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Paciorek and Wehner raise important questions around our use of the Mann‐Kendall nonparametric trend test on smoothed data for analyzing long‐term hydrometeorological trends in Zhang et al. (2021, https://doi.org/10.1029/2020gl092293). We thank them for initiating this important conversation and their gracious cooperation in exploring the issues addressed in their comment. In this reply we confirm the inflation of significant p‐values by our choice to smooth, illustrate the relatively minor impacts on the main conclusions of our paper, and add our voices to those of Paciorek and Wehner in highlighting the lack of methodology for hypothesis testing across multiple stations that have spatial structure (i.e., testing for regionally consistent trends). Plain Language Summary: Our colleagues Drs. Paciorek and Wehner have raised concerns about our paper (Zhang et al., 2021, https://doi.org/10.1029/2020gl092293), which showed widespread increases in the duration of drought events over the last five decades in the western United States. They point out that our decision to smooth the data using a moving average inflated the number of weather stations at which the trends toward longer droughts were deemed significant by a statistical test. We agree with them on this point, and we have recomputed all our results using unsmoothed data to determine the impacts. We find that for most stations and regions, trend magnitudes remained largely unchanged, with many stations nearby one another often suggesting similar trends. Finally, we agree with Paciorek and Wehner that there is a lack of statistical methods to test such coherent regional patterns, and we caution that over‐reliance on p‐values limits the power of regional data to identify important climate trends. Key Points: We agree that smoothing to 5‐year moving windows introduced serial correlation into time series of annual statistics of daily rainfall data, inflating the number of weather stations individually showing significant trends (p < 0.05) with the Mann‐Kendall testRecomputation with unsmoothed values produced substantially the same dry intervals trend magnitude and direction at most stations individually and had only minimal impacts on dry interval trends computed for National Ecological Observatory Network domains using the Regional Kendall testNo perfect statistical approach leverages the capacity of coherent regional patterns among spatially correlated weather stations, and an over‐reliance on p‐values as a binary (significant vs. insignificant) determinant of trends limits the power of regional data [ABSTRACT FROM AUTHOR]

It is shown that a recently developed hybrid modeling approach that combines machine learning (ML) with an atmospheric global circulation model (AGCM) can serve as a basis for capturing atmospheric processes not captured by the AGCM. This power of the approach is illustrated by three examples from a decades‐long climate simulation experiment. The first example demonstrates that the hybrid model can produce sudden stratospheric warming, a dynamical process of nature not resolved by the low resolution AGCM component of the hybrid model. The second and third example show that introducing 6‐hr cumulative precipitation and sea surface temperature (SST) as ML‐based prognostic variables improves the precipitation climatology and leads to a realistic ENSO signal in the SST and atmospheric surface pressure. Plain Language Summary: This paper introduces and tests schemes for efficiently enabling significant expansion of the utility and scope of a recently introduced hybrid modeling technique that combines machine learning with an atmospheric global circulation model (AGCM). Simulation experiments are carried out with an implementation of the approach on a low resolution simplified AGCM. An examination of the simulated atmospheric circulation suggests that the hybrid model can capture dynamical process not captured by the AGCM. Moreover, the addition of precipitation and sea surface temperature (SST) as machine learning predicted physical quantities to the model improves the precipitation climatology and leads to a realistic El Niño‐La Niña signal in the SST and atmospheric surface pressure. Key Points: A hybrid system combining an atmospheric global circulation model (AGCM) with a machine‐learning component can capture processes not captured by the AGCMMachine learning provides a flexible framework to introduce additional prognostic variables into the hybrid modelThe prototype hybrid model tested in the paper is stable and has a realistic climate in decades‐long simulation experiments [ABSTRACT FROM AUTHOR]

