Future climate projections (Urban Climate Processes, Trends, and Projections) Part 4

Climate change adaptation in Kokkola, Finland

Kokkola, a medium-sized town on the west coast of Finland, was one case study of the Developing Policies & Adaptation Strategies to Climate Change in the Baltic Sea Region (ASTRA) project. The award-winning ASTRA project was co-financed by the European Regional Development Fund (ERDF) under the INTERREG IIIB Programme. The ASTRA (www.astra-project.org) and SEAREG (www.gtk.fi/dsf) projects are the predecessors of the currently ongoing BaltCICA project (www. baltcica.org). The aim of the projects is to support planners and decision-makers in understanding the potential impacts of climate change on regional development and to support the implementation of adaptation strategies. While SEAREG (2002-2005) mainly focused on awareness raising, ASTRA (2005-2007) went a step further to support the development of adaptation strategies. BaltCICA (2009-2012) builds on the results of the projects by implementing adaptation measures in cooperation with stakeholders. All three projects are managed by the Geological Survey of Finland (GTK) and count on partners from the Baltic Sea Region.

Kokkola was founded in 1620 adjacent to the Bothnian Bay (Baltic Sea). The postglacial rebound (land uplift) in this area amounts to 9 mm per year, and due to the retreating sea the original city center now lies about 2 km inland from the shoreline. Rising sea levels have made the glacial rebound less effective over recent years so that the net land rise has dropped to about 4-5 mm per year relative to the mean sea level. Normal sea level variation in Kokkola is between -1.0 m and +1.5 m relative to mean sea level. The city planning office of Kokkola was thus interested in sea level rise scenarios for the twenty-first century. The background is that Kokkola experiences a strong pressure for coastal housing development. If the coastal land uplift continued as at present, the coastal areas could be easily developed, even with the lower glacial rebound effect of 5 mm per year. But what if the sea level rise and storm flood events become stronger and flood patterns change?

Kokkola participated in the ASTRA project to better understand the climate change scenarios and to evaluate how these can be implemented into local planning. The uncertainties of the climate change scenarios especially played an important role in the assessments. Finally the city chose to use the MPIA2 "high case" sea level change scenario originally developed under the SEAREG project. According to these scenarios it is possible that the land uplift will be neutralized by sea level rise; in other words, the present coastline would not change over the twenty-first century. Consequently, the often predicted increasing wind speed peaks during storm events and the increase in heavy rainfalls would lead to flood-prone area changes. Two important locations for future housing development in Kokkola are the area of the 2011 housing fair and Bride Island.

The area for the housing fair, to be held in 2011, was planned several years ago. Such a housing fair is an important event in Finland, as the houses built for the fair are later to be used for housing, which is an important asset for the investors. The housing fair in Kokkola is planned in a new housing area on the sea shore. In the course of the ASTRA project the location of the housing fair 2011 was not changed, but the minimum elevation of the building ground above mean sea level was raised by 1.0-1.2 m compared to previous plans on the sea shore and is about 3.5 m (streets 3.0 m) above the mean sea level. In other words, the decision was taken that sea shore plots may be built up, but it has to be made sure that the lowest floor of the houses is well above potential flood levels. The cost of each plot and house was calculated, including the artificial elevation of the building ground, and the investors were willing to accept this extra cost because the demand for houses located on the sea shore is still rising.

The second example, Bride Island, is a very popular place for summer cottages in the close vicinity of the city. The current trend in many European countries is to improve these temporary summer homes into cottages that can be used all year round, and even to convert them into permanent homes. If the land were to continue to rise out of the sea as it has done so far, such a conversion from a temporary to a permanent home would pose no problem. The interest of the land owners is not only in converting the houses; the investments certainly would also be justified by rising land and house prices. The city of Kokkola, on the other hand, carries responsibilities if land use plans are changed and natural hazards start to threaten housing areas. Due to the scenarios used in the ASTRA project, land use plan changes for Bride Island were put on hold until improved climate change scenarios and observed trends have been analyzed. However, sea level change scenarios are taken into account in the minimum elevation of buildings above mean sea level, e.g., when old cottages are renovated. Lowest building elevation for the newest building permits has been raised to 2.5 m above the mean sea level – so, in building renovation the adaptation to sea level rise is put into practice in small steps or plot by plot.

