Are the alternative ecosystem states produced by positive fire-flammability feedbacks reversible?

Historical and future global burned area with changing climate and human demography

Effect difference of climate change and urbanization on extreme precipitation over the Guangdong-Hong Kong-Macao Greater Bay Area

Crop rotation has been widely used to enhance crop yields and mitigate adverse climate impacts. The existing research predominantly focuses on the impacts of crop rotation under growing season (GS) climates, neglecting the influences of non-GS (NGS) climates on agroecosystems. This oversight limits our understanding of the comprehensive climatic impacts on crop rotation and, consequently, our ability to devise effective adaptation strategies in response to climate warming. In this study, we examine the impacts of both GS and NGS climate conditions on the yield effect of the preceding crop in corn-soybean rotation systems from 1999 to 2018 in the US Midwest. Using causal forest analysis, we estimate that crop rotation increases corn and soybean yields by 0.96 and 0.22 t/ha on average, respectively. We then employ statistical models to indicate that increasing temperatures and rainfall in the NGS reduce corn rotation benefits, while warming GS enhances rotation benefits for soybeans. By 2051-2070, we project that warming climates will reduce corn rotation benefits by 6.74% under Shared Socioeconomic Pathway (SSP) 1-2.6 and 17.18% under SSP 5-8.5. For soybeans, warming climates are expected to increase rotation benefits by 8.36% under SSP 1-2.6 and 13.83% under SSP 5-8.5. Despite these diverse climate impacts on both crops, increasing crop rotation could still improve county-average yields, as neither corn nor soybean was fully rotated. If we project that all continuous corn and continuous soybeans are rotated by 2051-2070, county-average corn yields will increase by 0.265 t/ha under SSP 1-2.6 and 0.164 t/ha under SSP 5-8.5, while county-average soybean yields will gain 0.064 t/ha under SSP 1-2.6 and 0.076 t/ha under SSP 5-8.5. These findings highlight the effectiveness of crop rotation in the face of warming NGS and GS in the future and can help evaluate opportunities for adaptation.

Measurement of China's provincial social cost of carbon under the integrated socioeconomic-climate framework

The new scenario framework for climate change research envisions combining pathways of future radiative forcing and their associated climate changes with alternative pathways of socioeconomic development in order to carry out research on climate change impacts, adaptation, and mitigation. Here we propose a conceptual framework for how to define and develop a set of Shared Socioeconomic Pathways (SSPs) for use within the scenario framework. We define SSPs as reference pathways describing plausible alternative trends in the evolution of society and ecosystems over a century timescale, in the absence of climate change or climate policies. We introduce the concept of a space of challenges to adaptation and to mitigation that should be spanned by the SSPs, and discuss how particular trends in social, economic, and environmental development could be combined to produce such outcomes. A comparison to the narratives from the scenarios developed in the Special Report on Emissions Scenarios (SRES) illustrates how a starting point for developing SSPs can be defined. We suggest initial development of a set of basic SSPs that could then be extended to meet more specific purposes, and envision a process of application of basic and extended SSPs that would be iterative and potentially lead to modification of the original SSPs themselves.

Estimation of ambient PM2.5-related mortality burden in China by 2030 under climate and population change scenarios: A modeling study.

