Jeremy Hoffman, Ph.D.

The emergence of urban heat as a climate-induced health stressor is receiving increasing attention among researchers, practitioners, and climate educators. However, the measurement of urban heat poses several challenges with current methods leveraging either ground based, in situ observations, or satellite-derived surface temperatures estimated from land use emissivity. While both techniques contain inherent advantages and biases to predicting temperatures, their integration may offer an… Show more

The emergence of urban heat as a climate-induced health stressor is receiving increasing attention among researchers, practitioners, and climate educators. However, the measurement of urban heat poses several challenges with current methods leveraging either ground based, in situ observations, or satellite-derived surface temperatures estimated from land use emissivity. While both techniques contain inherent advantages and biases to predicting temperatures, their integration may offer an opportunity to improve the spatial resolution and global application of urban heat measurements. Using a combination of ground-based measurements, machine learning techniques, and spatial analysis, we addressed three research questions: (1) How much do ambient temperatures vary across time and space in a metropolitan region? (2) To what extent can the integration of ground-based measurements and satellite imagery help to predict temperatures? (3) What landscape features consistently amplify and temper heat? We applied our analysis to the cities of Baltimore, Maryland, and Richmond, Virginia, and the District of Columbia using geocomputational machine learning processes on data collected on days when maximum air temperatures were above the 90th percentile of historic averages. Our results suggest that the urban microclimate was highly variable across all of the cities—with differences of up to 10 °C between coolest and warmest locations at the same time—and that these air temperatures were primarily dependent on underlying landscape features. Additionally, we found that integrating satellite data with ground-based measures provided highly accurate and precise descriptions of temperatures in all three study regions. These results suggest that accurately identifying areas of extreme urban heat hazards for any region is possible through integrating ground-based temperature and satellite data. Show less

Editor's summary: Understanding how warm intervals affected sea level in the past is vital for projecting how human activities will affect it in the future. Hoffman et al. compiled estimates of sea surface temperatures during the last interglacial period, which lasted from about 129,000 to 116,000 years ago. The global mean annual values were ∼0.5°C warmer than they were 150 years ago and indistinguishable from the 1995–2014 mean. This is a sobering point, because sea levels during the last… Show more

Editor's summary: Understanding how warm intervals affected sea level in the past is vital for projecting how human activities will affect it in the future. Hoffman et al. compiled estimates of sea surface temperatures during the last interglacial period, which lasted from about 129,000 to 116,000 years ago. The global mean annual values were ∼0.5°C warmer than they were 150 years ago and indistinguishable from the 1995–2014 mean. This is a sobering point, because sea levels during the last interglacial period were 6 to 9 m higher than they are now. Show less

Living in a region of imminent threat of a magnitude-9.0 earthquake is a daily reality for the millions of people predicted to be directly affected by a full rupture of the Cascadia Subduction Zone (CSZ), a fault line extending for hundreds of miles off the western coast of North America. Many coastal residents and visitors will also be affected by the tsunami caused by the rupture. How can the scientific community effectively communicate with those who are unaware of the threat and unprepared… Show more

Living in a region of imminent threat of a magnitude-9.0 earthquake is a daily reality for the millions of people predicted to be directly affected by a full rupture of the Cascadia Subduction Zone (CSZ), a fault line extending for hundreds of miles off the western coast of North America. Many coastal residents and visitors will also be affected by the tsunami caused by the rupture. How can the scientific community effectively communicate with those who are unaware of the threat and unprepared to respond? We are studying the effects of a novel approach to science outreach we have called Flash Mob Science.

You have probably seen examples of flash mobs staging dynamic musical and dance routines to unsuspecting audiences. Similarly, Flash Mob Science takes the challenging (and often avoided) topic of earthquake and tsunami awareness and preparedness to unsuspecting audiences. However, Flash Mob Science seeks to move beyond having an audience of observers by engaging others as participants who enact important roles in an unfolding drama. We simulate the effects of seismic and tsunami events (e.g., prolonged surface shaking, falling debris, repeated tsunami surges) and model best practices in response (e.g., “Drop, Cover, Hold On” and moving quickly to high ground). True to the general flash mob model, when the Cascadia event inevitably does occur, it will come suddenly, and everyone affected will unavoidably be involved as actors in a real-life drama of immense scale. We seek to embed the learning of basic understandings and practices for an actual Cascadia event in a very small-scale, memorable, and sometimes even humorous, dramatization.

