Climate

17 pages, 2912 KiB

Open AccessEditor’s ChoiceArticle

Statistical Analysis of Recent and Future Rainfall and Temperature Variability in the Mono River Watershed (Benin, Togo)

by Lawin Agnidé Emmanuel, Nina Rholan Hounguè, Chabi Angelbert Biaou and Djigbo Félicien Badou

Climate 2019, 7(1), 8; https://doi.org/10.3390/cli7010008 - 06 Jan 2019

Cited by 29 | Viewed by 5746

Abstract

This paper assessed the current and mid-century trends in rainfall and temperature over the Mono River watershed. It considered observation data for the period 1981–2010 and projection data from the regional climate model (RCM), REMO, for the period 2018–2050 under emission scenarios RCP4.5 [...] Read more.

This paper assessed the current and mid-century trends in rainfall and temperature over the Mono River watershed. It considered observation data for the period 1981–2010 and projection data from the regional climate model (RCM), REMO, for the period 2018–2050 under emission scenarios RCP4.5 and RCP8.5. Rainfall data were interpolated using ordinary kriging. Mann-Kendall, Pettitt and Standardized Normal Homogeneity (SNH) tests were used for trends and break-points detection. Rainfall interannual variability analysis was based on standardized precipitation index (SPI), whereas anomalies indices were considered for temperature. Results revealed that on an annual scale and all over the watershed, temperature and rainfall showed an increasing trend during the observation period. By 2050, both scenarios projected an increase in temperature compared to the baseline period 1981–2010, whereas annual rainfall will be characterized by high variabilities. Rainfall seasonal cycle is expected to change in the watershed: In the south, the second rainfall peak, which usually occurs in September, will be extended to October with a higher value. In the central and northern parts, rainfall regime is projected to be characterized by late onsets, a peak in September and lower precipitation until June and higher thereafter. The highest increase and decrease in monthly precipitation are expected in the northern part of the watershed. Therefore, identifying relevant adaptation strategies is recommended. Full article

(This article belongs to the Special Issue Climate Variability and Change in the 21th Century)

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19 pages, 6919 KiB

Open AccessEditor’s ChoiceArticle

Decadal Ocean Heat Redistribution Since the Late 1990s and Its Association with Key Climate Modes

by Lijing Cheng, Gongjie Wang, John P. Abraham and Gang Huang

Climate 2018, 6(4), 91; https://doi.org/10.3390/cli6040091 - 19 Nov 2018

Cited by 19 | Viewed by 9394

Abstract

Ocean heat content (OHC) is the major component of the earth’s energy imbalance. Its decadal scale variability has been heavily debated in the research interest of the so-called “surface warming slowdown” (SWS) that occurred during the 1998–2013 period. Here, we first clarify that [...] Read more.

Ocean heat content (OHC) is the major component of the earth’s energy imbalance. Its decadal scale variability has been heavily debated in the research interest of the so-called “surface warming slowdown” (SWS) that occurred during the 1998–2013 period. Here, we first clarify that OHC has accelerated since the late 1990s. This finding refutes the concept of a slowdown of the human-induced global warming. This study also addresses the question of how heat is redistributed within the global ocean and provides some explanation of the underlying physical phenomena. Previous efforts to answer this question end with contradictory conclusions; we show that the systematic errors in some OHC datasets are partly responsible for these contradictions. Using an improved OHC product, the three-dimensional OHC changes during the SWS period are depicted, related to a reference period of 1982–1997. Several “hot spots” and “cold spots” are identified, showing a significant decadal-scale redistribution of ocean heat, which is distinct from the long-term ocean-warming pattern. To provide clues for the potential drivers of the OHC changes during the SWS period, we examine the OHC changes related to the key climate modes by regressing the Pacific Decadal Oscillation (PDO), El Niño-Southern Oscillation (ENSO), and Atlantic Multi-decadal Oscillation (AMO) indices onto the de-trended gridded OHC anomalies. We find that no single mode can fully explain the OHC change patterns during the SWS period, suggesting that there is not a single “pacemaker” for the recent SWS. Our observation-based analyses provide a basis for further understanding the mechanisms of the decadal ocean heat uptake and evaluating the climate models. Full article

(This article belongs to the Special Issue Postmortem of the Global Warming Hiatus)

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18 pages, 5046 KiB

Open AccessEditor’s ChoiceArticle

Changes in Earth’s Energy Budget during and after the “Pause” in Global Warming: An Observational Perspective

by Norman G. Loeb, Tyler J. Thorsen, Joel R. Norris, Hailan Wang and Wenying Su

Climate 2018, 6(3), 62; https://doi.org/10.3390/cli6030062 - 11 Jul 2018

Cited by 64 | Viewed by 24274

Abstract

This study examines changes in Earth’s energy budget during and after the global warming “pause” (or “hiatus”) using observations from the Clouds and the Earth’s Radiant Energy System. We find a marked 0.83 ± 0.41 Wm⁻² reduction in global mean reflected shortwave [...] Read more.