Life on Earth appears to have evolved under the influence of supernovae activity in the solar neighborhood. Supernovae frequency regulates the flux of cosmic ray particles arriving at the top of the Earth's atmosphere, where empirical evidence supports a close connection between cosmic rays, clouds, and climate. Burial of organic matter in marine sediments follows cosmic rays variations for more than 3.5 Gyr and in detail during the last 500 Myr. The supernovae link to the burial of organic matter may be due to climate‐induced changes in the atmospheric and oceanic circulation affecting the availability of nutrients and the bioproductivity in the oceans. A higher bioproductivity then leads to a more extensive burial of organic matter. Support for this scenario comes from a proxy of nutrient concentrations in the ocean which covaries with the supernovae frequency. The results suggest a fundamental connection between supernovae rates and life on Earth. Plain Language Summary: The study proposes a surprising link between the burial of organic matter in sediments and stellar processes. The paper has two components; the first component concerns empirical evidence: A close correlation between the fraction of organic matter buried in sediments and changes in supernovae frequency. This correlation is evident during the last 3.5 billion years (see Figure 2) and in close detail over the previous 500 Myr (see Figure 4). All astrophysical data, for example, changes in star formation and the inferred changes in supernovae frequency, are based on peer‐reviewed works, as is the carbon 13 data. The second component of the paper gives a possible justification for the observed correlations. The assumption is that changes in supernovae frequency result in climate change, which changes the mixing in oceans and river runoff and ultimately influences nutrient availability—a high nutrient concentration results in a larger bioproductivity and a larger burial of organic matter in sediments. Again empirical evidence for this connection comes from concentrations of trace elements in pyrite (a proxy of ocean nutrient concentrations) which correlate with supernovae frequency changes over the previous 500 Myr (see Figure 5). Key Points: The fraction of organic carbon buried in marine sediments covaries with changes in supernova frequency over most of the Earth's historySupernovae influence Earth via a link between atmospheric ionization, clouds and climate. High cosmic ray flux leads to a cold climateClimatic induced ocean circulation regulates nutrients to the biosphere. A larger bioproductivity results in increased organic matter burial [ABSTRACT FROM AUTHOR]

A machine learning method is used to identify sources of long‐term ENSO predictability in the ocean (sea surface temperature (SST) and heat content) and the atmosphere (near‐surface zonal wind (U10)). Tropical SST represents the primary source of predictability skill. While U10 does not increase the skill when associated with SST, our analysis suggests U10 alone has apredictive skill comparable to that of SST between 11 and 21 months in advance, from late fall up to late spring. The long‐lead signal originates from coupled wind‐SST interactions across the Indian Ocean (IO) and propagates across the Pacific via an atmospheric bridge mechanism. A linear correlation analysis supports this mechanism, suggesting a precursor link between anomalies in SST in the western and wind in the eastern IO. Our results have important implications for ENSO predictions beyond 1 year ahead and identify the key role of U10 over the IO. Plain Language Summary: Many extreme events, such as floods or droughts, can be attributed to the El Niño Southern Oscillation, a mode of large‐scale ocean‐atmosphere coupled variability in the tropical Pacific Ocean occurring with a period of approximately 4 years. In this analysis, we use a machine learning methodology to disentangle the key atmospheric and oceanic ENSO components' relative contribution to its predictability, particularly the role of near‐surface 10‐m zonal wind. We quantify the potential for improved ENSO predictions for up to 2 years in advance and present a mechanistic understanding of the location of the sources of predictability. While equatorial sea surface temperature represents the primary source of ENSO predictability, the equatorial U10 plays a vital role from late spring to fall, from 1 to 2 years in advance. The enhanced predictability skill is shown to be linked to an SST anomaly originating in the Indian Ocean. The ML model used provides a new way to get new insights into the sources of predictability for ENSO and can be used as a simple but powerful tool to improve the underlying mechanistic understanding. Key Points: A deep learning‐based approach suggests near‐surface 10 m wind to play a significant role in providing skills for long‐term ENSO predictabilityThe skill of the 10‐m zonal wind is large from 12 months up to 23 months in advance (depending on the season)The signal is generated by coupled wind‐SST interactions in the Indian Ocean and later propagates across the Pacific [ABSTRACT FROM AUTHOR]

