history and defined as lying in the most unusual ten percent. In recent years some extreme weather events have been attributed to human-induced global warming, with studies indicating an increasing threat from extreme weather in the future.
Severe weather refers to any dangerous meteorological phenomena with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atmospheric conditions. High winds, hail, excessive precipitation, and wildfires are forms and effects of severe weather, as are thunderstorms, downbursts, tornadoes, waterspouts, tropical cyclones, and extratropical cyclones. Regional and seasonal severe weather phenomena include blizzards (snowstorms), ice storms, and duststorms.
Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the lowest level of the atmosphere, the troposphere, just below the stratosphere. Weather refers to day-to-day temperature and precipitation activity, whereas climate is the term for the averaging of atmospheric conditions over longer periods of time. When used without qualification, "weather" is generally understood to mean the weather of Earth.
Global warming is a long-term rise in the average temperature of the Earth's climate system, an aspect of climate change shown by temperature measurements and by multiple effects of the warming. Though earlier geological periods also experienced episodes of warming, the term commonly refers to the observed and continuing increase in average air and ocean temperatures since 1900 caused mainly by emissions of greenhouse gasses in the modern industrial economy. In the modern context the terms global warming and climate change are commonly used interchangeably, but climate change includes both global warming and its effects, such as changes to precipitation and impacts that differ by region. Many of the observed warming changes since the 1950s are unprecedented in the instrumental temperature record, and in historical and paleoclimate proxy records of climate change over thousands to millions of years.
According to IPCC (2011) estimates of annual losses have ranged since 1980 from a few billion to above US$200 billion (in 2010 dollars), with the highest value for 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.
Hurricane Katrina was an extremely destructive and deadly Category 5 hurricane that made landfall on Florida and Louisiana, particularly the city of New Orleans and the surrounding areas, in August 2005, causing catastrophic damage from central Florida to eastern Texas. Subsequent flooding, caused largely as a result of fatal engineering flaws in the flood protection system known as levees around the city of New Orleans, precipitated most of the loss of lives. The storm was the third major hurricane of the record-breaking 2005 Atlantic hurricane season, as well as the fourth-most intense Atlantic hurricane on record to make landfall in the United States, behind only the 1935 Labor Day hurricane, Hurricane Camille in 1969, and Hurricane Michael in 2018.
Ecosystem services are the many and varied benefits that humans freely gain from the natural environment and from properly-functioning ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystems, grassland ecosystems and aquatic ecosystems. Collectively, these benefits are becoming known as 'ecosystem services', and are often integral to the provisioning of clean drinking water, the decomposition of wastes, and the natural pollination of crops and other plants.
Heat waves are periods of abnormally high temperatures and heat index. Definitions of a heatwave vary because of the variation of temperatures in different geographic locations.Excessive heat is often accompanied by high levels of humidity, but can also be catastrophically dry.
The heat index (HI) or humiture is an index that combines air temperature and relative humidity, in shaded areas, to posit a human-perceived equivalent temperature, as how hot it would feel if the humidity were some other value in the shade. The result is also known as the "felt air temperature", "apparent temperature", "real feel" or "feels like". For example, when the temperature is 32 °C (90 °F) with 70% relative humidity, the heat index is 41 °C (106 °F). This heat index temperature has an implied (unstated) humidity of 20%. This is the value of relative humidity for which the heat index number equals the actual air temperature.
Humidity is the amount of water vapour present in air. Water vapour, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. The amount of water vapour needed to achieve saturation increases as the temperature increases. As the temperature of a parcel of air decreases it will eventually reach the saturation point without adding or losing water mass. The amount of water vapour contained within a parcel of air can vary significantly. For example, a parcel of air near saturation may contain 28 grams of water per cubic metre of air at 30 °C, but only 8 grams of water per cubic metre of air at 8 °C.
Because heat waves are not visible as other forms of severe weather are, like hurricanes, tornadoes, and thunderstorms, they are one of the less known forms of extreme weather.Severe heat weather can damage populations and crops due to potential dehydration or hyperthermia, heat cramps, heat expansion and heat stroke. Dried soils are more susceptible to erosion, decreasing lands available for agriculture. Outbreaks of wildfires can increase in frequency as dry vegetation has increased likeliness of igniting. The evaporation of bodies of water can be devastating to marine populations, decreasing the size of the habitats available as well as the amount of nutrition present within the waters. Livestock and other animal populations may decline as well.
