Editing Extreme weather (section)

== Causes and attribution ==
=== Attribution research ===
{{Further|Extreme event attribution}}

Generally speaking, one event in extreme weather cannot be attributed to any one cause. However, certain system wide changes to global weather systems can lead to increased frequency or intensity of extreme weather events.<ref name=":0" />

Early research in extreme weather focused on statements about predicting certain events. Contemporary research focuses more on the attribution of causes to trends in events.<ref name=":0" /> In particular the field is focusing on [[climate change]] alongside other causal factors for these events.<ref name=":0" />

A 2016 report from the [[National Academies of Sciences, Engineering, and Medicine]], recommended investing in improved shared practices across the field working on attribution research, improving the connection between research outcomes and weather forecasting.<ref name=":1">{{cite report|url=https://www.nap.edu/read/21852/chapter/7|title=Attribution of Extreme Weather Events in the Context of Climate Change |publisher=The National Academies Press|doi=10.17226/21852|pages=127–136|year=2016|isbn=978-0-309-38094-2|place=Washington, DC|access-date=2020-02-22|archive-date=2022-02-15|archive-url=https://web.archive.org/web/20220215232008/https://www.nap.edu/read/21852/chapter/7|url-status=live}}</ref>

As more research is done in this area, scientists have begun to investigate the connection between climate change and extreme weather events and what future impacts may arise. Much of this work is done through climate modeling. Climate models provide important predictions about the future characteristics of the atmosphere, oceans, and Earth using data collected in the modern day.<ref name=":2" /> However, while climate models are vital for studying more complex processes such as climate change or ocean acidification, they are still only approximations.<ref name=":2" /> Moreover, weather events are complex and cannot be tied to a singular cause—there are often many atmospheric variables such as temperature, pressure, or moisture to note on top of any influences from climate change or natural variability.<ref name=":2" />

=== Natural variability ===
{{Further|Climate variability and change}}

Aspects of our climate system have a certain level of natural variability, and extreme weather events can occur for several reasons beyond human impact, including changes in pressure or the movement of air. Areas along the coast or located in tropical regions are more likely to experience storms with heavy precipitation than temperate regions, although such events can occur. 

The atmosphere is a complex and dynamic system, influenced by several factors such as the natural tilt and orbit of the Earth, the absorption or reflection of solar radiation, the movement of air masses, and the [[water cycle]]. Due to this, weather patterns can experience some variation, and so extreme weather can be attributed, at least in part, to the natural [[Climate variability and change|climate variability]] that exists on Earth. 

Climatic phenomena such as the [[El Niño–Southern Oscillation|El Niño-Southern Oscillation]] (ENSO) or the [[North Atlantic oscillation]] (NAO) impact weather patterns in specific regions of the world, influencing temperature and precipitation.<ref name=":4">{{Cite journal|last=Trenberth|first=Kevin E.|date=November 2011|title=Attribution of climate variations and trends to human influences and natural variability: Attribution of the human influence|journal=Wiley Interdisciplinary Reviews: Climate Change|language=en|volume=2|issue=6|pages=925–930|doi=10.1002/wcc.142|s2cid=140147654|doi-access=free}}</ref> The record-breaking extreme weather events that have been catalogued throughout the past two hundred years most likely arise when climate patterns like ENSO or NAO work "in the same direction as human‐induced warming."<ref name=":4" />

