| 1. |
- Cohen, Judah, et al.
(författare)
-
ARCTIC CHANGE AND POSSIBLE INFLUENCE ON MID-LATITUDE CLIMATE AND WEATHER - A US CLIVAR White Paper
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Arctic has warmed more than twice as fast as the global average since the mid 20th century, a phenomenon known as Arctic amplification (AA). These profound changes to the Arctic system have coincided with a period of ostensibly more frequent events of extreme weather across the Northern Hemisphere (NH) mid-latitudes, including extreme heat and rainfall events and recent severe winters. Though winter temperatures have generally warmed since 1960 over mid-to-high latitudes, the acceleration in the rate of warming at high-latitudes, relative to the rest of the NH, started approximately in 1990. Trends since 1990 show cooling over the NH continents, especially in Northern Eurasia. The possible link between Arctic change and mid-latitude climate and weather has spurred a rush of new observational and modeling studies. A number of workshops held during 2013-2014 have helped frame the problem and have called for continuing and enhancing efforts for improving our understanding of Arctic-mid-latitude linkages and its attribution to the occurrence of extreme climate and weather events. Although these workshops have outlined some of the major challenges and provided broad recommendations, further efforts are needed to synthesize the diversified research results to identify where community consensus and gaps exist. Building upon findings and recommendations of the previous workshops, the US CLIVAR Working Group on Arctic Change and Possible Influence on Mid-latitude Climate and Weather convened an international workshop at Georgetown University in Washington, DC, on February 1-3, 2017. Experts in the fields of atmosphere, ocean, and cryosphere sciences assembled to assess the rapidly evolving state of understanding, identify consensus on knowledge and gaps in research, and develop specific actions to accelerate progress within the research community. With more than 100 participants, the workshop was the largest and most comprehensive gathering of climate scientists to address the topic to date. In this white paper, we synthesize and discuss outcomes from this workshop and activities involving many of the working group members.
|
|
| 2. |
- Kreibich, Heidi, et al.
(författare)
-
Panta Rhei benchmark dataset : Socio-hydrological data of paired events of floods and droughts
- 2023
-
Ingår i: Earth System Science Data. - : Copernicus Publications. - 1866-3508 .- 1866-3516. ; 15:5, s. 2009-2023
-
Tidskriftsartikel (refereegranskat)abstract
- As the adverse impacts of hydrological extremes increase in many regions of the world, a better understanding of the drivers of changes in risk and impacts is essential for effective flood and drought risk management and climate adaptation. However, there is currently a lack of comprehensive, empirical data about the processes, interactions, and feedbacks in complex human-water systems leading to flood and drought impacts. Here we present a benchmark dataset containing socio-hydrological data of paired events, i.e. two floods or two droughts that occurred in the same area. The 45 paired events occurred in 42 different study areas and cover a wide range of socio-economic and hydro-climatic conditions. The dataset is unique in covering both floods and droughts, in the number of cases assessed and in the quantity of socio-hydrological data. The benchmark dataset comprises (1) detailed review-style reports about the events and key processes between the two events of a pair; (2) the key data table containing variables that assess the indicators which characterize management shortcomings, hazard, exposure, vulnerability, and impacts of all events; and (3) a table of the indicators of change that indicate the differences between the first and second event of a pair. The advantages of the dataset are that it enables comparative analyses across all the paired events based on the indicators of change and allows for detailed context- and location-specific assessments based on the extensive data and reports of the individual study areas. The dataset can be used by the scientific community for exploratory data analyses, e.g. focused on causal links between risk management; changes in hazard, exposure and vulnerability; and flood or drought impacts. The data can also be used for the development, calibration, and validation of socio-hydrological models. The dataset is available to the public through the GFZ Data Services (Kreibich et al., 2023, 10.5880/GFZ.4.4.2023.001).
|
|
| 3. |
- Kreibich, Heidi, et al.
(författare)
-
The challenge of unprecedented floods and droughts in risk management
- 2022
-
Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 608:7921, s. 80-86
-
Tidskriftsartikel (refereegranskat)abstract
- Risk management has reduced vulnerability to floods and droughts globally, yet their impacts are still increasing. An improved understanding of the causes of changing impacts is therefore needed, but has been hampered by a lack of empirical data4,5. On the basis of a global dataset of 45 pairs of events that occurred within the same area, we show that risk management generally reduces the impacts of floods and droughts but faces difficulties in reducing the impacts of unprecedented events of a magnitude not previously experienced. If the second event was much more hazardous than the first, its impact was almost always higher. This is because management was not designed to deal with such extreme events: for example, they exceeded the design levels of levees and reservoirs. In two success stories, the impact of the second, more hazardous, event was lower, as a result of improved risk management governance and high investment in integrated management. The observed difficulty of managing unprecedented events is alarming, given that more extreme hydrological events are projected owing to climate change.
|
|
| 4. |
- Persoiu, Aurel, et al.
