Increase In Global Mean Temperature Research Articles

Carbon budget concept and its deviation through the pulse response lens

Abstract. The carbon budget concept states that the global mean temperature (GMT) increase is roughly linearly dependent on cumulative emissions of CO2. The proportionality is measured as the transient climate response to cumulative emissions of carbon dioxide (TCRE). In this paper, the deviations of the carbon budget from the strict linear relationship implied by the TCRE are examined through the lens of a temperature response to an emission pulse (i.e., pulse response) and its relationship with a nonlinear TCRE. Hereby, two sources of deviation are distinguished: emission scenario and climate state dependence. The former stems from the scenario choice, i.e., the specific emission pathway for a given level of cumulative emissions and the latter from the change in TCRE with changing climatic conditions. Previous literature argues for scenario independence using a stylized set of emission scenarios, and offers a way to fit a nonlinear carbon budget equation. This paper shows how the pulse response, viewed as a Green's function, gives a unifying perspective on both scenario and state dependence. Moreover, it provides an optimization program that tests the scenario independence under the full range of emission pathways for a given set of constraints. In a setup chosen in this paper, the deviations stemming from emission pathway choices are less than 10 % of the overall temperature increase and gradually diminish. Moreover, using the pulse response as a Green's function, the scenario-dependent effects of a reduced-complexity climate model were replicated to a high degree, confirming that the behavior of scenario-dependent deviations can be explained and predicted by the shape of the pulse response. Additionally, it is shown that the pulse response changes with climatic conditions, through which the carbon budget state dependency is explained. Using a pulse response as an approximation for a state-dependent TCRE, an alternative method to derive a nonlinear carbon budget equation is provided. Finally, it is shown how different calibrations of a model can lead to different degrees of carbon budget nonlinearities. The analysis is done using FaIRv2.0.0, a simple climate emulator model that includes climate feedback modifying the carbon cycle, along with a one-box model used for comparison purposes. The Green's function approach can be used to diagnose both models' carbon budget scenario dependency, paving the way for future investigations and applications with other and more complex models.

The atlas of unburnable oil for supply-side climate policies

To limit the increase in global mean temperature to 1.5 °C, CO2 emissions must be drastically reduced. Accordingly, approximately 97%, 81%, and 71% of existing coal and conventional gas and oil resources, respectively, need to remain unburned. This article develops an integrated spatial assessment model based on estimates and locations of conventional oil resources and socio-environmental criteria to construct a global atlas of unburnable oil. The results show that biodiversity hotspots, richness centres of endemic species, natural protected areas, urban areas, and the territories of Indigenous Peoples in voluntary isolation coincide with 609 gigabarrels (Gbbl) of conventional oil resources. Since 1524 Gbbl of conventional oil resources are required to be left untapped in order to keep global warming under 1.5 °C, all of the above-mentioned socio-environmentally sensitive areas can be kept entirely off-limits to oil extraction. The model provides spatial guidelines to select unburnable fossil fuels resources while enhancing collateral socio-environmental benefits.

Limited reversal of regional climate signals in overshoot scenarios

Without stringent reductions in emission of greenhouse gases in the coming years, an exceedance of the 1.5 °C temperature limit is increasingly likely. This has given rise to so-called temperature overshoot scenarios, in which the global mean surface air temperature exceeds a certain limit (i.e. 1.5 °C above pre-industrial levels) before bringing temperatures back below that limit. Despite their prominence in the climate mitigation literature, the implications of an overshoot for local climate impacts is still understudied. Here we present a comprehensive analysis of implications of an overshoot for regional temperature and precipitation changes as well as climate extremes indices. Based on a multi-model comparison from the Coupled Model Intercomparison Project we find that temperature changes are largely reversible in many regions, but also report significant land–ocean and latitudinal differences after an overshoot. For precipitation, the emerging picture is less clear. In many regions the drying or wetting trend is continued throughout the overshoot irrespective of a change in the global mean temperature trend with resulting consequences for extreme precipitation. Taken together, our results indicate that even under a reversal of global mean temperature increase, regional climate changes may only be partially reversed in the decades after peak warming. We thus provide further evidence that overshooting of a warming level implies considerable risks on the regional level.