Today, volcanic sulfur emissions into the atmosphere are measured spectroscopically from the ground, air and space. For eruptions prior to the satellite era, two main sulfur proxies are used, the rock and ice core records, as illustrated by Peccia et al. (2023, https://doi.org/10.1029/2023gl103334). The first approach is based on calculations of the sulfur content of the magma, while the second uses traces of sulfur deposited in ice. Both approaches have their limitations. For glaciochemistry, the volcano responsible for a sulfur anomaly is often unknown and the atmospheric pathway by which the sulfur reached the ice uncertain. The petrologic method relies, too, on uncertain estimates of eruption size and a number of geochemical assumptions that are hard to verify. A deeper knowledge of processes occurring both within magma bodies prior to eruption, and within volcanic plumes in the atmosphere is needed to further our understanding of the impacts of volcanism on climate. Plain Language Summary: Volcanic emissions of sulfur gases during large eruptions can change the global climate. Today, advanced spectroscopic tools allow us to measure sulfur from the ground, air and space. But to understand the impacts of volcanic activity on climate back through history we need to estimate volcanic sulfur releases in other ways. Clues can be found in the pumice deposits found around a volcano and, perhaps more surprisingly, in the ice caps of the polar regions, which receive the eventual fallout from large eruptions. Both approaches have limitations that are addressed in a recent work by Peccia et al. (2023, https://doi.org/10.1029/2023gl103334) and that are at the focus of our commentary. Key Points: The impact of volcanic activity on climate remains difficult to quantify for eruptions prior to the instrumental eraThe petrological and glaciochemical methods each provide answers, but are still fraught with large uncertaintiesWe need to further our understanding of the physicochemical processes occurring both within magma reservoirs and volcanic plumes [ABSTRACT FROM AUTHOR]

While some previous studies examined the contribution of Eastern Pacific (EP) hurricanes toward precipitation in the arid Southwest US (SWUS), their potential to influence wildfires in that region has not been explored. Here we show, using observations and simulations from the Energy Exascale Earth System Model (E3SM), that recurving EP hurricanes modulate the wildfire environment in the SWUS by increasing precipitation and soil moisture, and reducing the vapor pressure deficit. This is especially the case during late season months of September–October when the likelihood of storms to recurve and make landfall increases. Further, analysis of burnt area observations reveals that for the months of September–October, recurving EP hurricanes may significantly reduce the prevalence of wildfires in the SWUS. Finally, E3SM simulations indicate that late season EP hurricanes have been on the decline, with important implications for wildfires in the SWUS. Plain Language Summary: A majority of Eastern Pacific (EP) hurricanes form and traverse westwards away from the North American coastline. Therefore, compared to tropical cyclones in some other basins, EP hurricanes have historically received less attention. However, some previous studies have shown that recurving EP hurricanes can contribute significantly to precipitation in the arid Southwest US (SWUS) region. Here, we build on these studies and demonstrate that recurving EP hurricanes significantly modulate the SWUS wildfire environment. During years with recurving EP hurricanes, the precipitation and soil moisture are enhanced, and the vapor pressure deficit is reduced, over the SWUS region. Therefore, during late season months of September–October, when recurving EP hurricanes occur, they make the environment less favorable for wildfires in the SWUS region. With climate models showing a long‐term decline in recurving EP hurricanes and the precipitation associated with them over the SWUS region, our study has substantial implications for autumn wildfires of that region. Key Points: Eastern Pacific (EP) hurricanes that recurve tend to enhance precipitation and reduce vapor pressure deficit in the Southwest US regionDuring September–October, recurving EP hurricanes may make the environment less favorable for wildfires in the Southwest USClimate model simulations suggest that Southwest US precipitation associated with recurving EP hurricanes has decreased [ABSTRACT FROM AUTHOR]

Abstract Paciorek and Wehner raise important questions around our use of the Mann‐Kendall nonparametric trend test on smoothed data for analyzing long‐term hydrometeorological trends in Zhang et al. (2021, https://doi.org/10.1029/2020gl092293). We thank them for initiating this important conversation and their gracious cooperation in exploring the issues addressed in their comment. In this reply we confirm the inflation of significant p‐values by our choice to smooth, illustrate the relatively minor impacts on the main conclusions of our paper, and add our voices to those of Paciorek and Wehner in highlighting the lack of methodology for hypothesis testing across multiple stations that have spatial structure (i.e., testing for regionally consistent trends).

