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doi: 10.1007/s10584-019-02458-xpmid: N/A
The ice core glacial-interglacial record of the last 450 kyr (Cortese et al. Paleogeogr Paleoclimatol 22:4, 2007), development of cold ice meltwater regions at fringes of the Greenland and the West Antarctic ice sheets, and climate projections by Hansen et al. (Atmos Chem Phys 16:3761–3812, 2016), support a relation between ice sheet melting and the cooling of neighboring ocean zones by ice meltwater. Several factors lead to cooling of parts of the North Atlantic Ocean and adjacent lands, including the following: (A) a slowdown of the Atlantic meridional overturning circulation (AMOC); (B) flow of cold ice meltwater from the Greenland ice sheet into the North Atlantic Ocean; (C) undulation and weakening of the jet stream at the Arctic boundary due to a rise in temperature in the Arctic circle at twice the rate of warming at lower latitudes and the ice-water albedo flip. Penetration of Arctic-derived cold air masses southward through a weakened jet stream boundary ensues in extreme weather events in North America and Europe. The slowdown of the AMOC (Caesar et al. Nature 556:191–196, 2018; Praetorius Nat Clim Chang 5:475–480, 2018; Thornalley et al. Nature 556:227–230, 2018; Smeed et al. Geophys Res Lett 45(3):1527–1533, 2018) and growing cold ocean region (Rahmstorf et al. Nat Clim Chang 5:475–480, 2015) may herald the onset of a stadial event. A large-scale stadial event, possibly on the scale of the 8.3–8.2 kyr-old Laurentian melt event, or even the 12.9–11.7-kyr-old Younger Dryas stadial (Carlson Encycl Quat Sci 3:126–134, 2013), could ensue from advanced melting of both the Greenland ice sheet and the Antarctic ice sheet. A stadial would be succeeded by the resumption of warming driven by a continuing rise in greenhouse gas concentrations and amplifying feedback effects. These projections need to be examined vis-a-vis the continuous linear IPCC temperature rise models.
doi: 10.1007/s10584-019-02467-wpmid: N/A
This research examines the role that large-scale circulation plays in local storminess for the North Atlantic islands of Orkney and Shetland, using the ERA-20C (1900–2009) reanalysis dataset. Automatic Lamb weather type classification is applied to daily mean sea level pressure (MSLP) data at 0.125° × 0.125° resolution to typify large-scale circulation patterns and calculate measures of storminess (frequencies of severe gale days, very severe gale days, and gale days that are not severe), calibrated using available observations from meteorological stations on the islands, which were made available by the UK Met Office. Analysis of the reanalysis-based gale day record indicates that while the frequency of cyclonic (C) weather type days does not vary over the study period, this weather type is coinciding more often with gale days and especially very severe gale days, which may indicate an increase in the intensity of cyclonic weather types in the region.
Fotso-Nguemo, Thierry; Diallo, Ismaïla; Diakhaté, Moussa; Vondou, Derbetini; Mbaye, Mamadou; Haensler, Andreas; Gaye, Amadou; Tchawoua, Clément
doi: 10.1007/s10584-019-02492-9pmid: N/A
This study explores the potential response of the seasonal cycle of extreme rainfall indices over Central Africa (CA) to the global warming for both the middle (2029–2058) and late twenty-first century (2069–2098), based on analysis of multi-model ensembles mean of fifteen regional climate models (RCMs) simulations. Although few dry/wet biases are still evident, for the present day climate, the RCMs ensemble mostly outperforms the driving global climate models, with a better representation of the seasonal cycle of various rainfall indices over two key sub-regions of CA chosen according to their particular rainfall patterns. Both middle and late twenty-first century project a non-significant decrease in total wet-day rainfall amount over the two analysed sub-regions, with peaks found during pre-monsoon months. We also found a significant decrease in wet-day frequency which was consistent with decreases in total wet-day rainfall amount, while wet-day intensity is projected to significantly increase. These results suggest that the decrease in total wet-day rainfall amount could be associated with less frequent events and not with their intensity. The results also have shown that dry (wet) spells are projected to significantly increase (decrease) over both sub-regions with shorter (longer) dry (wet) spells projected during pre-monsoon months. Consequently, countries within these two sub-regions could experience a more extended dry season, and therefore would be exposed to high drought risk in the future under global warming. However, changes in maximum 1-day rainfall amount, maximum 5-day rainfall amount, and 95th percentile are projected to significantly increase during monsoon months, with the maximum 1-day rainfall amount recording largest increases. Additionally, the total amount of rainfall events above the 95th percentile projects a significant increase of about 10–45 % during monsoon months, while the total number of occurrence of rainfall events above the 95th percentile projects a slight significant decrease of 4–8 % during pre-monsoon months but more pronounced for the late twenty-first century. This implies that in the future, extremes rainfall events could be more intense both in terms of rainfall amount and intensity during monsoon months. Such changes are likely to amplify the probability of flood risks during monsoon months over CA, particularly the two sub-regions. This study could therefore be an important input for disaster preparedness, adaptation planning, and mitigation strategies for Central African countries.