Recommendations of the ASTRA report were also taken into account in building and city planning regulations. Several regulations are in place to protect from rising wind speeds, cold winds, and storms on the shore. For example, low houses with optimal roof pitch against wind turbulence on yards; inner courtyards towards the south; plantations and fencing against cold wind directions; and also directing main streets crosswise to the coldest winds to avoid wind tunnel effects.

The city of Kokkola is not taking part in the ASTRA follow-up project BaltCICA because, for now, all important decisions on climate change adaptation have been taken or are under discussion. Nevertheless, the city stays in close contact with the Geological Survey of Finland in order to be informed in a timely manner about the latest research results.

Despite their brief duration, extreme events can have large impacts on cities, so they are a critical component of climate change impact assessment. Table 3.6 indicates how the frequency of heat waves, cold events, intense precipitation, drought, and coastal flooding in the New York City region are projected to change in the coming decades. The average number of extreme events per year for the baseline period is shown, along with the central 67 percent of the range of the model-based projections.

The total number of hot days, defined as days with a maximum temperature over 32 or 38 °C, is expected to increase as the twenty-first century progresses. The frequency and duration of heat waves, defined as three or more consecutive days with maximum temperatures above 32 °C, are also expected to increase. In contrast, extreme cold events, defined as the number of days per year with minimum temperature below 0 °C, are expected to become rarer.

Although the percentage increase in annual precipitation is expected to be relatively small in New York, larger percentage increases are expected in the frequency, intensity, and duration of extreme precipitation (defined as more than 25 mm, 50 mm, and 100 mm per day). This projection is consistent both with theory – a warmer atmosphere is expected to hold more moisture, and while evaporation is a gradual process, precipitation tends to be concentrated in extreme events – and observed trends nationally over the twentieth century (Karl and Knight, 1998).

Due to higher projected temperatures, twenty-first century drought projections reflect the competing influences of more total precipitation and more evaporation. By the end of the twenty-first century the effect of higher temperatures, especially during the warm months, on evaporation is expected to outweigh the increase in precipitation, leading to more droughts, although the timing and levels of drought projections are marked by relatively large uncertainty. The rapid increase in drought risk through time is reflective of a non-linear response, because as temperature increases in summer become large, potential evaporation increases dramatically. Because the New York Metropolitan Region has experienced severe multi-year droughts during the twentieth century – most notably the 1960s "drought of record" – any increase in drought frequency, intensity, or duration could have serious implications for water resources in the region. Changes in the distribution of precipitation throughout the year, and timing of snow-melt, could potentially make drought more frequent as well. According to the IPCC, snow season length is very likely to decrease over North America (IPCC, 2007).

Table 3.6: Quantitative changes in extreme events.

	Extreme event	Baseline (1971-2000)	2020s	2050s	2080s
	Number of days/year with maximum temperature exceeding:
	~32 °C	14	23 to 29	29 to 45	37 to 64
	~38 °C	0.4a	0.6 to 1	1 to 4	2 to 9
	Number of heat waves/yearb	2	3 to 4	4 to 6	5 to 8
	Average duration (in days)	4	4 to 5	5	5 to 7
	Number of days/year with minimum temperature at or below 0 °C	72	53 to 61	45 to 54	36 to 49
	Number of days per year with rainfall exceeding ~25 mm	13	13 to 14	13 to 15	14 to 16
	Drought to occur, on averagec	~once every 100 years	~once every 100 years	~once every 50 to 100 years	~once every 8 to 100 years
	1-in-10 year flood to reoccur, on average	~once every 10 years	~once every 8 to 10 years	~once every 3 to 6 years	~once every 1 to 3 years
	Flood heights (m) associated with 1-in-10 year flood	1.9	2.0 to 2.1	2.1 to 2.2	2.3 to 2.5
	1-in-100 year flood to reoccur, on average	~once every 100 years	~once every 65 to 80 years	~once every 35 to 55 years	~once every 15 to 35 years
	Flood heights (m) associated with 1-in-100 year flood	2.6	2.7 to 2.8	2.8 to 2.9	2.9 to 3.2