Snow depth on sea ice is an Essential Climate Variable and a major source of uncertainty in satellite altimetry‐derived sea ice thickness. During winter of the MOSAiC Expedition, the "KuKa" dual‐frequency, fully polarized Ku‐ and Ka‐band radar was deployed in "stare" nadir‐looking mode to investigate the possibility of combining these two frequencies to retrieve snow depth. Three approaches were investigated: dual‐frequency, dual‐polarization and waveform shape, and compared to independent snow depth measurements. Novel dual‐polarization approaches yielded r2 values up to 0.77. Mean snow depths agreed within 1 cm, even for data sub‐banded to CryoSat‐2 SIRAL and SARAL AltiKa bandwidths. Snow depths from co‐polarized dual‐frequency approaches were at least a factor of four too small and had a r2 0.15 or lower. r2 for waveform shape techniques reached 0.72 but depths were underestimated. Snow depth retrievals using polarimetric information or waveform shape may therefore be possible from airborne/satellite radar altimeters. Plain Language Summary: Data collected using a surface‐based radar instrument on sea ice during the MOSAiC Arctic expedition were used to develop new techniques to estimate the depth of the overlying snow. We used different polarizations of the radiation to detect the depths of the upper and lower snow surfaces, and subtracted them to give snow depth. These depths agreed well with an independently collected snow depth data set. Estimates of snow depth using two different radar frequencies were less accurate, whilst using information of the shape of the returning pulse of radiation also showed a relationship with the independent snow depths, though not as strong as the polarization method. These results indicate that polarimetry (using a new satellite mission) and/or waveform shape (using existing missions) could be used to estimate snow depth on sea ice from airborne or satellite platforms. Key Points: Novel polarization‐based snow depth estimation techniques were developed using surface‐based Ku‐ and Ka‐band polarimetric radar altimeter dataThe dominant scattering surface was the air/snow and snow/ice interface in co‐ and cross‐polarized data, respectively, at both frequenciesRadar‐derived snow depths agreed with independent measurements, with r2 up to 0.77 and accuracy of 1 cm for best‐performing techniques [ABSTRACT FROM AUTHOR]

In the absence of consistent meteorological data on Mars, the morphology of dunes can be employed to study its atmosphere. Specifically, barchan dunes, which form under approximately unimodal winds, are reliable proxies for the dominant wind directions. Here, we characterize near‐surface winds on Mars from the morphology of >700,000 barchans mapped globally on the planet by a convolutional neural network. Barchan migration is predominantly aligned with known southern‐summer atmospheric circulation patterns—northerly at mid‐latitudes and cyclonic near the north pole—with the addition of an anti‐cyclonic north‐polar component that likely originates from winds emerging from the ice cap. Locally, migration directions deviate from regional trends in areas with high topographic roughness. Notably, obstacles <100 km such as impact craters are efficient at deflecting surface winds. Our database, which provides insights into planetary‐scale aeolian processes on modern‐day Mars, can be used to constrain global circulation models to assist with predictions for future missions. Plain Language Summary: Crescent‐shaped sand dunes are prevalent across the deserts of Mars. Here, we use the physical relationship between the shape of these dunes and the winds that form them to infer the directions of surface winds on Mars on a global scale. We find that dunes typically adhere to the global circulation patterns of Mars' atmosphere, and that local topographic winds are mostly important in areas with high topographic roughness such as inside deep impact craters. Our global wind map can serve to calibrate numerical climate models, which in turn can help us learn about the recent and modern‐day climate of Mars. Key Points: We derive global barchan dune migration directions on Mars using a convolutional neural networkAeolian sediment pathways on Mars are largely controlled by the planet's global circulationSurface winds are locally deflected by topographic obstacles with horizontal scales <100 km [ABSTRACT FROM AUTHOR]

Standard climate projections represent future volcanic eruptions by a constant forcing inferred from 1850 to 2014 volcanic forcing. Using the latest ice‐core and satellite records to design stochastic eruption scenarios, we show that there is a 95% probability that explosive eruptions could emit more sulfur dioxide (SO2) into the stratosphere over 2015–2100 than current standard climate projections (i.e., ScenarioMIP). Our simulations using the UK Earth System Model with interactive stratospheric aerosols show that for a median future eruption scenario, the 2015–2100 average global‐mean stratospheric aerosol optical depth (SAOD) is double that used in ScenarioMIP, with small‐magnitude eruptions (<3 Tg of SO2) contributing 50% to SAOD perturbations. We show that volcanic effects on large‐scale climate indicators, including global surface temperature, sea level and sea ice extent, are underestimated in ScenarioMIP because current climate projections do not fully account for the recurrent frequency of volcanic eruptions of different magnitudes. Plain Language Summary: Climate projections are the simulations of Earth's climate in the future using complex climate models. Standard climate projections, as in Intergovernmental Panel on Climate Change Sixth Assessment Report, assume that explosive volcanic activity over 2015–2100 are of the same level as the 1850–2014 period. Using the latest ice‐core and satellite records, we find that explosive eruptions could emit more sulfur dioxide into the upper atmosphere for the period of 2015–2100 than standard climate projections. Our climate model simulations show that the impacts of volcanic eruptions on climate, including global surface temperature, sea level and sea ice extent, are underestimated because current climate projections do not fully account for the recurrent frequency of volcanic eruptions. We also find that small‐magnitude eruptions occur frequently and can contribute a significant effect on future climate. Key Points: There is a 95% chance that the time‐averaged 2015–2100 volcanic SO2 flux from explosive eruptions exceeds the time‐averaged 1850–2014 fluxStandard climate projections very likely underestimate the 2015–2100 stratospheric aerosol optical depth and volcanic climate effectsSmall‐magnitude eruptions (<3 Tg SO2) contribute 30%–50% of the volcanic climate effects in a median future eruption scenario [ABSTRACT FROM AUTHOR]