The loss of our glaciers over the 21st century: a future we can contro

The loss of glaciers affects sea level, water availability, and natural hazards resulting in socioeconomic impacts for communities around the world, even for those located far from these icy giants. Our study found that limiting future increases in global mean temperature to +1.5°C will still cause the loss of more than 25% of their current mass but would prevent widespread ice-loss in many high-mountain regions.

Orbitally-paced coastal sedimentary records and global sea-level changes in the early Permian

Orbital forcing affects climate system by regulating the amount of solar radiation received at the Earth's surface, which is vital for global hydrological cycles. However, a systematic understanding of the global water cycle with synergistic changes in ice sheets and sea levels under orbital forcing during the late Paleozoic ice age (LPIA) remains elusive. Here, we perform cyclostratigraphic analysis and sedimentary noise modeling for coastal sedimentary records (Well Greer #2 in the Permian Basin) from the early Permian and two sets of high-resolution paleoclimate simulation experiments using the Community Earth System Model. We provide the first high-resolution absolute astronomical time scale for the Permian Basin, which suggests that the timing of the early Permian Lower Leonard and Upper Wolfcamp Formations range from 286.29 ± 0.55 Ma to 289.05 ± 0.55 Ma, and the Lower Wolfcamp Formation ranges from 292.97 ± 0.16 Ma to 298.9 ± 0.15 Ma, respectively. In addition, we find a coupled phase relationship between high sea levels and eccentricity maxima, suggesting that eccentricity may have played a critical role in the early Permian sea-level oscillations. Paleoclimate simulations show that eccentricity and obliquity maxima lead to an overall increase in global mean temperature. Significant changes in surface temperature at middle to high latitudes are manifested as the polar amplification effect during the LPIA. Compared with obliquity, eccentricity leads to higher annual and summer variability in global surface temperature, and enhanced polar amplification results in ice retreat and sea-level rise. Evidence from Earth system modeling elucidates the phase relationship between orbital cycles and sea levels. Therefore, eccentricity, as the leading driving force in low latitudes, may dominate climate changes in the Earth's climate system and regulates global hydrological cycles during the LPIA.

Different trends of vegetation activity over northern extratropics during two multidecadal warming periods in the 20th century

There have been two periods (1916–1945 and 1982–2014) of rapid and comparable rates (0.054 °C/year vs. 0.055 °C/year) of increase in Global Mean Temperature (GMT). However, little is known about different trends in vegetation activity over the northern extratropics during these two periods, especially for vegetation dynamics in response to the earlier global warming in the 20th century. In this study, we find that although the global warming rates are comparable between the two warming periods, regional warming over the northern extratopics has significant differences. Meanwhile, vegetation greening trends are significantly different, with the latter period being 3–4 times greater than the former. Further analysis of the leading causes reveals that the impacts of the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) on regional climate are critical to these differences. In 1916–1945, the in-phase combination of AMO and PDO offsets each other's impact on the climate factors and weakens the greening trend, while in 1982–2014, the effects of AMO and PDO are synergetic for the out-of-phase combination and enhance the greening trend. Our findings highlight the role of internal climate variability in modulating vegetation dynamics under global warming and suggest that future projections of vegetation change may be improved by considering decadal and multidecadal climate oscillations.

