Extreme Weather

At a global scale, climate change is altering precipitation patterns to increase the probability of extreme weather events.  The IPCC concluded with medium confidence that climate change has already intensified precipitation events worldwide.^[1]  This finding is supported by recent attribution studies that evaluate the likelihood of extreme weather in regions already affected by record-setting storms.  One such study, completed after Louisiana’s flooding rains in 2016, found that heavy precipitation events along were Gulf of Mexico were 40% more likely than in years pasts.^[2]  Other attribution studies conducted to assess recent natural disasters show a clear relationship between ongoing temperature increases and the likelihood extreme weather.^[3]  By 2100, these events will occur more frequently (a 1-in-20-year event may become a 1-in-5-year event) even if total precipitation does not change.  Thus, a larger proportion of future rainfall may occur during intense precipitation events that cause damaging floods and threaten vulnerable coastal communities.^[1]

Extreme Weather at MIT

MIT and the surrounding Cambridge and Boston areas are inherently vulnerable to the effects of severe weather, like storm surge and freshwater flooding. Its low elevation, high percentage of impermeable surface cover, and proximity to both the Boston Harbor and Charles River raise significant concerns about its ability to survive extreme weather events.

Freshwater Flooding

Because MIT’s campus is a heavily populated and developed urban area, it is primarily covered in impermeable surfaces–asphalt, concrete and rooftops. This means that drainage can quickly become a major problem in the event of heavy storm rains, because none of these surfaces absorb water. In the past decade, temperatures in New England have risen by an average of 2°, and precipitation has increased by 10% annually–and this figure is usually even higher for storms. Even routine severe storm precipitation has already shown to have a major effect on the city. In October 1996, 8 inches of rainfall flooded parts of the Green Line tunnels for days: currently, Boston and Cambridge are simply not equipped to handle this amount of rainfall.^[4] Though the area around MIT has not yet faced a devastating precipitation event like Hurricane Harvey, which left a recordbreaking 51.9 inches of rainfall in Cedar Bayou, Texas, the likelihood of such an event is constantly increasing as climate change intensifies storm.^[5]

Figure 1: The frequency of extreme precipitation events is increasing remarkably rapidly.^[6]

Source: Global Change: Extreme Weather^[6]

For the past six decades, the frequency of extreme weather events like Hurricanes Harvey, Sandy and Irma have been increasing dramatically in proportion to the total number of storms. This only intensifies the urgency with which coastal regions need to increase their resilience.

Storm Surge

Storm surges occur when wind and waves from an offshore storm push water onto land, creating a powerful flow of water that floods inland above sea level. Because of its low elevation, Cambridge is very vulnerable to damage from storm surge in the event of a severe storm. The area is both low-lying and quite flat, and its predominantly impermeable surface cover contributes to the vulnerability as well. And, as sea levels in the Boston Harbor rise, in the future less severe storm surges will have the same effects as a more severe one today. Currently, the Cambridge area simply does not have adequate drainage systems in place for large amounts of stormwater. This means that storm surge floodwater will have nowhere to go, rendering transportation systems unusable, damaging buildings, and causing a major public health risk due to sewer and waste leakage. Rising sea levels also mean that stormwater “backflows”–areas designed to hold stormwater–may exceed capacity and backflow, extending the duration of storm aftereffects.

Currently, there is a 1% annual risk of a flood occurring that inundates 5% of the city. In the coming decades, this figure will increase to a 10% annual chance, and by the end of the century, it is predicted that such a magnitude of flooding will occur monthly from high tide flooding alone: a storm surge under these conditions would be disastrous.

Figure 2: Areas marked in blue are ones which would be flooded in the event of a major storm surge in combination with projected 2050 high tide levels.^[7]

Source: Climate Ready Boston^[7]

Energy Dependence

Flood risks not only pose a threat to buildings, transportation systems and human lives, but also have the potential to severely impact our energy networks: power plants and grid systems. The Union of Concerned Scientists found that in 1992, weather caused roughly 25% of power outages in the transmission grid, while in 2011, weather was responsible for 75%. The increasing frequency of weather-induced outages is a warning of the grid’s vulnerability. Not only are issues posed to energy transmission, but also to generation: power plants cannot run if, for example, the trains bringing them fuel are stopped due to flooded tracks.^[8] A 2013 report stated that weather-related blackouts cost the U.S. an average of $18 to $33 billion annually in the preceding decade. Not only are these outages financially costly, but they pose a threat to human well-being. A reported 50 deaths from Hurricane Sandy were direct results of power outages, from senior citizens who could not handle hypothermia to those poisoned by carbon monoxide from flooded generators.^[9]