At most latitudes, the seasonal cycle of zonal‐mean surface air temperature is notably asymmetric: the length of the warming season is not equal to the length of the cooling season. The asymmetry varies spatially, with the cooling season being ∼40 days shorter than the warming season in the subtropics and the warming season being ∼100 days shorter than the cooling season at the poles. Furthermore, the asymmetry differs between the Northern Hemisphere and the Southern Hemisphere. Here, we show that these observed features are broadly captured in a simple model for the evolution of temperature forced by realistic insolation. The model suggests that Earth's orbital eccentricity largely determines the hemispheric contrast, and obliquity broadly dictates the meridional structure. Clouds, atmospheric heat flux convergence, and time‐invariant effective surface heat capacity have minimal impacts on seasonal asymmetry. This simple, first‐order picture has been absent from previous discussions of the surface temperature seasonal cycle. Plain Language Summary: Away from the equator, most places on Earth experience a noticeable seasonal cycle in surface air temperature. The seasonal cycle of temperature governs many aspects of human and ecosystem behavior. Observations show that, at most latitudes, the length of the warming season is not equal to the length of the cooling season, that is, the seasonal cycle is asymmetric. For example, at 25°N, the average warming season is 35 days longer than the cooling season. Here, we look at how this asymmetry varies with distance from the equator. We find that the asymmetry can largely be explained as a result of variations in the amount of radiation from the sun that reaches Earth, which are determined by Earth's orbit. Key Points: The seasonal cycle in zonal‐mean surface air temperature is asymmetricThe warming period tends to be shorter than 6 months in high latitudes and longer than 6 months in low latitudesThe asymmetry can largely be explained by variations in top‐of‐atmosphere insolation, dictated by Earth's orbit [ABSTRACT FROM AUTHOR]

Water ice in the Martian mid‐latitudes has advanced and retreated in response to variations in the planet's orbit, obliquity, and climate. A 150 m‐diameter new impact crater near 35°N provides the lowest‐latitude impact exposure of subsurface ice on Mars. This is the largest known ice‐exposing crater and provides key constraints on Martian climate history. This crater indicates a regional, relatively pure ice deposit that is unstable and has nearly vanished. In the past, this deposit may have been tens of meters thick and extended equatorward of 35°N. We infer that it is overlain by pore ice emplaced during temporary stable intervals, due to recent climate variability. The marginal survival of ice here suggests that it is near the edge of shallow ice that regularly exchanges with the atmosphere. Plain Language Summary: A 150 m‐diameter new impact crater on Mars exposes water ice, constraining the nature of past and present ice sheets and paleoclimate. The past climate has varied, gradually removing a massive ice deposit that has nearly been lost at 35°N but survives at higher latitude. Key Points: Water ice is exposed in a 150 m‐diameter new impact crater near 35°N on MarsThe ice includes both massive ice and a covering layer of pore iceThis ice marks the southern margin of remaining ice deposits from high‐obliquity periods [ABSTRACT FROM AUTHOR]

