Climate Forcing Research Articles

Biomarker reconstructions of temperature and hydroclimate variability in Vietnam during Marine Isotope Stage 3

Limited hydrological data coupled with a reliance on the monsoon rains for agriculture make Southeast (SE) Asia vulnerable to climate change. To develop a better understanding of how SE Asia responds to climatic forcings, we provide a paleoclimate perspective by reconstructing temperature and hydroclimate from a wetland outcrop in the Central Highlands of Vietnam (CHV) during Marine Isotope Stage 3 (MIS 3). Mean annual atmospheric temperatures inferred from brGDGTs (branched glycerol dialkyl glycerol tetraethers) indicate an increase from 23 to 26 °C between ∼54 and 37 cal ka BP, which follows an increase in mean annual insolation at the latitude of the site. δDwax data show a shift from a greater proportion of summer monsoon rain derived from the Bay of Bengal between 54 and 49 cal ka BP toward more autumn rain from the South China Sea (also known as the Vietnam East Sea) for most of the rest of the record. brGDGT-inferred soil pH suggests that the climate was wetter at 54 to 49 cal ka BP, then became drier, then returned to wet conditions approaching 37 cal ka BP. Both orbital forcing and changes in the exposure of the Sunda Shelf likely influenced hydroclimate in the CHV. δ13Cwax indicates that C4 plants dominate the vegetation cover during MIS 3. Comparison between our new record from the CHV with existing water isotope proxy records reveals coherent changes with nearby speleothem data, but regional differences between the history of hydroclimate in SE Asia and in the central Indian Monsoon domain. As a snapshot of glacial climate conditions, our data provide new information on the past drivers of climate in an understudied region.

Stable hydrogen isotope evidence of late-Holocene precipitation variability on the Caribbean slope of the Cordillera Central, Costa Rica

In Central America and the Caribbean, periods of increased aridity that correspond to the Terminal Classic Drought (TCD; 1200–850 cal yr BP) and the Little Ice Age (LIA; 500–100 cal yr BP) have been documented in many paleoclimate records. Compound-specific hydrogen (δDalkane) and carbon (δ13Calkane) isotopic compositions of n-alkanes in lake sediment can be used to interpret changes in paleoprecipitation and terrestrial paleovegetation, respectively. To assess the climate forcing mechanisms that drove the TCD and LIA, we established a multidecadal to centennial-scale late-Holocene reconstruction of precipitation variability and vegetation change at mid-elevation on the Caribbean slope of Costa Rica, developed from new δDalkane, δ13Calkane, and geochemical analyses and previous pollen and microscopic charcoal analyses from a sediment core from Laguna María Aguilar. Laguna María Aguilar is a freshwater lake located at 770 m elevation on the Caribbean slope of the Cordillera Central. During the TCD, δDalkane data for María Aguilar indicate relatively wet conditions compared to the mean δDalkane value for the entire record. Other proxy records for the TCD indicate that the Pacific slope of Costa Rica and sites above 3400 m near the continental divide experienced generally drier conditions than mid- and low-elevations on the Caribbean slope. We conclude that the TCD may have been driven by both Pacific and Atlantic climate-forcing mechanisms. During the LIA, the Laguna María Aguilar δDalkane record indicates an increase in hydroclimate variability, with some of the highest recorded δDalkane values (driest conditions) during the earliest portions of the LIA, but conditions were not persistently dry for the entirety of the LIA. Based on regional paleoclimate records overall, the LIA drought appears to be more clearly expressed on the Caribbean slope than on the Pacific slope of Costa Rica, indicating that the LIA was perhaps driven primarily by Atlantic Ocean conditions and climate dynamics.