The central range (middle 67 percent of values from model-based probabilities) across the GCMs and greenhc a Decimal places shown for values less than 1 (and for all flood heights). b Defined as three or more consecutive days with maximum temperature exceeding ~32 °C. c Based on minima of the Palmer Drought Severity Index (PDSI) over any 12 consecutive months. d Does not include the rapid ice-melt scenario.

As sea level rises, coastal flooding associated with storms will very likely increase in intensity, frequency, and duration. The changes in coastal floods shown here are solely due to the IPCC model-based projections of gradual changes in sea level through time. Any increase in the frequency or intensity of storms themselves would result in even more frequent future flood occurrences. By the end of the twenty-first century, projections based on sea level rise alone suggest that coastal flood levels that currently occur on average once per decade may occur once every one-to-three years (see Table 3.6).

The projections for flooding associated with more severe storms (e.g., the 1-in-100 year storm) are less well characterized than those for less severe storms (e.g., the 1-in-10 year events), for multiple reasons. The historical record is not sufficiently long to allow precise estimates of the flood level associated with the once per century storm. Furthermore, the storm risk may vary on multi-decadal to centennial ocean circulation-driven timescales that are currently not well understood. Keeping these uncertainties in mind, we estimate that, due to sea level rise alone, the 1-in-100 year flood may occur approximately four times as often by the 2080s.

Tropical cyclones

One extreme climate event that impacts many cities around the globe is tropical cyclones. Of the cities used in the topic, several are at risk of being impacted by these storms, which bring heavy rainfall, high winds, and coastal storm surge. Kingston is one city at risk of tropical cyclones and, in recent years, several storms have affected the island of Jamaica. These storms include Ivan (2004), Emily (2005), Dean (2007), and Gustav (2008). Figure 3.19 shows the tracks of these storms along with two others, Charlie (1951) and Gilbert (1988).

Figure 3.19: Hurricane tracks near Kingston, Jamaica.

Perhaps the most devastating storm to hit the island was Hurricane Gilbert in 1988, which had winds over 50 m/s as it passed over the island. Heavy rainfall and a storm surge close to 3 m caused 45 deaths and over US$2 billion in damage (Lawrence and Gross, 1989).

There is much uncertainty as to how the frequency and strength of tropical cyclones will change with global climate change. Patterns of natural climate variability, including El Nino-Southern Oscillation (ENSO) and Atlantic Multidecadal

Lessons from a major climate event: Hurricane Katrina and New Orleans

Few cities in developed countries have felt the impacts of climatic processes as has New Orleans. On the morning of August 29, 2005, Hurricane Katrina made landfall in south Louisiana and again in Mississippi. It produced storm surges that ruptured levees on drainage and navigation canals that catastrophically flooded the City of New Orleans. Rapidly rising waters were met by an inadequate governmental response. In the process, well over 1400 people died, and many more lives were forever changed.

Katrina was a massive storm, fueled by very warm waters in the Gulf of Mexico; however, uncertainty exists as to whether Katrina’s strength was exacerbated by climate change. The northern Gulf of Mexico is historically hurricane prone, and has experienced large storms throughout the past 3000 years (Liu and Fearn, 2000). The power of Atlantic hurricanes appears to have increased over the past three decades (Emanuel, 2005), though this view is not accepted by all experts (Trenberth and Fasullo, 2008). However, climate models generally predict that global warming will increase the severity and/or intensity of tropical cyclones (IPCC, 2007), and Hurricane Katrina provides important lessons into how cities choose to adapt to and mitigate future climate change.