This study examines changes in Earth’s energy budget during and after the global warming “pause” (or “hiatus”) using observations from the Clouds and the Earth’s Radiant Energy System. We find a marked 0.83 ± 0.41 Wm⁻² reduction in global mean reflected shortwave (SW) top-of-atmosphere (TOA) flux during the three years following the hiatus that results in an increase in net energy into the climate system. A partial radiative perturbation analysis reveals that decreases in low cloud cover are the primary driver of the decrease in SW TOA flux. The regional distribution of the SW TOA flux changes associated with the decreases in low cloud cover closely matches that of sea-surface temperature warming, which shows a pattern typical of the positive phase of the Pacific Decadal Oscillation. Large reductions in clear-sky SW TOA flux are also found over much of the Pacific and Atlantic Oceans in the northern hemisphere. These are associated with a reduction in aerosol optical depth consistent with stricter pollution controls in China and North America. A simple energy budget framework is used to show that TOA radiation (particularly in the SW) likely played a dominant role in driving the marked increase in temperature tendency during the post-hiatus period. Full article

(This article belongs to the Special Issue Postmortem of the Global Warming Hiatus)

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21 pages, 4034 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Increasing Surface Albedo on Urban Climate and Air Quality: A Detailed Study for Sacramento, Houston, and Chicago

by Zahra Jandaghian and Hashem Akbari

Climate 2018, 6(2), 19; https://doi.org/10.3390/cli6020019 - 21 Mar 2018

Cited by 45 | Viewed by 8139

Abstract

Increasing surface reflectivity in urban areas can decrease ambient temperature, resulting in reducing photochemical reaction rates, reducing cooling energy demands and thus improving air quality and human health. The weather research and forecasting model with chemistry (WRF-Chem) is coupled with the multi-layer of [...] Read more.

Increasing surface reflectivity in urban areas can decrease ambient temperature, resulting in reducing photochemical reaction rates, reducing cooling energy demands and thus improving air quality and human health. The weather research and forecasting model with chemistry (WRF-Chem) is coupled with the multi-layer of the urban canopy model (ML-UCM) to investigate the effects of surface modification on urban climate in a two-way nested approach over North America focusing on Sacramento, Houston, and Chicago during the 2011 heat wave period. This approach decreases the uncertainties associated with scale separation and grid resolution and equip us with an integrated simulation setup to capture the full impacts of meteorological and photochemical reactions. WRF-ChemV3.6.1 simulated the diurnal variation of air temperature reasonably well, overpredicted wind speed and dew point temperature, underpredicted relative humidity, overpredicted ozone and nitrogen dioxide concentrations, and underpredicted fine particular matters (PM_2.5). The performance of PM_2.5 is a combination of overprediction of particulate sulfate and underprediction of particulate nitrate and organic carbon. Increasing the surface albedo of roofs, walls, and pavements from 0.2 to 0.65, 0.60, and 0.45, respectively, resulted in a decrease in air temperature by 2.3 °C in urban areas and 0.7 °C in suburban areas; a slight increase in wind speed; an increase in relative humidity (3%) and dew point temperature (0.3 °C); a decrease of PM_2.5 and O₃ concentrations by 2.7 µg/m³ and 6.3 ppb in urban areas and 1.4 µg/m³ and 2.5 ppb in suburban areas, respectively; minimal changes in PM_2.5 subspecies; and a decrease of nitrogen dioxide (1 ppb) in urban areas. Full article

(This article belongs to the Special Issue Urban Overheating - Progress on Mitigation Science and Engineering Applications)

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1746 KiB

Open AccessEditor’s ChoiceArticle

The Uncertain Role of Biogenic VOC for Boundary-Layer Ozone Concentration: Example Investigation of Emissions from Two Forest Types with a Box Model

by Boris Bonn, Jürgen Kreuzwieser, Felicitas Sander, Rasoul Yousefpour, Tommaso Baggio and Oladeinde Adewale

Climate 2017, 5(4), 78; https://doi.org/10.3390/cli5040078 - 06 Oct 2017

Cited by 10 | Viewed by 5957

Abstract

High levels of air pollution including ground level ozone significantly reduce humans’ life expectancy and cause forest damage and decreased tree growth. The French Vosges and the German Black Forest are regions well-known for having the highest tropospheric ozone concentrations at remote forested [...] Read more.