We present here the lessons we have learned in the background, planning, and implementation of Flash Mob Science. We highlight the successes, limitations, and preliminary results evaluating the effectiveness of this outreach in developing learners’ understandings and preparedness in an Oregon community affected by the CSZ. Show less

The last interglaciation (LIG; ~130-116 ka) was the most recent period in Earth history with higher-than-present global sea level (≥6 m) under similar-to-preindustrial concentrations of atmospheric CO2, suggesting additional feedbacks related to albedo, insolation, and ocean circulation in generating the apparent climatic differences between the LIG and present Holocene. However, our understanding of how much warmer the LIG sea surface was relative to the present interglaciation remains… Show more

The last interglaciation (LIG; ~130-116 ka) was the most recent period in Earth history with higher-than-present global sea level (≥6 m) under similar-to-preindustrial concentrations of atmospheric CO2, suggesting additional feedbacks related to albedo, insolation, and ocean circulation in generating the apparent climatic differences between the LIG and present Holocene. However, our understanding of how much warmer the LIG sea surface was relative to the present interglaciation remains uncertain, with current estimates suggesting from 0°C to 2°C warmer than late-20thcentury average global temperatures. Moreover, the timing, spatial expression, and amplitude of regional and global sea surface temperature variability related to other climate forcing during the LIG are poorly constrained, largely due to uncertainties in age control and proxy temperature reconstructions. An accurate characterization of global and regional temperature change during the LIG can serve as a benchmark for paleoclimate modeling intercomparison projects and help improve understanding of sea-level sensitivity to temperature change. We will present a global compilation (~100 published records) of sea surface temperature (SST) and other climate reconstructions spanning the LIG. Using a Monte Carlo-enabled cross-correlation maximization algorithm to climatostratigraphically align proxy records and then account for both the resulting chronologic and proxy calibration uncertainties with Bayesian statistical inference, our results quantify the spatial timing, amplitude, and uncertainty in estimates of global and regional sea surface temperature change during the LIG and its relation to potential forcings. Show less

Can we use surprising, immersive, and theatrical performances to engage science learners? In this presentation, I will talk about the intersection of informal science, earthquakes & tsunamis, and a novel exploration of "flash mob education." Neuroscience tells us that surprises drastically affect our brain function. "Surprise" is experienced when novel stimuli trigger our hippocampus, the so-called "novelty detector" of the brain, to say "Hey! This looks differently! Pay attention!" Multiple… Show more

Can we use surprising, immersive, and theatrical performances to engage science learners? In this presentation, I will talk about the intersection of informal science, earthquakes & tsunamis, and a novel exploration of "flash mob education." Neuroscience tells us that surprises drastically affect our brain function. "Surprise" is experienced when novel stimuli trigger our hippocampus, the so-called "novelty detector" of the brain, to say "Hey! This looks differently! Pay attention!" Multiple studies have shown marked increases in overall attention, learning, and knowledge retention when a subject was surprised during the learning transaction - in other words, humans tend to learn and remember better in the context of novelty! "Flash mobs" are sudden and surprising short-lived performances that captivate their unsuspecting audiences. So, how do we combine flash mobs, surprise, and science into a learning experience? Where could these be implemented to produce a measureable learning outcome? I invite fans of improvisational comedy, flash mobs, and neuroscience along for the ride. Show less

The last interglaciation (LIG; Marine Isotope Stage 5, ~129-116 ka) was the most recent period in Earth history with significantly higher-than-present global sea level (≥6 m) and as such is commonly used as an intercomparison target for global paleoclimate modeling efforts. However, the spatio-temporal expression and amplitude of temperature variability during the LIG remain poorly constrained, primarily confounded by spurious chronostratigraphic control across ocean basins and between… Show more

The last interglaciation (LIG; Marine Isotope Stage 5, ~129-116 ka) was the most recent period in Earth history with significantly higher-than-present global sea level (≥6 m) and as such is commonly used as an intercomparison target for global paleoclimate modeling efforts. However, the spatio-temporal expression and amplitude of temperature variability during the LIG remain poorly constrained, primarily confounded by spurious chronostratigraphic control across ocean basins and between hemispheres. In contrast to the relatively well-dated Holocene, age models for the LIG are problematic in that both the onset and duration of peak interglacial conditions are assigned different ages and lengths based on the record and/or chronometer considered (e.g., ice cores, speleothems, corals, marine sediment cores). Moreover, marine proxy records spanning the LIG are frequently aligned to reference time series targets and assigned some somewhat arbitrary chronological uncertainty. Building a spatially coherent time frame for the LIG must include a robust characterization of age-model uncertainty, as this greatly affects what climatic features and patterns can be confidently resolved in global and regional LIG temperature estimates. Here, we assess the total chronological uncertainty that results from developing an age model based on climatostratigraphic alignment of high-latitude Southern Ocean sea-surface temperature reconstructions to an Antarctic ice-core deuterium record using a modified version of a cross-correlation maximization algorithm. Combining this modified cross-correlation maximization algorithm with a Monte Carlo randomization scheme, we generate a coherent and robust quantification of climatostratigraphic LIG age-model uncertainty to refine regional and global estimates of LIG temperatures. Show less