In physiology, dehydration is a deficit of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mild dehydration can also be caused by immersion diuresis, which may increase risk of decompression sickness in divers.
Hyperthermia is a condition where an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme temperature elevation occurs, it becomes a medical emergency requiring immediate treatment to prevent disability or death.
Heat cramps, a type of heat illness, are muscle spasms that result from loss of large amount of salt and water through exercise. Heat cramps are associated with cramping in the abdomen, arms and calves. This can be caused by inadequate consumption of fluids or electrolytes. Heavy sweating causes heat cramps, especially when the water is replaced without also replacing salt or potassium.
During excessive heat plants shut their leaf pores (stomata), a protective mechanism to conserve water but also curtails plants' absorption capabilities. This leaves more pollution and ozone in the air, which leads to a higher mortality in the population. It has been estimated that extra pollution during the hot summer 2006 in the UK, cost 460 lives.The European heat waves from summer 2003 are estimated to have caused 30,000 excess deaths, due to heat stress and air pollution. Over 200 U.S cities have registered new record high temperatures. The worst heatwave in the USA occurred in 1936 and killed more than 5000 people directly. The worst heat wave in Australia occurred in 1938-39 and killed 438. The second worst was in 1896.
The 1936 North American heat wave was one of the most severe heat waves in the modern history of North America. It took place in the middle of the Great Depression and Dust Bowl of the 1930s and caused catastrophic human suffering and an enormous economic toll. The death toll exceeded 5,000, and huge numbers of crops were destroyed by the heat and lack of moisture. Many state and city record high temperatures set during the 1936 heat wave stood until the summer 2012 North American heat wave. The 1936 heat wave followed one of the coldest winters on record.
Power outages can also occur within areas experiencing heat waves due to the increased demand for electricity (i.e. air conditioning use).The urban heat island effect can increase temperatures, particularly overnight.
An urban heat island (UHI) is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference usually is larger at night than during the day, and is most apparent when winds are weak. UHI is most noticeable during the summer and winter. The main cause of the urban heat island effect is from the modification of land surfaces. Waste heat generated by energy usage is a secondary contributor. As a population center grows, it tends to expand its area and increase its average temperature. The less-used term heat island refers to any area, populated or not, which is consistently hotter than the surrounding area.
A cold wave is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in temperature within a 24-hour period requiring substantially increased protection to agriculture, industry, commerce, and social activities. The precise criterion for a cold wave is determined by the rate at which the temperature falls, and the minimum to which it falls. This minimum temperature is dependent on the geographical region and time of year.Cold waves generally are capable of occurring any geological location and are formed by large cool air masses that accumulate over certain regions, caused by movements of air streams.
A cold wave can cause death and injury to livestock and wildlife. Exposure to cold mandates greater caloric intake for all animals, including humans, and if a cold wave is accompanied by heavy and persistent snow, grazing animals may be unable to reach necessary food and water, and die of hypothermia or starvation. Cold waves often necessitate the purchase of fodder for livestock at considerable cost to farmers.Human populations can be inflicted with frostbites when exposed for extended periods of time to cold and may result in the loss of limbs or damage to internal organs.
Extreme winter cold often causes poorly insulated water pipes to freeze. Even some poorly protected indoor plumbing may rupture as frozen water expands within them, causing property damage. Fires, paradoxically, become more hazardous during extreme cold. Water mains may break and water supplies may become unreliable, making firefighting more difficult.
Cold waves that bring unexpected freezes and frosts during the growing season in mid-latitude zones can kill plants during the early and most vulnerable stages of growth. This results in crop failure as plants are killed before they can be harvested economically. Such cold waves have caused famines. Cold waves can also cause soil particles to harden and freeze, making it harder for plants and vegetation to grow within these areas. One extreme was the so-called Year Without a Summer of 1816, one of several years during the 1810s in which numerous crops failed during freakish summer cold snaps after volcanic eruptions reduced incoming sunlight.
In general climate models show that with climate change, the planet will experience more extreme weather.In particular temperature record highs outpace record lows and some types of extreme weather such as extreme heat, intense precipitation, and drought have become more frequent and severe in recent decades. Some studies assert a connection between rapidly warming arctic temperatures and thus a vanishing cryosphere to extreme weather in mid-latitudes.
