Natural Climate Variability Research Articles

Natural climate variability is an important aspect of future projections of snow water resources and rain-on-snow events

Abstract. Climate projection studies of future changes in snow conditions and resulting rain-on-snow (ROS) flood events are subject to large uncertainties. Typically, emission scenario uncertainties and climate model uncertainties are included. This is the first study on this topic to also include quantification of natural climate variability, which is the dominant uncertainty for precipitation at local scales with large implications for runoff projections, for example. To quantify natural climate variability, a weather generator was applied to simulate inherently consistent climate variables for multiple realizations of current and future climates at 100 m spatial and hourly temporal resolution over a 12×12 km high-altitude study area in the Swiss Alps. The output of the weather generator was used as input for subsequent simulations with an energy balance snow model. The climate change signal for snow water resources stands out as early as mid-century from the noise originating from the three sources of uncertainty investigated, namely uncertainty in emission scenarios, uncertainty in climate models, and natural climate variability. For ROS events, a climate change signal toward more frequent and intense events was found for an RCP 8.5 scenario at high elevations at the end of the century, consistently with other studies. However, for ROS events with a substantial contribution of snowmelt to runoff (> 20 %), the climate change signal was largely masked by sources of uncertainty. Only those ROS events where snowmelt does not play an important role during the event will occur considerably more frequently in the future, while ROS events with substantial snowmelt contribution will mainly occur earlier in the year but not more frequently. There are two reasons for this: first, although it will rain more frequently in midwinter, the snowpack will typically still be too cold and dry and thus cannot contribute significantly to runoff; second, the very rapid decline in snowpack toward early summer, when conditions typically prevail for substantial contributions from snowmelt, will result in a large decrease in ROS events at that time of the year. Finally, natural climate variability is the primary source of uncertainty in projections of ROS metrics until the end of the century, contributing more than 70 % of the total uncertainty. These results imply that both the inclusion of natural climate variability and the use of a snow model, which includes a physically based process representation of water retention, are important for ROS projections at the local scale.

Observed climate trends, perceived impacts and community adaptation practices in Côte d’Ivoire

Abstract Climate change is a serious threat to local communities in West Africa. This study evaluated climatic trends and the perceptions of farmers to climate change in central Côte d’Ivoire. We surveyed 259 households across three agro-ecological zones. The knowledge of farmers about climate change was compared to observed trends of various climatic parameters from meteorological records (1973-2016). Results from trend analysis and descriptive analysis showed that the minimum, maximum and mean temperatures and rainfall showed a significant upward trend in all ecoregions. The average temperature and amount of rainfall increased by 3.2% (0.89°C) and 166.58% (645.5 mm) respectively over the 44 years. Local farmers perceived an increasing trend in temperature (all respondents) and a decreasing trend in rainfall (91.51%). Most of the respondents identified deforestation (76.83%), natural climate variation (50.97%) and wildfires (31.27%) as the main causes of these climatic disturbances, which induced plant dieback (92.66%), poor crop growth (59.46%) and crop loss (20.46%). The impacts on people and their assets encompassed a decrease in household income (63.71%), demolition of roofs (44..4%) and walls (43.91%) of houses, the scarcity of water points (39.38%) and the emergence of new diseases (30.89%). These climatic disturbances resulted in specific endogenous on-farm and off-farm strategies to adapt to the impacts of observed changes on their livelihoods.

Livelihood vulnerability of smallholder farmers to climate change: A comparative analysis based on irrigation access in South Sulawesi, Indonesia

