 | The examples and perspective in this article deal primarily with North America and do not represent a worldwide view of the subject.(February 2023) |
A megadrought is an exceptionally severe drought, lasting for many years and covering a wide area.
| The examples and perspective in this article deal primarily with North America and do not represent a worldwide view of the subject.(February 2023) |
A megadrought is an exceptionally severe drought, lasting for many years and covering a wide area.
There is no exact definition of a megadrought. [2] The term was first used by Connie Woodhouse and Jonathan Overpeck in their 1998 paper, 2000 Years of Drought Variability in the Central United States. [2] [3] In this, it referred to two periods of severe drought in the US – one at the end of the 13th century and the other in the middle of the 16th century. [3] The term was then popularised as a similar severe drought affected the Southwestern US from the year 2000. [2]
Benjamin Cook suggested that the definition be a drought which is exceptionally severe compared to the weather during the previous 2,000 years. [2] This was still quite imprecise and so research has suggested quantitative measures based on a Standard Precipitation Index. [4]
Past megadroughts in North America have been associated with persistent multiyear La Niña conditions (cooler than normal water temperatures in the tropical eastern Pacific Ocean). [5]
Megadroughts have historically led to the mass migration of humans away from drought affected lands, resulting in a significant population decline from pre-drought levels. They are suspected of playing a primary role in the collapse of several pre-industrial civilizations, including the Anasazi of the North American Southwest, [6] the Khmer Empire of Cambodia, [7] the Mayan of Mesoamerica, [8] the Tiwanaku of Bolivia, [9] and the Yuan Dynasty of China. [10]
The African Sahel region in particular has suffered multiple megadroughts throughout history, with the most recent lasting from approximately 1400 AD to 1750 AD. [11] North America experienced at least four megadroughts during the Medieval Warm Period. [12]
There are several sources for establishing the past occurrence and frequency of megadroughts, including:
Angkor, also known as Yasodharapura, was the capital city of the Khmer Empire. The city and empire flourished from approximately the 9th to the 15th centuries. The city houses the Angkor Wat, one of Cambodia's most popular tourist attractions.
The Khmer Empire was a Hindu-Buddhist empire in Southeast Asia, centered around hydraulic cities in what is now northern Cambodia. Known as Kambuja by its inhabitants, it grew out of the former civilisation of Chenla and lasted from 802 to 1431. Historians call this period of Cambodian history the Angkor period, after the empire's most well-known capital, Angkor. The Khmer Empire ruled or vassalised most of mainland Southeast Asia and stretched as far north as southern China. At its peak, the Empire was larger than the Byzantine Empire, which existed around the same time.
Mount Aniakchak is a 3,600-year-old volcanic caldera approximately 10 kilometers (6 mi) in diameter, located in the Aleutian Range of Alaska, United States. Although a stratovolcano by composition, the pre-existing mountain collapsed in a major eruption forming the caldera. The area around the volcano is the Aniakchak National Monument and Preserve, maintained by the National Park Service. In November 1967, Aniakchak Caldera was designated as a National Natural Landmark by the National Park Service.
The Sahel region of Africa has long experienced a series of historic droughts, dating back to at least the 17th century. The Sahel region is a climate zone sandwiched between the Sudanian Savanna to the south and the Sahara desert to the north, across West and Central Africa. While the frequency of drought in the region is thought to have increased from the end of the 19th century, three long droughts have had dramatic environmental and societal effects upon the Sahel nations. Famine followed severe droughts in the 1910s, the 1940s, and the 1960s, 1970s and 1980s, although a partial recovery occurred from 1975-80. The most recent drought occurred in 2012.
Mineral dust is atmospheric aerosol originated from the suspension of minerals constituting the soil, composed of various oxides and carbonates. Human activities lead to 30% of the airborne dust load in the atmosphere. The Sahara Desert is the major source of mineral dust, which subsequently spreads across the Mediterranean and Caribbean seas into northern South America, Central America, and eastern North America, and Europe. Additionally, it plays a significant role in the nutrient inflow to the Amazon rainforest. The Gobi Desert is another source of dust in the atmosphere, which affects eastern Asia and western North America.
The 4.2-kiloyear BP aridification event was one of the most severe climatic events of the Holocene epoch. It defines the beginning of the current Meghalayan age in the Holocene epoch.
In archaeology, the classic Maya collapse is the decline of the Classic Maya civilization and the abandonment of Maya cities in the southern Maya lowlands of Mesoamerica between the 7th and 9th centuries. At Ceibal, the Preclassic Maya experienced a similar collapse in the 2nd century.
The Hatepe eruption, named for the Hatepe Plinian pumice tephra layer, sometimes referred to as the Taupō eruption or Horomatangi Reef Unit Y eruption, is dated to 232 CE ± 10 and was Taupō Volcano's most recent major eruption. It is thought to be New Zealand's largest eruption within the last 20,000 years. The eruption ejected some 45–105 km3 (11–25 cu mi) of bulk tephra, of which just over 30 km3 (7.2 cu mi) was ejected in approximately 6–7 minutes. This makes it one of the largest eruptions in the last 5,000 years, comparable to the Minoan eruption in the 2nd millennium BCE, the 946 eruption of Paektu Mountain, the 1257 eruption of Mount Samalas, and the 1815 eruption of Mount Tambora.