In the PNAS, Steven C. Sherwood and Matthew Huber state that humans and other mammals cannot tolerate a wet-bulb temperature of over 35 °C for extended periods, and that this "would begin to occur with global-mean warming of about 7 °C ... With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning."
There has been long ongoing debate about a possible increase of tropical cyclones as an effect of global warming.However, the 2012 IPCC special report on extreme events SREX states that "there is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities." Increases in population densities increase the number of people affected and damage caused by an event of given severity. The World Meteorological Organization and the U.S. Environmental Protection Agency have in the past linked increasing extreme weather events to global warming, as have Hoyos et al. (2006), writing that the increasing number of category 4 and 5 hurricanes is directly linked to increasing temperatures. Similarly, Kerry Emanuel in Nature writes that hurricane power dissipation is highly correlated with temperature, reflecting global warming.
Hurricane modeling has produced similar results, finding that hurricanes, simulated under warmer, high CO2 conditions, are more intense than under present-day conditions. Thomas Knutson and Robert E. Tuleya of the NOAA stated in 2004 that warming induced by greenhouse gas may lead to increasing occurrence of highly destructive category-5 storms.Vecchi and Soden find that wind shear, the increase of which acts to inhibit tropical cyclones, also changes in model-projections of global warming. There are projected increases of wind shear in the tropical Atlantic and East Pacific associated with the deceleration of the Walker circulation, as well as decreases of wind shear in the western and central Pacific. The study does not make claims about the net effect on Atlantic and East Pacific hurricanes of the warming and moistening atmospheres, and the model-projected increases in Atlantic wind shear.
In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes and dust devils lie within smaller mesoscale. Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the tropical upper tropospheric trough during the summer months in the Northern Hemisphere. Cyclones have also been seen on extraterrestrial planets, such as Mars and Neptune. Cyclogenesis is the process of cyclone formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones. These zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their life cycle, extratropical cyclones occlude as cold air masses undercut the warmer air and become cold core systems. A cyclone's track is guided over the course of its 2 to 6 day life cycle by the steering flow of the subtropical jet stream.
Hurricane Catarina was an extremely rare South Atlantic tropical cyclone that hit Southern Brazil in late March 2004. The storm developed out of a stationary cold-core upper-level trough on March 12. Almost a week later, on March 19, a disturbance developed along the trough and traveled towards the east-southeast until March 22 when a ridge stopped the forward motion of the disturbance. The disturbance was in an unusually favorable environment with a slightly below-average wind shear and above-average sea surface temperatures. The combination of the two led to a slow transition from an extratropical cyclone to a subtropical cyclone by March 24. The storm continued to obtain tropical characteristics and became a tropical storm the next day while the winds steadily increased. The storm attained wind speeds of 75 mph (120 km/h)—equivalent to a low-end Category 1 hurricane on the Saffir–Simpson scale—on March 26. At this time it was unofficially named Catarina and was also the first hurricane-strength tropical cyclone ever recorded in the Southern Atlantic Ocean. Unusually favorable conditions persisted and Catarina continued to intensify and was estimated to have peaked with winds of 100 mph (155 km/h) on March 28. The center of the storm made landfall later that day at the time between the cities of Passo de Torres and Balneário Gaivota, Santa Catarina. Catarina rapidly weakened upon landfall and dissipated on the next day.
This is a list of meteorology topics. The terms relate to meteorology, the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting.
The effects of global warming are the environmental and social changes caused by human emissions of greenhouse gases. There is a scientific consensus that climate change is occurring, and that human activities are the primary driver. Many impacts of climate change have already been observed, including glacier retreat, changes in the timing of seasonal events, and changes in agricultural productivity. Anthropogenic forcing has likely contributed to some of the observed changes, including sea level rise, changes in climate extremes, declines in Arctic sea ice extent and glacier retreat.
A mesoscale convective system (MCS) is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than extratropical cyclones, and normally persists for several hours or more. A mesoscale convective system's overall cloud and precipitation pattern may be round or linear in shape, and include weather systems such as tropical cyclones, squall lines, lake-effect snow events, polar lows, and Mesoscale Convective Complexes (MCCs), and generally form near weather fronts. The type that forms during the warm season over land has been noted across North America, Europe, and Asia, with a maximum in activity noted during the late afternoon and evening hours.
