Managed culls mean extinction for a marine mammal population when combined with extreme climate impacts

Human actions led to the worldwide decline of marine mammal populations in the 18th-19th centuries. However, the global uptake in protective legislation during the 20th century has recently allowed many marine mammal populations to recover. This positive trend is particularly true of pinnipeds (e.g., seals and sea lions), whose recovering populations are increasingly in conflict with fisheries. Many fisheries organisations call for managed culls of sea lion populations to reduce competition for target fish species as well as damage to catch and fishing gear through operational interactions. However, despite widespread perceptions that sea lion populations are generally increasing, to-date culls have been considered or implemented without quantitative evidence of their impacts on seal lion population viability. This knowledge gap is particularly concerning given the expected increase in extreme climate conditions, such as extreme El Niño events, which together with culls could push sea lion populations in some parts of the world into the extinction vortex. In this analysis, I develop and parameterise stochastic matrix population models of the South American sea lion (Otaria flavescens) to project the impact of (1) three cull scenarios with different intensity and temporal frequency targeting adult females, (2) extreme El Niño events whose frequency is modelled using a Markovian transition matrix, (3) and the interaction of culls and extreme climate events on population dynamics. I focus on the Chilean population of O. flavescens, where recent increases in sea lion numbers have triggered widespread conflict with small-scale fisheries, and where sea lion populations will increasingly be affected by extreme El Niño conditions. I find that sea lion populations decline below minimum viable population sizes under all scenarios involving culls and extreme climate events. By explicitly considering parameter uncertainty, this approach is a call to action for future research to focus on collecting stage-specific, annual population data to reduce uncertainty regarding marine mammal vital rates.

Assessing Socioeconomic Risks of Extreme Weather Events: Lessons from El Niño-Related Road Damages in Peru

Periodically, heavy rainfall associated with extreme El Niño events severely damage the Peruvian road-network. This study aims to assess the socio-economic effects of these non-frequent but recurrent climate shocks. For this purpose, we build a Computable General Equilibrium model that addresses the consequences of El Niño-related damages through an increase in interregional transportation costs and a negative externality effect on activities’ output, which has been estimated beforehand using a firm database. For designing simulation scenarios over a ten-year period where extreme El Niño events occurs at random as observed in the past in Peru, we model the occurrence of these events as a stochastic process with a VAR representation based on historical climatic data. Within this framework, we first show that such events constitute a significant one-off disaster risk for the country, threatening shifts of − 2.8% in GDP and + 1.9% in poverty rates with an annual probability p = 1.4%. We further show that they also present a longer-term risk, leading to average annual deviations from normal trend by − 0.8% in GDP and + 0.4% in poverty rate with a probability p = 12.6% over a ten-year period. However, we finally show that Peru might reduce these risks in constructing more disaster-resilient road infrastructure.

Effects of Excessive Equatorial Cold Tongue Bias on the Projections of Tropical Pacific Climate Change. Part II: The Extreme El Niño Frequency in CMIP5 Multi-Model Ensemble

Under increased greenhouse gas (GHG) forcing, climate models tend to project a warmer sea surface temperature in the eastern equatorial Pacific than in the western equatorial Pacific. This El Niño-like warming pattern may induce an increase in the projected occurrence frequency of extreme El Niño events. The current models, however, commonly suffer from an excessive westward extension of the equatorial Pacific cold tongue accompanied by insufficient equatorial western Pacific precipitation. By comparing the Representative Concentration Pathway (RCP) 8.5 experiments with the historical simulations based on the Coupled Model Intercomparison Project phase 5 (CMIP5), a “present–future” relationship among climate models was identified: models with insufficient equatorial western Pacific precipitation error would have a weaker mean El Niño-like warming pattern as well as a lower increase in the frequency of extreme El Niño events under increased GHG forcing. Using this “present–future” relationship and the observed precipitation in the equatorial western Pacific, this study calibrated the climate projections in the tropical Pacific. The corrected projections showed a stronger El Niño-like pattern of mean changes in the future, consistent with our previous study. In particular, the projected increased occurrence of extreme El Niño events under RCP 8.5 forcing are underestimated by 30–35% in the CMIP5 multi-model ensemble before the corrections. This implies an increased risk of the El Niño-related weather and climate disasters in the future.