Camuffo, Dario; Becherini, Francesca; Valle, Antonio
doi: 10.1007/s10584-019-02482-xpmid: N/A
The precipitation record taken by J.B. Beccari in Bologna from 1723 to 1765, with three observations a day, has been recovered from the original Logs and analysed. Although metadata are scarce or even missing, a thorough investigation of the contemporary sources, the interactions between Beccari, his colleagues in Padua, and the Royal Society London, as well as the record analysis, have allowed reconstruction of most of the information concerning the instrument, its location and exposure, the measuring protocol and units. Daily, monthly and yearly amounts and frequencies, as well as extreme events, have been analysed. The first decade (i.e. 1723–1733) was drier than the 1961–1990 reference period and the subsequent decades wetter. During the calendar year, summer was dryer and October was characterized by a stronger activity of Atlantic perturbations.
Arnell, N.; Lowe, J.; Challinor, A.; Osborn, T.
doi: 10.1007/s10584-019-02464-zpmid: N/A
The assessment of the impacts of climate change at different levels of global warming helps inform national and international policy discussion around mitigation targets. This paper provides consistent estimates of global and regional impacts and risks at increases in global mean temperature up to 5 °C above pre-industrial levels, for over 30 indicators representing temperature extremes and heatwaves, hydrological change, floods and droughts and proxies for impacts on crop yields. At the global scale, all the impacts that could plausibly be either adverse or beneficial are adverse, and impacts and risks increase with temperature change. For example, the global average chance of a major heatwave increases from 5% in 1981–2010 to 28% at 1.5 °C and 92% at 4 °C, of an agricultural drought increases from 9 to 24% at 1.5 °C and 61% at 4 °C, and of the 50-year return period river flood increases from 2 to 2.4% at 1.5 °C and 5.4% at 4 °C. The chance of a damaging hot spell for maize increases from 5 to 50% at 4 °C, whilst the chance for rice rises from 27 to 46%. There is considerable uncertainty around these central estimates, and impacts and risks vary between regions. Some impacts—for example heatwaves—increase rapidly as temperature increases, whilst others show more linear responses. The paper presents estimates of the risk of impacts exceeding specific targets and demonstrates that these estimates are sensitive to the thresholds used.
Fu, Xinyu; Sun, Bowen; Frank, Kathryn; Peng, Zhong-Ren
doi: 10.1007/s10584-019-02488-5pmid: N/A
Many coastal communities around the world are increasingly faced with pressure from sea level rise (SLR). Adapting to the impacts of SLR is now considered inevitable. Many coastal communities in the USA have started to invest in vulnerability assessments that seek to identify the degree of future risk induced by SLR and key vulnerable sectors as well as to provide a sound factual basis for designing and implementing adaptations. However, no study has systematically analyzed the content of these emerging assessments and their quality. This study aims to address this gap by evaluating 64 SLR vulnerability assessments in the USA using an established multi-criteria evaluation framework and by identifying governance factors that affect assessment quality. This study is the first baseline study to understand how the vulnerability of SLR has been assessed by US governments and, more importantly, shed light on pathways for their future improvement. Our analysis finds that the content and quality of the existing assessments vary widely. One-sided assessments that only consider physical exposure are common, and most assessments do not include plans for adaptations. The wealth of the area, amount of funding, mainstreaming efforts, and public awareness are all positively correlated with the assessment quality. We also find that assessments primarily authored by planning staff are lower in quality than those conducted through collaboration. Our findings offer comparative, empirical knowledge for urban planners and coastal managers to improve future vulnerability assessments and adaptation planning for SLR.