=== Climate change===
{{Further|Effects of climate change#Weather|Effects of climate change on the water cycle}}
[[File:20211107_Projected_extremes_for_different_degrees_of_global_warming_-_3x10yr_area_chart_-_IPCC_AR6_WG1_SPM.svg|thumb|The [[IPCC Sixth Assessment Report]] (2021) projects progressively large increases in both the frequency (horizontal bars) and intensity (vertical bars) of extreme weather events, for increasing degrees of global warming—including more than a 5{{nbsp}}°C increase in extreme heat events for a 4{{nbsp}}°C global average temperature increase.<ref>{{cite web |date=9 August 2021 |title=Climate Change 2021 / The Physical Science Basis / Working Group I contribution to the WGI Sixth Assessment Report of the Intergovernmental Panel on Climate Change / Summary for Policymakers |url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final.pdf |url-status=live |archive-url=https://web.archive.org/web/20211104175351/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final.pdf |archive-date=4 November 2021 |website=Intergovernmental Panel on Climate Change |at=Fig. SPM.6 (p. 18), 23}}</ref>]]
Some studies assert a connection between rapidly warming arctic temperatures and thus a vanishing [[cryosphere]] to extreme weather in mid-latitudes.<ref>{{cite journal|last1=Francis|first1=Jennifer A.|last2=Vavrus|first2=Stephen J.|year=2012|title=Evidence linking Arctic amplification to extreme weather in mid-latitudes|journal=[[Geophysical Research Letters]]|volume=39|issue=6|pages=L06801|bibcode=2012GeoRL..39.6801F|doi=10.1029/2012GL051000|doi-access=free}}</ref><ref>{{cite journal|author1=Vladimir Petoukhov|author2=Vladimir A. Semenov|date=November 2010|title=A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents|url=http://oceanrep.geomar.de/8738/1/2009JD013568-pip.pdf|journal=Journal of Geophysical Research: Atmospheres|volume=115|issue=21|pages=D21111|bibcode=2010JGRD..11521111P|doi=10.1029/2009JD013568|doi-access=free|access-date=2019-09-24|archive-date=2017-08-09|archive-url=https://web.archive.org/web/20170809050422/http://oceanrep.geomar.de/8738/1/2009JD013568-pip.pdf|url-status=live}}</ref><ref name="Screen 2013">{{cite journal|author=J A Screen|date=November 2013|title=Influence of Arctic sea ice on European summer precipitation|journal=Environmental Research Letters|volume=8|issue=4|page=044015|bibcode=2013ERL.....8d4015S|doi=10.1088/1748-9326/8/4/044015|doi-access=free|hdl=10871/14835|hdl-access=free}}</ref><ref>{{cite journal|author1=Qiuhong Tang|author2=Xuejun Zhang|author3=Jennifer A. Francis|date=December 2013|title=Extreme summer weather in northern mid-latitudes linked to a vanishing cryosphere|journal=Nature Climate Change|volume=4|issue=1|pages=45–50|bibcode=2014NatCC...4...45T|doi=10.1038/nclimate2065}}</ref> 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.<ref>{{Cite journal|last1=Golledge|first1=Nicholas R.|last2=Keller|first2=Elizabeth D.|last3=Gomez|first3=Natalya|last4=Naughten|first4=Kaitlin A.|last5=Bernales|first5=Jorge|last6=Trusel|first6=Luke D.|last7=Edwards|first7=Tamsin L.|date=February 2019|title=Global environmental consequences of twenty-first-century ice-sheet melt|url=http://www.nature.com/articles/s41586-019-0889-9|journal=Nature|language=en|volume=566|issue=7742|pages=65–72|doi=10.1038/s41586-019-0889-9|pmid=30728520|bibcode=2019Natur.566...65G|s2cid=59606358|issn=0028-0836|access-date=2021-05-05|archive-date=2021-06-19|archive-url=https://web.archive.org/web/20210619182658/https://www.nature.com/articles/s41586-019-0889-9|url-status=live}}</ref> 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.<ref name=":6">{{Cite journal|last1=Caesar|first1=L.|last2=McCarthy|first2=G. D.|last3=Thornalley|first3=D. J. R.|last4=Cahill|first4=N.|last5=Rahmstorf|first5=S.|date=March 2021|title=Current Atlantic Meridional Overturning Circulation weakest in last millennium|url=http://www.nature.com/articles/s41561-021-00699-z|journal=Nature Geoscience|language=en|volume=14|issue=3|pages=118–120|doi=10.1038/s41561-021-00699-z|bibcode=2021NatGe..14..118C|s2cid=232052381|issn=1752-0894|access-date=2021-05-05|archive-date=2021-06-17|archive-url=https://web.archive.org/web/20210617050415/https://www.nature.com/articles/s41561-021-00699-z|url-status=live}}</ref> 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.<ref name=":6" /> Thus, as increasing temperatures cause glaciers to melt, mid-latitudes could experience shifts in weather patterns or temperatures.<ref name=":6" />

There were around 6,681 climate-related events reported during 2000-2019, compared to 3,656 climate-related events reported during 1980–1999.<ref name=":3">{{Cite book |title=Human Cost of Disasters |date=2020 |publisher=United Nations |isbn=978-92-1-005447-8 |doi=10.18356/79b92774-en |s2cid=243258946}}</ref> 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.<ref name=":3" /> While there is evidence that a changing global climate, such as an increase in temperature, has impacted the frequency of extreme weather events, the most significant effects are likely to arise in the future. This is where climate models are useful, for they can provide simulations of how the atmosphere may behave over time and what steps need to be taken in the present day to mitigate any negative changes.<ref name=":2">{{Citation |last=Oreskes |first=Naomi |author-link=Naomi Oreskes |title=Why Believe a Computer? Models, Measures, and Meaning in the Natural World |date=2018-02-19 |work=The Earth Around Us |pages=70–82 |publisher=Routledge |doi=10.4324/9780429496653-8 |isbn=978-0-429-49665-3}}</ref>