Few discoveries have galvanized the interest of the paleoclimate community more so than Heinrich events (Heinrich, 1988). Nevertheless, the cause of Heinrich events remains poorly understood. Commonly attributed to an internal ice-sheet instability (MacAyeal, 1993), the coincidence of Heinrich events during times of maximum reduction in AMOC instead suggests a climate control (Bond et al., 1993). Shaff?er et al. (2004) proposed that during times of reduced AMOC, transmission of warmer… Show more

Few discoveries have galvanized the interest of the paleoclimate community more so than Heinrich events (Heinrich, 1988). Nevertheless, the cause of Heinrich events remains poorly understood. Commonly attributed to an internal ice-sheet instability (MacAyeal, 1993), the coincidence of Heinrich events during times of maximum reduction in AMOC instead suggests a climate control (Bond et al., 1993). Shaff?er et al. (2004) proposed that during times of reduced AMOC, transmission of warmer southern-sourced intermediate waters into the North Atlantic basin increases basal melt rates of submarine grounding lines of the Laurentide Ice Sheet, resulting in ice mass destabilization and triggering a Heinrich event (Sha?ffer et al., 2004). A recent study has supported this hypothesis by identifying subsurface warming leading up to several Heinrich events in one core at ~1,200 m depth from the Labrador Sea (Marcott et al., 2011). These observations must be reproduced in spatially distributed core sites to establish the spatio-temporal relation of these subsurface anomalies to Heinrich events. Results could identify future behavior of similarly confi?gured Antarctic Ice Sheet sectors. Show less

The last interglaciation (LIG; ~130-116 ka) was the most recent period in Earth history with higher-than-present global sea level (>6 m). Our understanding of how much warmer the climate was relative to today remains unclear, however, with current estimates suggesting 1-2 °C warmer-than-present average global temperatures. Moreover, the timing, spatial pattern, and amplitude of temperature variability during the LIG are poorly constrained, confounded by ambiguous chronostratigraphic control… Show more

The last interglaciation (LIG; ~130-116 ka) was the most recent period in Earth history with higher-than-present global sea level (>6 m). Our understanding of how much warmer the climate was relative to today remains unclear, however, with current estimates suggesting 1-2 °C warmer-than-present average global temperatures. Moreover, the timing, spatial pattern, and amplitude of temperature variability during the LIG are poorly constrained, confounded by ambiguous chronostratigraphic control across ocean basins and between hemispheres. An accurate characterization of global and regional temperature during the LIG can serve as a baseline comparison for future changes under anthropogenic climate change, potentially identifying likely candidate areas for increased mass loss from continental ice sheets and attendant sea level rise. We will present a global compilation (110 published records) of temperature reconstructions spanning the LIG, the majority of which are for sea-surface temperatures (SSTs). We use basin-specific benthic δ18O stacks to generate a common chronology for SST records, attempting to minimize the bias associated with diachronous benthic δ18O signals between the deep ocean basins during glacial terminations, which may exceed 4,000 years. We account for both chronologic and proxy calibration uncertainties with a Monte Carlo randomization scheme. Results will further quantify the spatial timing and amplitude of global and regional temperature change during the LIG. Show less

The 8.2 ka event was the last deglacial abrupt climate event. A reduction in the Atlantic meridional overturning circulation (AMOC) attributed to the drainage of glacial Lake Agassiz may have caused the event, but the freshwater signature of Lake Agassiz discharge has yet to be identified in δ18O of foraminiferal calcite records from the Labrador Sea, calling into question the connection between freshwater discharge to the North Atlantic and AMOC strength. Using Mg/Ca-paleothermometry, we… Show more

The 8.2 ka event was the last deglacial abrupt climate event. A reduction in the Atlantic meridional overturning circulation (AMOC) attributed to the drainage of glacial Lake Agassiz may have caused the event, but the freshwater signature of Lake Agassiz discharge has yet to be identified in δ18O of foraminiferal calcite records from the Labrador Sea, calling into question the connection between freshwater discharge to the North Atlantic and AMOC strength. Using Mg/Ca-paleothermometry, we demonstrate that ~3 °C of near-surface ocean cooling masked an ~1.0‰ decrease in western Labrador Sea δ18O of seawater concurrent with Lake Agassiz drainage. Comparison with North Atlantic δ18O of seawater records shows that the freshwater discharge was transported to regions of deep-water formation where it could perturb AMOC and force the 8.2 ka event. Show less