Human Influence On Global Climate: Legal Protection For Sustenance Of Life On Earth

Changes in solar irradiance may have affected global climate, the importance of the climate change issue stems from the impact of changes in climate on human and natural systems. The two most well-known consequences of climate change are an increase in global-mean temperature and a rise in sea level. The primary components of sea-level rise are thermal expansion and the melting of small glaciers. However, there are other changes in climate could be as important, or even so, than changes in the mean climate state. These include changes in precipitation and climate variability, particularly changes in the intensity and/or severity of extreme events such as droughts, floods, or tropical storms.
 Physics deals with the structure of matter and how the fundamental constituents of the universe interact. The impact of humans on the environment revolves around the need of physical science to understand how human beings change a natural system, an understanding of global warming and the associated climate change. Hence, physicists will approach numerous troubles from more than one direction. Physicists had to constantly keep attentive to changes, to visualize one factor going on in nature, to discover new phenomena and to document it in order that they will describe it later. Thus studying physics strengthens quantitative reasoning and problem solving skills. The environment is the natural world but with toxic chemicals, spacecraft, and nuclear bombs, humans seem to be moving further and further away from what could be called 'natural' every day. As physics strengthens quantitative reasoning and problem-solving skills, it should be dealt transdisciplinary with Law will surely helps in reducing human influence on global climate and render legal protection for sustenance of life on earth. Hence the paper concentrates on the importance of application of physical principles to environmental problems and the proactive role played by judiciary in different countries in protecting life on earth by adopting policies relating to climate change, enhancing ethical principles by setting regulations and standards for operating industries.

Public support for phasing out carbon-intensive technologies: the end of the road for conventional cars in Germany?

ABSTRACT Limiting the global mean temperature increase to 1.5°C requires phasing out fossil fuel combustion almost entirely within the next three decades and replacing carbon-intensive technologies with low-carbon alternatives. Such socio-technical transitions are politically feasible only if public acceptance is sufficiently high. Here we investigate German citizens’ views on the phase-out of internal combustion engine vehicles (ICEVs) using a random forest (decision trees) classification and logistic regression model. We surveyed a demographically representative sample (N = 1,663) in 2021, finding that the majority of respondents (67%) approve of an ICEV phase-out by 2040 or hold a neutral stance. Acceptability is best predicted by the degree to which environmental problems are attributed to ICEVs, followed by respondents’ willingness to abandon cars altogether or adopt electric vehicles (EVs). Our results further indicate that acceptability can be increased by providing people with information that present EVs in a more favourable, and ICEVs in a less favourable light. When the European Commission proposed to ban the sale of ICEVs by 2035, we conducted a follow-up survey to investigate whether this had influenced acceptability in Germany – with the result that it had not. In terms of concrete policies, pull measures such as public transport or electric vehicle purchase subsidies are preferred by the public over more restrictive policies such as taxes or bans. The findings of this study shed light on different dimensions of public opinion and their important implications for policymaking and the political feasibility of this socio-technical transition. Insights from this research can help policymakers in designing effective yet widely acceptable transport decarbonization policies.

What Does Global Land Climate Look Like at 2°C Warming?

AbstractConstraining an increase in global mean temperature below 2°C compared to pre‐industrial levels is critical to limiting dangerous and cascading impacts of anthropogenic climate change. Understanding future climatic changes and their spatial heterogeneity at 2°C warming is thus important for policy makers to prepare actionable adaptation and mitigation plans by identifying where and to what extent lives and livelihoods will be impacted. This study uses the recently released NASA Earth eXchange Global Daily Downscaled Projections (NEX‐GDDP) CMIP6 data to provide a broad overview of projected changes in six key climate variables and two climate impact indicators at a time when warming exceeds 2°C. Analysis of global mean temperature changes indicates the 2040s as the decade when most CMIP6 models reach 2°C warming with respect to a pre‐industrial period (1850–1900). During the 2040s, we find that global mean temperature, precipitation, relative humidity, downwelling shortwave and longwave radiation, and wind speed over land under the high emission scenario are projected to change by +2.8°C, +22.4 mm/year, −0.73%, −2.23 , +15.9 W/m2, and −0.04 m/s, respectively. Many of the future changes are expected to exacerbate climate impacts including heat stress and fire danger. Our analysis shows geographic patterns of policy‐relevant climatic changes, as parts of the globe will experience significant climate impacts even if the goal to keep warming below 2°C goal is achieved. Our results highlight the urgent need for further studies focused on identifying key hotspots and advancing region‐specific actionable adaptation and mitigation plans.