High levels of air pollution including ground level ozone significantly reduce humans’ life expectancy and cause forest damage and decreased tree growth. The French Vosges and the German Black Forest are regions well-known for having the highest tropospheric ozone concentrations at remote forested sites in Central Europe. This box model study investigates the sensitivity of atmospheric chemistry calculations of derived ozone on differently resolved forest tree composition and volatile organic compound emissions. Representative conditions were chosen for the Upper Rhine area including the Alsatian Vosges/France and the Black Forest/Germany during summer. This study aims to answer the following question: What level of input detail for Alsace and Black Forest tree mixtures is required to accurately simulate ozone formation? While the French forest in Alsace—e.g., in the Vosges—emits isoprene to a substantially higher extent than the forest at the German site, total monoterpene emissions at the two sites are rather similar. However, the individual monoterpene structures, and therefore their reactivity, differs. This causes a higher ozone production rate for Vosges forest mixture conditions than for Black Forest tree mixtures at identical NO_x levels, with the difference increasing with temperature. The difference in ozone formation is analyzed in detail and the short-comings of reduced descriptions are discussed. The outcome serves as a to-do-list to allow accurate future ozone predictions influenced by the climate adaptation of forests and the change in forest species composition. Full article

(This article belongs to the Special Issue Modeling Interactions Among Atmosphere, Hydrosphere, and Biosphere)

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7141 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Relationship between Atmospheric Carbon Dioxide Concentration and Global Temperature for the Last 425 Million Years

by W. Jackson Davis

Climate 2017, 5(4), 76; https://doi.org/10.3390/cli5040076 - 29 Sep 2017

Cited by 33 | Viewed by 67572

Abstract

Assessing human impacts on climate and biodiversity requires an understanding of the relationship between the concentration of carbon dioxide (CO₂) in the Earth’s atmosphere and global temperature (T). Here I explore this relationship empirically using comprehensive, recently-compiled databases of stable-isotope proxies [...] Read more.

Assessing human impacts on climate and biodiversity requires an understanding of the relationship between the concentration of carbon dioxide (CO₂) in the Earth’s atmosphere and global temperature (T). Here I explore this relationship empirically using comprehensive, recently-compiled databases of stable-isotope proxies from the Phanerozoic Eon (~540 to 0 years before the present) and through complementary modeling using the atmospheric absorption/transmittance code MODTRAN. Atmospheric CO₂ concentration is correlated weakly but negatively with linearly-detrended T proxies over the last 425 million years. Of 68 correlation coefficients (half non-parametric) between CO₂ and T proxies encompassing all known major Phanerozoic climate transitions, 77.9% are non-discernible (p > 0.05) and 60.0% of discernible correlations are negative. Marginal radiative forcing (ΔRF_CO₂), the change in forcing at the top of the troposphere associated with a unit increase in atmospheric CO₂ concentration, was computed using MODTRAN. The correlation between ΔRF_CO₂ and linearly-detrended T across the Phanerozoic Eon is positive and discernible, but only 2.6% of variance in T is attributable to variance in ΔRF_CO₂. Of 68 correlation coefficients (half non-parametric) between ΔRF_CO₂ and T proxies encompassing all known major Phanerozoic climate transitions, 75.0% are non-discernible and 41.2% of discernible correlations are negative. Spectral analysis, auto- and cross-correlation show that proxies for T, atmospheric CO₂ concentration and ΔRF_CO₂ oscillate across the Phanerozoic, and cycles of CO₂ and ΔRF_CO₂ are antiphasic. A prominent 15 million-year CO₂ cycle coincides closely with identified mass extinctions of the past, suggesting a pressing need for research on the relationship between CO₂, biodiversity extinction, and related carbon policies. This study demonstrates that changes in atmospheric CO₂ concentration did not cause temperature change in the ancient climate. Full article

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632 KiB

Open AccessEditor’s ChoiceArticle

Germination Phenological Response Identifies Flora Risk to Climate Change

by Sarala Budhathoki Chhetri and Deepa Shree Rawal

Climate 2017, 5(3), 73; https://doi.org/10.3390/cli5030073 - 18 Sep 2017

Cited by 5 | Viewed by 3821

Abstract

Climate change is prevalent across the world and can have large influence on plant regeneration, recruitment, survival and diversity. Regeneration and recruitment are the key phases in the plant life cycle and these two aspects are related to survival, adaptation and distribution of [...] Read more.

