We have finally reached the end of this four
month long project. This has been one of the most challenging piece of work
done in my three years of university as it calls for a high level of consistency and
effort to be put in every week. But I’m glad I did because it gave me a chance
to dive deep into a topic that I have been so interested in.
Thank you to all who have followed my
posts week after week and participated in the discussions through the comments
section.
Here are the compiled links to all my posts in the Journey series,
so for those who have missed any do check them out!
In all the posts thus far in this blog, we
have sought a better understanding of the links between climate change and
natural disasters and can conclude that in most cases, there are possibilities
that recent anthropogenic climate change can have significant impacts on the
future trends of natural disasters. Indeed, large uncertainties are still
involved in these studies but as Bill
McGuire asserts, human’s climate-changing activities seem to be loading the
dice in favour of more natural disasters. In face of this imminent doom and
gloom, is there still hope for future societies?
Looking in the past, previous studies have
revealed that climate change might have played a part in the demise of some
civilisations. Hodell
et al. (1995) and Haug et al. (2003)
found evidence that show that the collapse of the Maya Civilisation coincided
with an extended period of aridity and abrupt drought events between
750-900A.D. Cullen
and deMenacol (2000) showed that the North Atlantic Oscillation has an
influence on the streamflow of the Tigris and Euphrates Rivers and that cooling
of the North Atlantic occurred just before the fall of the Akkadian empire. Over
in East Asia, Zhang
et al. (2005) suggested that most of the dynastic transitions and
nationwide social unrests and 70-80% of war peaks in China occurred in cold
phases. They argue that colder temperatures limited food productivity of the
land and thus caused deficiency of livelihood resources across society. All of
these studies have been careful to avoid the notion of environmental
determinism. They are not trying to show that climate is a determinant of societal progress but that environmental conditions can impose limits on societies through things like
food production and land use (Marshall
2012).
Map showing how climate change might have been associated with the fall of some civilizations across the world in the past. Source: New Scientist
That said, however, climate change is only
one factor, out of many others, that can alter the risks of natural disasters (Mercer
2010). Disaster risk can still be exacerbated even without climate change due
to poor land use planning and population increase. For example, rapid
urbanisation has overwhelmed the infrastructure of Manila, causing many of the
poor to settle at the city periphery and other landslide-prone areas. It has
been estimated that almost three
million people are living in makeshift quarters in unstable areas. Meanwhile,
during the Szechuan Earthquake in 2008, the poor construction quality of buildings,
known as tofu
buildings, were blamed for the high death tolls. In Florida, people continue
to flock towards
Tofu buildings that collapsed during the Szechuan earthquake in 2008. Credits: AFP
the coast, with more
than 90% of its residents living on the coast despite the mounting threats
of hurricanes and sea level rise by the end of the century. As such, the
outcomes of extreme events are also dependent on the development choices of human
societies. In the SREX report (IPCC
2012), the IPCC acknowledges that climate change is often viewed as a
slow-onset, long-term problem and that adaptation strategies invariably require
trade-offs to be made. Hence governments with short terms of office are often
reluctant to invest in climate adaptation measures, since they might not
produce any tangible results within their term of office. For many poor
countries, the priority would often be to channel money into places that
require them most urgently instead of building climate and disaster resilience.
Therefore, what is needed over time is a high level of trust between the people
and the government, a more long-term approach to planning, a willingness to experiment
and innovate new ways to deal with climate change and disasters, flexibility in
systems, engagement of civil society in planning and help given to poorer countries
to build their resilience (IPCC 2012; Norris
et al. 2008; Pearce 2003).
Given that there are also still large uncertainties involved, governments need
develop and prepare for different possible scenarios that could happen in the
future.
Nonetheless over the years, there has been
encouraging evidence from around the world to show that all hope is not lost with
regards to natural disasters. Human societies have been able to bounce back up
time and time again after being hit with natural disasters. It has been nine
years since the Boxing Day Indian Ocean tsunami of 2004. Survivors have been
trying to rebuild their lives ever since including those on the island
of Dhavaafuru in the Maldives, where infrastructure such as road and school
are being built from scratch. Moreover, while there was a lack of early warning
systems back in 2004, there is now an operating tsunami early warning system
made up of a network of seismographic centres and tsunami-detection buoys in
the region that can alert the public of a tsunami quickly. Likewise in the Mohak
Sharif village in rural Pakistan, a new eco-village has been rebuilt after
being devastated by floods back in 2011 through the combined efforts of its residents
and the Heritage Foundation. Meanwhile, we have also seen cases where innovative
solutions have been implemented to help develop the resilience of communities
towards natural disasters. The Netherlands has been known to be consistently
suffering from floods due to its low-lying location. However, they have
actively been trying to build their resilience towards floods,
An artist's impression of the Room for the River project. Credits:http://www.ruimtevoorderivier.nl
with their
latest plan to redesign their cities to make
room for their river. Instead of building their dykes higher to restrict
floodwaters from entering the city, they are digging a new channel for
the river and to move their dykes further inland so that there is more space for
water to flow. All these have only been possible due to sheer will and effort
by all members of the society.
Is there hope? I believe there is hope for
the future but only if governments and societies are willing to commit
themselves to climate adaptation and disaster resilience and reconcile both their
short-term and long-term values and goals. It is hence a political choice that
must be made and one that ought to be made soon so that there will be more time
available to prepare for what is to come.