Analisis Kejadian El Nino dan Dampaknya Terhadap Musim Tanam dan Produktivitas Kacang Tanah (Arachis hypogaea L.) di Pulau Kei Kecil Kabupaten Maluku Tenggara

Climate change has an impact that includes extreme climate events such as El Nino. Experience in recent decades has shown that the El Nino climate anomaly has caused prolonged droughts. Peanut are susceptible to drought in part or all of its growth phases due to below-normal rainfall. This study aimed to describe the occurrence of extreme El-Nino rainfall on Kei Kecil Island, Maluku Province, and how much the El-Nino events affected the planting season and peanut production on Kei Kecil Island. This was carried out using the algebraic average technique for calculating the average (normal) rainfall and the FAO (1978) method for determining the growing season. The variables observed were rainfall data and peanut plant productivity data. Data were analyzed using simple regression analysis. The results of the study showed that the El Nino phenomenon generally took place in the period from April to November; mostly starting in April, May, June and September, October and November. Drought events on Kei Kecil Island did not always coincide with El Nino events, and El Nino events did not always cause drought or rainfall below normal. In 1993, 2003, 2007, and 2012 the amount of rainfall on Kei Kecil Island was below normal (<2,308 mm per year) but these years were not recorded as El Nino years. Whereas, 1994, 2009, 2014, and 2018 were recorded as El Nino years but did not cause drought or rainfall under normal conditions on Kei Kecil Island. During the last 30 years, this incident occurred 3 times, i.e. in 1991, 1997, and 2015. The results of the analysis of the growing season showed that the planting season on Kei Kecil Island under conditions of average (normal) rainfall lasted for 289 days or 9 months 16 days (November 1 to August 16). Meanwhile, the growing season when extreme El Nino rainfall occurred, lasted for 201 days or 6 months 20 days (November 1 to May 20). This indicated that when El Nino occurred on Kei Kecil Island, there was a shift in the growing season (ending sooner). The results of the regression analysis illustrated that the increase of the value of rainfall would increase the productivity of peanut crop. Keywords: El Nino phenomenon, growing season, peanut, productivity, rainfall ABSTRAK Perubahan iklim berdampak di antaranya terhadap kejadian iklim ekstrim seperti El Nino. Pengalaman dalam beberapa dekade terakhir ini menunjukkan bahwa anomali iklim El Nino telah menyebabkan kekeringan berkepanjangan. Kacang tanah rentan oleh deraan kekeringan pada sebagian ataupun seluruh fase pertumbuhannya akibat curah hujan yang di bawah normal. Penelitian ini bertujuan untuk mempelajari kejadian curah hujan ekstrim El-Nino di Pulau Kei Kecil, Provinsi Maluku, dan seberapa besar kejadian El-Nino mempengaruhi musim tanam dan produksi kacang tanah di Pulau Kei Kecil. Ini dilaksanakan dengan menggunakan metode teknik rata-rata aljabar untuk perhitungan curah hujan rata-rata (normal) dan metode FAO (1978) untuk penentuan musim tanam. Variabel yang diamati adalah data curah hujan dan data produktifitas tanaman kacang tanah. Data dianalisis menggunakan analisis regresi sederhana. Hasil penelitian menunjukkan fenomena El Nino umumnya berlangsung dalam periode April hingga November; terbanyak mulai bulan April, Mei, Juni dan September, Oktober dan November. Kejadian kekeringan di Pulau Kei Kecil tidak selalu bersamaan dengan kejadian El Nino, dan kejadian El Nino tidak selalu menyebabkan kekeringan atau curah hujan di bawah normal. Pada tahun 1993, 2003, 2007, dan 2012 jumlah curah hujan di Pulau Kei Kecil berada pada kondisi di bawah normal (<2.308 mm per btahun) tetapi tahun-tahun tersebut tidak tercatat sebagai tahun-tahun El Nino. Sementara itu, tahun 1994, 2009, 2014, dan 2018 tercatat sebagai tahun-tahun El Nino tetapi tidak menyebabkan kekeringan atau curah hujan di bawah kondisi normalnya di Pulau Kei Kecil. Selama periode 30 tahun terakhir kejadian ini berlangsung selama 3 kali, yaitu pada tahun 1991, 1997, dan 2015. Hasil analisis musim tanam menunjukkan bahwa musim tanam di Pulau Kei Kecil pada kondisi curah hujan rata-rata (normal) berlangsung selama 289 hari (1 November sampai dengan 16 Agustus; 9 bulan 16 hari). Sedangkan musim tanam ketika curah hujan ekstrim El Nino berlangsung selama 201 hari (1 November sampai dengan 20 Mei). Hal ini mengindikasikan bahwa ketika El Nino berlangsung di Pulau Kei Kecil, akan terjadi pergeseran musim tanam (berakhir lebih cepat). Hasil analisis regresi menggambarkan bahwa penigkatan nilai curah hujan akan menigkatkan produktivitas tanaman kacang tanah. Kata kunci: curah hujan, fenomena El Nino, kacang tanah, musim tanam, produktivitas