Climate change is prevalent across the world and can have large influence on plant regeneration, recruitment, survival and diversity. Regeneration and recruitment are the key phases in the plant life cycle and these two aspects are related to survival, adaptation and distribution of species. This study thus aims to explore the effect of projected climate change on germination and establishment response of some timber tree species from the tropical/subtropical broad leaf forests of Nepal. Germination experiments were carried out under three different temperature regimes (20, 25 and 30 °C) and germination parameters identified from the experimental component were calibrated in the mechanistic model Tree and Climate Assessment—Germination and Establishment Module (TACA-GEM) that helped in identifying species vulnerability to climate change. The model outcome under varied climatic conditions helped in determining the species risk to projected climatic conditions. The model demonstrates that the studied species were able to increase germination under the projected climate change however, establishment consistently failed for most of the species across the hot tropical sites. This finding indicates that spatial vulnerability may limit recruitment in the future. The species-specific responses suggest that, in general, all three species (Alnus nepalensis, Adina cordifolia, and Bombax ceiba) exhibited enhanced germination and establishment in moderately warm and colder sites, indicating that these species may more likely shift their range towards the north in future. Thus, the general species response exhibited in this study may aid in regional climate change adaptation planning in the sector of forest conservation and management. Full article

(This article belongs to the Special Issue Climate Impacts and Resilience in the Developing World)

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5563 KiB

Open AccessEditor’s ChoiceArticle

Variations of Rainfall Rhythm in Alto Pardo Watershed, Brazil: Analysis of Two Specific Years, a Wet and a Dry One, and Their Relation with the River Flow

by Pedro Augusto Breda Fontão and João Afonso Zavattini

Climate 2017, 5(3), 47; https://doi.org/10.3390/cli5030047 - 04 Jul 2017

Cited by 4 | Viewed by 6626

Abstract

This research aims to understand the variability and rhythm of rainfall for two specific standard-years, and their relation with the river flow of the Alto Pardo watershed, located in southeastern Brazil, and thus identify atmospheric systems that can cause extreme events, and which [...] Read more.

This research aims to understand the variability and rhythm of rainfall for two specific standard-years, and their relation with the river flow of the Alto Pardo watershed, located in southeastern Brazil, and thus identify atmospheric systems that can cause extreme events, and which may be reflected in heavy rainfall, floods, or drought episodes. Therefore, the research chose to investigate the years 1983 and 1984, rainy and dry standard-years respectively in the study area, where rainfall was described and spatialized through the geostatistical method of kriging at the monthly level and the rhythmic analysis technique was applied in order to identify what weather types are usual and extreme in the area. The results indicate that a high involvement of the frontal system in the year 1983 was responsible for the episodes of greater rainfall and peak water flow, especially in stationary front episodes. The year 1984 presented low rainfall in summer, a meteorological drought during the year, and the predominance of tropical air masses in relation to the frontal systems. The comparison between the two extreme years, a wet and a dry one, made it possible to understand the frequency and the chaining of the atmospheric systems during this period for the Alto Pardo watershed. Full article

(This article belongs to the Special Issue Studies and Perspectives of Climatology in Brazil)

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221 KiB

Open AccessEditor’s ChoiceReview

The Vulnerability of Rice Value Chains in Sub-Saharan Africa: A Review

by Fanen Terdoo and Giuseppe Feola

Climate 2016, 4(3), 47; https://doi.org/10.3390/cli4030047 - 19 Sep 2016

Cited by 12 | Viewed by 9635

Abstract

Rice is one of the most important food crops in sub-Saharan Africa. Climate change, variability, and economic globalization threatens to disrupt rice value chains across the subcontinent, undermining their important role in economic development, food security, and poverty reduction. This paper maps existing [...] Read more.