Exploring risks and benefits of overshooting a 1.5 °C carbon budget over space and time

Temperature targets of the Paris Agreement limit global net cumulative emissions to very tight carbon budgets. The possibility to overshoot the budget and offset near-term excess emissions by net-negative emissions is considered economically attractive as it eases near-term mitigation pressure. While potential side effects of carbon removal deployment are discussed extensively, the additional climate risks and the impacts and damages have attracted less attention. We link six models for an integrative analysis of the climatic, environmental and socio-economic consequences of temporarily overshooting a carbon budget consistent with the 1.5 °C temperature target along the cause-effect chain from emissions and carbon removals to climate risks and impact. Global climatic indicators such as CO2-concentration and mean temperature closely follow the carbon budget overshoot with mid-century peaks of 50 ppmv and 0.35 °C, respectively. Our findings highlight that investigating overshoot scenarios requires temporally and spatially differentiated analysis of climate, environmental and socioeconomic systems. We find persistent and spatially heterogeneous differences in the distribution of carbon across various pools, ocean heat content, sea-level rise as well as economic damages. Moreover, we find that key impacts, including degradation of marine ecosystem, heat wave exposure and economic damages, are more severe in equatorial areas than in higher latitudes, although absolute temperature changes being stronger in higher latitudes. The detrimental effects of a 1.5 °C warming and the additional effects due to overshoots are strongest in non-OECD countries (Organization for Economic Cooperation and Development). Constraining the overshoot inflates CO2 prices, thus shifting carbon removal towards early afforestation while reducing the total cumulative deployment only slightly, while mitigation costs increase sharply in developing countries. Thus, scenarios with carbon budget overshoots can reverse global mean temperature increase but imply more persistent and geographically heterogeneous impacts. Overall, the decision about overshooting implies more severe trade-offs between mitigation and impacts in developing countries.

Bioclimatic change as a function of global warming from CMIP6 climate projections

Abstract. Climate change is predicted to lead to major changes in terrestrial ecosystems. However, substantial differences in climate model projections for given scenarios of greenhouse gas emissions continue to limit detailed assessment. Here we show, using a traditional Köppen–Geiger bioclimate classification system, that the latest CMIP6 Earth system models actually agree well on the fraction of the global land surface that would undergo a major change per degree of global warming. Data from “historical” and “SSP585” model runs are used to create bioclimate maps at various degrees of global warming and to investigate the performance of the multi-model ensemble mean when classifying climate data into discrete categories. Using a streamlined Köppen–Geiger scheme with 13 classifications, global bioclimate classification maps at 2 and 4 K of global warming above a 1901–1931 reference period are presented. These projections show large shifts in bioclimate distribution, with an almost exclusive change from colder, wetter bioclimates to hotter, drier ones. Historical model run performance is assessed and examined by comparison with the bioclimatic classifications derived from the observed climate over the same time period. The fraction (f) of the land experiencing a change in its bioclimatic class as a function of global warming (ΔT) is estimated by combining the results from the individual models. Despite the discrete nature of the bioclimatic classification scheme, we find only a weakly saturating dependence of this fraction on global warming f =1-e-0.14ΔT, which implies about 13 % of land experiencing a major change in climate per 1 K increase in global mean temperature between the global warming levels of 1 and 3 K. Therefore, we estimate that stabilizing the climate at 1.5 K rather than 2 K of global warming would save over 7.5 million square kilometres of land from a major bioclimatic change.

