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- Title
Climate Change Signal in Atlantic Tropical Cyclones Today and Near Future.
- Authors
Lee, Chia‐Ying; Sobel, Adam H.; Tippett, Michael K.; Camargo, Suzana J.; Wüest, Marc; Wehner, Michael; Murakami, Hiroyuki
- Abstract
This manuscript discusses the challenges in detecting and attributing recently observed trends in the Atlantic tropical cyclone (TC) and the epistemic uncertainty we face in assessing future risk. We use synthetic storms downscaled from five CMIP5 models by the Columbia HAZard model (CHAZ), and directly simulated storms from high‐resolution climate models. We examine three aspects of recent TC activity: the upward trend and multi‐decadal oscillation of the annual frequency, the increase in storm wind intensity, and the decrease in forward speed. Some data sets suggest that these trends and oscillation are forced while others suggest that they can be explained by natural variability. Projections under warming climate scenarios also show a wide range of possibilities, especially for the annual frequencies, which increase or decrease depending on the choice of moisture variable used in the CHAZ model and on the choice of climate model. The uncertainties in the annual frequency lead to epistemic uncertainties in TC risk assessment. Here, we investigate the potential for reduction of these epistemic uncertainties through a statistical practice, namely likelihood analysis. We find that historical observations are more consistent with the simulations with increasing frequency than those with decreasing frequency, but we are not able to rule out the latter. We argue that the most rational way to treat epistemic uncertainty is to consider all outcomes contained in the results. In the context of risk assessment, since the results contain possible outcomes in which TC risk is increasing, this view implies that the risk is increasing. Plain Language Summary: We use a set of computer model simulations to study recent trends in Atlantic tropical cyclones. We looked at three aspects of these storms: the number of tropical cyclones each year, which has fluctuated up and down over time (but generally increased over the last several decades); the strength of their winds, which has been increasing; and the speed at which they move, which has been decreasing. These trends could be caused either by human‐induced global warming or by natural variability; determining which cause is more important to overall risk requires us to understand how the number of tropical cyclones per year responds to warming. In our simulations, this number can either increase or decrease with warming, depending on which of two nearly identical versions of our model we use to simulate the storms. This uncertainty prevents us from reaching definitive conclusions about either present or future hurricane risk. Nonetheless, our analysis suggests that the risk of Atlantic tropical cyclones is more likely increasing than decreasing, and we argue that from a broader point of view, this is effectively equivalent to saying the risk is increasing. Key Points: Changes in the Atlantic tropical cyclone (TC) risk are uncertain due to epistemic uncertainty in the projected annual frequency under global warmingLikelihood analysis shows that observations are more consistent with simulations with upward frequency projections than those withoutIt is more likely that the risk of increased TC impacts in Atlantic is increasing than that it is decreasing, though not by a large margin
- Subjects
TROPICAL cyclones; WINDSTORMS; ATMOSPHERIC models; CLIMATE change; EPISTEMIC uncertainty; GLOBAL warming
- Publication
Earth's Future, 2023, Vol 11, Issue 11, p1
- ISSN
2328-4277
- Publication type
Article
- DOI
10.1029/2023EF003539