Studying the interaction between hydrology, land use, and climate change is necessary to support sustainable water resources management. In this study, we assessed the effects of both land use and predicted climate change on the Arpa Catchment water yield using the ArcSWAT model. The influence of changing climate on water yield was evaluated for different emission scenarios using CMIP6 Global Climate Models (GCM). Three GCM namely BCC-CSM2- MR, EC-Earth3-Veg and NorESM2-LM were ensemble and used for this study. Two ‘Shared Socioeconomic Pathways’ (SSP) scenarios (SSP.2_4.5, and SSP.5_8.5) were used for future climate prediction in the current study area. Land use land cover, meteorology and soil type data used as inputs to analyze the spatial and temporal pattern of water yield in the Arpa catchment from 1990 to 2020 and the impact of land use change on water yield in the basin simulated with ArcSWAT Model. Water yield compare to baseline scenario (1990) increased by 98.36 mm (18.48%) in decadal year 2000, increased by 144.51 mm (27.15%) in year 2010 and in decadal year 2020 water yield increased by 154.20 mm (28.98%). Climatic scenario (SSP2_4.5 and SSP5_8.5) changes in water components were simulated with ArcSWAT model. Model was run for three future time slices i.e. Near future (2030s), Mid future (2060s), and Far future (2090s). Water yield with reference to baseline period (646.02 mm) increased by 71.69% under SSP2_4.5 during 2090s. Similarly, under SSP5_8.5 water yield increased by 106.87% for the far future (2090s).

Climate change is anticipated to have long-term effects on hydrological processes and patterns, leading to water stress in agroecological catchments. Climate change escalates water scarcity in the Usangu catchment, as evidenced by the drying up of rivers during the dry season. Therefore, this study was undertaken to assess climate change impacts on hydrology by utilizing the Soil Water Assessment Tool (SWAT) model and an ensemble mean of five Global Circulation Models (GCMs) under two shared socio-economic pathway (SSP) emission scenarios. Downscaling of GCMs was performed by the LARS-WG statistical downscaling tool. In comparison to the baseline period, short rain intervals are expected to occur between 2030 and 2060, with a mean annual precipitation increase of 7 and 17% in SSP 2–4.5 and SSP 5–8.5, respectively. Maximum and minimum temperatures are expected to rise by 0.6–2 °C. Corresponding to future temperature increases, evapotranspiration would increase to about 30% and decrease water yield and groundwater recharge by 7 and 26% in SSP 2–4.5 than in SSP 5–8.5. However, the effect of precipitation increase is shown by increased surface runoff and streamflow during wetter months. These findings provide watershed managers with crucial information for planning and managing the catchment in light of a changing climate.

Background: Fine particulate matter (PM2.5) pollution is one of the most critical environmental and public health problems in China, which has caused enormous disease burden, especially long-term PM2.5 exposure. Global climate change is another environmental challenge in the coming decades, which is also an essential factor affecting PM2.5 pollution. Moreover, China is embracing an aging population. However, little evidence exists evaluating the potential impact of climate change and population ageing on long-term PM2.5 exposure-related disease burden. This study aims to quantify the impact of climate and population changes on changes in the disease burden attributed to long-term PM2.5 exposure from 2015 to 2030 in mainland China. Methods: This modeling study investigated long-term PM2.5 exposure-related mortality across China based on PM2.5 projections under Intergovernmental Panel on Climate Change Representative Concentration Pathways (RCPs) and population scenarios from the Shared Socioeconomic Pathways (SSPs). Three types of population projections in 2030 relative to 2015 were set up as follow: (i) population remained the same from 2015; (ii) the population size changed under SSPs but age structure remained same; (iii) both population size and age structure changed under SSPs. Global Exposure Mortality Model was adopted to estimate PM2.5-related premature deaths. Findings: Ambient PM2.5 concentrations showed a decrease from 2015 to 2030 under two climate and emission scenarios. Estimates of related premature mortality in 2030 declined compared with 2015 due to lower PM2.5 concentrations (RCP4.5: -16.8%; RCP8.5: -16.4%). If the age structure of population remained no change and the population size changed under SSPs, the premature mortality also showed a decrease ranging from -18.6% to -14.9%. When both population size and age structure changed under SSPs, the premature mortality would sharply increase by 35.7%-52.3% (with net increase of 666-977 thousand) in 2030. Interpretations: The PM2.5 pollution in 2030 under both RCP4.5 and RCP8.5 would slightly improve. However, the modest decrease due to air pollution improvement would be offset by population ageing. Funding Statement: None. Declaration of Interests: The authors declare that they have no conflicts of interests.