The Paris Agreement and Climate Justice: Inequitable Impacts of Sea Level Rise Associated With Temperature Targets

AbstractAnthropogenic greenhouse gas emissions are causing unprecedented changes to the climate. In 2015, at the United Nations (UN) Conference of the Parties in Paris, France, countries agreed to limit the global mean temperature (GMT) increase to 2°C above preindustrial levels, and to pursue efforts to limit warming to 1.5°C. Due to the long‐term irreversibility of sea level rise (SLR), risks to island and coastal populations are not well encapsulated by the goal of limiting GMT warming by 2100. This review article investigates the climate justice implications of temperature targets in light of our increasing understanding of the spatially variable impact and long temporal commitment to rising seas. In particular we highlight the impact that SLR will have on island states and the role of the Alliance of Small Island States (AOSIS) in UN climate negotiations. As a case study we review dual impacts from the Antarctic Ice Sheet under a changing climate: (a) recent climate and ice sheet modeling shows that Antarctic melt has the potential to cause rapid SLR with a distinct spatial pattern leading to AOSIS nations experiencing SLR at least 11% higher than the global average and up to 33% higher; and (b) future ice sheet melt will result in a negative feedback on GMT, thus delaying temperature rise. When considering these impacts in conjunction, justice concerns associated with the Paris Agreement are exacerbated.

Unmasking the Effects of Aerosols on Greenhouse Warming Over Europe

AbstractAerosol optical thickness (AOT) has decreased substantially in Europe in the summer half year (April–September) since 1980, with almost a 50% reduction in Central and Eastern Europe, according to Modern‐Era Retrospective analysis for Research and Applications, Version 2 (MERRA‐2) reanalysis. At the same time, strong positive trends in ERA5 reanalysis surface solar radiation downward for all‐sky and clear‐sky conditions (SSRD and SSRDc, respectively) and temperature at 2 m are found for Europe in summer during the period 1979–2020. The GEBA observations show as well strong increases in SSRD during the latest four decades. Estimations of changes in SSRDc, using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model, show similarly strong increases when fed by MERRA‐2 AOT. The estimates of warming in this study, caused by increases in SSRD and SSRDc, are based on energy budget approximations and the Stefan Boltzmann law. The increases in near surface temperature, estimated both for clear‐sky and all‐sky conditions, are up to about 1°C for Central and Eastern Europe. The total warming over large parts of this region for clear‐sky conditions is however nearly double the global mean temperature increase of 1.1°C, while somewhat less for all‐sky conditions. The effects of aerosols on warming over the southerly Iberian Peninsula are weaker compared to countries further north. The rapid total warming over the Iberian Peninsula is probably caused by greenhouse warming, drier surface conditions, and to some degree decline in aerosols. Reduced cloud cover is found for large parts of Europe in summer during the latest four decades.

Unburnable Fossil Fuels and Climate Finance: Compensation for Rights Holders

Abstract To limit the increase in global mean temperature to 1.5°C, CO2 emissions should be capped at 440 gigatons. To achieve this, about 89 percent, 59 percent, and 58 percent of existing coal and conventional gas and oil reserves, respectively, need to remain unburned. This implies an economic cost for fossil fuel rights owners, and any successful climate policy will rely on resolving the distributional challenge of how to allocate the right to use the remaining burnable reserves. We discuss the possibility of compensating rights holders of unburnable oil and gas reserves, producing the first estimates of the financial resources needed to secure full compensation. We estimate that approximately US$ 5,400 billion (109) would be needed. Despite the vast amounts required, compensation is nevertheless economically feasible. We suggest a Keynesian “whatever it takes” approach for climate action, combining partial compensation for unburnable fuels and investment in low-carbon technologies to drastically reduce emissions in the rapidly closing window of opportunity before 2030.

How has aridity changed over West Africa in the past four decades?