Opportunities beyond net-zero CO2 for cost-effective greenhouse gas mitigation in China

Achieving net-zero CO2 emissions is the current main focus of China’s carbon neutrality goal. However, non-CO2 greenhouse gases (GHGs) are more powerful climate forcers, making their emission reduction an opportunity to rapidly mitigate future warming. Here, we evaluate non-CO2 mitigation potentials, costs and climate benefits in the context of China’s carbon neutrality goals. The assessment is conducted by coupling the integrated assessment model GCAM with a climate emulator. The findings indicate that mitigation technologies can largely reduce fluorinated gas emissions from industrial sectors, but long-term non-CO2 reductions of energy sector activities rely heavily on fuel switching. Furthermore, the cumulative costs of deploying non-CO2 mitigation technologies are projected to be less than 10% of the total costs of achieving carbon neutrality from 2020 to 2060. If non-CO2 mitigation measures are included in the overall mitigation portfolio, the benefits of avoided warming would by far outweigh the total mitigation cost increase. Our results thus highlight that incorporating a wider suite of GHGs into climate change mitigation strategies can enhance the cost-effectiveness of mitigation efforts.

Source identification of carbon monoxide over the greater Tokyo area: Tower measurement network and evaluation of global/regional model simulations at different resolutions

Because of its relatively long lifetime among short-lived climate forcers in the atmosphere, carbon monoxide (CO) is utilized as a tracer, and is expected to be simulated at coarse resolution. To better grasp the behavior of CO in the atmosphere, multi-altitude measurement is required because the main sources of CO emissions are automobiles (surface) and industry (aloft). In this work, using CO measurements obtained at remote sites and through a tower measurement network in Japan (37 m and 250 m above ground level (AGL) in an urban area, and 32 m AGL at a rural site in the greater Tokyo area), the performances of a global model (2° × 2.5°) and a regional model at various resolutions (12, 4, and 1.3 km) were comprehensively evaluated. The global model successfully simulated CO at remote sites but not for high-concentration peaks at rural and urban sites, whereas the regional model increasingly improved its performance in capturing CO peaks at urban sites with resolutions up to 4 km. Therefore, we concluded that a 4 km resolution was suitable for capturing CO at urban sites, and furthermore estimated the source contributions. The regions surrounding the greater Tokyo area were dominated by the concentration from the lateral boundaries (approximately 180 ppbv), while the higher CO in central Tokyo was attributed to local sources. These local sources accounted for up to 80% of the annual average at the surface level and just 10% aloft (corresponding to the 250 m AGL site). Sensitivity simulations assessing CO sources (automobiles, industry, and others) demonstrated the important role of automobiles, while higher altitudes had more sources attributed to industry. Local sources were found to make more prominent contributions at higher concentration ranges. The appropriate modeling resolution for CO behavior can be drawn from our findings and the usefulness of simultaneous measurements at the surface level and using a tower for capturing the three-dimensional CO structure can be demonstrated as an important approach.

Toward Low‐Latency Estimation of Atmospheric CO2 Growth Rates Using Satellite Observations: Evaluating Sampling Errors of Satellite and In Situ Observing Approaches

AbstractThe atmospheric CO2 growth rate is a fundamental measure of climate forcing. NOAA's growth rate estimates, derived from in situ observations at the marine boundary layer (MBL), serve as the benchmark in policy and science. However, NOAA's MBL‐based method encounters challenges in accurately estimating the whole‐atmosphere CO2 growth rate at sub‐annual scales. Here we introduce the Growth Rate from Satellite Observations (GRESO) method as a complementary approach to estimate the whole‐atmosphere CO2 growth rate utilizing satellite data. Satellite CO2 observations offer extensive atmospheric coverage that extends the capability of the current NOAA benchmark. We assess the sampling errors of the GRESO and NOAA methods using 10 atmospheric transport model simulations. The simulations generate synthetic OCO‐2 satellite and NOAA MBL data for calculating CO2 growth rates, which are compared against the global sum of carbon fluxes used as model inputs. We find good performance for the NOAA method (R = 0.93, RMSE = 0.12 ppm year−1 or 0.25 PgC year−1). GRESO demonstrates lower sampling errors (R = 1.00; RMSE = 0.04 ppm year−1 or 0.09 PgC year−1). Additionally, GRESO shows better performance at monthly scales than the NOAA method (R = 0.76 vs. 0.47, respectively). Due to CO2's atmospheric longevity, the NOAA method accurately captures growth rates over 5‐year intervals. GRESO's robustness across partial coverage configurations (ocean or land data) shows that satellites can be promising tools for low‐latency CO2 growth rate information, provided the systematic biases are minimized using in situ observations. Along with accurate and calibrated NOAA in situ data, satellite‐derived growth rates can provide information about the global carbon cycle at sub‐annual scales.