One lesson is that a city’s physical landscape strongly affects its response to climate events. New Orleans developed along a series of natural levees at the banks of the Mississippi River and its former distributaries and the city’s geography can be traced to alluvial processes. Rivers deposit their largest and heaviest particles closest to the main channel, and these natural levees were the high stable grounds where the city was originally settled (Coleman et al., 1998; Coleman and Prior, 1980; Gould, 1970). As the city expanded in the late 19th and 20th centuries, lower-lying areas comprised of muddy, organic-rich sediments were developed. These areas were drained, and once dried out, subsided rapidly (Rogers et al., 2008; Nelson and LeClair, 2006; Kolb and Saucier, 1992). In the present city of New Orleans elevation, subsidence rates and depth of flooding following Katrina are roughly proportional to age, with younger regions typically being the lower, wetter, and more rapidly subsiding (Dixon et al., 2006; Seed et al., 2008; Russell, 2005).

New Orleans’s geology also has important implications for the stability of the city’s levees and its vulnerability to sea level rise. High subsidence rates in the delta plain contributed to one of the highest rates of relative sea level rise on Earth (Tornqvist et al., 2008, Reed, 2002; Day et al., 2007), which makes New Orleans a data-rich model for examining how cities respond to climatically driven sea-level rise. Subsidence lowered elevation of many of the city’s levees while and peat and sand bodies below them allowed for subsurface water flow that undermined their stability (Rogers et al., 2008, Seed et al., 2008). Levee instability was also caused by engineering failures that are discussed below. Human activities have exacerbated wetland loss in the Mississippi Delta plain, at rates that now stand near 50 km2 yr-1 (Day et al., 2007; Barras et al., 2003; Morton, Benier and Barras, 2006). A simple linear relationship between wetland area and storm surge does not exist, as surge magnitude is affected by factors including the storm’s size, wind speeds, track and the shape of the continental shelf (Chen et al., 2008). However, wetland loss has allowed storms surges to propagate further inland, increasing the city’s vulnerable to storms over time.

The second lesson from Katrina is simply that the climate system is capable of delivering vast quantities of energy. The maximum wind speed of Hurricane Katrina exceeded 77 m s-1 (> 175 mph), the maximum eye wall radius reached 110 km and tropical storm force winds extended 370 km from the storm’s center (McTaggart-Cowan et al., 2007). Storm surges that reached 10.4 m in Biloxi, MS, and ranged between 5.6 -6.9 m at Shell Beach east of New Orleans, and 3.95 – 4.75 m along the shore of Lake Pontchartrain at the northern edge of the city (Fritz et al., 2008). Despite the vast power of Hurricane Katrina, it is important to recognize that the storm did not make landfall at New Orleans. This occurred at Buras, LA and again near Gulfport MS, which are 83 and 68 km from New Orleans, which was on the west, less intense side of the storm (Seed et al., 2008).

These two lessons lead to a third, that climate disasters are often the product of an interaction between natural processes and human actions. A smaller storm would have produced a smaller storm surge and less pressure on the levees while properly constructed and maintained levees should have been able to withstand many of Katrina’s surges in New Orleans. The catastrophe in New Orleans was exacerbated by inadequate local and federal governmental actions that include a poor assessment of the risks of flooding, an inadequate communication of these risks, poor levee design, poor levee maintenance, and an inadequate ability to evacuate people and provide for them in times of need (Seed et al., 2008).