Bulukumba Regency is one of the major rice-producing areas in South Sulawesi, Indonesia and has experienced frequent climate disasters over the past decade. Several downstream villages within the Bettu River irrigation area have been affected by the drought, culminating in reduced lowland rice production and increasing the vulnerability of farmers’ livelihoods. This study aims to evaluate the vulnerability of the livelihood system among rice farmers in the Bettu River irrigation area by classifying the area into two zones based on the distance from the main irrigation canal, namely the upstream area and downstream area. The livelihood vulnerability index (LVI) framework and livelihood vulnerability index-Intergovernmental Panel on Climate Change (LVI-IPCC) approach were applied by selecting geographic and socio-demographic indicators that affected the farmer households, including 8 major components and 26 sup-components. The data for LVI-IPCC estimation were collected by randomly selecting 132 households from villages in the two areas. The empirical results showed that farmers in the downstream area were more vulnerable to climate change than farmers in the upstream area. The major components causing the livelihood vulnerability of the downstream farmers were livelihood strategy, food, water, land, health, as well as natural disasters and climate variability. In particular, the sub-components of agricultural livelihood diversification, consistent water supply for farming, and drought events were important in the downstream area. Farmers in the upstream area were vulnerable to socio-demographic profile and social network components. The LVI-IPCC findings suggested that the government should prioritize farmers in the downstream area to develop resilience strategies, particularly by increasing irrigation infrastructure and the number of reservoirs and drilling holes. Furthermore, to increase their adaptive capacity in terms of diversification of agricultural livelihood systems, the government and donor agencies need to provide trainings on the development of home food industries for poor farmers and vulnerable households that were affected by disasters.

Spatial distribution of the trends in potential evapotranspiration and its influencing climatic factors in Iraq

Understanding the spatial variations in potential evapotranspiration (PET) and its influencing climatic variables is essential for sustainable agriculture and water resources management. However, little published research has investigated the alternation of PET due to climate change in the case of Iraq. The objective of the present study was to analyze the spatial trends in annual and seasonal PET in Iraq. Accordingly, the latest global ERA5-Land dataset of the European Centre for Medium-Range Weather Forecasts for 1981–2021 was employed. The PET was estimated using the FAO-Penman–Monteith method. The modified Mann–Kendall statistical test was applied to evaluate the significance of the trends in PET, which can separate unidirectional trends caused by climate change from the natural variability of climate. The attained results indicate that: (1) Over the past four decades, the annual and seasonal PET witnessed a significant increasing trend in almost all of Iraq, except for the alluvial plain in the eastern and southeastern parts. (2) The increasing trend in PET confirmed the patterns of the trend significance, with the highest increase of 0.28–0.65 mm/decade in southwest Iraq. (3) Summer had the highest upward trend of 0.35–0.65 mm/decade, followed by spring, autumn, and winter. (4) The air temperature was the predominant driving factor of rising PET, showing a positive correlation ranging from 0.77 to 0.88 and a contribution of 26 to 94%, mainly in the south, central, and northwest regions. The reverse contribution of wind speed and surface pressure to PET, particularly in the southeast and southwest, remains offset by the influence of air temperature and net solar radiation. Overall, the PET has risen drastically due to global climate change, indicating the potential for increased atmospheric water demand in the region.

Long-term ecological trajectories of a disturbed Mediterranean coastal lagoon (Biguglia lagoon): Ecosystem-based approach and considering its resilience for conservation?

Coastal lagoons are subjected to ever-increasing direct or indirect anthropic pressures and are inexorably deteriorating with serious issues regarding their resilience. In this paper, we assessed the functioning and evolution of the highly disturbed Biguglia coastal lagoon (Mediterranean Sea, Corsica) through an ecosystem-based approach (EBA), using multiple biotic and abiotic proxies (hydro-climatic context and eutrophication), considering its connectivity to sea and watershed and biological compartments (macrophytes, phytoplankton, and invasive species) and taking into account human influence (management actions and fishing activities). The aim of this work is firstly to provide a comprehensive analysis of its long-term (2000–2021) ecological evolution trajectory and then, based on these results, to anticipate management strategies for supporting its conservation and restoration, and the maintenance of ecosystem services it offers. Results revealed that while the lagoon showed these days a good capacity to recover after disturbance and absorb change, it recently exhibited considerable changes in its phytoplankton community composition, developed an increased susceptibility to biological invasion, and experienced a drastic reduction in fish stocks. The major interannual variations of the mean salinity, strongly dependent on management interventions beyond natural climatic variability, summarized this instability. In the future, the lagoon may no longer be able to cope with even small disturbances, which could then be sufficient to reach a breakpoint and tip the system permanently into undesired/degraded states. We demonstrated that local and punctual management actions are not always beneficial for the entire ecosystem or even detrimental in some instances. Such a retrospective ecosystem-based approach is fundamental for producing the holistic insights required to implement efficient integrated ecosystem management. This further helps enhance lagoon resilience and hence preserve its ecosystem services in the context of increasing global changes. Such lessons are useful anywhere for comparable ecosystems.

From Stamps to Parabolas.

