Department of Geography

The recovery of long-term climate proxy records with seasonal resolution is rare because of natural smoothing processes, discontinuities and limitations in measurement resolution. Yet insolation forcing, a primary driver of multimillennial-scale climate change, acts through seasonal variations with direct impacts on seasonal climate¹. Whether the sensitivity of seasonal climate to insolation matches theoretical predictions has not been assessed over long timescales. Here, we analyse a continuous record of water-isotope ratios from the West Antarctic Ice Sheet Divide ice core to reveal summer and winter temperature changes through the last 11,000 years. Summer temperatures in West Antarctica increased through the early-to-mid-Holocene, reached a peak 4,100 years ago and then decreased to the present. Climate model simulations show that these variations primarily reflect changes in maximum summer insolation, confirming the general connection between seasonal insolation and warming and demonstrating the importance of insolation intensity rather than seasonally integrated insolation or season duration^2,3. Winter temperatures varied less overall, consistent with predictions from insolation forcing, but also fluctuated in the early Holocene, probably owing to changes in meridional heat transport. The magnitudes of summer and winter temperature changes constrain the lowering of the West Antarctic Ice Sheet surface since the early Holocene to less than 162 m and probably less than 58 m, consistent with geological constraints elsewhere in West Antarctica^4-7.

The Little Ice Age (LIA; ca. 1450-1850 C.E.) is the best documented cold period of the past millennium, characterized by high-frequency volcanism, low solar activity, and high variability of Arctic sea-ice cover. Past studies of LIA Atlantic circulation changes have referenced the North Atlantic Oscillation (NAO), but recent studies have noted that LIA climate patterns appear to possess complexity not captured by an NAO analogue. Here, we present a new precipitation-sensitive stalagmite record from northern Italy that covers the past 800 years. We show that in the early LIA (1470-1610 C.E.), increased atmospheric ridging over northern Europe split the climatological westerlies away from central and northern Europe, possibly caused by concurrent Artic sea-ice reduction. With ongoing ice melting in the northern high latitudes and decreasing solar irradiance in the coming years, the early LIA may potentially serve as an analogue for European hydroclimatic conditions in the coming decades.

The Energy Exascale Earth System Model (E3SM) project is an ongoing, state-of-the-science Earth system modeling, simulation, and prediction project developed by the US Department of Energy (DOE). With an emphasis on supporting the DOE's energy mission, understanding and quantifying how well the model simulates water cycle processes is of particular importance. Here, we evaluate E3SM version 1.0 (v1.0) for its ability to represent atmospheric rivers (ARs), which play significant roles in water vapor transport and precipitation. The characteristics and precipitation associated with global ARs in E3SM at standard resolution (1×1) are compared to the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA2). Global patterns of AR frequencies in E3SM show high degrees of correlation (≥0.97) with MERRA2 and low mean absolute errors (MAEs; <1%) annually, seasonally, and across different ensemble members. However, some large-scale condition biases exist, leading to AR biases - most significant of which are the double intertropical convergence zone (ITCZ), a stronger and/or equatorward-shifted subtropical jet during boreal and austral winters, and enhanced Northern Hemisphere westerlies during summer. By comparing atmosphere-only and fully coupled simulations, we attribute the sources of the biases to the atmospheric component or to a coupling response. Using relationships revealed in , we provide evidence showing the stronger North Pacific jet in winter and the enhanced Northern Hemisphere westerlies during summer, associated with E3SM's double ITCZ and related weaker Atlantic meridional overturning circulation (AMOC), respectively, which are significant sources of the AR biases found in the coupled simulations.

This article analyzes the spontaneous production of graffiti art and murals covering the entrances of businesses in the central business district of Oakland, CA, in the wake of the global protest movements, in 2020, against state violence and systemic racism. I argue that the art made legible what gets hidden through the violent processes of gentrification, neoliberal urbanism, and displacement/dispossession. The paper rethinks what borders, policing, and reclamation mean in a time of economic instability and a global health crisis, through the placement of these vernacular expressions in Downtown Oakland. What is revealed through the art is the convergence of two co-constitutive publics–a segregated, decaying city mostly inhabited by poor and working-class Black and Latinx residents and laborers, and a modern, prosperous, neoliberal city that caters to a privileged class of white residents and tourists–especially as the city grappled with the management and regulation of public space in the midst of a global pandemic. The article thus theorizes public space as layered and always contested, and not simply a space of conflict but also collective engagement.

Rainbands that migrate northward from spring to summer are persistent features of the East Asian summer monsoon. This study employs a machine learning algorithm to identify individual East Asian rainbands from May to August in the 6-hourly ERA-Interim reanalysis product and captures rainband events during these months for the period 1979–2018. The median duration of rainband events at any location in East Asia is 12 h, and the centroids of these rainbands move northward continuously from approximately 288N in late May to approximately 338N in July, instead of making jumps between quasi-stationary periods. Whereas the length and overall area of the rainbands grow monotonically from May to June, the intensity of the rainfall within the rainband dips slightly in early June before it peaks in late June. We find that extratropical northerly winds on all pressure levels over East China are the most important anomalous flow accompanying the rainband events. The anomalous northerlies augment climatological background northerlies in bringing low moist static energy air and thus generate the front associated with the rainband. Persistent lower-tropospheric southerly winds bring in moisture that feeds the rainband and are enhanced a few days prior to rainband events, but they are not directly tied to the actual rainband formation. The background northerlies could originate as part of the Rossby waves resulting from the jet stream interaction with the Tibetan Plateau. The ageostrophic circulation in the jet entrance region peaks in May and weakens in June and July and does not prove to be critical to the formation of the rainbands.