A hydrogeological conceptual model of aquifers in catchments headed by temperate glaciers

Abstract. For reliable forecasting of the evolution of critical water resources, as well as of potential flood and landslide hazards and their response to climate change, it is necessary to improve the understanding and quantification of unknown aquifer systems in glacierized catchments. We focus on four southeastern outlet glaciers of the main Icelandic ice cap, Vatnajökull. A multidisciplinary approach is carried out, including the acquisition of new in situ data to characterize aquifers and their groundwater dynamics. Moreover, the recharge to aquifers from glacial melt and effective rainfall is estimated. From a detailed analysis of all available data and the determination of the dynamic characteristics of the aquifers, a hydrogeological conceptual model of glacierized catchments is constructed: (i) two distinct aquifers, their hydraulic conductivities and their hydrodynamic responses to climate forcing are identified; (ii) a comprehensive water balance for the whole catchment is obtained; (iii) the subglacial recharge to the aquifers is shown to be 4 times higher than in the proglacial area; and (v) the importance of the impact of the glacial melt recharge on the groundwater system is demonstrated. Thus, we highlight the major role that the groundwater component has in the hydrodynamic functioning of glacierized catchments.

Astronomically forcing salinity variations in a marginal-marine environment, Bohai Bay Basin, NE China

Exploring the interdependence between watermass conditions and climate change in marginal marine regions is essential for gaining insights into contemporary environmental challenges arising from global warming. Salinity, a key parameter of watermass conditions in coastal areas, plays a crucial role in influencing nutrient availability, stratification, and the spatial-temporal distribution of redox conditions. Here, we focus on the cyclostratigraphic analysis of gamma-ray (GR) data obtained from Eocene strata in the Luo-69 drillcore from the Bohai Bay Basin (NE China). This analysis establishes a high-resolution astronomical time scale (ATS) for the lower third member of the Shahejie Formation (Es3l), spanning 39.04 Ma to 41.46 million years ago (Ma). Various proxies for watermass conditions, such as salinity, sedimentary structures, mineral content, total organic carbon (TOC), organic carbon isotopes and nitrogen isotopes (δ13Corg and δ15N), exhibit a strong correlation with 405-kyr long orbital eccentricity climate forcing. Notably, spectral analysis of salinity data (represented by the Sr/Ba proxy) reveals a clear astronomical control, with 405-kyr eccentricity cycles that align closely with variations in the GR data. Peaks in paleosalinity, as indicated by Sr/Ba (as well as B/Ga and S/TOC), correspond with maxima in 405-kyr long orbital eccentricity cycles in the GR data. As such, we infer that astronomical forcing regulated long-term changes in watermass conditions, likely through mediation of the East Asia monsoon system. Specifically, during eccentricity maxima, the basin would have experienced a warm and humid climate with pronounced seasonality and a robust summer monsoon. During such periods, increased continental runoff would lead to a rise in lake-levels, facilitating better connections with the ocean, and hence increased salinity. By contrast, during eccentricity minima, cooler and more arid conditions with weaker seasonality would result in lower lake levels which together with a global eustatic lowstand would result in as weakened connection with the open ocean restricting the ingress of seawater into the basin lowering salinity. Our dataset spans the Middle Eocene Climatic Optimum (MECO, ∼40.60–40.10 Ma), identified by elevated GR values and a conspicuous negative excursion in oxygen isotopes. This interval is characterized by a significant decline in salinity, likely attributed to enhanced freshwater runoff driven by an extremely warm and humid climate. The paleosalinity fluctuation recorded by the proxies B/Ga, Sr/Ba, and S/TOC in Bohai Bay Basin demonstrate the sensitivity of marginal-marine environment to subtle changes in climate driven by astronomical forcing. Our results provide new insights into how elemental salinity proxies can be utilized in paleoenvironmental reconstruction studies.