Aguayo, Rodrigo; León-Muñoz, Jorge; Vargas-Baecheler, José; Montecinos, Aldo; Garreaud, René; Urbina, Mauricio; Soto, Doris; Iriarte, José
doi: 10.1007/s10584-019-02495-6pmid: N/A
Oceanographic conditions in coastal Chilean northern Patagonia (41–46°S) are strongly influenced by freshwater inputs. Precipitation and streamflow records have shown a marked decrease in this area during the last decades. Given this hydro-climatic scenario, we evaluated the hydrological sensitivity driven by climate change in the Puelo River (average annual streamflow = 640 m3 s−1), one of the most important sources of freshwater in the fjords and inland seas of Chile’s Northern Patagonia. A lumped hydrological model was developed to evaluate the potential impacts of climate change under the Representative Concentration Pathways (RCP) 2.6, 4.5, and 8.5 scenarios in the near future (2030–2060) using the delta change method based on 25 General Circulation Models. The model was fed by local hydro-meteorological data and remote sensors, simulating well the magnitude and seasonality of Puelo River streamflow. Considering the Refined Index of Agreement (RIA), the model achieved a high performance in the calibration (RIA = 0.79) and validation stages (RIA = 0.78). Under the RCP 8.5 scenario (multi-model mean), the projections suggest that the annual input of freshwater from the Puelo River to the Reloncaví Fjord would decrease by − 10% (1.6 km3 less freshwater); these decreases would mainly take place in summer (~ − 20%) and autumn (~ − 15%). The recurrence of extreme hydroclimatic events is also projected to increase in the future, with the probability of occurrence of droughts, such as the recent 2016 event with the lowest freshwater input in the last 70 years, doubling with respect to the historical records.
Huang, Richao; Chen, Xi; Hu, Qi
doi: 10.1007/s10584-019-02475-wpmid: N/A
Elevated atmospheric CO2 concentration alters vegetation growth and composition, increases plant water use efficiency (WUE), and changes surface water balance. These changes and their differences between wet and dry climate are studied at a mid-latitude experiment site in the Loess Plateau of China. The study site, the Jinghe River basin (JRB), covers an area of 43,216 km2 and has a semiarid climate in the north and a semi-humid climate in the south. Two simulations from 1965 to 2012 are made using a site-calibrated Lund–Potsdam–Jena dynamic global vegetation model: one with the observed rise of the atmospheric CO2 from 319.7–391.2 ppmv, and the other with a fixed CO2 at the level of 1964 (318.9 ppmv). Analyses of the model results show that the elevated atmospheric CO2 promotes growth of woody vegetation (trees) and causes a 6.0% increase in basin-wide net primary production (NPP). The NPP increase uses little extra water however because of higher WUE. Further examination of the surface water budget reveals opposite CO2 effects between semiarid and semi-humid climates in the JRB. In the semiarid climate, plants sustain growth in higher CO2 because of the higher level of intracellular CO2 and therefore WUE, thus consuming more water and causing a greater decrease of surface runoff than in the fixed-lower CO2 case. In the semi-humid climate, NPP also increases but by a smaller amount than in the semiarid climate. Plant transpiration (E T ) and total evapotranspiration (E) decrease in the elevated CO2 environment, yielding the increase of runoff. This asymmetry of the effects of elevated atmospheric CO2 exacerbates drying in the semiarid climate and enhances wetness in the semi-humid climate. Furthermore, plant WUE (=NPP/E T ) is found to be nearly invariant to climate but primarily a function of the atmospheric CO2 concentration, a result suggesting a strong constraint of atmospheric CO2 on biophysical properties of the Earth system.
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