The single-family rental (SFR) industry became a new site of institutional investment in the aftermath of the 2008 foreclosure crisis and the wider macroeconomic and policy shifts that ensued. Together with these political economic conditions, rapid advances in digital technologies, data, and analytics have been a crucial factor in the corporate transformation of SFR and the housing landscape more broadly. The four largest public and private SFR operators together control over 200,000 homes, and the SFR asset class has boomed in the pandemic, drawing interest from a wide range of investors and spawning new business models and partnerships. In this report we examine SEC filings and quarterly investor calls for Invitation Homes, American Homes 4 Rent, Tricon American Homes, and Front Yard Residential to trace how institutional narratives and market strategies have evolved in the SFR asset class. As the pool of foreclosed properties has largely dried up, SFR companies are developing new strategies to increase growth and returns for shareholders, including build-for rent and partnerships with builders. During the COVID-19 pandemic, corporate SFR landlords pushed major rent increases and devoted energy to increasing revenues through ancillary fees that further add to tenants’ housing costs. Corporate landlords are actively finding ways to cut down costs, particularly through technology and the built environment of homes, as well as appealing property tax assessments. What does it mean for the rest of us when a handful of landlords have so much power? For regular people, the structural advantage enjoyed by corporate landlords amplifies the inequalities endemic to capitalist housing systems. Amid the new round of investor-led growth, corporate landlords are poised to expand their portfolios further. As they take on an outsized role in the markets where their footprint is the largest, access to billions in investment capital seeking returns in the hot housing market and troves of data from their in-house operations put corporate landlords in a position of structural power in the market.

This article centers the role of digital technologies in extending financial accumulation into new sectors of the US housing market in the wake of the global financial crisis. I argue that while post-crisis market conditions provided an opportunity for large investors to acquire foreclosed single-family homes, convert them to rental housing, and roll out an new asset class based on bundled rent checks, these conditions were insufficient on their own. Digital innovations coming to prominence since the 2008 crisis were required to automate core functions, such as rent collection and maintenance, in order to efficiently manage large, geographically dispersed property portfolios. New information technologies enabled investors to aggregate ownership of resources, extract income flows, and securely convey these flows to capital markets. Such advances have, therefore, given rise to the “automated landlord”, whereby the management of tenants and properties is increasingly not only mediated, but governed, by smartphones, digital platforms, and apps, and the data and analytics these devices and infrastructures gather and enable. This article shows how technological transformations actively participate in the ongoing, dynamic process of financial accumulation strategies, and contends that digital technologies, therefore, also comprise a crucial terrain of struggles over housing’s place in contemporary capitalism.

Methyl bromide (CH₃Br) and methyl chloride (CH₃Cl) are major carriers of atmospheric bromine and chlorine, respectively, which can catalyze stratospheric ozone depletion. However, in our current understanding, there are missing sources associated with these two species. Here we investigate the effect of copper(II) on CH₃Br and CH₃Cl production from soil, seawater and model organic compounds: catechol (benzene-1,2-diol) and guaiacol (2-methoxyphenol). We show that copper sulfate (CuSO₄) enhances CH₃Br and CH₃Cl production from soil and seawater, and it may be further amplified in conjunction with hydrogen peroxide (H₂O₂) or solar radiation. This represents an abiotic production pathway of CH₃Br and CH₃Cl perturbed by anthropogenic application of copper(II)-based chemicals. Hence, we suggest that the widespread application of copper(II) pesticides in agriculture and the discharge of anthropogenic copper(II) to the oceans may account for part of the missing sources of CH₃Br and CH₃Cl, and thereby contribute to stratospheric halogen load.

The range of synoptic patterns that North Pacific landfalling atmospheric rivers form under are objectively identified using genesis day 500 hPa geopotential height anomalies in a self-organizing map (SOM). The SOM arranges the synoptic patterns to differentiate between two groups of climate modes—the first group with ENSO (El Niño Southern Oscillation), PDO (Pacific Decadal Oscillation), PNA (Pacific North American) and NP (North Pacific index) and the second group with AO (Arctic Oscillation), EPO (East Pacific Oscillation), and WPO (West Pacific Oscillation). These two groups have their positive and negative modes organized in opposite corners of the SOM. The ARs produced in each of the synoptic patterns have distinct lifecycle characteristics (such as genesis and landfall location, duration, velocity, meridional/zonal movement) and precipitation impacts (magnitude and spatial distribution). The conditions that favour AR trajectories closer to the tropics tend to produce higher amounts of precipitation. The large-scale circulation associated with AR genesis shows a close relationship between the genesis location and the location and intensity of the upper-level jet in the west/central pacific as well as anomalous, low-level southwesterly winds in the east pacific.