Earths Future最新文献

The impacts of extreme events are seldom caused by a single climatic variable but rather arise from the interaction of multiple climate drivers. This study employs observational data sets with high spatiotemporal resolution to analyze the risk of occurrence of compound dry-hot events in China over the past 120 years (i.e., 1901–2020). Simultaneously, attribution analysis based on distribution functions explores whether and to what extent human activities influence the occurrence of compound events. The results indicate that over the historical 120-year period, the frequency of compound dry-hot events in China has gradually increased, with the highest frequency observed in the most recent 40 years (i.e., 1981–2020). The frequency of compound dry-hot events during this period is approximately four times that of 1901–1940 and about twice that of 1941–1980. The analysis of the relative importance of different factors reveals that temperature changes contribute more (56%) to the occurrence of compound events than precipitation (23%), and also exceed the interaction between them (21%). The substantial increase in compound dry-hot events is largely attributed to the influence of human activities. Across seven sub-regions, human activities have led to an increase in the probability of compound events occurring, ranging from 7.9% to 31.6%. The findings of this study indicate that human activities have significant implications for explaining the observed increase in compound hot and dry events over the past 40 years.

Rising atmospheric CO₂ is anticipated to influence global runoff through its radiative effect and physiological effect, thereby resulting in profound impacts on water availability and security. While existing literature has explored the two effects on global total runoff, there is still a lack of attention to changes in runoff components (surface and subsurface runoff). Here, based on idealized 1% yr⁻¹ CO₂ increase experiments and 14 Earth system models, we decouple the two effects on changes in runoff components and disentangle the contributions of three influencing factors, namely water supply, atmospheric water demand, and vegetation regulation, which are closely intertwined with the two effects. Global total runoff is expected to increase with rising CO₂, and this increase mainly comes from subsurface runoff, leading to an elevated subsurface runoff ratio. Vegetation regulation emerges as the most important factor for the increase in subsurface runoff ratio, with the contribution of 49.3%, followed by water supply (41.7%) and atmospheric water demand (8.9%). Increased total runoff implies potentially more flood risk, while the increase in subsurface runoff ratio could decrease some of the risk. The results indicate the necessity of emphasizing changes in subsurface runoff under climate change.

Formulating equitable climate policies should not overlook the challenges faced by less developed regions. African countries are at a crucial stage of economic development and deeper integration into global trade. Therefore, understanding their carbon footprints (i.e., consumption-based CO₂ emissions) is essential for crafting a sustainable development pathway for Africa and developing comprehensive and fair climate policies. Here, we investigate consumption-based CO₂ emissions in 55 African economics using a new Multi-Regional Input-Output model called “EMERGING” for 2015–2019; we also analyze the impacts of global trade participation on emissions, the decoupling status of emissions and economic, and hidden influencing factors. Results show that 65% of African countries experienced rapid growth in consumption-based emissions, with an average annual growth rate of 6.4%. Significantly, 87% of African countries are net emissions importers, predominantly attributed to their trade relations with other developing countries (i.e., South-South trade), a condition characterizing 68% of all trade interactions; The embodied carbon in imports is primarily concentrated in the transportation, petroleum refining, metal products, and machinery sectors. The decoupling analysis indicates that 15 countries strongly decoupled from production-based carbon emissions, and 14 from consumption-based; however, only 9 have concurrently achieved decoupling in both domains of emissions. Optimizing the carbon emission efficiency of final demand, particularly within the tertiary sector, is a key for successful decoupling and emissions reduction. The findings provide essential insights from consumption-based emissions that could guide more effective, targeted climate policies contributing to the mitigation of climate impacts and fostering sustainable development in African nations.

