Climate Change 1:The Impact of Climate Change on Floods and Droughts
The Significant Implications of Climate Change on Flood Events and Drought Periods: Patterns of Water Resource Availability
Abstract
The article under discussion examines the impacts of climate change on the water cycle, with a particular emphasis on rising greenhouse gas emissions as a primary factor. A study by Hossein Tabari, published in "Scientific Reports" in 2020, provides new insights into how climate change affects extreme weather events and water accessibility. This research specifically analyzes the intensification of severe climate-related incidents such as floods and droughts, highlighting regional disparities in their effects based on varying water availability levels. The study's findings are crucial for understanding the broader implications of climate change on global water resources and developing effective disaster management strategies.
- Introduction
Over the past two decades, the impacts of climate change have become more prominent, particularly manifesting as more intense and frequent floods and droughts. Beyond environmental concerns, these events have caused significant disruptions to global human populations. Research conducted by Mujumdar has highlighted this critical issue, revealing that floods alone have affected approximately 1.65 billion people, while droughts have impacted around 1.43 billion individuals. These figures underscore the severe nature of such climatic events across the globe. Gaining a deeper understanding of these changes is essential for adequately preparing to address the challenges posed by a warming world. Developing adaptive strategies tailored to this evolving climate landscape is crucial, with a particular emphasis on effective water management systems that can cope with both flood-related abundance and drought-related scarcity (Mujumdar, 2020).
- Background and Previous Work
The traditional view of climate change's impact on the hydrological cycle primarily focuses on basic increases in atmospheric water-holding capacity resulting from rising temperatures. This process is generally anticipated to lead to more intense precipitation events and subsequent flooding (Kundzewicz, 2008). However, as climate continues to evolve, water may traverse landmasses, oceans, and atmosphere into other regions. This challenges assumptions about using past behavior of our water resources as direct predictors of future conditions. The Geophysical Fluid Dynamics Laboratory (GFDL) has long been a leading institution in this field, dedicated to studying how changes in the hydrological cycle fit into broader Earth-atmosphere dynamics.
Research conducted by Li et al. has explored a range of steady-state challenges, including water supply issues, flood risks, and drought conditions. Predecessors might underestimate the likelihood that these scenarios will persist into the future or recognize that energy balance interactions with Earth's hydrological cycle will remain constant. However, this perspective is flawed. The occurrence rate for these events is notably elevated due to additional factors such as global warming. Their studies have further investigated how land surfaces influence climate dynamics, particularly focusing on how changes in land use can affect regional patterns and how surface exchanges of heat and moisture contribute to atmospheric processes like convection and precipitation (Li et al., 2022).
The latest report from the Sixth IPCC emphasizes how global warming is influencing land's global hydrological cycle. This study highlights regional variations and notes inconsistencies in these changes. The discrepancies primarily arise because thorough observation-based evaluation of concurrent trends in various aspects of the hydrological cycle has been lacking. Hobeichi conducted a comprehensive analysis of vegetation greenness and hydrological cycle trends between 1980 and 2012. He observed that significant changes occurred across more than 50% of land areas, with evapotranspiration exhibiting the most change and precipitation showing minimal variation. Notably, evapotranspiration exhibited a new trend pattern without corresponding robust precipitation trends, supporting Hobeichi's hypothesis that "wet gets wetter, but dry does not get drier" (2022).
研究者们对该流域进行了长期观察
The recent report by the World Meteorological Organization highlights the effects of climate change on the hydrological cycle. By emphasizing the importance of understanding and managing freshwater resources, it notes that over 50% of global catchment areas have deviated from normal conditions, often drier. Additionally, it points out increased evapotranspiration and decreased soil moisture in regions such as Europe, which impacts rivers and energy production. In contrast, parts of Asia and Africa experienced severe droughts and floods, affecting millions. This necessitates a comprehensive approach to water management, taking into account regional variations and the frequency of extreme weather events (World Meteorological Organization., 2022).
These through a series of findings show that understanding how water cycles respond to changing climates requires a comprehensive approach. Therefore, in terms of water management and policy-making there must be a multi-faceted strategy adopted. Previous studies indicate that addressing regional differences enhancing the frequency of extreme weather events as well as integrating interactions between climatic environmental and social factors are crucial. The study by Hossein Tabari serves as an exemplary case demonstrating these various interconnections.
3. Hossein Tabari's Study: Advances and Methodology
Hossein Tabari conducted in-depth research in 2020 concerning how climate change impacts extreme hydrological events. The study is notable for its detailed examination of links between fluctuations in extreme rainfall, flood severity, and water availability as we approach the end of the 21st century. His study highlights how significant and severe these climatic shifts are. He employed MATLAB toolbox to conduct climate predictions across various climatic regions.
Additionally, using MATLAB's Mapping Toolbox with historical data from 1971 to 2000, he analyzed changes in area coverage for each of these five climate types between 2070 and 2099 (see Figure c).
Figure 1显示干旱指数及其对未来预期变化。（a）部分展示历史阶段（1971-20年）的气候变化状况。（b）则呈现未来时期的气候变化预测（至公元后年）。（c）部分描绘了预期在世纪末至世纪中叶期间的变化趋势与历史阶段相比的情况。（d）部分展示了预计占全球陆地面积百分比的五个气候类型
Additionally, this study innovatively assessed changes in flood risks by employing two distinct hazard assessment methods based on a multi-model ensemble approach. This comprehensive strategy effectively addressed all significant uncertainties associated with flood risk analysis. Notably, it accounted for potential limitations arising from relying solely on a single hydrological model. The spatial distribution of projected changes in extreme precipitation intensity was examined across various climatic regions including tropical, subtropical, semi-arid, and arid areas spanning 2070 to 2099. These regions collectively represent potential areas prone to flooding or drought conditions. Meanwhile, these projected climate scenarios were determined by two distinct modeling approaches (different climate zones), as illustrated in Figures 2 and 3. According to these visualizations, there is a strong likelihood of increased intense precipitation due to global warming trends within tropical and subtropical regions. The robustness of these projections is evident from the high level of agreement (92%) observed among models regarding precipitation trend directions within tropical areas depicted in Figure 2. All categories demonstrated statistically significant changes across different quantile levels consistent with projected trends related to climate change effects rather than random variations.