The increasing probability of record week-long heat extremes occurrence depends on warming rate, rather than global warming level.<ref>{{cite news |date=28 July 2021 |title=Extreme heat waves in a warming world don't just break records – they shatter them |language=en-us |work=PBS NewsHour |url=https://www.pbs.org/newshour/science/extreme-heat-waves-in-a-warming-world-dont-just-break-records-they-shatter-them |url-status=live |access-date=13 August 2021 |archive-url=https://web.archive.org/web/20210812163807/https://www.pbs.org/newshour/science/extreme-heat-waves-in-a-warming-world-dont-just-break-records-they-shatter-them |archive-date=12 August 2021}}</ref><ref>{{cite journal |last1=Fischer |first1=E. M. |last2=Sippel |first2=S. |last3=Knutti |first3=R. |date=August 2021 |title=Increasing probability of record-shattering climate extremes |journal=Nature Climate Change |language=en |volume=11 |issue=8 |pages=689–695 |bibcode=2021NatCC..11..689F |doi=10.1038/s41558-021-01092-9 |issn=1758-6798 |s2cid=236438374 |doi-access=free|pmid=39650282 |pmc=7617090 }}</ref>

Some researchers attribute increases in extreme weather occurrences to more reliable reporting systems.<ref name=":3" /> A difference in what qualifies as 'extreme weather' in varying climate systems could also be argued. Over or under reporting of casualties or losses can lead to inaccuracy in the impact of extreme weather.  However, the UN reports show that, although some countries have experienced greater effects, there have been increases in extreme weather events on all continents.<ref name=":3" /> Current evidence and climate models show that an increasing global temperature will intensify extreme weather events around the globe, thereby amplifying human loss, damages and economic costs, and ecosystem destruction.{{Citation needed|date=August 2022}}

====Tropical cyclones and climate change====
{{ multiple image |total_width=450
| image1= 1980- Atlantic region category 4 and 5 hurricanes - NYTimes and NOAA.svg |caption1= The 20-year average of the number of annual Category 4 and 5 hurricanes in the Atlantic region has approximately doubled since the year 2000.<ref name=NYTimes_20220929>{{cite news |last1=Leonhardt |first1=David |last2=Moses |first2=Claire |last3=Philbrick |first3=Ian Prasad |title=Ian Moves North / Category 4 and 5 Atlantic hurricanes since 1980 |url=https://www.nytimes.com/2022/09/29/briefing/hurricane-ian-storm-climate-change.html |newspaper=The New York Times |date=29 September 2022 |archive-url=https://web.archive.org/web/20220930003545/https://www.nytimes.com/2022/09/29/briefing/hurricane-ian-storm-climate-change.html |archive-date=30 September 2022 |quote=Source: NOAA - Graphic by Ashley Wu, ''The New York Times'' |url-status=live }} ([https://commons.wikimedia.org/wiki/File:1980-_Atlantic_region_category_4_and_5_hurricanes_-_NYTimes_and_NOAA.svg cites for 2022— data])</ref>
| image2= 1980- Cost of billion dollar hurricanes - US - variwide chart - NOAA data.svg |caption2= The number of $1&nbsp;billion Atlantic hurricanes almost doubled from the 1980s to the 2010s, and inflation-adjusted costs have increased more than elevenfold.<ref name=NYTimes_20221202/> The increases have been attributed to climate change and to greater numbers of people moving to coastal areas.<ref name=NYTimes_20221202>{{cite news |last1=Philbrick |first1=Ian Pasad |last2=Wu |first2=Ashley |title=Population Growth Is Making Hurricanes More Expensive |url=https://www.nytimes.com/2022/12/02/briefing/why-hurricanes-cost-more.html |newspaper=The New York Times |date=2 December 2022 |archive-url=https://web.archive.org/web/20221206130032/https://www.nytimes.com/2022/12/02/briefing/why-hurricanes-cost-more.html |archive-date=6 December 2022 |url-status=live }} Newspaper states data source: NOAA.</ref>
}}
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.<ref>{{Cite web |last=Knutson |first=Tom |title=Global Warming and Hurricanes |url=https://www.gfdl.noaa.gov/global-warming-and-hurricanes/ |url-status=live |archive-url=https://web.archive.org/web/20200416100717/https://www.gfdl.noaa.gov/global-warming-and-hurricanes/ |archive-date=2020-04-16 |access-date=2020-08-29 |website=www.gfdl.noaa.gov |language=en-US}}</ref>