Temporal characteristics of a 6.2 Ma-long ash-fall history in the NW Pacific

Explosive volcanism is one of the most dangerous and far-reaching natural hazards. The largest eruptions are the rarest, so studies of their temporal patterns have to rely on long archives. In this paper, we apply fractal and spectral analyses to the 6.2 Ma-long record of ash-falls at the Detroit Seamount (DS6M), > 600 km east of the Kamchatka Peninsula, NW Pacific, combined with a terrestrial record for the last 30 ka (T30ka). These datasets are the most complete for volcanism in the North Pacific, and DS6M spans all Pleistocene glaciations. In both datasets, events are grouped (Weibull parameter k < 0.84) with no characteristic scale of grouping in the time domain of thousands to millions of years. The fractal dimension of the studied data below the unity may be intrinsic to the volcanism (e.g. as a proxy of fractal composition and topography of a subducting plate) or represent uneven deposition and recovery of tephra. Only for the last 700 ka of DS6M, an increase in the correlation dimension values suggests the applicability of spectral analysis; however, no Milankovitch frequencies have been detected in this dataset. When compared to other North Pacific data for areas repeatedly glaciated in the Middle and Late Pleistocene and to a climate proxy of 18O isotopic stack LR04, the studied data suggest that variation in timing of ash-falls among the sites predominates over hemispheric-scale climatic forcing. If so, Quaternary glaciations had a limited effect on the timing of large explosive eruptions in North Pacific, still affecting the transit and deposition of erupted material.

Paleoclimate Controls on West African Dust Inferred from Rb/Sr and Si/Al of Sediments in an Eastern Equatorial Atlantic Marine Core

Increased dust emissions from dryland areas and their effects on human health, ecosystem viability, and environmental change are a global concern in the face of the growing climate crisis. Dust plume emissions from the West African landmass, Sahara, and Sahel areas comprise a major fraction of the global aerosol budget. Dust plume intensity is closely related to regional winds (e.g., Harmattan, Sahara Air Layer), the Intertropical Convergence Zone, monsoonal seasonality, marine currents, and physiography. To study terrigenous material emitted from the continent over the last ~260 kyr (late Quaternary), we used X-ray fluorescence spectroscopy (XRF) to analyze a ~755 cm long marine sediment core from the eastern equatorial Atlantic Ocean, resulting in nearly 1400 discrete measurements. Spectral analysis results suggest that concentrations of elements (Rb, Sr, Si, Al) preserved in the sediments are correlated to different types of orbital climate forcing. Chemical weathering intensity indicated by the Rb/Sr ratio was sensitive to seasonal insolation variations controlled by precession cycles (23–18 kyr), which presumably reflects the relationship between monsoonal rainfall and sensible heating of the continent. Spectral analysis of silicate mineral grain size (Si/Al) showed significant 40 kyr cycles that were paced by obliquity. Based on these data, we infer that winter tradewind activity accelerated in response to the intertropical insolation gradient induced by high obliquity. High Rb/Sr ratios during the last glacial maximum and penultimate glacial maximum may have been due to a predominance of mechanical weathering over chemical weathering under dry/cool climates or the dissolution of Sr-bearing carbonates by corrosive glacial bottom waters.