该图展示不同气候区域极端降水强度变化的分布情况：(a) 湿性气候区、(b) 半湿性气候区、(c) 半干旱气候区、(d) 干性气候区、以及(e) 不同气候类型在21世纪中叶的变化趋势。
Figure 3 illustrates how flood intensity is predicted to rise dramatically under a high emissions scenario in humid regions and noticeably less in semi-humid and semi-arid regions under the RCP8.5 situation. The RCP8.5 means a specific scenario when the radiative forcing level reaches 8.5 W/m^2. This is people's current projections of the future climate situation in the climate if people don't take effective action to face climate change. The unanimous agreement among models for the humid region indicates high confidence in these projections, while there is a slightly lower agreement for semi-humid and semi-arid regions (75% agreement). The analysis excludes grid cells with annual maxima close to 0 cubic meters per second (m³ s⁻¹) from the historical model period, as these would not be relevant for flood intensity changes.
The figure illustrates the distribution of changes in extreme precipitation intensity across various climatic regions: including humid areas, semi-humid areas, semi-arid areas, and projected changes under the RCP8.5 scenario compared to the historical period of 1971-2000.
4. Key Findings and Implications
This groundbreaking research by Tabari in 2020 demonstrates comprehensive understanding of how climate change differently impacts hydrological extremes across various regions. A notable finding from the study highlights the uneven intensification of extreme weather events, including heavy rainfall and flooding, across varied geographic regions. The study reveals that regions with higher water availability experience a significantly greater rise in extreme precipitation and flooding compared to drier areas. This disparity underscores the critical role of regional development strategies for disaster management, necessitating tailored adaptation measures based on differing levels of water availability.
Additionally, this research highlights how the intensification of extreme precipitation events leads to an amplification in both the severity and frequency of flooding. Such intensification poses significant challenges across aquatic ecosystems, terrestrial environments, human populations, and economic systems alike. The study underscores how flood characteristics are shaped not only by precipitation distribution and temporal patterns but additionally by soil moisture conditions prior to flood events as well as the timing of snow melt in areas with substantial winter snow cover. This intricate relationship demonstrates how flood alterations are interconnected with a host of factors including regional climatic moisture shifts (Tabari, 2020).
Furthermore, Tabari's study, under different climate sensitivities of the CMIP5 GCMs, predicts an overall increase in flood intensity globally with notable differences across various climate zones (whether considering the RCP8.5 situation or not) . The result as shown in Figure 2 and Figure 3 above, in sharp contrast to smaller percentages in semi-arid and semi-humid regions, around 75.9% of land in humid areas is anticipated to face an increase in flood severity. This research emphasizes how crucial it is to take into account a variety of flood-causing factors, including precipitation, soil moisture, and snowmelt, when assessing flood risks in light of various climate change scenarios (Tabari, 2020). Comparing Figure 2 and Figure 3, it is obvious that the probability of humidity happening will increase under the RCP8.5. People need to take measures to face this serious situation.
5. Conclusion and Future Directions
研究显示，在应对气候变化方面取得进展的同时，在全球范围内水资源管理面临着多样化挑战。气候影响可能因区域而异，在一个地区的洪水或干旱事件可能与另一个地区截然不同。根据这一发现，在制定水资源管理和防洪准备时需要据此进行规划。未来的研究应进一步探讨水资源、气候变化与极端天气事件（如洪水和干旱）之间的相互作用。这将帮助我们制定更有针对性的应对措施，并考虑不同地区可能需要采取的具体做法以减轻不利影响。理解并适应这些地区差异变得愈发关键。
Tabari's research indicates that these climatic changes are both vast and severe. In my opinion, adapting to these shifts becomes increasingly necessary as the planet continues to warm. It entails more than merely acknowledging the issue; it demands actively devising mitigation and adaptation strategies. Central to this effort is the crucial need for effective water management, which plays a vital role in both flood and drought scenarios. In regions experiencing floods, our focus should be on managing excessive water levels to prevent infrastructure damage, protect human health, and safeguard agriculture. Conversely, in areas facing droughts, efficient management of limited water resources becomes essential to sustain communities and prevent ecological harm.
References
What impact do alterations in climate and land use have on the water cycle? What is the focus of an investigation modeling future drought occurrences utilizing validated drought indicators?
Analyzing past modifications to the hydrological cycle over land: a comprehensive review of recent studies.
Li et al. conducted a comparative analysis between CMIP5 and CMIP6 in their study titled "Impact of Global Climate Change on Hydrological Cycles and Crop Growth under Intensive Irrigation Strategies." The research was published in Computers and Electronics in Agriculture with the specific volume and page number as mentioned.
The study explores both droughts and floods as critical environmental factors. An analysis conducted by the Ministry of Earth Sciences (MoES) evaluates climate change trends across India during this period.
Kundzewicz, Z. W. (2008). This study examines the effects of climate change on the hydrological processes. Ecohydrology & Hydrobiology, 8(2-4), 195-203.
Tabari, H. (2020). Climate change impacts on floods and extreme precipitation are increasing as water availability increases. Scientific reports, 10(1), 13768.
The World Meteorological Agency ( meteorological agency ). ( 2022 ). Global Water Resources Status 2022. Acquired from UN News.)