I am a child of Sputnik, the satellite launched by the Soviet Union in 1957. That event created opportunities for me to escape the horrors of apartheid by emigrating from South Africa to the United States. There, fortuitously, I was given excellent opportunities to explore how an interplay between the waves and currents influences climate variability, from interannual El Niño events to millennial ice ages. During my career, I also witnessed intriguing facets of the interactions between the profoundly different worlds of science and of human affairs. Up to 1957, El Niño was welcomed as a blessing, but by 1982 it had become a curse-not because it changed, but because our human activities are making us vulnerable to natural climate variability. We have learned to cope admirably with the occasional failures of the Indian monsoons; the resultant famines are not as calamitous as they once were. What guidance does that limited success provide for a response to global warming, a climate change we humans are inducing? This article briefly summarizes how my career as a geoscientist brought me to the conclusion that a strategy to promote responsible stewardship of planet Earth should be based on love rather than fear. We can only love what we know, so warnings of imminent gloom and doom should be complemented with efforts to make everyone aware of the wonders of our amazing planet-the only one in the universe known to be habitable.

Current Siberian heating is unprecedented during the past seven millennia

The Arctic is warming faster than any other region on Earth. Putting this rapid warming into perspective is challenging because instrumental records are often short or incomplete in polar regions and precisely-dated temperature proxies with high temporal resolution are largely lacking. Here, we provide this long-term perspective by reconstructing past summer temperature variability at Yamal Peninsula – a hotspot of recent warming – over the past 7638 years using annually resolved tree-ring records. We demonstrate that the recent anthropogenic warming interrupted a multi-millennial cooling trend. We find the industrial-era warming to be unprecedented in rate and to have elevated the summer temperature to levels above those reconstructed for the past seven millennia (in both 30-year mean and the frequency of extreme summers). This is undoubtedly of concern for the natural and human systems that are being impacted by climatic changes that lie outside the envelope of natural climatic variations for this region.

Influences of El Niño-Southern Oscillation on summertime ozone pollution over central-eastern China during 1950-2014.

Summertime ozone pollution has become increasingly severe over many parts of China in recent years. Due to lack of historical ozone observations, few studies have analyzed the linkage between natural climate variability and ozone levels for a long time series. This study uses the simulation datasets from CMIP6 to explore the effects of El Niño-Southern Oscillation (ENSO) on summertime (June/July/August) surface ozone concentrations in central-eastern China (CEC; 20°N-42°N, 100°E-123°E) during the period of 1950-2014. Our results show that, after excluding the emission-related trend, the detrended summertime daily mean surface ozone concentrations averaged over CEC in El Niño years (30.69ppb) are higher than those in La Niña events (29.34ppb). Compared to the summertime mean ozone of 1950-2014 (30.25ppb), the maximum anomalies in CMIP6 are 2.88ppb (9.52% higher) and - 5.52ppb (18.25% lower) in El Niño and La Niña years, respectively. In addition, the summertime MDA8 ozone of CEC is significantly correlated with the central-eastern equatorial Pacific SST (5°N-5°S, 170°W-120°W) (R = 0.29, P-value = 0.02). Such ozone increases/declines in El Niño/La Niña years are also found in satellite observations of OMI ozone. The results show that the ENSO affects the large-scale circulations over central-eastern China, which regulate the regional atmospheric stability and meteorological conditions (including horizontal wind fields, geopotential height, vertical velocity, surface air temperature, and precipitation) to influence the efficiency of ozone photochemical formation and transport. Our study makes better estimation and attribution of future surface ozone pollution in China.

Unveiling four decades of intensifying precipitation from tropical cyclones using satellite measurements