Notable dryland expansion from changes in global aridity has been documented in previous studies, particularly with the increase in global mean temperature. Here, we examined the changes in the aridity of the western region of Africa over the past four decades. Using the aridity index (P/PET) as an indicator, the Climate Research Unit (CRU TS) data was used to identify drying and wetting areas of the region. The result showed that intense warming of 0.018 °C per year has occurred which was more evident in the last two decades. The warming in the past two decades caused a significant increase in PET. The first two decades were the driest compared to the last decades, particularly the first decade which also had major drought occurrences across the region. The aridity index increased by 0.86 (x10−3) per year within the past four decades, with the greatest change at the semi-arid zone. Result showed that precipitation exerts dominant control on aridity changes in the region despite a significant increase in PET. This was evident in the expansion of the wet areas between 2000 and 2019 compared to the 1979–1998 period.

Counteracting increased heat-related mortality through adaptation: a quantitative assessment in a multi-country multi-city setting.

Background & aims: Climate change is exacerbating the current heat-related health burden and will continue to do so at a higher speed in the coming decades if no adaptation occurs. Although previous studies have suggested potential paths of adaptation, there is little quantitative evidence on the degree of adaptation needed to counteract the increased heat-related mortality under different climate change scenarios. Methods: We performed a health impact projection analysis using observed data on 451 locations in 23 countries included in the MCC database and modelled temperature from 3 global circulation models (CMIP5 - ISMIP2b). For each city, we combined present-time risk functions, represented by the exposure-response association obtained from a two-stage time series analysis of the observed temperature-mortality data, with projected daily temperature in 20-year warming scenarios consistent with an increase in global mean temperature of 2, 3 and 4ºC from the preindustrial period. Using a novel optimization method, we estimated a risk reduction factor to be applied to the present-time exposure-response association representing the level of adaptation needed to counteract the increased heat-mortality burden under each warming target. Results: Assuming constant vulnerability and population, climate change would progressively amplify heat-related mortality reaching 3.9% (95%CI:0.6;0.9) of all-cause mortality due to heat at 4ºC warming scenario (vs. 0.4% (0.2-0.6) in baseline 1986-2005). To counteract the impact of the progressive increase of temperatures, present-time heat-related risks should reduce on average by 70% (35;104), 84% (60;104) and 91% (80;103) under the 2, 3 and 4ºC scenarios, respectively. Conclusions: Our preliminary findings show that substantial reductions in vulnerability would be required to counteract the increase in heat-mortality burden driven by climate change. Further steps will aim to extend the current analysis over a larger sample of locations and consider scenarios of population development. Keywords: climate change, adaptation, heat, mortality, projections, methods.

Spatial-temporal distribution of tropical cyclone activity on the eastern sea area of China since the late 1940s

Among all marine hazards, storm surges cause the most severe damage, and East Asia is one of the regions in the world most affected by tropical cyclones (TCs). With the increase in global mean temperature, the future changes of tropical cyclone (TC) activities are of great concern in East Asian countries. However, due to the inconsistency among different TC datasets, there is no uniform understanding of the spatial and temporal distribution and trends of TC activities in the eastern sea area of China (ESAC). In this study, all TC wind fields affecting ESAC during 1949–2019 were calculated using the Fujita-Takahashi formula, and a new TC dataset with a spatial resolution of 0.1° × 0.1° was thus obtained. Based on this dataset, the spatial-temporal variations of TC activity were analyzed. Three stages (1949–1967, 1968–1993, 1994–2019) of TC activities in ESAC can be identified using Mann Kendall Trend Test, which is closely related to El Niño-Southern Oscillation, sunspot activity, and Pacific Decadal Oscillation. A comparison of the accumulative number and duration of TCs in the three stages shows increasing trend toward the coasts and an northward. To address the issue of shelf storm deposition records on ESAC, we compared the published storm depositional records retrieved from several cores with typhoon impact data from the same sites based on the dataset of this study. We found that the preservation potential of the storm deposition record on ESAC ranged from 8% to 33%, with a high preservation potential in shallow water. These findings reveal the distribution and variability of TC impacts, which can be used to provide a scientific basis for disaster prevention and mitigation planning and adjustment of key coastal protection zones, as well as to evaluate the value of marine sedimentary records better.