Groundwater is an invaluable global resource, but its long‐term viability as a resource for consumption, agriculture, and ecosystems depends on precipitation recharging aquifers. How much precipitation recharges groundwaters varies enormously across Earth's surface, yet recharge rates often remain uncertain. Here we use a global synthesis of field‐estimated recharge across six continents to show that globally recharge first‐order follows a simple function of climatic aridity. We use this relationship to estimate long‐term recharge in energy‐limited systems outside of permafrost regions. Our aridity‐based recharge estimates are consistent with the global field data but, on average, double previous estimates of global models. Our higher recharge estimates are likely caused by preferential groundwater recharge and discharge occurring at grid scales finer than global models. The higher recharge estimates suggest that more groundwater contributes to evapotranspiration and streamflow than previously represented by global hydrological models and global water cycle diagrams. Plain Language Summary: Groundwater is an essential resource for societies and ecosystems. The rate at which rainfall and snow replenish groundwater storage is important as it dictates the upper limit of sustainable groundwater use. Here we use measurements of groundwater recharge to show how climate determines groundwater recharge rates. Measured recharge rates, on average, strongly exceed those of models. This suggests there is more recharge globally than currently acknowledged. Consequently, also more groundwater recharge must get back to Earth's surface via river flow or water use of vegetation. Key Points: A global recharge data set indicates that climate strongly shapes the fraction of precipitation that will recharge groundwatersThis recharge data set indicates more recharge globally than existing global hydrological models suggestThus, more groundwater must contribute to evaporation and streamflow than represented by current global models and water cycle diagrams [ABSTRACT FROM AUTHOR]

Hurricanes often cause severe damage and loss of life, and storms that intensify close to the coast pose a particularly serious threat. While changes in hurricane intensification and environment have been examined at basin scales previously, near‐coastal changes have not been adequately explored. In this study, we address this using a suite of observations and climate model simulations. Over the 40‐year period of 1979–2018, the mean 24‐hr hurricane intensification rate increased by ∼1.2 kt 6‐hr−1 near the US Atlantic coast. However, a significant increase in intensification did not occur near the Gulf coast over the same period. The enhanced hurricane intensification along the Atlantic coast is consistent with an increasingly favorable dynamic and thermodynamic environment there, which is well simulated by climate models over the historical period. Further, multi‐model projections suggest a continued enhancement of the storm environment and hurricane intensification near the Atlantic coast in the future. Plain Language Summary: While hurricanes pose a significant socioeconomic threat in general, those that intensify close to the coast are particularly challenging for operational forecasters and decision makers. Past studies examined basin‐scale changes in hurricane intensification and the large‐scale environment in the Atlantic. However, near‐coastal changes in hurricane intensification have not been extensively studied. Herein, we address this using a combination of observations and numerical model simulations. Analysis of hurricane track data for the period 1979–2018 indicates that the mean hurricane intensification rate has increased significantly near the Atlantic coast. In contrast, significant increases in nearshore hurricane intensification are not seen for the Gulf coast. Observed changes in the ambient storm environment over the same period, which are in good agreement with these changes in hurricane intensification, are well reproduced by climate models. Finally, models project a continued enhancement of the hurricane environment near the Atlantic coast in the future. These results are well supported by direct simulation of hurricanes in high‐resolution climate models. Key Points: Hurricane intensification rate has significantly increased near the US Atlantic coast over the last 40 yearsClimate models accurately simulate the observed trends with an enhanced environment conducive for hurricanesMulti‐model projections suggest that the environment will increasingly favor hurricane intensification near the Atlantic coast [ABSTRACT FROM AUTHOR]

Structural hydrologic connections, formed by the coaction of tectonic and climatic processes, facilitate the transfer of matter across Earth's surface. Large‐scale analysis of hillslope connectivity controls is lacking, thus limiting our understanding of the drivers of extremes, like floods and landslides, and benefits, like wetlands. Here, we model hillslope connectivity using the Index of Connectivity, at 10‐m resolution for the contiguous United States. We show the dominance of tectonic drivers, like river steepness (ρ = 0.84) and seismic activity (ρ = 0.48), over climatic drivers, like precipitation (ρ = −0.31) and aridity (ρ = −0.07), in controlling the strength of connectivity. Highly connected basins were associated with landslide occurrence (ρ = 0.69) while poorly connected basins had greater wetland density (ρ = −0.50). Lastly, we share our results in an open access data portal for land managers to leverage structural connectivity maps in their respective study domains. Plain Language Summary: Hillslopes are critical landscape features that intercept, store, and route water, from its source as rainfall to its fate as river discharge. The strength of this routing is a function of climatic and tectonic forces, but their relative importance to hillslope connectivity is uncertain. We simulated the Index of Connectivity, a topographic analogue for structural connectivity, for 75 billion locations in contiguous United States (CONUS), across a range of climatic and tectonic settings. At the CONUS‐scale, we found that hillslope connectivity is largely driven by tectonic forces, including uplift and seismic activity, and that highly connected hillslopes are more susceptible to landslides while poorly connected hillslopes promote wetland development. We provide a web data portal to serve as a tool for stakeholders to visualize and leverage structural connectivity data in their respective study areas. Key Points: Hillslope connectivity shows high spatial variability across the United StatesTectonics is a primary control of the strength of structural hillslope connectivityOpen access data portal of connectivity maps created for stakeholders [ABSTRACT FROM AUTHOR]