Increases in precipitation rates and volumes from tropical cyclones (TCs) caused by anthropogenic warming are predicted by climate modeling studies and have been identified in several high intensity storms occurring over the last half decade. However, it has been difficult to detect historical trends in TC precipitation at time scales long enough to overcome natural climate variability because of limitations in existing precipitation observations. We introduce an experimental global high-resolution climate data record of precipitation produced using infrared satellite imagery and corrected at the monthly scale by a gauge-derived product that shows generally good performance during two hurricane case studies but estimates higher mean precipitation rates in the tropics than the evaluation datasets. General increases in mean and extreme rainfall rates during the study period of 1980–2019 are identified, culminating in a 12–18%/40-year increase in global rainfall rates. Overall, all basins have experienced intensification in precipitation rates. Increases in rainfall rates have boosted the mean precipitation volume of global TCs by 7–15%/year, with the starkest rises seen in the North Atlantic, South Indian, and South Pacific basins (maximum 59–64% over 40 years). In terms of inland rainfall totals, year-by-year trends are generally positive due to increasing TC frequency, slower decay over land, and more intense rainfall, with an alarming increase of 81–85% seen from the strongest global TCs. As the global trend in precipitation rates follows expectations from warming sea surface temperatures (11.1%/°C), we hypothesize that the observed trends could be a result of anthropogenic warming creating greater concentrations of water vapor in the atmosphere, though retrospective studies of TC dynamics over the period are needed to confirm.

Livelihood Vulnerability Index: Gender Dimension to Climate Change and Variability in REDD + Piloted Sites, Cross River State, Nigeria

Vulnerability to climate change and variability impacts has been identified as a major cog in the wheel of both livelihood and resilience, particularly in vulnerable groups in rural areas. This study aims to assess genders’ vulnerability dimension to climate change and variability in REDD + (Reducing Emission from Deforestation and Forest Degradation+) piloted site/clusters, Cross River State, Nigeria. Data were proportionately collected from selected 200 respondents on gender disaggregated level using questionnaires. The assessment adopted the sustainable livelihood approach (livelihood vulnerability index) and compared the results with the IPCC vulnerability standard of exposure, sensitivity and adaptive capacity weighted mean. The results revealed a significant difference in the vulnerability dimension of both women and men disaggregated levels (LVI: men 0.509, women 0.618). The women category was more vulnerable to six out of seven major components of LVI assessed: (livelihood strategies (0.646), social networks (0.364), water (0.559), health (0.379), food and nutrition (0.507), and natural hazards and climate variability (0.482), while men only vulnerable to socio-demographic major component (0.346). Vulnerability indices also showed women to be more exposed (0.482), and sensitive (0.489) with the least adaptive capacities (0.462) to the climate change and variability impacts. Overall, on the IPCC-LVI index, women are more vulnerable (0.0098) to climate change and variability impacts than men (−0.0093). The study recommends that the women’s category resilience and adaptive capacity should be empowered in adaptation projects in climate change such as REDD + (Reducing Emissions from Deforestation and Forest Degradation+) to reduce their vulnerability to impacts of climate change and variability in the context of exposure, sensitivity, and adaptive capacities. This will be instrumental in formulating policies to address the specific needs of gender categories in reducing vulnerability to climate change and variability. This pragmatic approach may be used to monitor gender vulnerability dimension, and livelihood enhancement and evaluate potential climate change adaptation programs. Additionally, the introduction of IPCC-LVI as a baseline instrument will enhance information on gender resilience and adaptive capacity for policy effectiveness in a data-scarce region particularly Africa.

Tropical cyclone activity in the Solomon Islands region: Climatology, variability, and trends

AbstractThis study examines the climatology, variability, and trends of tropical cyclones (TCs) affecting the Solomon Islands (SI) territory, in the wider southwest Pacific (SWP), using the South Pacific Enhanced Archive for Tropical Cyclones (SPEArTC) database. During the period 1969/1970–2018/2019, 168 TCs were recorded in the SI territory. A cluster analysis is used to objectively partition these tracks into three clusters of similar TC trajectories to obtain better insights into the effects of natural climate variability, particularly due to the El Niño–Southern Oscillation (ENSO) phenomenon, which otherwise is not very apparent for TCs when considered collectively in the SI region. We find that TCs in clusters 1 and 3 show enhanced activity during El Niño phase, whereas TCs in cluster 2 are enhanced during La Niña and neutral phases. In addition to being modulated by ENSO, TCs in clusters 2 and 3 show statistically significant modulation at an intraseasonal timescale due to the Madden–Julian Oscillation (MJO) phenomenon. There are also some indications through sophisticated Bayesian modelling that TCs in clusters 2 and 3 are slightly influenced by the Interdecadal Pacific Oscillation (IPO). These results can have substantial implications for cluster‐specific development of TC prediction schemes for the SI region.