(författare)
-
Holocene winter climate variability in Central and Eastern Europe
- 2017
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Among abundant reconstructions of Holocene climate in Europe, only a handful has addressed winter conditions, and most of these are restricted in length and/or resolution. Here we present a record of late autumn through early winter air temperature and moisture source changes in East-Central Europe for the Holocene, based on stable isotopic analysis of an ice core recovered from a cave in the Romanian Carpathian Mountains. During the past 10,000 years, reconstructed temperature changes followed insolation, with a minimum in the early Holocene, followed by gradual and continuous increase towards the mid-to-late-Holocene peak (between 4-2 kcal BP), and finally by a decrease after 0.8 kcal BP towards a minimum during the Little Ice Age (AD 1300-1850). Reconstructed early Holocene atmospheric circulation patterns were similar to those characteristics of the negative phase of the North Atlantic Oscillation (NAO), while in the late Holocene they resembled those prevailing in the positive NAO phase. The transition between the two regimes occurred abruptly at around 4.7 kcal BP. Remarkably, the widespread cooling at 8.2 kcal BP is not seen very well as a temperature change, but as a shift in moisture source, suggesting weaker westerlies and increased Mediterranean cyclones penetrating northward at this time.
|
|
| 5. |
- Rimbu, Norel, et al.
(författare)
-
Atmospheric circulation patterns associated with the variability of River Ammer floods : Evidence from observed and proxy data
- 2016
-
Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 12:2, s. 377-385
-
Tidskriftsartikel (refereegranskat)abstract
- The relationship between the frequency of River Ammer floods (southern Germany) and atmospheric circulation variability is investigated based on observational Ammer River discharge data back to 1926 and a flood layer time series from varved sediments of the downstream Lake Ammer for the pre-instrumental period back to 1766. A composite analysis reveals that, at synoptic timescales, observed River Ammer floods are associated with enhanced moisture transport from the Atlantic Ocean and the Mediterranean towards the Ammer region, a pronounced trough over western Europe as well as enhanced potential vorticity at upper levels. We argue that this synoptic-scale configuration can trigger heavy precipitation and floods in the Ammer region. Interannual to multidecadal increases in flood frequency, as detected in the instrumental discharge record, are associated with a wave train pattern extending from the North Atlantic to western Asia, with a prominent negative center over western Europe. A similar atmospheric circulation pattern is associated with increases in flood layer frequency in the Lake Ammer sediment record during the pre-instrumental period. We argue that the complete flood layer time series from Lake Ammer sediments covering the last 5500 years contains information about atmospheric circulation variability on interannual to millennial timescales.
|
|
| 6. |
- Van Loon, Anne F., et al.
(författare)
-
Review article: Drought as a continuum: memory effects in interlinked hydrological, ecological, and social systems
- 2024
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Droughts are often long lasting phenomena, without a distinct start or end, and with impacts cascading across sectors and systems, creating long-term legacies. Nevertheless, our current perception and management of droughts and their impacts is often event-based, which can limit the effective assessment of drought risks and reduction of drought impacts. Here, we advocate for changing this perspective and viewing drought as a hydro-eco-social continuum. We take a systems theory perspective and focus on how “memory” causes feedback and interactions between parts of the interconnected systems at different time scales. We first discuss the characteristics of the drought continuum with a focus on the hydrological, ecological, and social systems separately; and then study the system of systems. Our analysis is based on a review of the literature and a study of five cases: Chile, the Colorado River Basin in the US, Northeast Brazil, Kenya, and the Rhine River Basin in Northwest Europe. We find that the memories of past dry and wet periods, carried by both bio-physical (e.g. groundwater, vegetation) and social systems (e.g. people, governance), influence how future drought risk manifests. We identify four archetypes of drought dynamics: Impact & recovery; Slow resilience-building; Gradual collapse; and High resilience, big shock. The interactions between the hydrological, ecological and social systems result in systems shifting between these types, which plays out differently in the five case studies. We call for more research on drought preconditions and recovery in different systems, on dynamics cascading between systems and triggering system changes, and on dynamic vulnerability and maladaptation. Additionally, we argue for more continuous monitoring of drought hazards and impacts, modelling tools that better incorporate memories and adaptation responses, and management strategies that increase social and institutional memory to better deal with the complex hydro-eco-social drought continuum and identify effective pathways to adaptation.
|
|
| 7. |
- Zhang, Peng, et al.
(författare)
-
Can tree-ring density data reflect summer temperature extremes and associated circulation patterns over Fennoscandia?
- 2017
-
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 49:7-8, s. 2721-2736
-
Tidskriftsartikel (refereegranskat)abstract
- Tree-ring maximum latewood density (MXD) records from Fennoscandia have been widely used to infer regional- and hemispheric-scale mean temperature variability. Here, we explore if MXD records can also be used to infer past variability of summer temperature extremes across Fennoscandia. The first principal component (PC1) based on 34 MXD chronologies in Fennoscandia explains 50% of the total variance in the observed warm-day extremes over the period 1901–1978. Variations in both observed summer warm-day extremes and PC1 are influenced by the frequency of anomalous anticyclonic pattern over the region, summer sea surface temperatures over the Baltic, North and Norwegian Seas, and the strength of the westerly zonal wind at 200 hPa across Fennoscandia. Both time series are associated with nearly identical atmospheric circulation and SST patterns according to composite map analysis. In a longer context, the first PC based on 3 millennium-long MXD chronologies in central and northern Fennoscandia explains 83% of the total variance of PC1 from the 34 MXD chronologies over the period 1901–1978, 48% of the total variance of the summer warm-day extreme variability over the period 1901–2006, and 36% of the total variance in the frequency of a summer anticyclonic pattern centered over eastern-central Fennoscandia in the period 1948–2006. The frequency of summer warm-day extremes in Fennoscandia is likely linked to a meridional shift of the northern mid-latitude jet stream. This study shows that the MXD network can be used to infer the variability of past summer warm-day extremes and the frequency of the associated summer anticyclonic circulation pattern over Fennoscandia.
|
|