The United States' contiguous western and especially southwestern region has experienced widespread drought since about year 2000. Below normal precipitation leads to drought, and is caused by an above average persistence of high pressure over the affected area. Changes in the track of extratropical cyclones, which can occur during climate cycles such as the El Niño-Southern Oscillation, or ENSO, as well as the North Atlantic Oscillation, Pacific Decadal Oscillation, and Atlantic multidecadal oscillation, modulate which areas are more prone to drought. Increased drought frequency and severity is also expected to be one of the effects of global warming.
The historical and ongoing droughts in California result from various complex meteorological phenomena, some of which are not fully understood by scientists.
The Cocoliztli Epidemic or the Great Pestilence was an outbreak of a mysterious illness characterized by high fevers and bleeding which caused 5–15 million deaths in New Spain during the 16th century. The Aztec people called it cocoliztli, Nahuatl for pestilence. It ravaged the Mexican highlands in epidemic proportions, resulting in the demographic collapse of some Indigenous populations.
In 1257, a catastrophic eruption occurred at the Samalas volcano on the Indonesian island of Lombok. The event had a probable Volcanic Explosivity Index of 7, making it one of the largest volcanic eruptions during the current Holocene epoch. It left behind a large caldera that contains Lake Segara Anak. Later volcanic activity created more volcanic centres in the caldera, including the Barujari cone, which remains active.
Lisa J. Graumlich is an American paleoclimatologist who studies the interactions between the climate, ecosystems and humans. She is the inaugural dean of College of the Environment at the University of Washington. Graumlich is a Fellow of the American Association for the Advancement of Science and the Ecological Society of America, and is president-elect of the American Geophysical Union.
The Medieval Warm Period (MWP), also known as the Medieval Climate Optimum or the Medieval Climatic Anomaly, was a time of warm climate in the North Atlantic region that lasted from c. 950 to c. 1250. Climate proxy records show peak warmth occurred at different times for different regions, which indicate that the MWP was not a globally uniform event. Some refer to the MWP as the Medieval Climatic Anomaly to emphasize that climatic effects other than temperature were also important.
The 1540 drought in Europe was a climatic event in Europe. In various palaeoclimatic analyses the temperature and precipitation regimes were reconstructed and compared to present-day conditions.
A drought developed in the Western, Midwestern, and Northeastern United States in the summer of 2020. Similar conditions started in other states in August 2020, including Iowa, Nebraska and certain parts of Wisconsin and Minnesota. At the same time, more than 90% of Utah, Colorado, Nevada and New Mexico were in some level of drought. Also in drought conditions were Wyoming, Oregon and Arizona.
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The southwestern North American megadrought is an ongoing megadrought in the southwestern region of North America that began in 2000. 23 years in length, the drought is the driest multi-decade period the region has seen since at least 800 CE. The megadrought has prompted the declaration of a water shortage at Lake Mead, the largest reservoir in the United States. Climate change models project drier conditions in the region through the end of the 21st century, though climate change mitigation may avoid the most extreme impacts.
2020s in climate history refers to major events pertaining to the climate, this includes extreme weather, as well as new scientific phenomena and occurrences which pertain to the climate. This article will be structured by category of data, and then chronologically within those broader sections.
Connie A. Woodhouse is a regents professor at the University of Arizona who is known for her use of tree rings to reconstruct the hydroclimate of the past, especially in western North America. In 2022 she was elected a fellow of the American Geophysical Union
Consequently, despite considerable limitations of the proxy evidence, to date it does support the idea that, during medieval times, the global hydroclimate tended towards what we would now call a La Niña-like state.
New findings suggest that a decades-long drought at about the time the kingdom began fading away in the 14th century may have been a major culprit. Evidence for a megadrought comes from centuries-old conifers that survived the Angkor era.
This far-reaching rainfall chronology also provides the first independent confirmation of the so-called Terminal Classic drought, a megadrought some anthropologists relate to the collapse of the Mayan civilization.
In medieval times the California droughts coincided roughly with a warmer climate in Europe, which allowed the Vikings to colonize Greenland and vineyards to grow in England, and with a severe dry period in South America, which caused the collapse of that continent's most advanced pre-Inca empire, the rich and powerful state of Tiwanaku, other recent studies have found.
Although the relationship between climate and societal change is complex and not necessarily deterministic, the widespread societal changes across monsoon Asia between the mid 13th to 15th centuries, which include famines and significant political reorganization within India ([Dando, 1980], [Pant et al., 1993] and [Maharatna, 1996]), the collapse of the Yuan dynasty in China (Zhang et al., 2008); Rajarata civilization in Sri Lanka (Indrapala, 1971), and the Khmer civilization of Angkor Wat fame in Cambodia (Buckley et al., 2010), strongly suggest that the MMDs may have played a major contributing role in shaping these societal changes.
As well as the periodic droughts lasting decades, there was evidence that the Sahel region has undergone several droughts lasting a century or more....The most recent mega-drought was just 500 years ago, spanning 1400 to 1750 and coinciding with Europe's Little Ice Age.
The new record sheds light on a drought-prone 400-year period between A.D. 900 and 1300. It is punctuated by four decades-long, regionwide megadroughts centered on the years 936, 1034, 1150 and 1253.
The evidence for the big droughts comes from an analysis of the trunks of trees that grew in the dry beds of lakes, swamps and rivers in and adjacent to the Sierra Nevada, but died when the droughts ended and the water levels rose. Immersion in water has preserved the trunks over the centuries.
Marine coral records from the core ENSO region of the tropical Pacific also support the concept of decadal and longer ENSO variability during the last millennium (Cobb et al., 2003), with some indication that the MCA period experienced persistent La Niña-like SST conditions that would be drought-inducing over North America.
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