Tree-growth synchrony index, an effective indicator of historical climatic extremes

BackgroundTree rings play an important role in reconstructing past climate. Growth differences among individual trees due to microclimatic conditions and local disturbances are averaged in developing tree-ring chronologies. Here, we addressed the problem of averaging by investigating growth synchrony in individual trees. We used tree-ring data of 1046 juniper trees from 32 sites on the Tibetan Plateau and 538 pine trees from 20 sites in the subtropical region of eastern China and calculated the tree-growth synchrony index (TGS).ResultsOur results showed that both the TGS index and tree-ring index could be indicators of interannual variation of climatic factors. The TGS index identified 20% more climatic extremes than tree-ring index over the last 50 years that high synchrony indicates extreme climate forcing in controlling forest growth.ConclusionsThe TGS index can identify extreme climatic events effectively than tree-ring index. This study provides a novel perspective for climate reconstruction, especially in the realm of tree growth response to extreme climate. Our findings contribute to understanding of the spatiotemporal dynamics and the causes of historical climate extremes and provide guidance for protecting trees from climate extremes in the future.

Impacts of climate change and variability on drought characteristics and challenges on sorghum productivity in Babile District, Eastern Ethiopia

ABSTRACT Examining the characteristics of drought indices in the context of climate variability and change, particularly in semi-arid water-stressed regions, requires adaptation. Observed climate data of the Babile station from 1980 to 2009 were used as a baseline for climate projection. Future climate projection was established under two Representative Concentration Pathway (RCP4.5 and RCP8.5) climate scenarios for the 21st century. Two drought indices, namely standard precipitation index and standard evapotranspiration index (SPI and SPEI) were employed based on temperature and rainfall to characterize droughts. Our study revealed that drought severity and intensity are more likely to increase under RCP4.5 climate forcing in the middle of the 21st century. The average drought severity (S) was 1.1, 1.53, 1.55, and 1.8 in SPEI 3-month time scale; 1.51, 2.1, 2.38, and 2.29 in SPEI 4-month time scale; and 2.15, 2.77, 3.44, and 2.91 in SPEI 6-month time scale, whereas, the drought severity (S) was 1.33, 1.37, and 1.79 in SPEI 3-month time scale; 1.79, 2.05, and 2.19 in SPEI 4-month time scale; and 2.47, 3.19, and 2.69 in SPEI 6-month time scale in observed, near, mid and end of the 21st century under RCP4.5 and 8.5 scenarios, respectively. Increase in drought frequency and severity occurrences under RCP4.5 scenario would have a negative impact on sorghum crop productivity. We recommended further study on practical soil water conservation to drought management in the study area.

Implications of Variability and Trends in Coastal Extreme Water Levels

AbstractProbabilities of coastal extreme water levels (EWLs) are increasing as sea levels rise. Using a time‐dependent statistical model on tide gauge data along U.S. and Pacific Basin coastlines, we show that EWL probability distributions also shift on an annual basis from climate forcing and long‐period tidal cycles. In some regions, combined variability (&gt;15 cm) can be as large or larger than the amount of sea level rise (SLR) experienced over the past 30 years and projected over the next 30 years. Considering SLR and variability by 2050 at a location like La Jolla, California suggests a moderate‐level (damaging) flood today with a 50‐year return level (2% annual chance) would occur about 3–4 times a year during an El Nino nearing the peak of the nodal tide cycle. If interannual variability is overlooked, SLR related impacts could be more severe than anticipated based solely upon decadal‐scale projections.

User-friendly carbon-cycle modelling and aspects of Phanerozoic climate change

Carbon-cycle modelling is essential for testing the main carbon sources and sinks as climate forcings, and we introduce and describe GEOCARB_NET, a graphical user interface for the geologic carbon and sulfur cycle model GEOCARBSULFvolc. The software system is menu-driven, user-friendly, and the user is never far removed from the basic input parameters from which atmospheric CO2 and O2 concentrations can be derived. GEOCARB_NET is supplied with several published models and the user can easily test and refine these models with different parametrizations. GEOCARB_NET also contains libraries of models and proxy data, which easily can be compared with each other. Our examples focus on how to use GEOCARB_NET in the context of Phanerozoic climate change and highlights how certain key input parameters can seriously affect reconstructed CO2 levels.