{{excerpt|Tropical cyclones and climate change|paragraphs=1-2}}

==== Floods ====
{{See also|Effects of climate change#Effects on weather|Effects of climate change on the water cycle}}
[[File:Day_185_-_what_California's_drought_conditions_look_like_from_the_air.jpg|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 it's driest periods in recorded history.'''<ref>{{Cite web |title=California Is No Stranger to Dry Conditions, but the Drought from 2011-2017 Was Exceptional {{!}} Drought.gov |url=https://www.drought.gov/california-no-stranger-dry-conditions-drought-2011-2017-was-exceptional |access-date=2025-04-04 |website=www.drought.gov |language=en}}</ref>''']]
[[Climate change]] has led to an increase in the frequency and/or intensity of certain types of extreme weather.<ref>{{Cite book |last1=Seneviratne |first1=Sonia I. |title={{Harvnb|IPCC AR6 WG1|2021}} |last2=Zhang |first2=Xuebin |last3=Adnan |first3=M. |last4=Badi |first4=W. |last5=Dereczynski |first5=Claudine |last6=Di Luca |first6=Alejandro |last7=Ghosh |first7=S. |year=2021 |page=1517 |chapter=Chapter 11: Weather and climate extreme events in a changing climate |display-authors=4 |access-date=2022-05-13 |chapter-url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_11.pdf |archive-url=https://web.archive.org/web/20220529195626/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_11.pdf |archive-date=2022-05-29 |url-status=live}} in {{Cite book |author=IPCC |author-link=IPCC |url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf |title=Climate Change 2021: The Physical Science Basis |publisher=Cambridge University Press (In Press) |year=2021 |isbn= |editor1-last=Masson-Delmotte |editor1-first=V. |series=Contribution of Working Group I to the [[IPCC Sixth Assessment Report|Sixth Assessment Report]] of the Intergovernmental Panel on Climate Change |place= |ref={{harvid|IPCC AR6 WG1|2021}} |access-date=2022-05-13 |editor2-last=Zhai |editor2-first=P. |editor3-last=Pirani |editor3-first=A. |editor4-last=Connors |editor4-first=S. L. |editor5-last=Péan |editor5-first=C. |editor6-last=Berger |editor6-first=S. |editor7-last=Caud |editor7-first=N. |editor8-last=Chen |editor8-first=Y. |editor9-last=Goldfarb |editor9-first=L. |display-editors=4 |archive-url=https://web.archive.org/web/20210813201719/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf |archive-date=2021-08-13 |url-status=live |editor10-first=M. I. |editor10-last=Gomis}}</ref> 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.<ref name=":5">{{Cite web |last=US EPA |first=OAR |date=2016-06-27 |title=Climate Change Indicators: U.S. and Global Precipitation |url=https://www.epa.gov/climate-indicators/climate-change-indicators-us-and-global-precipitation |url-status=live |archive-url=https://web.archive.org/web/20210616125220/https://www.epa.gov/climate-indicators/climate-change-indicators-us-and-global-precipitation |archive-date=2021-06-16 |access-date=2021-05-05 |website=US EPA |language=en}}</ref> 

=== 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.<ref name=":7">{{Cite book |title=The Routledge Handbook of Urban Ecology |date=2010 |isbn=978-1-136-88341-5 |editor-last=Douglas |editor-first=Ian |doi=10.4324/9780203839263 |hdl=11603/25230 |editor2-last=Goode |editor2-first=David |editor3-last=Houck |editor3-first=Michael C. |editor4-last=Maddox |editor4-first=David}}</ref> The destruction of wetlands, which act as a natural reservoir by absorbing water, can intensify the impact of floods and extreme precipitation.<ref>{{Cite book |last=Rome |first=Adam |title=The Bulldozer in the Countryside |date=2001 |publisher=Cambridge University Press |isbn=978-0-521-80490-5 |doi=10.1017/cbo9780511816703}}</ref> 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.<ref>{{Cite web |title=Louisiana Resiliency Assistance Program |url=https://resiliency.lsu.edu/ |archive-url=https://web.archive.org/web/20210507015406/https://resiliency.lsu.edu/ |archive-date=2021-05-07 |access-date=2021-05-05 |website=Louisiana Resiliency Assistance Program |language=en-US}}</ref> 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.<ref name=":7" /> With these thunderstorms comes increased precipitation, which, because of the large amounts of impervious surfaces in cities, can have devastating impacts.<ref name=":7" /> Impervious surfaces also absorb energy from the sun and warm the atmosphere, causing drastic increases in temperatures in urban areas. This, along with pollution and heat released from cars and other anthropogenic sources, contributes to urban heat islands.<ref>{{Cite journal |last1=Kleerekoper |first1=Laura |last2=van Esch |first2=Marjolein |last3=Salcedo |first3=Tadeo Baldiri |date=July 2012 |title=How to make a city climate-proof, addressing the urban heat island effect |url=https://linkinghub.elsevier.com/retrieve/pii/S0921344911001303 |url-status=live |journal=Resources, Conservation and Recycling |language=en |volume=64 |pages=30–38 |doi=10.1016/j.resconrec.2011.06.004 |bibcode=2012RCR....64...30K |archive-url=https://web.archive.org/web/20220120123547/https://linkinghub.elsevier.com/retrieve/pii/S0921344911001303 |archive-date=2022-01-20 |access-date=2021-05-05}}</ref>