Mann Michael E.

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Michael E.

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  • Preprint
    Increased threat of tropical cyclones and coastal flooding to New York City during the anthropogenic era
    ( 2015-08) Reed, Andra J. ; Mann, Michael E. ; Emanuel, Kerry A. ; Lin, Ning ; Horton, Benjamin P. ; Kemp, Andrew C. ; Donnelly, Jeffrey P.
    In a changing climate, future inundation of the United States’ Atlantic coast will depend on both storm surges during tropical cyclones and the rising relative sea-levels on which those surges occur. However, the observational record of tropical cyclones in the North Atlantic basin is too short (AD 1851-present) to accurately assess long-term trends in storm activity. To overcome this limitation, we use proxy sealevel records, and downscale three CMIP5 models to generate large synthetic tropical cyclone data sets for the North Atlantic basin; driving climate conditions span from AD 850 to AD 2005. We compare preanthropogenic era (AD 850 – AD 1800) and anthropogenic era (AD 1970 – AD 2005) storm-surge model results for New York City, exposing links between increased rates of sea-level rise and storm flood heights. We find that mean flood heights increased by ~1.24 m (due mainly to sea level rise) from ~AD 850 to the anthropogenic era, a result that is significant at the 99% confidence level. Additionally, changes in tropical cyclone characteristics have led to increases in the extremes of the types of storms that create the largest storm surges for New York City. As a result, flood risk has greatly increased for the region; for example, the 500 year return period for a ~2.25 m flood height during the preanthropogenic era has decreased to ~24.4 years in the anthropogenic era. Our results indicate the impacts of climate change on coastal inundation, and call for advanced risk management strategies.
  • Preprint
    Climate related sea-level variations over the past two millennia
    ( 2011-03) Kemp, Andrew C. ; Horton, Benjamin P. ; Donnelly, Jeffrey P. ; Mann, Michael E. ; Vermeer, Martin ; Rahmstorf, Stefan
    We present new sea-level reconstructions for the past 2100 years based on salt-marsh sedimentary sequences from the US Atlantic coast. The data from North Carolina reveal four phases of persistent sea-level change after correction for glacial isostatic adjustment. Sea level was stable from at least BC 100 until AD 950. It then increased for 400 years at a rate of 0.6 mm/yr, followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century. Since then, sea level has risen at an average rate of 2.1 mm/yr, representing the steepest, century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892. Using an extended semi-empirical modeling approach, we show that these sea-level changes are consistent with global temperature for at least the past millennium.
  • Preprint
    Atlantic hurricanes and climate over the past 1,500 years
    ( 2009-06) Mann, Michael E. ; Woodruff, Jonathan D. ; Donnelly, Jeffrey P. ; Zhang, Zhihua
    Atlantic Tropical Cyclone (TC) activity, as measured by annual storm counts, reached anomalous levels over the past decade. The short nature of the historical record and potential issues with its reliability in earlier decades, however, has prompted an ongoing debate regarding the reality and significance of the recent rise. Here, we place recent activity in a longer-term context, by comparing two independent estimates of TC activity over the past 1500 years. The first estimate is based on a composite of regional sedimentary evidence of landfalling hurricanes, while the second estimate employs a previously published statistical model of Atlantic TC activity driven by proxy-reconstructions of past climate changes. Both approaches yield consistent evidence of a peak in Atlantic TC activity during Medieval times (around AD 1000) followed by a subsequent lull in activity. The Medieval peak, which rivals or even exceeds (within uncertainties) recent levels of activity, results in the statistical model from a ‘perfect storm’ of La Niña-like climate conditions and relative tropical Atlantic warmth.
  • Preprint
    Impact of climate change on New York City’s coastal flood hazard : increasing flood heights from the preindustrial to 2300 CE
    ( 2017-09) Garner, Andra J. ; Mann, Michael E. ; Emanuel, Kerry A. ; Kopp, Robert E. ; Lin, Ning ; Alley, Richard B. ; Horton, Benjamin P. ; DeConto, Robert M. ; Donnelly, Jeffrey P. ; Pollard, David
    The flood hazard in New York City depends on both storm surges and rising sea levels. We combine modeled storm surges with probabilistic sea-level rise projections to assess future coastal inundation in New York City from the preindustrial era through 2300 CE. The storm surges are derived from large sets of synthetic tropical cyclones, downscaled from RCP8.5 simulations from three CMIP5 models. The sea-level rise projections account for potential partial collapse of the Antarctic ice sheet in assessing future coastal inundation. CMIP5 models indicate that there will be minimal change in storm-surge heights from 2010 to 2100 or 2300, because the predicted strengthening of the strongest storms will be compensated by storm tracks moving offshore at the latitude of New York City. However, projected sea-level rise causes overall flood heights associated with tropical cyclones in New York City in coming centuries to increase greatly compared with preindustrial or modern flood heights. For the various sea-level rise scenarios we consider, the 1-in-500-y flood event increases from 3.4 m above mean tidal level during 1970–2005 to 4.0–5.1 m above mean tidal level by 2080–2100 and ranges from 5.0–15.4 m above mean tidal level by 2280–2300. Further, we find that the return period of a 2.25-m flood has decreased from ∼500 y before 1800 to ∼25 y during 1970–2005 and further decreases to ∼5 y by 2030–2045 in 95% of our simulations. The 2.25-m flood height is permanently exceeded by 2280–2300 for scenarios that include Antarctica’s potential partial collapse.