Coupled ocean and prescribed sea surface temperature (SST) experiments are performed to investigate the drivers of Northern Hemisphere (NH) midlatitude winter circulation and blocking changes in warmer climates. In coupled experiments, a historical simulation is compared to a simulation following an end of the twenty-first-century shared socioeconomic pathway (SSP5-8.5) emission scenario. The SSP5-8.5 simulation yields poleward-shifted jets and an enhanced stationary wave pattern compared to the historical simulation. In terms of blocking, a reduction is found across North America and over the Pacific Ocean with the suggestion of more blocking over parts of Eurasia. Separately, prescribed SST experiments are performed decomposing the SSP5-8.5 SST response into a uniform warming component plus a spatially dependent change in SST pattern. SSP5-8.5 changes in circulation are primarily driven by a uniform warming of SST. Uniform warming is also found to account for most of the SSP5-8.5 blocking reduction over North America and the Pacific Ocean, but not over Eurasia. El Niño–like changes to the SST pattern also yield less blocking over the Pacific and North America. However, adding the responses of uniform and pattern experiments yields a nonlinear overreduction of blocking compared to the SSP5-8.5 experiment. Regional analyses of block energetics suggest that much of the reductions in blocking in warming simulations are driven by decreased baroclinic conversion in some regions and enhanced dissipation from diabatic sources in others. Significance Statement Atmospheric blocks are persistent anticyclones that can cause severe weather such as heat waves and cold spells. Climate models generally project that on a warmer Earth, blocking frequency is poised to decrease in the Northern Hemisphere by the end of the twenty-first century. The cause, however, remains unclear. In this study, we investigate the response of mean atmospheric circulation and atmospheric blocking when separately considering the warming of sea surface temperatures (SST) and changing the SST pattern. We find that most of the reduction in blocking can be explained by a uniform warming of SST. Energetics analyses suggest that this reduction is driven by blocks’ inhibited extraction of mean flow potential energy in some regions and by enhanced diabatic dissipation in others.

Temporal and spatial evolutionary trends of regional extreme precipitation under different emission scenarios: Case study of the Jialing River Basin, China

Polar lows (PLs) are intense mesoscale cyclones that form over polar oceans during colder months. Characterized by high wind speeds and heavy precipitation, they profoundly impact coastal communities, shipping, and offshore activities. Amid the substantial environmental changes in polar regions due to global warming, PLs are expected to undergo noteworthy transformations. In this study, we investigate the response of PL development in the Barents Sea to climate warming based on two representative PLs. Sensitivity experiments were conducted including the PLs in the present climate and the PLs in a pseudo–global warming scenario projected by the late twenty-first century for Shared Socioeconomic Pathway (SSP) 2-4.5 and SSP 3-7.0 scenarios from phase 6 of the Coupled Model Intercomparison Project (CMIP6). In both warming climate scenarios, there is an anticipated decrease in PL intensity, in terms of the maximum surface wind speed and minimum sea level pressure. Despite the foreseen increase in latent heat release in the future climate, contributing to the enhancement of PL intensity, other primary factors such as decreased baroclinic instability, heightened atmospheric static stability, and reduced overall surface heat fluxes play pivotal roles in the overall decrease in PL intensity in the Barents Sea under warming conditions. The augmentation of surface latent heat flux, however, results in increased precipitation associated with PLs by enhancing the latent heat release. Furthermore, the regional steering flow shifts in the warming climate can influence the trajectory of PLs during their development. Significance Statement Global warming is anticipated to impact cyclone systems worldwide. Polar lows (PLs), intense mesocyclones in polar regions with potential socioeconomic and human life implications, pose uncertainties regarding intensity changes in a warming climate. In this study, we aimed to better understand how PLs over the Barents Sea will respond to the environmental changes in future climate conditions [Shared Socioeconomic Pathway (SSP) 2-4.5 and SSP 3-7.0] by the end of the twenty-first century. Our results find that the intensity of PLs is expected to decrease in the future while there is an expected increase in precipitation associated with PLs in the warming climate. These findings aim to contribute valuable insights for disaster management strategies in the face of evolving climate scenarios.