Looking to the future, New Orleans faces threats and opportunities. Global sea levels are predicted to rise, storms may increase in severity and frequency, lands surrounding New Orleans will continue to subside and wetland loss is likely remain problematic. While coastal restoration is needed on a massive scale, New Orleans finds itself hampered by jurisdictional difficulties: many coastal restoration decisions are made by a range of state, federal and local authorities that sometimes must balance restoration against other economic or environmental concerns (Carbonell and Meffert, 2009). While it may be impossible to restore the entire Mississippi Delta plain, sediment loads are high enough to substantially contribute to coastal restoration if managed wisely. Coastal progradation and wetland accretion will likely buffer storm surge and provide opportunities for carbon sequestration. Regional groups are also promoting a "multiple lines of defense" strategy (Lopez, 2006) that views flood protection as an integrated system of natural and man-made components, including barrier islands and beach ridges, wetlands, levees and evacuation plans. New Orleans was settled on high, stable grounds at the mouth of the continent’s largest river and this strategic location made it desirable for nations looking to establish a claim to the continent’s interior. Such strategic thinking relating a city to its broader environmental assets and liabilities is key to the future of this and perhaps other coastal cities.

Oscillation (AMO), have documented relationships with tropical cyclone activity. For example, when the AMO, a mode of natural variability of sea surface temperatures in the North Atlantic Ocean is in the cold phase, hurricane activity increases (Golden-berg et al., 2001).

As far as changes in hurricane strength and frequency due to anthropogenic climate change go, there is no concrete evidence that global warming is having an influence. Although some scientific studies suggest that warming caused by increased greenhouse gases will increase hurricane intensity (Emanuel, 2005), the connection between the two is not conclusive. There are a number of issues that play into this debate. Sea surface temperatures and upper ocean heat content are very likely to increase in the North Atlantic’s main hurricane development regions, and this increase alone will likely favor more intense hurricanes (Emanuel, 2005). However, changes in other key factors (not all of which are mutually exclusive) that influence hurricane number and intensity are more uncertain. These factors include: (1) vertical wind shear, which is dependent on uncertain changes in a range of factors (Vecchi and Soden, 2007) including the ENSO cycle (Gray, 1984; Mann et al., 2009); (2) vertical temperature gradients in the atmosphere (Emanuel, 2007); (3) Saharan dust (Dunion and Velden, 2004; Evan et al., 2006); (4) easterly waves and the West African monsoon (Gray, 1979; Donnelly and Woodruff, 2007); and (5) steering currents, which are influenced by a range of factors including highly uncertain changes in the NAO (Mann et al., 2009).

Conclusions and key research questions

Climate change is expected to bring warmer temperatures to virtually the entire globe, including all 12 cities analyzed here. Heat events are projected to increase in frequency, severity and duration. Total annual precipitation is expected to increase in some cities, especially in the mid/high latitudes and tropics, and decrease in other cities, especially in the subtropics. Most cities are expected to experience an increase in the percentage of their precipitation in the form of intense rainfall events. In many cities, droughts are expected to become more frequent, more severe, and of longer duration. Additionally, rising sea levels are extremely likely in all the coastal cities, and are likely to lead to more frequent and damaging flooding related to coastal storm events in the future.

Climate change impacts on cities are enhanced by factors including high population density, extensive infrastructure, and degraded natural environments. Vulnerabilities will be great in many regions that currently experience frequent climate hazards, such as low-lying areas already exposed to frequent flooding.

Vulnerabilities will also be large among resource-poor populations, especially in developing countries, where infrastructure may be sub-standard or non-existent, governmental response to disasters may be limited, and adaptation options may be few for reasons including limited capital.

One implication from this topic is the need for more and improved climate data, especially in cities of developing countries. In many cities, the historical record is either too short or the quality too uncertain to support trend analysis and climate change attribution. Without long historical records, the role of climate variability cannot be adequately described, and climate change projections will not have as strong a historical footing. However, even in cities that have a high quality, lengthy record of temperature and precipitation, there is a need for additional station data and climate variables at high temporal resolution to improve our understanding of the microclimates that help define the urban setting and climate risk. If these data can be integrated into monitoring systems and real time networks – which can be an expensive proposition for some cities – weather forecasting can be improved as well.