Volcanic stratospheric sulfur injections and aerosol optical depth during the Holocene (past 11 500 years) from a bipolar ice-core array

Abstract. The injection of sulfur into the stratosphere by volcanic eruptions is the dominant driver of natural climate variability on interannual to multidecadal timescales. Based on a set of continuous sulfate and sulfur records from a suite of ice cores from Greenland and Antarctica, the HolVol v.1.0 database includes estimates of the magnitudes and approximate source latitudes of major volcanic stratospheric sulfur injection (VSSI) events for the Holocene (from 9500 BCE or 11 500 years BP to 1900 CE), constituting an extension of the previous record by 7000 years. The database incorporates new-generation ice-core aerosol records with a sub-annual temporal resolution and a demonstrated sub-decadal dating accuracy and precision. By tightly aligning and stacking the ice-core records on the WD2014 chronology from Antarctica, we resolve long-standing inconsistencies in the dating of ancient volcanic eruptions that arise from biased (i.e., dated too old) ice-core chronologies over the Holocene for Greenland. We reconstruct a total of 850 volcanic eruptions with injections in excess of 1 teragram of sulfur (Tg S); of these eruptions, 329 (39 %) are located in the low latitudes with bipolar sulfate deposition, 426 (50 %) are located in the Northern Hemisphere extratropics (NHET) and 88 (10 %) are located in the Southern Hemisphere extratropics (SHET). The spatial distribution of the reconstructed eruption locations is in agreement with prior reconstructions for the past 2500 years. In total, these eruptions injected 7410 Tg S into the stratosphere: 70 % from tropical eruptions and 25 % from NH extratropical eruptions. A long-term latitudinally and monthly resolved stratospheric aerosol optical depth (SAOD) time series is reconstructed from the HolVol VSSI estimates, representing the first Holocene-scale reconstruction constrained by Greenland and Antarctica ice cores. These new long-term reconstructions of past VSSI and SAOD variability confirm evidence from regional volcanic eruption chronologies (e.g., from Iceland) in showing that the Early Holocene (9500–7000 BCE) experienced a higher number of volcanic eruptions (+16 %) and cumulative VSSI (+86 %) compared with the past 2500 years. This increase coincides with the rapid retreat of ice sheets during deglaciation, providing context for potential future increases in volcanic activity in regions under projected glacier melting in the 21st century. The reconstructed VSSI and SAOD data are available at https://doi.org/10.1594/PANGAEA.928646 (Sigl et al., 2021).

The 852/3 CE Mount Churchill eruption: examining the potential climatic and societal impacts and the timing of the Medieval Climate Anomaly in the North Atlantic region

Abstract. The 852/3 CE eruption of Mount Churchill, Alaska, was one of the largest first-millennium volcanic events, with a magnitude of 6.7 (VEI 6) and a tephra volume of 39.4–61.9 km3 (95 % confidence). The spatial extent of the ash fallout from this event is considerable and the cryptotephra (White River Ash east; WRAe) extends as far as Finland and Poland. Proximal ecosystem and societal disturbances have been linked with this eruption; however, wider eruption impacts on climate and society are unknown. Greenland ice core records show that the eruption occurred in winter 852/3 ± 1 CE and that the eruption is associated with a relatively moderate sulfate aerosol loading but large abundances of volcanic ash and chlorine. Here we assess the potential broader impact of this eruption using palaeoenvironmental reconstructions, historical records and climate model simulations. We also use the fortuitous timing of the 852/3 CE Churchill eruption and its extensively widespread tephra deposition of the White River Ash (east) (WRAe) to examine the climatic expression of the warm Medieval Climate Anomaly period (MCA; ca. 950–1250 CE) from precisely linked peatlands in the North Atlantic region. The reconstructed climate forcing potential of the 852/3 CE Churchill eruption is moderate compared with the eruption magnitude, but tree-ring-inferred temperatures report a significant atmospheric cooling of 0.8 ∘C in summer 853 CE. Modelled climate scenarios also show a cooling in 853 CE, although the average magnitude of cooling is smaller (0.3 ∘C). The simulated spatial patterns of cooling are generally similar to those generated using the tree-ring-inferred temperature reconstructions. Tree-ring-inferred cooling begins prior to the date of the eruption suggesting that natural internal climate variability may have increased the climate system's susceptibility to further cooling. The magnitude of the reconstructed cooling could also suggest that the climate forcing potential of this eruption may be underestimated, thereby highlighting the need for greater insight into, and consideration of, the role of halogens and volcanic ash when estimating eruption climate forcing potential. Precise comparisons of palaeoenvironmental records from peatlands across North America and Europe, facilitated by the presence of the WRAe isochron, reveal no consistent MCA signal. These findings contribute to the growing body of evidence that characterises the MCA hydroclimate as time-transgressive and heterogeneous rather than a well-defined climatic period. The presence of the WRAe isochron also demonstrates that no long-term (multidecadal) climatic or societal impacts from the 852/3 CE Churchill eruption were identified beyond areas proximal to the eruption. Historical evidence in Europe for subsistence crises demonstrate a degree of temporal correspondence on interannual timescales, but similar events were reported outside of the eruption period and were common in the 9th century. The 852/3 CE Churchill eruption exemplifies the difficulties of identifying and confirming volcanic impacts for a single eruption, even when the eruption has a small age uncertainty.