Spatiotemporal variability and underlying large‐scale atmospheric mechanisms causing the change in the Black Sea surface temperature and associated extreme precipitation events in the northeastern of Turkiye

AbstractSea surface temperature (SST) has an important local and remote influence on global climate through the distribution and transport of heat and moisture. As a result of climate forcing, significant changes occur in the SSTs, which result in many natural disasters such as supercharged storms, higher wind speeds, heavier precipitation and flooding. This study investigates the spatiotemporal changes and underlying atmospheric mechanisms of the Black Sea (BLS) surface temperature. For this purpose, National Oceanicand Atmospheric Administration (NOAA) high‐resolution SST data (0.25°), which were verified with buoy observations, were used for the period 1982–2021. To investigate the circulation impacts, the relationship between North Atlantic Oscillation and East Atlantic/West Russia (EA/WR) phases and SSTs of the western BLS (WBLS) and eastern BLS (EBLS) was analysed. According to the results, SST values increased from 1.64°C (in winter) to 2.52°C (in summer) during the 40‐year period. Significant SST increases are shown in the EBLS during the summer and fall months. Statistically significant negative correlations (p &lt; 0.05) were found between EA/WR and winter (r = −0.57) and summer (r = −0.56) SSTs in the EBLS. During winter, surface high located in the eastern Anatolia causes southerly winds, which blows from the terrestrial areas to the EBLS and result in above‐normal SST values. During summer (under negative EA/WR phases), the Azores high‐pressure centre extends to the Balkan Peninsula and WBLS and as a consequence, a significant amount of moisture associated with high sea surface temperature (&gt;27°C, above‐normal 2.0°C) develops low‐level moisture convergence. Proper synoptic conditions, strong instability conditions between the surface and upper levels, and orographic forcing enable the occurrence of convective cloud cells. The movement of these cells to the northeastern part of Turkiye by strong northwesterly winds causes extreme precipitation and associated flash‐flood events in a limited area where land–sea interaction occurs (i.e., Artvin, Rize and Hopa provinces of Turkiye).

Possible impact of the 43 BCE Okmok volcanic eruption in Alaska on the climate of China as revealed in historical documents

Abstract. The Okmok volcanic eruption in Alaska has recently been discovered and is precisely dated to have occurred in 43 BCE. Some Chinese climate records of 43–33 BCE have been found in historical documents that provide descriptions of observed environmental abnormities that appear to be consistent with the anticipated changes due to volcanic climate forcing. In this paper, we provide a full translation with discussions of the Chinese climate records that may be related to the Okmok eruption. We have converted ancient Chinese calendar dates to modern Gregorian dates and provided the latitudes and longitudes of the geographical locations mentioned in the records. Relevant climate information in similar areas of China in the decades after the 1783 Laki eruption is also briefly summarized for comparison. We believe the detailed information contained in these records will be useful for further research on the climate impact of volcanic eruptions.

Land-Use Feedback under Global Warming—A Transition from Radiative to Hydrological Feedback Regime