Rice is one of the most important food crops in sub-Saharan Africa. Climate change, variability, and economic globalization threatens to disrupt rice value chains across the subcontinent, undermining their important role in economic development, food security, and poverty reduction. This paper maps existing research on the vulnerability of rice value chains, synthesizes the evidence and the risks posed by climate change and economic globalization, and discusses agriculture and rural development policies and their relevance for the vulnerability of rice value chains in sub-Saharan Africa. Important avenues for future research are identified. These include the impacts of multiple, simultaneous pressures on rice value chains, the effects of climate change and variability on parts of the value chain other than production, and the forms and extent to which different development policies hinder or enhance the resilience of rice value chains in the face of climatic and other pressures. Full article

(This article belongs to the Special Issue Climate Impacts and Resilience in the Developing World)

9728 KiB

Open AccessEditor’s ChoiceArticle

Future Water Availability from Hindukush-Karakoram-Himalaya upper Indus Basin under Conflicting Climate Change Scenarios

by Shabeh ul Hasson

Climate 2016, 4(3), 40; https://doi.org/10.3390/cli4030040 - 26 Aug 2016

Cited by 45 | Viewed by 10314

Abstract

Future of the crucial Himalayan water supplies has generally been assessed under the anthropogenic warming, typically consistent amid observations and climate model projections. However, conflicting mid-to-late melt-season cooling within the upper Indus basin (UIB) suggests that the future of its melt-dominated hydrological regime [...] Read more.

Future of the crucial Himalayan water supplies has generally been assessed under the anthropogenic warming, typically consistent amid observations and climate model projections. However, conflicting mid-to-late melt-season cooling within the upper Indus basin (UIB) suggests that the future of its melt-dominated hydrological regime and the subsequent water availability under changing climate has yet been understood only indistinctly. Here, the future water availability from the UIB is presented under both observed and projected—though likely but contrasting—climate change scenarios. Continuation of prevailing climatic changes suggests decreased and delayed glacier melt but increased and early snowmelt, leading to reduction in the overall water availability and profound changes in the overall seasonality of the hydrological regime. Hence, initial increases in the water availability due to enhanced glacier melt under typically projected warmer climates, and then abrupt decrease upon vanishing of the glaciers, as reported earlier, is only true given the UIB starts following uniformly the global warming signal. Such discordant future water availability findings caution the impact assessment communities to consider the relevance of likely (near-future) climate change scenarios—consistent to prevalent climatic change patterns—in order to adequately support the water resource planning in Pakistan. Full article

(This article belongs to the Special Issue Impact of Climate Change on Water Resources)

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2238 KiB

Open AccessEditor’s ChoiceReview

Hydrological Climate Change Impact Assessment at Small and Large Scales: Key Messages from Recent Progress in Sweden

by Jonas Olsson, Berit Arheimer, Matthias Borris, Chantal Donnelly, Kean Foster, Grigory Nikulin, Magnus Persson, Anna-Maria Perttu, Cintia B. Uvo, Maria Viklander and Wei Yang

Climate 2016, 4(3), 39; https://doi.org/10.3390/cli4030039 - 24 Aug 2016

Cited by 47 | Viewed by 13867

Abstract

Hydrological climate change impact assessment is generally performed by following a sequence of steps from global and regional climate modelling, through data tailoring (bias-adjustment and downscaling) and hydrological modelling, to analysis and impact assessment. This “climate-hydrology-assessment chain” has been developed with a primary [...] Read more.

Hydrological climate change impact assessment is generally performed by following a sequence of steps from global and regional climate modelling, through data tailoring (bias-adjustment and downscaling) and hydrological modelling, to analysis and impact assessment. This “climate-hydrology-assessment chain” has been developed with a primary focus on applicability to a medium-sized rural basin, which has been and still is the main type of domain investigated in this context. However, impact assessment is to an increasing degree being performed at scales smaller or larger than the medium-sized rural basin. Small-scale assessment includes e.g., impacts on solute transport and urban hydrology and large-scale assessment includes e.g., climate teleconnections and continental modelling. In both cases, additional complexity is introduced in the process and additional demands are placed on all components involved, i.e., climate and hydrology models, tailoring methods, assessment principles, and tools. In this paper we provide an overview of recent progress with respect to small- and large-scale hydrological climate change impact assessment. In addition, we wish to highlight some key issues that emerged as a consequence of the scale and that need further attention from now on. While we mainly use examples from work performed in Europe for illustration, the progress generally reflects the overall state of the art and the issues considered are of a generic character. Full article

(This article belongs to the Special Issue Impact of Climate Change on Water Resources)

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