Solutions Addressing Extreme Weather at MIT:

Efficient Emergency Transportation Plans Emergency Planning Education External Flooding Barriers Green Space Incorporating Drainage MBTA Stations NRL Safety Preparation For Flooding Reliable Back-up Energy Systems Water Resistant Utilities   

Extreme Weather in Bangladesh

Bangladesh is vulnerable to tropical cyclones and intense monsoon precipitation events, both phenomena that will be affected by climate change.  Because most of Bangladesh lies within 5 meters of sea level, these weather events inundate at least 21% of the country’s land area each year.^[10] Bangladesh’s proximity to the Himalayan Mountains also worsens inland floods when severe rainfall corresponds with summer glacier melt.  In addition, the shape of the country’s coastline funnels water from the Bay of Bengal far inland when tropical cyclones push storm surges ashore.  These unique geographic characteristics make Bangladesh among the most vulnerable countries to climate change, suggesting the importance of adaptation strategies that reduce its susceptibility to severe weather events.^[11]

Tropical Cyclones

Tropical cyclones form in the Indian Ocean and strike Bangladesh during the early summer (May-July) and after the monsoon (September-December).^[11]  Although these storms bring strong winds and intense rainfall, Bangladesh is most vulnerable to storm surge.  These floods damage much of the country’s transportation infrastructure and sanitation services that ensure public access to clean food and water.  Severe cyclonic storms, which affect Bangladesh once every three years, are detrimental to its basic infrastructure and result in dramatic loss of life.^[12]  In 1970, Cyclone Bhola caused over 250,000 deaths, eliminating up to half the population of some coastal provinces.  Cyclone shelters and advancements in weather forecasting allowed Bangladesh to weather more recent storms with fewer casualties.^[10]  Cyclone Sidr, which affected the country in 2007, claimed over 3,000 lives and cost Bangladesh 2.6% of its GDP, figures well below the damages inflicted by previous storms.^[11]  However, these improvements did not prevent the displacement of 2 million coastal Bangladeshis.  These mass migrations threaten Bangladesh’s political stability and illustrate the need for improved tropical cyclone preparedness.

Climate change will affect tropical cyclone development in uncertain ways.  Global models predict a decline in storm frequency and an increase in cyclone intensity but produce variable results when applied to individual ocean basins.  Thus, tropical cyclone predictions developed for Bangladesh may follow general global trends but provide little quantitative information about impacts specific to the region.  Similar uncertainty exists in predictions of tropical cyclone rainfall rates, an important metric of cyclone severity to flood-prone regions like Bangladesh.  However, climate models agree that sea level rise will occur at all warming thresholds, worsening the effects of tropical cyclones regardless of their intensity.^[13]  Cost projections suggest that current economic growth may improve Bangladesh’s ability to recover from severe tropical cyclones.^[11]  Storms enhanced by sea level rise and other climate threats may dampen this growth or inflict damages that overwhelm gains from ongoing development initiatives.

Monsoon Precipitation

When the tropical cyclone season is inactive, Bangladesh receives 72% of its annual rainfall from summer monsoon storms.  Farmers rely on this large pulse of moisture to support their communities and produce fewer crops during abnormally wet or dry monsoon seasons.  Excessive summer precipitation causes severe floods that inundate large portions of Bangladesh.  When flooding exceeds 25% of the country’s land area, low-lying farming communities suffer significant crop losses and are often evacuated.  Larger events damage urban communities, displace millions of Bangladeshis, and overwhelm the ability of Bangladesh’s government to provide necessary humanitarian aid.  The most severe flood occurred in 1998, when rainfall inundated 70% of Bangladesh and displaced 31 million farmers and urban residents. Although these floods are rare—the 1998 flood was a 1 in 20-year event—their long-lasting effects on all regions of Bangladesh leave the country vulnerable to subsequent natural disasters.^[14]

Climate models suggest that total monsoon rainfall may increase or decrease as climate change progresses.^[15]  Complex interactions between Northern and Southern Indian Ocean currents limit the ability of these models to accurately predict future precipitation regimes.^[16]  However, numerous models agree that climate change will increase the proportion of rainfall that arrives in extreme events.  These powerful yet infrequent storms would produce severe floods separating by lengthy dry periods, leaving cropland vulnerable to inundation and drought.^[15]

Figure 3: Change in percentage of rainfall from large events, 2081-2100 vs 1981-2000. 