Contributions of internal climate variability in driving global and ocean temperature variations using multi-layer perceptron neural network

Roles of internal climate variabilities regulating global and ocean temperature changes is a hot but complex issue of scientific concern, influencing the comprehensive policy-making in response to global and regional warming. In this study, the time series of monthly global and ocean mean surface temperature (GST and OST, respectively) since 1866 is successfully reconstructed via natural and anthropogenic forcing factors and internal climate variability by using a Multi-Layer Perceptron (MLP) neural network technique. The MLP demonstrates prominent monthly GST and OST reconstruction skills on both interannual and annual time scales. Most of the warming in GST and OST since 1866 is found to be attributable to anthropogenic forcing, while the multidecadal and interannual GST and OST variations are considerably dominated by Atlantic Multidecadal Oscillation (AMO). Internal climate variabilities like Interdecadal Pacific Oscillation (IPO) can amplify the GST and OST changes and explain the global warming slowdown since 1998. Southern Oscillation Index (SOI) performs a similar role as IPO but to a lesser extent. Changes in OST caused by solar forcing are more considerable than those in GST. Moreover, the ‘biased warmth’ during the Second World War is successfully reconstructed in MLP. AMO and IPO can explain most annual and even sub-annual temperature variations during this period, offering an explanation for the existence of this abnormal warm period other than that it was entirely caused by instrumental errors. The generally high accuracy of reconstructions on interannual and annual time scales can enhance the ability to monitor the prompt feedback of specific external radiative forcings and internal variabilities to changes in climate.

Utility of Dendrochronology Crossdating Methods in the Development of Arctic Coralline Red Algae Clathromorphum compactum Growth Increment Chronology for Sea Ice Cover Reconstruction

Paleoclimate and paleoenvironmental reconstructions from increment-yielding archives strongly depend on precise age models. Like bivalves, corals, trees, and speleothems, the coralline alga Clathromorphum compactum produces annual growth increments and shows considerable promise as an environmental archive for arctic and subarctic regions. Though their growth increment widths correlate with temperature and sea ice cover in high Arctic regions, existing timeseries have not been crossdated. In fact, previous studies have shown a lack of inter-sample correlation in non-crossdated timeseries suggesting possible age model dating errors. Here, we use dendrochronology crossdating techniques and COFECHA software to ensure and validate synchrony between C. compactum timeseries (<141 years) from three specimens collected near Beechey Island, Nunavut, Canada. Results showed that non-crossdated timeseries constructed by four coralline red algae researchers using annual increments of the same C. compactum samples were highly variable and showcase the likelihood of dating errors in non-crossdated timeseries. Crossdating improved inter-series correlations, and correlations to sea ice-related records, suggesting that at least three crossdated timeseries are required to isolate paleoclimate signals. Our findings suggest that future reconstructions with C. compactum should employ crossdating techniques to reduce dating errors and allow for more precise climate reconstructions.Lay AbstractLong-term environmental records provide a critical baseline to examine how humans have impacted Earth’s natural climate. An important piece to consider is sea ice’s role in natural climate variability because its brightness limits warming by reflecting solar irradiation back to space. However, instrumental records of sea ice rarely extend beyond the early satellite era (late 1970s), limiting our understanding of how sea ice affects natural climate variability in the preindustrial era. A lack of historical baseline prompted the development of sea ice proxies, including the long-lived marine alga, Clathromorphum compactum. Similar to tree-rings, C. compactum produces a new mineralized layer each year, and layer thicknesses have been shown to respond to sea ice cover, making them useful to record long-term sea ice variability. However, a recent study showed that records had replicability problems, maybe due to dating mistakes. Our study applies tree-ring dating methods (dendrochronology) to match annual algal growth layers across algal specimens. Results showed that these new methods reduced dating errors, allowing for more precise past sea ice cover reconstructions.