Differential reproductive plasticity under thermal variability in a freshwater fish (Danio rerio).

Human-driven increases in global mean temperatures are associated with concomitant increases in thermal variability. Yet, few studies have explored the impacts of thermal variability on fitness-related traits, limiting our ability to predict how organisms will respond to dynamic thermal changes. Among the myriad organismal responses to thermal variability, one of the most proximate to fitness—and, thus, a population's ability to persist—is reproduction. Here, we examine how a model freshwater fish (Danio rerio) responds to diel thermal fluctuations that span the species's viable developmental range of temperatures. We specifically investigate reproductive performance metrics including spawning success, fecundity, egg provisioning and sperm concentration. Notably, we apply thermal variability treatments during two ontogenetic timepoints to disentangle the relative effects of developmental plasticity and reversible acclimation. We found evidence of direct, negative effects of thermal variability during later ontogenetic stages on reproductive performance metrics. We also found complex interactive effects of early and late-life exposure to thermal variability, with evidence of beneficial acclimation of spawning success and modification of the relationship between fecundity and egg provisioning. Our findings illuminate the plastic life-history modifications that fish may undergo as their thermal environments become increasingly variable.

Population and GDP Exposure to Extreme Precipitation Events on Loess Plateau under the 1.5 °C Global Warming Level

To mitigate the adverse effects of climate warming, the Paris Agreement proposed the goal to reduce global warming up to an increase of 1.5 °C above the preindustrial level. Study of the population and GDP exposure to precipitation extreme events under the 1.5 °C warming target is fundamental for disaster risk mitigation and adaptation on the Loess Plateau. This study projected the population and GDP exposure to extreme precipitation events under the 1.5 °C global warming level on the Loess Plateau using daily precipitation data from CMIP6 outputs and population and GDP data under a Shared Socioeconomic Pathway 1(SSP1) 2.6 scenario. The population and GDP exposure were evaluated by combing the frequency and the areal coverage of the extreme precipitation events. Results show that population and GDP exposure to extreme precipitation events on the Loess Plateau will increase under the 1.5 °C global warming level. The population exposure was projected from 1.32 × 106 to 2.68 × 106 person-year. The population exposure of eastern and southern Loess Plateau is significantly higher than that of the northern region. The annual exposure of GDP ranges from USD 2.9 to 12.3 billion, and the regions with the highest GDP exposure are Zhengzhou, Xi’an, Taiyuan, and Lanzhou. Our results reveal that limiting the increase of global mean temperature to 1.5 °C warming level is of great significance to reduce the social and economic exposure to extreme precipitation events on the Loess Plateau.

Significance of a 1 °C increase in global temperature

The Intergovernmental Panel on Climate Change reports indicate that the global mean temperature is about 1 °C higher than pre-industrial levels, that this increase is anthropogenic, and that there is a causal relationship between this higher temperature and an increase in frequency and magnitude of extreme weather events. This causal relationship seems at odds with common sense, and may be difficult to explain to non-experts. Thus to appreciate the significance of a one degree increase in global mean temperature, we perform back-of-the-envelope calculations relying on simple physics. We estimate the excess thermal energy trapped in the climate system (oceans, land, atmosphere) from a 1 °C increase in global mean temperature, and show that it is thousands of times larger than the estimated energy required to form and maintain a hurricane. Our estimates show that global warming is forming a very large pool of excess energy that could in principle power heatwaves, heavy precipitation, droughts, and hurricanes. The arguments presented here are sufficiently simple to be presented in introductory physics classes, and can serve as plausibility arguments showing that even a seemingly small increase in global mean temperature can potentially lead to extreme weather events.