Lake Qinghai, the largest closed-basin lake on the Qinghai–Tibet Plateau, plays a crucial role in maintaining regional ecological stability through its hydrological functions. In recent decades, the lake has exhibited a continuous rise in water level and lake area expansion, sparking growing interest in the mechanisms driving these changes and their future evolution. This study integrates the Soil and Water Assessment Tool (SWAT), simulations under future Shared Socioeconomic Pathways (SSPs) and statistical analysis methods, to assess runoff dynamics and lake level responses in the Lake Qinghai Basin over the next 30 years. The model was developed using a combination of meteorological, hydrological, topographic, land use, soil, and socio-economic datasets, and was calibrated with the sequential uncertainty fitting Ver-2 (SUFI-2) algorithm within the SWAT calibration and uncertainty procedure (SWAT–CUP) platform. Sensitivity and uncertainty analyses confirmed robust model performance, with monthly R2 values of 0.78 and 0.79. Correlation analysis revealed that runoff variability is more closely associated with precipitation than temperature in the basin. Under SSP 1-2.6, SSP 3-7.0, and SSP 5-8.5 scenarios, projected annual precipitation increases by 14.4%, 18.9%, and 11.1%, respectively, accompanied by temperature rises varying with emissions scenario. Model simulations indicate a significant increase in runoff in the Buha River Basin, peaking around 2047. These findings provide scientific insight into the hydrological response of plateau lakes to future climate change and offer a valuable reference for regional water resource management and ecological conservation strategies.

ABSTRACTExtreme precipitation and temperature have large socioeconomic and human health impacts. This study aims to analyse the projected changes of extreme precipitation and temperature indices at 1.5°C and 2°C of warming over the Mississippi River Basin (MRB) under Shared Socio‐economic pathways (SSP) 2‐4.5 and SSP5‐8.5. We used a technique named bias correction constructed analogues with quantiles mapping reordering (BCCAQ) to downscale daily precipitation, minimum and maximum temperature from a set of 12 Coupled Models Intercomparison Project phase 6 (CMIP6) over MRB. The changes in extreme precipitation and temperature indices such as very heavy rainfall (R95p), warm days (TX90p), and warm spell duration (WSDI) are sensitive to warming targets and emission scenarios. Results indicate that both warming targets are expected to exacerbate R95p whilst intensifying extreme precipitation and temperature as a whole except for cumulative wet days (CWD) (many parts of MRB are experiencing reduced CWD at both warming targets and scenarios). However, the rainfall intensity (SDII) is more reduced under SSP5‐8.5 compared to SSP2‐4.5 with an additional 0.5°C highlighting the sensitivity of SDII to the emission scenario. An additional 0.5°C (from 1.5°C to 2°C) climate warming is expected to: (1) increase TX90p and WSDI by 50% under SSP2‐4.5 and nearly 100% under SSP5‐8.5 over much of the MRB subregions, (2) reduce extreme precipitation in the centre of the MRB. Uncertainty superimposes on the magnitude of changes with more than 75% contribution from internal climate variability to total variance, nearly 20% from climate models, and marginal contribution from climate scenarios. The predominance of natural climate variability underscores a decreased predictability in future extreme precipitation and extreme temperature due to anthropogenic forcings, particularly at the regional scale. So, a deep understanding of what drives climate and its variability on a local and regional scale is critical for future generations of climate models and climate projections assessment. However, climate warming will pose serious challenges to water availability over the MRB, with consequences for agriculture, crop yields, and ecosystems.

Land use projections in China under global socioeconomic and emission scenarios: Utilizing a scenario-based land-use change assessment framework