Abstract This study examines the effects of land-use (LU) change on regional climate, comparing historical and future scenarios using seven climate models from phase 6 of Coupled Model Intercomparison Project–Land Use Model Intercomparison Project experiments. LU changes are evaluated relative to land-use conditions during the preindustrial climate. Using the Community Earth System Model, version 2–Large Ensemble (CESM2-LE) experiment, we distinguish LU impacts from natural climate variability. We assess LU impact locally by comparing the impacts of climate change in neighboring areas with and without LU changes. Further, we conduct CESM2 experiments with and without LU changes to investigate LU-related climate processes. A multimodel analysis reveals a shift in LU-induced climate impacts, from cooling in the past to warming in the future climate across midlatitude regions. For instance, in North America, LU’s effect on air temperature changes from −0.24° ± 0.18°C historically to 0.62° ± 0.27°C in the future during the boreal summer. The CESM2-LE shows a decrease in LU-driven cooling from −0.92° ± 0.09°C in the past to −0.09° ± 0.09°C in future boreal summers in North America. A hydroclimatic perspective linking LU and climate feedback indicates LU changes causing soil moisture drying in the midlatitude regions. This contrasts with hydrology-only views showing wetter soil conditions due to LU changes. Furthermore, global warming causes widespread drying of soil moisture across various regions. Midlatitude regions shift from a historically wet regime to a water-limited transitional regime in the future climate. This results in reduced evapotranspiration, weakening LU-driven cooling in future climate projections. A strong linear relationship exists between soil moisture and evaporative fraction in midlatitudes. Significance Statement Land–atmosphere feedback involving soil moisture can increase local temperature and affect how land-use (LU) change impacts manifest in a warming climate. Conversely, an increased surface reflectance due to LU change can decrease local temperature in the midlatitude regions. Further, the LU change signal is often mixed with the internal climate variability, making it harder to separate. This study uses a novel technique to separate LU change impact from other climate forcing in the latest generation of climate and Earth system models. In the future climate, soil moisture drying lessens the cooling impact. A large-ensemble climate experiment analysis confirms a significant weakening of the LU-driven cooling impact in the midlatitudes. Both LU and climate changes exacerbate soil moisture drying, leading to a shift toward a water-limited system where hydrological feedback becomes more influential than radiative feedback.

Fish and tips: Historical and projected changes in commercial fish species' habitat suitability in the Southern Hemisphere

Global warming has significantly altered fish distribution patterns in the ocean, shifting towards higher latitudes and deeper waters. This is particularly relevant in high-latitude marine ecosystems, where climate-driven environmental changes are occurring at higher rates than the global average. Species Distribution Models (SDMs) are increasingly being used for predicting distributional shifts in habitat suitability for marine species as a response to climate change. Here, we used SDMs to project habitat suitability changes for a range of high-latitude, pelagic and benthopelagic commercial fish species and crustaceans (10 species); from 1850 to two future climate change scenarios (SSP1–2.6: low climate forcing; and SSP5–8.5: high climate forcing). The study includes 11 Large Marine Ecosystems (LME) spanning South America, Southern Africa, Australia, and New Zealand. We identified declining and southward-shifting patterns in suitable habitat areas for most species, particularly under the SSP5–8.5 scenario and for some species such as Argentine hake (Merluccius hubbsi) in South America, or snoek (Thyrsites atun) off Southern Africa. Geographical constraints will likely result in species from Southern Africa, Australia, and New Zealand facing the most pronounced habitat losses due to rising sea surface temperatures (SST). In contrast, South American species might encounter greater opportunities for migrating southward. Additionally, the SSP5–8.5 scenario predicts that South America will be more environmentally stable compared to other regions. Overall, our findings suggest that the Patagonian shelf could serve as a climate refuge, due to higher environmental stability highlighting the importance of proactive management strategies in this area for species conservation. This study significantly contributes to fisheries and conservation management, providing valuable insights for future protection efforts in the Southern Hemisphere.

Targeted use of paraffinic kerosene: Potentials and implications

Aviation contributes to anthropogenic climate change mainly by contrails, CO2 and NOx emissions, whereof contrails are considered the largest single contributor to the radiative forcing from aviation. Powering aircraft with kerosene containing fewer or no-aromatics, i.e., “Sustainable Aviation Fuels” (SAF) or hydroprocessed, fossil-based kerosene, can significantly reduce contrail climate forcing. However, such kerosene is currently scarcely available. Moreover, less than 10 % of the flights worldwide cause more than 80 % of the contrail climate forcing. Hence, this study investigates a targeted allocation of paraffinic, i.e., aromatics-free kerosene to flights and flight segments with the highest contrail climate forcing, by calculating the resulting contrail energy forcing (in J) on 844 364 flight trajectories worldwide departing from five large European airports in 2019.The contrail radiative forcing integrated over contrail evolution (i.e., contrail energy forcing [J]) is simulated for a reference fleet powered with conventional kerosene of 14.1 m - % hydrogen content. 5 % of overall kerosene demand assumed to be paraffinic kerosene with 15.3 m - % hydrogen content is allocated via a uniform, a flight-specific and a segment-specific approach. The uniform allocation assumes that all flights receive the same blend of 5 % paraffinic kerosene. The other cases target 100 % paraffinic kerosene either to flights or segments with highest contrail energy forcing. Compared to the reference, the results indicate a reduction on contrail energy forcing by 4 %, 36 % and 55 %, respectively. For market shares of paraffinic kerosene up to 30 %, a segment specific allocation appears advantageous compared to a flight specific allocation. However, they might require airport and aircraft modifications. Uncertainties in contrail climate benefits can be reduced by providing additional information on kerosene properties and accurate meteorological data. Overall, this study highlights robust potentials of paraffinic kerosene to significantly reduce the climate forcing from aviation.