Mexico City’s Virtual Center on Climate Change

Mexico City’s Virtual Center on Climate Change (CVCCCM: www.cycccm-atmosfera.unam.mx/cvccccm/) was created in 2008, with the objectives of: (1) building an entity that concentrates and organizes the information regarding climate change effects on Mexico City, as well as coordinating research efforts on the subject; (2) supporting the continuous development of public policies that aim to increase adapta-tive capacity and reduce vulnerability of different social sectors; (3) creating an Adaptation, Vulnerability and Mitigation Policy Framework for Mexico City.

The Center aspires to support the development of "useful" science that must answer the questions concerning climate variability and change posed by policymakers of the city.

City authorities have had to deal with extreme events related to the urban heat island, such as heat waves, heavy rains and the resulting floods, and reduced water availability associated with severe droughts in the catchment basin from which the city satisfies part of its water demand.

Generally, it could be said that cities now experience what could occur under projected climate change scenarios. For example, systems outside of Mexico City might be resilient to an increase of 1 °C in mean temperatures, but in the city the warming process has already reached more than 3 °C (Jauregui, 1997).

As a consequence of the uncontrolled growth of the city’s population and urbanization area, the increase in the occurrence of heavy rains since the 1960s has led to an increase in the frequency of severe floods. This provides an example of Mexico City’s high sensitivity to climate change.

The Virtual Center must be seen as necessary to face the climatic problems that could increase in the future.

The research priorities selected by the City Government are:

1. Assessment of Mexico City air quality, the effect on the health of people exposed to allergenic bio-particles (pollen), and its relation to climate change

2. Effect of the interaction of temperature and ozone on Mexico City’s hospital admissions

3. The impact of climate change on water availability in the Metropolitan Area of Mexico City

4. Vulnerability of potable water sources in Mexico City in the context of climate change

5. Energy consumption scenarios and emission of greenhouse gases produced by the transport sector in the Metropolitan Area of Mexico City

6. Assessment of the impacts in the Metropolitan Area of Mexico City related to solid waste under climate change conditions

7. Vulnerability of the ground of conservation of Mexico City to climate change and possible adaptation measures

8. Determination of the vulnerability of the conservation areas of Mexico City to climate change and possible adaptation measures

Of course, several problems have been detected during the development of this Virtual Center. In particular, "traditional" science has not yet been capable of achieving interdisciplinary research and being stakeholder driven. Currently, researchers are devoted to publishing papers instead of "translating" information for decision-making. Most of the policymakers’ decisions are more focused on resolving the immediate problems than on designing long-term strategies.

The actors of this Virtual Center are aware of these barriers, and these problems are being confronted, for example, through periodic meetings with diverse authorities of Mexico City, which allow direct answers to their questions. This motivates a rich discussion from different points of view, resulting in joint strategies that facilitate the incorporation of the found solutions into public policies. It is expected that this critical stage of the research could be fulfilled during 2010, when partial results will be presented to Mexico City’s authorities.

Furthermore, improved monitoring can help bridge the gaps between weather and climate, and climate regions and cities. This active area of research will enable analysts to use realtime ocean temperatures to better discern how the frequency of extreme events (including hurricanes) may vary by decade in the future. As predictions improve, adaptation strategies can be tailored to reflect these advances. Monitoring must include impact variables identified by stakeholders, such as water reservoir levels, frequency of power failures, and transportation delays. It is critical that this information not only be collected but also stored systematically in a unified database that facilitates the sharing of information and research results across agencies and cities.

Given the range of climate hazards and impacts described here, there is a critical need for climate change adaptation strategies that align with societal goals such as development, environmental protection (including greenhouse gas mitigation), and social justice and equity.