Observational evidence shows that Sahel summer precipitation has experienced a considerable increase since the 1980s, coinciding with significant diverging trends of increased sulfate emissions in Asia and decreased emissions in Europe (dipole pattern of aerosols between Asia and Europe). The decrease in European sulfate aerosols has substantial effects on the Sahel summer precipitation increase, but the corresponding effect of increased Asian sulfate is unknown. Multi-model simulations in the Precipitation Driver and Response Model Intercomparison Project (PDRMIP) show, compared to decreased European aerosols, that increased Asian aerosols similarly enhance the Sahel summer precipitation but with different large-scale atmospheric circulation changes. Further analysis of the Sixth Coupled Model Intercomparison Project (CMIP6) simulations under historical attribution and various emission scenarios reinforces the results about the climate impacts of anthropogenic aerosols and suggests that in future scenarios with strong international cooperation and rapid climate mitigations (SSP2-45), the Sahel drought will be intensified likely due to the decline in Asian aerosol emissions. Our results suggest that Asian anthropogenic aerosols are likely a non-negligible driver of the recent recovery in Sahel precipitation amounts.

Wildfires pose a significant threat to human society as severe natural disasters. The western United States (US) is one hotspot that has experienced dramatic influences from autumn wildfires especially after 2000, but what has caused its year-to-year variations remains poorly understood. By analyzing observational and atmospheric reanalysis datasets, we found that the West Pacific (WP) pattern centered in the western North Pacific acted as a major climatic factor to the post-2000 autumn wildfire activity by inducing anomalous high pressure over the western US via teleconnections with increased surface temperature, decreased precipitation, and reduced relative humidity. The WP pattern explains about one-third of the post-2000 years-to-year variance of the western US autumn wildfires. These effects were found to be much weaker in the 1980–1990s, as the active region of WP-associated high pressure was confined to the eastern North Pacific. Such eastward shift of the WP teleconnection pattern and its resultant, enhanced influence on the weather conditions of western US autumn wildfire after 2000 are also captured by the sea surface temperature (SST)-forced atmospheric model simulations with the Community Atmosphere Model version 6 (CAM6). The CAM6 ensemble-mean changes in the WP teleconnection pattern at 2000 is about half of the observed changes, which implies that external radiative forcing and/or SST changes have played an important role in the WP pattern shift. Our results highlight a pressing need to consider the joint impacts of atmospheric internal variability and externally forced climate changes when studying the interannual variations of wildfire activity.

In this study we analyse projections of future changes to the El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Southern Annular Mode (SAM) using the latest generation of climate models. Multiple future scenarios are considered. We quantify the fraction of models that project future increases or decreases in the frequency and amplitude of ENSO, IOD, and SAM events in the late 21st century. Changes to the frequency of co-occurring and consecutive driver phases are also examined. We find that while there is large inter-model spread, the most common pathways correspond to more frequent ENSO events; weaker, less frequent IOD events; and stronger, but less frequent austral spring SAM events. There is no clear consensus on the change to the frequency of concurrent events, though we find a significant increase in La Niña- and El Niño-only events occurring with neutral IOD and SAM. We also find a significant increase to the frequency of consecutive positive IOD events under a high emissions scenario, but no significant change to the frequency of consecutive ENSO or negative IOD events. In most models, the correlation between drivers, that is, ENSO and IOD, and ENSO and SAM, does not significantly change between the late 20th and late 21st century. These results indicate a high degree of internal variability in the models.

We introduce an impact-based framework to evaluate seasonal forecast model skill in capturing extreme weather and climate events over regions prone to natural disasters such as floods and wildfires. Forecasting hydroclimatic extremes holds significant importance in an era of increasing hazards such as wildfires, floods, and droughts. We evaluate the performance of five Copernicus Climate Change Service (C3S) seasonal forecast models (CMCC, DWD, ECCC, UK-Met, and Météo-France) in predicting extreme precipitation events from 1993 to 2016 using 14 indices reflecting timing and intensity (using absolute and locally defined thresholds) of precipitation at a seasonal timescale. Performance metrics, including Percent Bias, Kendall Tau Rank Correlation Score, and models' discrimination capacity, are used for skill evaluation. Our findings indicate that the performance of models varies markedly across regions and seasons. While models generally show good skill in the tropical regions, their skill in extra-tropical regions is markedly lower. Elevated precipitation thresholds (i.e., higher intensity indices) correlate with heightened model biases, indicating deficiencies in modeling severe precipitation events. Our analysis using an impact-based framework highlights the superior predictive capabilities of the UK-Met and Météo-France models in capturing the underlying processes that drive precipitation events, or lack thereof, across many regions and seasons. Other models exhibit strong performance in specific regions and/or seasons, but not globally. These results advance our understanding of an impact-based framework in capturing a broad spectrum of extreme weather and climatic events, and inform strategic amalgamation of diverse models across different regions and seasons, thereby offering valuable insights for disaster management and risk analysis.