The influence of atmospheric composition on the climates of present‐day and early Earth has been studied extensively, but the role of ocean composition has received less attention. We use the ROCKE‐3D ocean‐atmosphere general circulation model to investigate the response of Earth's present‐day and Archean climate system to low versus high ocean salinity. We find that saltier oceans yield warmer climates in large part due to changes in ocean dynamics. Increasing ocean salinity from 20 to 50 g/kg results in a 71% reduction in sea ice cover in our present‐day Earth scenario. This same salinity change also halves the pCO2 threshold at which Snowball glaciation occurs in our Archean scenarios. In combination with higher levels of greenhouse gases such as CO2 and CH4, a saltier ocean may allow for a warm Archean Earth with only seasonal ice at the poles despite receiving ∼20% less energy from the Sun. Plain Language Summary: The composition of the atmosphere, especially the abundance of greenhouse gases, famously influences Earth's climate system. We use a climate model to show that the composition of the ocean can also have a major impact on surface temperature and ice cover. We focus specifically on the amount of salt dissolved in seawater, and we find that saltier oceans tend to result in warmer climates. These effects are modest today, but salt may be a key ingredient for early Earth habitability in the distant past when the Sun was less bright. Key Points: Saltier oceans result in warmer climates with less sea iceWarming with increasing salinity is strongly affected by changing ocean dynamicsA saltier ocean may have helped keep early Earth warm when the Sun was less luminous [ABSTRACT FROM AUTHOR]

The COVID‐19 pandemic has been a life‐altering shock to society. However, there have been serendipitous outcomes from the associated lockdowns ranging from improved air quality to reductions in carbon emissions. Liu et al. (2022, https://doi.org/10.1029/2021GL096842) revealed that even the magnitude of the heat islands in Chinese cities were reduced due to a decline in human activities and their associated anthropogenic contributions. These surprising findings have significant implications for understanding intersections among climate, health, energy, urban planning, transportation, and infrastructure. Plain Language Summary: Cities are built with heat‐absorbing materials, contain less vegetation than surrounding rural landscapes, and host a variety of heat‐emitting activities. For this reason, the central business district and suburban areas are often warmer than their surroundings. These so‐called urban heat islands are often associated with inequities in health and energy consumption. Newly published research suggests that COVID‐19 lockdowns may have temporarily reduced these human‐caused heat islands in Chinese cities. Key Points: COVID‐19 lockdown led to reduced urban heat island (UHI) magnitude in ChinaAnthropogenic activity and waste heat is related to UHI magnitudeUHI mitigation has implication for health, energy, and equity within cities [ABSTRACT FROM AUTHOR]

Disturbance of marine sediments results in the remineralization of sedimentary organic matter (OM) and impacts upon natural burial processes. Management interventions which restrict or remove activities that cause seabed disturbance may offer effective strategies to protect the most vulnerable of these shelf sea OM stores, offering new opportunities to deliver climate mitigation actions. While the largest quantities of OM are often stored in the expansive offshore regions of continental shelves and might therefore suggest appropriate zones for management interventions to protect vulnerable OM stores, our results highlight that these offshore regions generally contain OM of low reactivity. Conversely, inshore and coastal sediments store significant quantities of highly reactive OM that is at greater risk of remineralization when disturbed. The marked spatial disparities between OM reactivity across shelf sea sedimentary environments highlights the need to focus emergent policy and future management interventions toward the protection of inshore and coastal sediments. Plain Language Summary: If disturbed, the organic carbon within seafloor sediments can potentially be converted to carbon dioxide and a portion lost to the atmosphere, where it potentially contributes to climate change. Our results highlight that the reactivity (biodegradability) of sedimentary carbon across shelf seas is highly variable with low reactivity organic matter found in the offshore region, while organic matter within inshore and coastal sediments can be highly reactive and potentially vulnerable to break‐down when disturbed. These differences in organic matter reactivity highlight the need to focus emergent management interventions that can deliver protection toward the most vulnerable organic matter stores in inshore and coastal sediments. Key Points: Within most shelf sediments organic matter (OM) is generally of low reactivity (i.e., low labile OM content) and resistant to remineralizationMuddy nearshore sediments hold large quantities of high reactivity OM which is at risk of remineralization when disturbedPolicy interventions that seek to protect reactive OM should prioritize near‐shore sediment OM over the resilient OM in many shelf seas [ABSTRACT FROM AUTHOR]