Insight into summer drought in southern Italy: palaeohydrological evolution of Lake Pergusa (Sicily) in the last 6700 years

AbstractThe Sicily region (central Mediterranean) is at high risk of drying and desertification caused by current warming and land management. The aim of this study is to place current climatic changes within the past trajectories and natural climatic variability of the Holocene. For this we re‐examine a sediment core retrieved at Lake Pergusa covering the last ca. 6700 years. A multiproxy investigation, and in particular the oxygen isotope composition of lacustrine carbonate (δ18Oc), allowed us to reconstruct decadal‐ to centennial‐scale hydrological changes. The wettest period occurred between ca. 6700 and 6000 cal a bp. The δ18Oc record indicates a new period of wetter conditions between ca. 3700 and 2400 cal a bp. In particular, a δ18Oc minimum between 2850 and 2450 cal a bp overlaps with the period of the ‘Great Solar Minimum’ and corresponds to a dramatic reduction of arboreal pollen (AP%) and to an increase in synanthropic pollen, marking the onset of Greek colonization in the region. The longest driest interval corresponds to the Medieval Climate Anomaly, whereas the highest δ18Oc values are recorded in the last 150 years. The trend of the last 3000 years suggests that, considering future climate projections, the area will experience unprecedented drying exacerbated by human impact.

Perceptions and attitudes towards climate change in fishing communities of the Sudd Wetlands, South Sudan.

The Sudd in South Sudan, formed by the White Nile’s Baḥr al-Jabal section, is one of the largest and most important wetlands in the world. Communities in the region almost exclusively depend on fisheries for food and livelihoods. Although threatened by over-exploitation and habitat changes, fish populations are also affected by climate change. Using semi-structured questionnaires, we assessed fisherfolk’s opinions of how recent variation in climate affected their livelihoods and the environment. Fisherfolk perceived that climate had changed in the past decade and were negatively impacted by this. Interviewees reported average higher temperatures, a greater frequency of floods and droughts, unpredictable timing of seasons, and erratic rainfall. Destruction of fishing villages/camps, loss and damage of fishing equipment, shifts in the fishing calendar, reduction of fish trade, and fish catch declines as well as psycho-social problems were given as the major consequences of climate change. Causes of climate change and variability were perceived to be linked to uncontrolled harvest of forest resources, anger of God and ancestors, and natural variability in climate. Most respondents expressed a desire to adopt more responsible behavior such as planting trees and establishing community nurseries, being educated on climate change risks, and sustainable fisheries management. Our results show that fisherfolk in the Sudd are troubled by climate change impacts on their livelihoods and on fish populations. In South Sudan, climate change has been reported from hydroclimatological data but concrete impacts on people remain largely unknown and of little concern because of recent wars and the poor economy. Our study provides an example of how fisherfolks’ local ecological knowledge (LEK) can be used as an early warning system of the negative impacts on livelihoods and fish populations and support adaptation to the changing climate.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10113-022-01928-w.

