Climate Change And Extreme Events: Floods
Floods are causing widespread loss and damage around the world, with impacts ranging from loss of lives and damage to infrastructure, to worsening health and food security. It is difficult for scientists to attribute most floods directly to climate change, but shifting extreme weather patterns are coinciding with the worsening of flooding disasters.
by Aryan Bajpai
The increasing impact of extreme weather events due to climate change has resulted in widespread loss and damage around the globe. Hydro-meteorological hazards such as floods, cyclones, and droughts that have an atmospheric, hydrological, or oceanographic origin are the leading disasters in terms of impacts on both humans and ecosystems as well as the economy.
In 2023 alone, more than 75% of the 399 natural disasters recorded globally were hydro-meteorological [1]. These disasters impacted more than 71.5 million people and caused losses amounting to $150 billion [1].
Hydro-meteorological hazards are complex phenomena that are difficult to study in the context of climate change due to lack of data as well as due to the influence from anthropogenic activities and infrastructure [2]. The complex nature of such events led the Working Group I of the Intergovernmental Panel on Climate Change (IPCC) to include a chapter on ‘Weather and Climate Extreme Events in a Changing Climate’ that assessed changes in weather and climate extremes on regional and global scales, including observed changes and their attribution [3]. Even though scientists showed ‘high confidence’ in attributing droughts and cyclones to climate change, the same could not be established for floods.
What are floods?
Floods, as defined by the IPCC, refer to the overflowing of the normal confines of a stream or other water body, or the accumulation of water over areas that are not normally submerged [4]. In simple terms, floods occur when the soil or any artificial surface is unable to absorb excessive quantities of water, leading to a runoff. Floods may be of different types, including river (fluvial) floods, flash floods, urban floods, rain (pluvial) floods, sewer floods, coastal floods, and glacial lake outburst floods (GLOF). The IPCC report focuses on “pluvial” floods, which include surface water and flash flooding, and “fluvial” floods, which occur when a river or stream overflows its banks.
Floods may be caused by a variety of factors, such as the amount and intensity of precipitation, soil moisture, seasonal snow cover, land use, and river and catchment engineering, etc. [3]. The figure below highlights factors that are important in determining changes in heavy precipitation and flooding [3].
Why is it difficult to link floods with climate change?
Attribution science is a relatively new field of study that is primarily conducted over a national or sub-national scale, which aims to determine the likelihood of a given cause of an event or disaster. Floods have historically been attributed to natural hydrological changes that may or may not be a product of climate change [5].
However, there are relatively few studies conducted over adequate temporal scales that attribute floods to climate change. Combined with the challenges faced by hydrological models in capturing the interplay of natural and anthropogenic factors, the attribution of floods to climate change remains a major gap [6]. This gap is also highlighted by the IPCC, which states that it has only medium confidence in the findings from global hydrological models that project “a larger fraction of land areas to be affected by an increase in river floods than by a decrease in river floods” [3].
Several studies on the attribution of floods to climate change have been published over the past few years addressing this gap. For example, a group of scientists in Europe identified an increase in the autumn and winter rainfall that resulted in increasing floods in north-western Europe [7]. They also found that a decrease in precipitation and an increase in evaporation led to fewer floods in medium and large catchments in southern Europe [7]. Another study, affiliated with World Weather Attribution, identified human-caused warming as a major contributor to the increase in the intensity of rainfall in Pakistan during the aftermath of the devastating floods in the region in 2022 [8].
The wide-ranging impacts of floods
As the world is highly likely to breach the annual average global temperature mark of 1.5 degrees Celsius at least once between 2024-2028 [9], the likelihood of floods being more intensive might be realised sooner. Several countries, especially those located in the Global South, such as India [10], Brazil [11], China [12], The United Arab Emirates [13], Kenya [14], and many more experienced heavy flooding in 2024 that caused severe impacts such as loss of lives and biodiversity, damage to infrastructure and economic losses.
Due to the poor adaptive capacity of countries in the Global South, floods also often result in challenges such as food insecurity [15], an increase in water-borne diseases [16], debt burden due to the impact on livelihoods [17], and in some cases even displacement of communities [18]. Intangible impacts such as mental health challenges [19] and the inability to access education [20] due to flooding have also been captured in a few cases.
It is pertinent to improve the understanding of attribution studies that link flooding with climate change. The availability of more data and studies on floods will lead to the enhancement of existing forecasting models, thus reducing losses and damage by enhancing anticipatory action.