Resetting tropospheric OH and CH4 lifetime with ultraviolet H2O absorption.

The decay of methyl chloroform, a banned ozone-depleting substance, has provided a clear observational metric of mean tropospheric hydroxyl radical (OH) abundance. Almost all current global chemistry models calculate about 15% too much OH and thus too rapid methane loss. Methane is a short-lived climate forcer, critical to achieving global warming targets, and this error affects our model projections of climate change. New observations of water vapor absorption in the ultraviolet region (290 to 350 nanometers) imply reductions in sunlight with key photolysis rates decreasing by 8 to 12% in the near-surface tropical atmosphere. Incorporation of this new mechanism in a chemistry-transport model reduces OH and methane loss by only 4%, but combined with other proposed mechanisms, such as tropospheric halogen chemistry (7%), we may be able to resolve this conundrum.

The water-insoluble organic carbon in PM2.5 of typical Chinese urban areas: light-absorbing properties, potential sources, radiative forcing effects, and a possible light-absorbing continuum

Abstract. Water-insoluble organic carbon (WIOC) constitutes a substantial portion of organic carbon (OC) and contributes significantly to light absorption by brown carbon (BrC), playing pivotal roles in climate forcing. China is a hotspot region with high levels of OC and BrC, but information regarding the sources and light-absorbing properties of WIOC on a national scale remains scarce. Here, we investigated the light-absorbing properties and sources of WIOC in 10 representative urban cities in China. On average, WIOC made up 33.4 ± 7.66 % and 40.5 ± 9.73 % of concentrations and light absorption at 365 nm (Abs365) of extractable OC (EX-OC), which includes relatively hydrophobic OC (WIOC and humic-like substances, HULIS-C) and hydrophilic OC (non-humic-like substances, non-HULIS-C). The mass absorption efficiency of WIOC at 365 nm (MAE365) was (1.59 ± 0.55 m2 (g C)−1) comparable to that of HULIS (1.54 ± 0.57 m2 (g C)−1) but significantly higher than non-HULIS (0.71 ± 0.28 m2 (g C)−1), indicating that hydrophobic OC possesses a stronger light-absorbing capacity than hydrophilic OC. Biomass burning (31.0 %) and coal combustion (31.1 %) were the dominant sources of WIOC, with coal combustion sources exhibiting the strongest light-absorbing capacity. Moreover, employing the simple forcing efficiency (SFE300–700 nm) method, we observed that WIOC exhibited the highest SFE300–700 nm (6.57 ± 5.37 W g−1) among the EX-OC fractions. The radiative forcing of EX-OC was predominantly contributed by hydrophobic OC (WIOC – 39.4 ± 15.5 % and HULIS – 39.5 ± 12.1 %). Considering the aromaticity, sources, and atmospheric processes of different carbonaceous components, we propose a light-absorbing carbonaceous continuum, revealing that components enriched with fossil sources tend to possess stronger light-absorbing capacity, higher aromatic levels, increased molecular weights, and greater recalcitrance in the atmosphere. Reducing fossil fuel emissions emerges as an effective means of mitigating both gaseous (CO2) and particulate light-absorbing carbonaceous warming components.