Public Policy of the Republic of Guinea

Under the UNFCCC, climate change is defined as climate change that is attributed directly or indirectly to human activity, modifies global atmospheric composition, and adds to the natural variability of climate observed over comparable time periods. This definition is different from that of the IPCC, which says that climate change refers to any change in climate whether it is human or natural. Vulnerability is the degree to which a system is sensitive to the adverse effects of climate change, including climate variability and its extremes. It is a function of the nature, magnitude and rate of the climate change to which the system under consideration is exposed, the sensitivity of this system and its capacity for adaptation.Vulnerability is thus a function of physical and socio-economic characteristics. One of the characteristics of Guinea is the very marked contrast between the different natural regions in terms of socio-economic conditions, population density, rainfall and hydrological regimes, relief, soil distribution, and wildlife. Flora. The populations of these different zones are to varying degrees, exposed to poverty (53% of the population live below the poverty line), to variability and to climate change (droughts, floods, extreme temperatures, disruption of the rainfall regime, etc.).Guinea, as a party, is receiving support so that, like other least developed countries, lacking the capacity to address the proven vulnerability of its resources and socio-economic groups, it is preparing its NAPA. This work falls within this framework and aims to outline urgent and immediate adaptation measures, any delay of which will cause increased vulnerability or increased cost. The document produced is the National Action Plan for Adaptation to Climate Change PANA. The document produced is structured as a foreword by His Excellency the Minister of Agriculture, Livestock, Environment, Waters and Forests, an introduction, five chapters, a conclusion, a list of bibliographical references and appendices.The first chapter provides the national context for NAPA: physical presentation, socio-economic aspects, and environmental constraints, institutional and legal framework.The second chapter deals with the NAPA framework. It outlines the climatic risks identified during the regional public consultation workshops, describes their consequences on means and modes of existence, and indicates their trend in the four natural regions. It establishes the vulnerability of socio-economic groups presents the predictable trends of each climate risk and ranks them in order of sensitivity. It shows the integration of NAPA into sectoral development policies and synergy with other multilateral environmental agreements. Finally, this chapter briefly presents the purpose, objectives and constraints of the implementation of the NAPA.The third chapter deals with basic needs for adaptation. Several options have been proposed by natural region. The in-depth analysis of these has allowed them to be grouped into thirteen adaptation options that have been weighted, prioritized and ranked according to six criteria including adaptability, coherence with local development plans, synergy with multilateral environmental agreements. . Keywords: Public Policy, Republic of Guinea DOI: 10.7176/RHSS/12-11-03 Publication date: June 30 th 2022

Coral‐Based Sea Surface Salinity Reconstructions and the Role of Observational Uncertainties in Inferred Variability and Trends

AbstractClimate observations in much of the tropical oceans are scarce during most of the 20th century, so paleoclimate proxies are needed to understand the full range of natural climate variability. Past proxy studies have focused primarily on sea surface temperatures, but there are comparatively few salinity reconstructions. Such reconstructions can extend our understanding of hydroclimate across the tropical oceans, including variability in precipitation, evaporation, and ocean circulation. Here we compile a network of salinity‐sensitive coral δ18O records, then apply a reduced‐space method based on empirical orthogonal function analysis to reconstruct annual tropical salinity anomalies over the 20th century. A comparison of surface salinity data sets, including reanalyzes (SODA2/3, Ocean ReAnalysis System 5 (ORAS5), Global Ocean Data Assimilation System) and objective analyses (Institute of Atmospheric Physics (IAP), EN4, Delcroix), show large discrepancies in the spatial structure, temporal evolution, and importance of the leading modes of variability. Two salinity data sets, IAP and ORAS5, are retained for climate reconstruction. Our coral‐based salinity reconstructions reveal significant long‐term trends over the 20th century, which are likely associated with hydrological cycle intensification and possibly a weakening of the Walker Circulation. These reconstructions also capture the spatial and temporal patterns of salinity anomalies associated with the El Niño‐Southern Oscillation, Interdecadal Pacific Oscillation, and Atlantic Multidecadal Oscillation. Ultimately, this approach can enhance our understanding of tropical hydroclimate prior to the observational era.

Documenting the Evolution of a Southern California Coastal Lagoon during the Late Holocene

Coastal wetlands are declining globally, and although wetland restoration looks to offset these losses, its success relies on anticipating environmental response to external forces. The purpose of this study is to investigate the sedimentological record of Los Peñasquitos Lagoon to determine the processes that drive environmental transitions in a Southern California coastal wetland. For this project, we analyze three sediment cores from the wetland for grain size, total organic matter, and shell assemblages to reconstruct environmental change over the past ~4000 years. From the results, we find that the lagoon was initially an open embayment that persisted for >2000 years; however, at ~1000 cal yrs BP, a short-lived wet climatic period triggered a fluvial deltaic progradation at the head of the lagoon. As the wet period ended and drier conditions returned, the delta began to retreat, and the lagoon infilled as the estuarine mouth bar was permanently established. The permanent establishment of the mouth bar resulted in a transition to a marsh-dominated environment throughout the wetland. Ultimately, these environmental transitions were driven by climate variability, although evidence of human impacts was observed more recently in the record. Therefore, future restoration efforts must consider both natural climatic variability and anthropogenic influences if they intend to sustain coastal wetlands.