As global temperatures climb, so too does the potential for more intense hurricanes in Atlantic Canada. This article sheds some light on the mechanics behind hurricanes, the observable impacts of climate change on these powerful storms, and the specific implications for Atlantic Canada based on recent research and climate projections.
Hurricanes are storm systems that originate over warm tropical oceans and are characterized by intense wind, heavy rain, and thunderstorms. These systems form under specific conditions: notably, warm sea surface temperatures[1], minimal changes in the direction and speed of wind with height (also known as vertical wind shear), sufficient atmospheric moisture[2], and at a latitude with sufficient Coriolis force to get the system rotating (Box 1).
Box 1: The Coriolis force, stemming from the Earth’s rotation, is crucial for hurricane development, as it is what gives the storm its rotation. This force is negligible at the equator, which is why hurricanes only form 500 km north or south of the equator and why hurricanes never cross the equator.
The energy needed for a hurricane to form comes from the heat released during the condensation of water vapour. Importantly, this is why hurricanes lose their energy once they make landfall; as soon as the storm’s source of moisture disappears, the energy driving the storm dissipates.
Climate change is expected to exacerbate existing risks associated with hurricanes. [3],[4] There is evidence that climate change has already resulted in rainier and windier hurricanes. Furthermore, there are indications that hurricanes are moving more slowly and are travelling further north.[5] Climate models project that these trends will likely continue.
Some specific impacts of concern moving forward include:
These changes in hurricane intensity are primarily driven by rising sea surface temperatures. Warmer water not only increases the intensity of hurricanes but also enhances their ability to hold moisture, leading to heavier rainfall during these events. When a hurricane passes over very warm water, the storm can quickly increase in size. Scientists refer to this as “rapid intensification.” In the span of just a few hours, a storm can grow from a relatively minor concern to a life-threatening situation.[7]
Hurricanes in Atlantic Canada pose economic, environmental, and health risks for communities and their residents. Observed impacts from hurricanes that have previously made landfall in Atlantic Canada include:
The 2024 Atlantic Hurricane Outlook
Citing the 2024 forecast from Environment and Climate Change Canada, the North Atlantic is experiencing higher-than-average sea temperatures, which are expected to contribute to an active hurricane season with an increased likelihood of major hurricanes[14]. Moreover, the warm ocean temperatures will be accompanied by a rapid transition from El Niño to La Niña conditions, which are conducive to Atlantic hurricane activity through reduced wind shear[15].
In response to these challenges, a broad approach is being implemented to adapt urban and land use planning and emergency management to the realities of a changing climate. Actions include updating infrastructure and building regulations to support higher flood risk levels and extreme weather events.
The Map of Adaptation Actions, an adaptation case-study tool available on changingclimate.ca, showcases numerous examples of communities taking measures to mitigate risks associated with rising seas and more powerful storm surges driven by hurricanes.
For example, the case study Using Climate Information to Drive Adaptation: Adapting to Floods and Storm Surges details how Saint John, New Brunswick partnered with the Atlantic Coastal Action Program (ACAP) to develop a Climate Change Adaptation Plan in 2020. The plan includes many examples of how this community is preparing for future flooding hazards, including using new data and tools to identify locations at greatest risk of flooding and erosion.
The implementation of nature-based solutions, adaptation actions that utilize natural processes, is an approach communities may take to prepare for a changing climate. For examples of adaptation actions that have been implemented in Atlantic Canada to prepare for the projected increases in hurricane activity and associated risks, see The Town of Mahone Bay and Living Shoreline and Carters Beach Dune Restoration Project case studies on the Map of Adaptation Actions. These actions emphasize the necessity to prepare for more intense and potentially more frequent hurricanes as sea surface temperatures continue to rise.
As the climate continues to warm, hurricanes are expected to become more powerful. Understanding these systems is crucial for developing effective response and adaptation strategies. By integrating scientific research with proactive policy measures, Canada can enhance its resilience to the evolving threat of hurricanes in a warming world.
[1] Studies indicate a water temperature of at least 26.5 degrees Celsius over a depth of 50 meters is needed to power a hurricane (https://oceanservice.noaa.gov)
[2] https://oceanservice.noaa.gov/facts/how-hurricanes-form.html
[3] Mendez-Tejeda R, Hernandez-Ayala JJ (2023) Links between climate change and hurricanes in the North Atlantic. PLOS Clim 2(4). https://doi.org/10.1371/journal.pclm.0000186
[4] Patricola, C. M., Hansen, G. E., & Sena, A. C. T. (2024). The influence of climate variability and future climate change on Atlantic hurricane season length. Geophysical Research Letters, 51.
[5]Seneviratne, S.I., X. Zhang, M. Adnan, W. Badi, C. Dereczynski, A. Di Luca, S. Ghosh, I. Iskandar, J. Kossin, S. Lewis, F. Otto, I. Pinto, M. Satoh, S.M. Vicente-Serrano, M. Wehner, and B. Zhou, 2021: Weather and Climate Extreme Events in a Changing Climate. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Pean, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekci, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 1513–1766, doi: 10.1017/9781009157896.013.
[6] It is important to note that while the proportion of major hurricanes is increasing, the overall number of storms may not change or could even decrease in some locations. This means we might not see more category 3-5 hurricanes in total, but a higher percentage of the storms that do form could be stronger. It is important to acknowledge the limitations in our current understanding of how hurricanes form and how climate change is likely to influence their formation and intensification.
[7] Li, L., Li, Y., & Tang, Y. (2024). On the duration of tropical cyclone rapid intensification. Geophysical Research Letters, 51, e2024GL108578. https://doi.org/10.1029/2024GL108578
[8] https://www.cbc.ca/news/canada/nova-scotia/looking-back-at-hurricane-juan-20-years-after-deadly-storm-hit-nova-scotia-1.6981082
[9] https://www.cbc.ca/news/canada/nova-scotia/weather-snoddon-fiona-recap-1.6976249
[10] https://www.ctvnews.ca/climate-and-environment/data-shows-fiona-s-impact-across-atlantic-canada-as-all-time-records-broken-1.6084819
[11] https://www.cbc.ca/news/canada/nova-scotia/weather-snoddon-fiona-recap-1.6976249
[12] National Hurricane Center Tropical Cyclone Report: Hurricane Fiona 14-23 september 2022 (pdf)
[13] https://www.ibc.ca/news-insights/news/hurricane-fiona-causes-660-million-in-insured-damage
[14] https://www.canada.ca/en/environment-climate-change/news/2024/05/environment-and-climate-change-canadas-canadian-hurricane-centre-expects-a-very-active-hurricane-season.html
[15] https://www.noaa.gov/news-release/noaa-predicts-above-normal-2024-atlantic-hurricane-season