Source: Jourdain et al.. The Indo-Australian monsoon and its relationship to ENSO and IOD in reanalysis data and the CMIP3/CMIP5 simulations.^[14]

Solutions Addressing Extreme Weather in Bangladesh:

Adapting Polders Atmospheric Water Generation Community-Based Adaptation Cyclone Shelters Emergency Alert System Fishing Green Roofs Hydroponics and Floating Agriculture Manmade Ponds Paved Roads and Waterway Transportation Rainwater Collection and Solar Distillation Reforestation Urine Diverting Dry Toilets Waste Management Water Security

By Jarek Kwiecinski and Julia Wyatt

References

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2. Lindsey, R. (2016). Extreme event attribution: the climate versus weather blame game. Retrieved from https://www.climate.gov/news-features/understanding-climate/extreme-event-attribution-climate-versus-weather-blame-game
3. Herring, S. C., A. Hoell, M. P. Hoerling, J. P. Kossin, C. J. Schreck III, and P. A. Stott, Eds., 2016: Explaining Extreme Events of 2015 from a Climate Perspective. Bull. Amer. Meteor. Soc., 97(12), S1–S145.
4. Turner, L. (2017, August 30). What would happen if Boston got 50 inches of rain? – The Boston Globe. Retrieved November 29, 2017, from https://www.bostonglobe.com/metro/2017/08/30/boston-got-inches-rain-all-swimming/TvGqCtjiKRDCtFJQ2DsJtO/story.html
5. This is how much rain has fallen in Houston – The Boston Globe. (2017, August 29). Retrieved November 29, 2017, from https://www.bostonglobe.com/news/nation/2017/08/29/this-how-much-rain-has-fallen-houston/xQPA13Ha2YDUtfGJ8oFPEO/story.html
6. Global Change: Extreme Weather. (n.d.). Retrieved from http://nca2014.globalchange.gov/highlights/report-findings/extreme-weather
7. Climate Ready Boston. (2017, November 16). Retrieved from https://www.boston.gov/departments/environment/climate-ready-boston
8. Bade, G. (2015, November 17). Maps: 5 US regions where the grid is under threat from climate change. Retrieved from https://www.utilitydive.com/news/maps-5-us-regions-where-the-grid-is-under-threat-from-climate-change/409346/
9. Boston Sea Level Rise [Digital image]. (n.d.). Retrieved from http://tactilegoods.com/wp-content/gallery/sea-level/95.jpg
10. Dastagir, M. R. (2015). Modeling recent climate change induced extreme events in Bangladesh: A review. Weather and Climate Extremes, 7(Supplement C), 49–60. https://doi.org/10.1016/j.wace.2014.10.003
11. The World Bank. (2010). Bangladesh – Economics of Adaptation to Climate Change, no.70266, 1–130.
12. Ali, A. (1996). Vulnerability of bangladesh to climate change and sea level rise through tropical cyclones and storm surges. Water, Air, and Soil Pollution, 92(1–2), 171–179. https://doi.org/10.1007/BF00175563
13. Srivastava, A. K., Landsea, C., Holland, G., Held, I., Kossin, J. P., McBride, J. L., … Knutson, T. R. (2010). Tropical cyclones and climate change. Nature Geoscience, 3(3), 157. https://doi.org/10.1038/ngeo779
14. Monirul Qader Mirza, M. (2002). Global warming and changes in the probability of occurrence of floods in Bangladesh and implications. Global Environmental Change, 12(2), 127–138. https://doi.org/10.1016/S0959-3780(02)00002-X
15. The World Bank. (2012). Turn down the heat : why a 4°C warmer world must be avoided (No. 74455) (pp. 1–106). The World Bank. Retrieved from http://documents.worldbank.org/curated/en/865571468149107611/Turn-down-the-heat-why-a-4-C-warmer-world-must-be-avoided
16. Jourdain, N. C., Gupta, A. S., Taschetto, A. S., Ummenhofer, C. C., Moise, A. F., & Ashok, K. (2013). The Indo-Australian monsoon and its relationship to ENSO and IOD in reanalysis data and the CMIP3/CMIP5 simulations. Climate Dynamics, 41(11–12), 3073–3102. https://doi.org/10.1007/s00382-013-1676-1