A shutdown or slowdown of the thermohaline circulation is a hypothesized effect of global warming on a major ocean circulation.
Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs. Tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment.
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of producing anything from cloudiness and mild showers to heavy gales, thunderstorms, blizzards, and tornadoes. These types of cyclones are defined as large scale (synoptic) low pressure weather systems that occur in the middle latitudes of the Earth. In contrast with tropical cyclones, extratropical cyclones produce rapid changes in temperature and dew point along broad lines, called weather fronts, about the center of the cyclone.
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean; in the south Pacific or Indian Ocean, comparable storms are referred to simply as "tropical cyclones" or "severe cyclonic storms".
The Atlantic Multidecadal Oscillation (AMO) is a climate cycle that affects the sea surface temperature (SST) of the North Atlantic Ocean based on different modes on multidecadal timescales. While there is some support for this mode in models and in historical observations, controversy exists with regard to its amplitude, and in particular, the attribution of sea surface temperature change to natural or anthropogenic causes, especially in tropical Atlantic areas important for hurricane development. The Atlantic multidecadal oscillation is also connected with shifts in hurricane activity, rainfall patterns and intensity, and changes in fish populations.
Natural disasters in India, many of them related to the climate of India, cause massive losses of life and property. Droughts, flash floods, cyclones, avalanches, landslides brought by torrential rains, and snowstorms pose the greatest threats. A natural disaster might be caused by earthquakes, flooding, volcanic eruption, landslides, hurricanes etc. In order to be classified as a disaster it will have profound environmental effect and/or human loss and frequently incurs financial loss. Other dangers include frequent summer dust storms, which usually track from north to south; they cause extensive property damage in North India and deposit large amounts of dust from arid regions. Hail is also common in parts of India, causing severe damage to standing crops such as rice and wheat and many more crops.
Hurricane Alley is an area of warm water in the Atlantic Ocean stretching from the west coast of northern Africa to the east coast of Central America and Gulf Coast of the Southern United States. Many hurricanes form within this area. The sea surface temperature of the Atlantic in Hurricane Alley has grown slightly warmer over the past decades. A particularly warm summer in 2005 led climate scientists to begin studying whether this trend would lead to an increase in hurricane activity. See Effects of Climate Change below.
Polar amplification is the phenomenon that any change in the net radiation balance tends to produce a larger change in temperature near the poles than the planetary average. On a planet with an atmosphere that can restrict longwave radiation to space, surface temperatures will be warmer than a simple planetary equilibrium temperature calculation would predict. Where the atmosphere or an extensive ocean is able to transport heat polewards, the poles will be warmer and equatorial regions cooler than their local net radiation balances would predict.
Climate change and the effects of global warming with regard to the climate in California primarily revolve around issues such as drought and the subsequent risk of wildfire and related occurrences. A 2011 study projected that the frequency and magnitude of both maximum and minimum temperatures would increase significantly as a result of global warming. The same study further projected that the frequency and magnitude of both maximum and minimum temperatures would likely increase as a result of global warming.
Regional effects of global warming are long-term significant changes in the expected patterns of average weather of a specific region due to global warming. The world average temperature is rising due to the greenhouse effect caused by increasing levels of greenhouse gases, especially carbon dioxide. When the global temperature changes, the changes in climate are not expected to be uniform across the Earth. In particular, land areas change more quickly than oceans, and northern high latitudes change more quickly than the tropics, and the margins of biome regions change faster than do their cores.
This article is about the physical impacts of climate change. For some of these physical impacts, their effect on social and economic systems are also described.
This article is about climate change, industry and society.
Tropical cyclones and climate change concerns how tropical cyclones have changed, and are expected to further change, under global warming. The topic receives considerable attention from climate scientists who study the connections between storms and climate, and notably since 2005 makes news during active storm seasons.
Climate change has brought about possibly permanent alterations to Earth's geological, biological and ecological systems. These changes have led to the emergence of a not so large-scale environmental hazards to human health, such as extreme weather, ozone depletion, increased danger of wildland fires, loss of biodiversity, stresses to food-producing systems and the global spread of infectious diseases. In addition, climatic changes are estimated to cause over 150,000 deaths annually.