References:
[1] EMDAT, (2023), Disasters in Numbers, EMDAT, https://files.emdat.be/reports/2023_EMDAT_report.pdf, [Accessed: 10.08.2024]
[2] McSweeney R., (10.08.2021), Explainer: What the new IPCC report says about extreme weather and climate change, Carbon Brief, https://www.carbonbrief.org/explainer-what-the-new-ipcc-report-says-about-extreme-weather-and-climate-change/, [Accessed: 09.08.2024]
[3] Seneviratne, S.I., X. Zhang, M. Adnan, W. Badi, C. Dereczynski, A. Di Luca, S. Ghosh, I. Iskandar, J. Kossin, S. Lewis, F. Otto, I. Pinto, M. Satoh, S.M. Vicente-Serrano, M. Wehner, and B. Zhou, 2021: Weather and Climate Extreme Events in a Changing Climate. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1513–1766, doi:10.1017/9781009157896.013, [Accessed: 08.08.2024]
[4] IPCC, 2022: Annex II: Glossary [Möller, V., R. van Diemen, J.B.R. Matthews, C. Méndez, S. Semenov, J.S. Fuglestvedt, A. Reisinger (eds.)]. In: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 2897–2930, doi:10.1017/9781009325844.029, [Accessed: 08.08.2024]
[5] Shao E., (10.07.2023), How Is Climate Change Affecting Floods?, New York Times, https://www.nytimes.com/article/flooding-climate-change.html, [Accessed: 09.08.2024]
[6] Scussolini P., Luu L. N., Philip S., Berghuijs W.R., Eilander D., Aerts J., Kew S.F., Oldenborgh G.J., Toonen W., Volkholz J., Coumou D., (26.12.2023), Challenges in the attribution of river flood events, Wiley Interdisciplinary Reviews, doi.org/10.1002/wcc.874, [Accessed: 09.08.2024]
[7] Blöschl, G., Hall, J., Viglione, A. et al. (28.08.2019), Changing climate both increases and decreases European river floods, Nature, doi.org/10.1038/s41586-019-1495-6, [Accessed: 08.08.2024]
[8] Otto F. et al. (17.03.2023), Climate change increased extreme monsoon rainfall, flooding highly vulnerable communities in Pakistan, Environmental Research: Climate, doi.org/10.1088/2752-5295/acbfd5, [Accessed: 09.08.2024]
[9] WMO, (2024), WMO Global Annual to Decadal Climate Update – Target years: 2024 and 2024-2028, WMO, https://library.wmo.int/records/item/68910-wmo-global-annual-to-decadal-climate-update, [Accessed: 10.08.2024]
[10] Reliefweb, (2024), India: Floods and Landslides – Jul 2024, Reliefweb, https://reliefweb.int/disaster/fl-2024-000109-ind, [Accessed: 10.08.2024]
[11] Disaster Philanthropy, (2024), 2024 Rio Grande do Sul Brazil Floods, https://disasterphilanthropy.org/disasters/2024-rio-grande-do-sul-brazil-floods, [Accessed: 10.08.2024]
[12] Reliefweb, (2024), China – Floods and landslides (media, CMA) (ECHO Daily Flash of 18 July 2024), Reliefweb, https://reliefweb.int/report/china/china-floods-and-landslides-media-cma-echo-daily-flash-18-july-2024, [Accessed: 10.08.2024]
[13] World Weather Attribution, (2024), Heavy precipitation hitting vulnerable communities in the UAE and Oman becoming an increasing threat as the climate warms, World Weather Attribution, https://www.worldweatherattribution.org/heavy-precipitation-hitting-vulnerable-communities-in-the-uae-and-oman-becoming-an-increasing-threat-as-the-climate-warms/, [Accessed: 10.08.2024]
[14] Reliefweb, (2024), Kenya: Heavy Rains and Flooding Update – Flash Update #7 (19 June 2024), Reliefweb, https://reliefweb.int/report/kenya/kenya-heavy-rains-and-flooding-update-flash-update-7-19-june-2024, [Accessed: 10.08.2024]
[15] UNFCCC, (18.03.2021), Climate Change-Related Disasters a Major Threat to Food Security – FAO, UNFCCC, https://unfccc.int/news/climate-change-related-disasters-a-major-threat-to-food-security-fao, [Accessed: 10.08.2024]
[16] British Red Cross, (21.09.2022), British Red Cross, https://www.redcross.org.uk/stories/disasters-and-emergencies/world/risk-of-waterborne-disease-after-pakistan-floods, [Accessed: 10.08.2024]
[17] Klomp J., (2017), Flooded with debt, Journal of International Money and Finance, https://www.sciencedirect.com/science/article/abs/pii/S0261560617300050, [Accessed: 10.08.2024]
[18] UNHCR, Climate crisis fuels flooding and deepens displacement, UNHCR, https://www.unhcr.org/in/news/stories/climate-crisis-fuels-flooding-and-deepens-displacement, [Accessed: 10.08.2024]
[19] Stanke C., Murray V., Amlot R., Nurse J., Williams R., (30.05.2012), Plos Currents, doi.org/10.1371/4f9f1fa9c3cae, [Accessed: 10.08.2024]
[20] Ahmed R., Barkat W., Ahmed A., Tahir M., Nasir A.M., (2022), Water Economics and Policy, doi.org/10.1142/S2382624X22400094, [Accessed: 10.08.2024]