Volcanic flood basalt eruptions have been linked to or are contemporaneous with major climate disruptions, ocean anoxic events, and mass extinctions throughout at least the last 400 M years of Earth's history. Previous studies and recent history have shown that volcanically‐driven climate cooling can occur through reflection of sunlight by H2SO4 aerosols, while longer‐term climate warming can occur via CO2 emissions. We use the Goddard Earth Observing System Chemistry‐Climate Model to simulate a 4‐year duration volcanic SO2 emission of the scale of the Wapshilla Ridge member of the Columbia River Basalt eruption. Brief cooling from H2SO4 aerosols is outweighed by dynamically and radiatively driven warming of the climate through a three orders of magnitude increase in stratospheric H2O vapor. Plain Language Summary: Volcanic flood basalt eruptions are linked to mass extinctions and climate change through Earth's history. Using model experiments, we show that a massive release of sulfur dioxide gas, as would happen in such an eruption, can warm the climate through feedback mechanisms linked to an increase in stratospheric water vapor. Key Points: Volcanic emission of SO2 produces warming through climate feedbacksThe warming is driven by a three orders of magnitude increase in stratospheric H2O vaporClimate cooling by H2SO4 aerosols persists for less time than the eruption itself [ABSTRACT FROM AUTHOR]

Central Asia hosts the most extensive and highest topography on Earth, which is the result of the feedbacks among rock uplift, atmospheric circulation and moisture transport, and erosion. Here, we analyze 2,511 published low‐temperature thermochronometric ages as a proxy of the regional‐scale erosion of Central Asia. We compare these ages to tectonic and climate proxies, and state‐of‐the‐art paleoclimate simulations to constrain the influences of climate and tectonics on the topographic architecture of Central Asia. We observe a first‐order relationship between younger cooling ages in areas of high precipitation and older ages (Mesozoic) in areas that have been sheltered from precipitation, despite high strain rates. Thus, we suggest that climate enhances erosion in areas where rock uplift produces significant orographic gradients, whereas in the continental interior, areas which are tectonically active but have been sheltered from significant precipitation record older ages and a longer erosional history. Plain Language Summary: Modern topography represents the product of the relationships among climate, tectonics, and erosion through time. Central Asia is one of the most topographically diverse regions on Earth. However, the relative role of tectonics versus climate on erosion of continental Asia remains one of the major debates in Earth sciences. One way to investigate this is through the analysis of erosional proxies. In this study, we present the first regional‐scale analysis of thermochronometric ages from Central Asia as a proxy of erosion. We compare these data to tectonic processes, climate proxies, and state‐of‐the‐art paleoclimate simulations in order to constrain the relative influences of climate and tectonics on the topographic architecture and erosion of Central Asia. There is a first‐order relationship between more recent erosion and active tectonic boundaries. However, more recent erosion is also associated with areas of high precipitation, whereas areas that have been sheltered from significant precipitation retain a signal of older erosional events. Thus, we suggest that climate plays a key role in enhancing erosion in areas with developed topography and high precipitation, whereas areas which experienced sustained aridity record less erosion and preserve a record of older erosion. Key Points: Despite the magnitude of the India‐Asia collision, erosion throughout Central Asia reflects Phanerozoic tectonicsRegions of "old" erosion are preserved in more arid areas, whereas more recent erosion is concentrated in areas of high precipitationTectonic mechanisms are required to initiate erosion; however, climate modulates the magnitude of erosion [ABSTRACT FROM AUTHOR]