With the backdrop of climate change and human activities, the complex interactions within the social-ecological system have brought unprecedented challenges to sustainable development. However, there is still a lack of quantitative methods for analyzing the dynamics of the social-ecological system. Here, we introduced a social-ecological network approach incorporating supply and demand of ecosystem services (ESs) as bridges and took the Dongting Lake basin in China as the research area. From 2000 to 2020, we discovered that the number of linkages among meteorological elements and ESs supply decreased from 5 to 0. Along with this, the network density (from 26 to 22) and network connectivity (from 43 to 28) showed the decoupling trends of the social-ecological networks. These results implied the decreasing impacts of meteorological elements and the importance of considering human activities impacts. Based on the average degree analysis of the networks, proportions of cultivated land and forest land were key for ESs supply (both around 0.900), while population density and artificial land proportion were important for the ESs demand (around 0.850 and 0.800, respectively). More management practices are required because these elements have significant impacts on the supply-demand alignments of multiple ESs. We further illustrated the spatial supply-demand mismatches of ESs, along with the negative effects of urbanization. This study highlighted the advantage of integrating the ecosystems services approach into the social-ecological network analysis, and provided policy insights serving for sustainable development of the typical great lake basins.

Warming in permafrost regions stimulates carbon (C) release through decomposition, but increasing atmospheric CO₂ and available soil nitrogen enhance plant productivity at the same time. To date, a large uncertainty in the regional C dynamics still remains. Here we use a process-based biogeochemical model by considering C exposure from thawed permafrost and observational data to quantify permafrost C emissions and ecosystem C budget in northern high latitudes in the 21st century. Permafrost degradation will make 119.3 Pg and 251.6 Pg C available for decomposition by 2100 under the Shared Socioeconomic Pathway (SSP)126 and SSP585, respectively. However, only 4–8% of the newly thawed permafrost C is expected to be released into the atmosphere by 2100. Cumulatively, permafrost degradation will reduce ecosystem C stocks by 3.37 Pg and 15.37 Pg under the SSP126 and SSP585, respectively. Additionally, CO₂ fertilization effects would stimulate plant productivity and increase ecosystem C stocks substantially. The combined effects of climate change, CO₂ fertilization, and permafrost degradation on C fluxes are typically more profound than any single factor, emphasizing the intricate interplay between these elements in shaping permafrost C-climate feedbacks. Our study suggests that the majority of the thawed C will remain sequestered in previously frozen layers in this century, posing a significant challenge to climate change mitigation efforts once any process accelerates the decomposition of this huge amount of thawed C.

Temperate rainforests are rare ecosystems globally; restricted to cool, moist conditions that are sensitive to a changing climate. Despite their crucial conservation importance, a global assessment of how temperate rainforests will be impacted by climate change is lacking. We calculated historical (1970–2000) climate conditions for the temperate rainforest biome using ERA5 reanalysis data for three key bioclimatic variables: warmest quarter temperature, annual precipitation and proportion of rainfall during warmest quarter. We used high-spatial resolution climate projections for these variables to identify regions likely to become unsuitable for temperate rainforests under four future shared socioeconomic pathway (SSP) scenarios. We predict unmitigated climate change (SSP 5–8.5) would lead to a 68.3 (95% confidence interval (95 CI): 53.4–81.3)% loss in the existing temperate rainforest biome by 2100 at a global scale with some national-level reductions exceeding 90%. Restricting global warming to <2°C (consistent with SSP 1–2.6), limits loss of global temperate rainforest biome to 9.7 (95 CI: 7.8–13.3)% by 2100 and is crucial to ensuring temperate rainforest persistence. Deforestation has resulted in loss of up to 43% of the current temperate rainforest biome with only 37% of primary forest remaining, and some regions like Europe with virtually none. Protection and restoration of the temperate rainforest biome, along with emissions reductions, are vital to its climate future.