Structure, dynamics, and trace gas variability within the Asian summer monsoon anticyclone in the extreme El Niño of 2015–2016

A weak El Niño during 2014–2015 boreal winter developed as a strong boreal summer event in 2015 which continued and even enhanced during the following winter. In this work, the detailed changes in the structure, dynamics, and trace gases within the Asian summer monsoon anticyclone (ASMA) during the extreme El Niño of 2015–2016 is delineated by using Aura Microwave Limb Sounder (MLS) measurements, COSMIC radio occultation (RO) temperature, and National Centers for Environmental Prediction (NCEP) reanalysis products. Our analysis concentrates only on the summer months of July and August 2015 when the Niño 3.4 index started to exceed values of 1.5. The results show that the ASMA structure was quite different in summer 2015 as compared to the long-term (2005–2014) mean. In July, the spatial extension of the ASMA is greater than the long-term mean in all the regions except over northeastern Asia, where it exhibits a strong southward shift in its position. The ASMA splits into two, and the western Pacific mode is evident in August. Interestingly, the subtropical westerly jet (STJ) shifted southward from its normal position over northeastern Asia, and as a result midlatitude air moved southward in 2015. Intense Rossby wave breaking events along with STJ are also found in July 2015. Due to these dynamical changes in the ASMA, pronounced changes in the ASMA tracers are noticed in 2015 compared to the long-term mean. A 30 % (20 %) decrease in carbon monoxide (water vapor) at 100 hPa is observed in July over most of the ASMA region, whereas in August the drop is strongly concentrated at the edges of the ASMA. A prominent increase in O3 (> 40 %) at 100 hPa is clearly evident within the ASMA in July, whereas in August the increase is strongly located (even at 121 hPa) over the western edges of the ASMA. Further, the temperature around the tropopause shows significant positive anomalies (∼ 5 K) within the ASMA in 2015. The present results clearly reveal the El-Niño-induced dynamical changes caused significant changes in the trace gases within the ASMA in summer 2015.

The North American Spring Coldness Response to the Persistent Weak Stratospheric Vortex Induced by Extreme El Niño Events

The stratospheric pathway is a major driver of El Niño–Southern Oscillation (ENSO) impacts on mid-latitude tropospheric circulation and winter weather. The weak vortex induced by El Niño conditions has been shown to increase the risk of cold spells, especially over Eurasia, but its role for North American winters is less clear. This study involved idealized experiments with the Whole Atmosphere Community Climate Model to examine how the weak winter vortex induced by extreme El Niño events is linked to North American coldness in spring. Contrary to the expected mid-latitude cooling associated with a weak vortex, extreme El Niño events do not lead to North American cooling overall, with daily cold extremes actually decreasing, especially in Canada. The expected cooling is absent in most of North America because of the advection of warmer air masses guided by an enhanced ridge over Canada and a trough over the Aleutian Peninsula. This pattern persists in spring as a result of the trapping of stationary waves from the polar stratosphere and troposphere, implying that the stratospheric influence on North America is sensitive to regional downward wave activities.