Over the past 14 weeks or so, we have
moved from looking at hurricanes to floods to droughts and to bushfires. The
links between climate change and these natural disasters have been relatively more
apparent and there is a massive pool of literature that has been dedicated to these
disasters. In this penultimate post of my three-month long project, we shall
explore the links between climate change and earthquakes and volcanic eruptions.
I have actually been looking forward to writing this blogpost ever since this
project started given that unlike the other natural disasters, volcanic
eruptions and earthquakes have not been commonly associated with recent climate
change. I have been eager to find out if there are indeed any credible theories
that suggest that recent/future climate change has/can affect the frequency and
intensity of earthquakes and volcanoes. So let’s begin!
Credits: European Geosciences Union and Associated Press
There has actually been very little peer-reviewed journal papers that discuss the links between recent climate change and earthquakes/volcanic eruptions. The papers that do have mostly been published in the Philosophical Transactions of the Royal Society in its Theme Issue ‘Climate forcing of geological and geomorphological hazards’. Hence, in this post, I will be basing my analyses on the book by McGuire as well as several journal articles from the themed issue mentioned above.
Given that climate change is mostly
associated to changes in the atmosphere and hydrosphere, it might be a little
far-fetched to some that climate change would affect the geosphere. However, if
we look to the past, there is evidence that climate change has indeed affected the
frequency and intensity of volcanic eruptions and earthquakes. After the Last
Glacial Maximum, rapid warming caused a major reorganisation of the global
hydrological cycle as the continental ice sheets melted and resulted in sea
level rise of the order of >100m. The unloading of mass through the melting
of ice reduced the pressure on the crust and induced significant stress changes
in the crust. Modifications of the pattern of stress and strain triggered
volcanic and seismic activity, marine landslides and tsunamis that were of much
greater intensity than those in the present climate (McGuire 2010). Meanwhile, the
loading of mass in the oceans basins as water is transferred from the ice
sheets into the oceans can also alter stress patterns and trigger earthquakes. Podolskiy (2009) highlights the case of the Caspian Sea, which underwent a natural rapid
rise in water level of 235cm between 1978 and 1995. This rapid filling of water
increased the weight on the basin within a short period of time and caused a
number of earthquakes on its coastline.
Likewise, changes in the distribution of
ice and water around the world also have consequences on volcanic activity. Volcanoes
erupt when the pressure increases past a tipping point as the magma builds up
from within. Hence, events that cause changes in stress can affect the pressure
build up within the volcano and trigger an eruption. The retreat of ice sheets
and ice caps, causing the reduction in pressure on the crust, can provide this
trigger (Palgi and Sigmundsson 2008). It is posited that the
decompression of the crust would reduce the pressure at depth in the mantle, promoting
melting and the generation of magma (Sigmundsson et al. 2010). This might have
caused volcanic activity to be ten times more frequent in Iceland just after
the last glacial period, just as the ice sheet that covered Iceland melted
(Sigmundsson et al. 2010). Moreover, recent studies on the Vatnajökull ice cap have
suggested that recent thinning under the present warming climate has produced an
additional 0.014km3/year of magma under Vatnajökull (Pagli and
Sigmundsson 2008).
However, the critical question is whether under
present/future climate change, will there be an increase in the seismic and volcanic
activity as seen in the past glacial/interglacial transition periods? Indeed,
the present climate is nowhere similar to the post-LGM period, however, McGuire (2012) speculates that present and future climate change would be sufficient to
induce a geospheric response. At present, small ice masses are already thinning
and retreating, as with the Vatnajökull ice cap, resulting in load pressure
reductions of 0.5MPa or more (Sauber et al. 2000; Tuffen 2010). Meanwhile, according
to the IPCC AR4 report, the projected sea level rise will range from 0.18 and
0.59m. A 0.59m of additional water mass would correspond to a 5.7kPa increase
in pressure on the crust in the ocean basins (Podolskiy 2009). Although these changes are
relatively small, both in terms of absolute values and rates, McGuire (2010)
argues that there is a growing body of evidence to show that small changes in
environmental conditions can still trigger seismic and volcanic activity. This
includes Hainzl et al. (2006) that suggested that at times when the Earth’s
crust is so close to failure, pore-pressure variations of less than 1kPa caused by heavy rainfall is
enough to trigger earthquakes.
The areas of greatest concerns are those
at the higher latitudes or altitudes in excess of 4000m (Tuffen 2010). At these
areas, ice bodies are still present and hence should they continue to undergo
melting and recession under a warming climate, they might be able to create
changes in patterns of stress and strain and induce seismic responses. Moreover,
as the ice sheets that buries volcanic systems such as the Vatnajökull, or ice
caps found on volcanoes such as Kilimanjaro disappear by the end of the century,
it is worried that the decompression might induce mantle melting and cause more frequent
eruptions.
As shown above, the links between climate
change and volcanic eruptions and earthquakes seem to be apparent. Indeed, there is a consensus among the scientific community that climate change had
affected the frequency and intensity of seismic and volcanic activity in the
past, especially during glacial/interglacial transitions. However, it is important to note that the hypothesis that future climate
change would have similar impacts on the geosphere have received a lukewarm
response thus far. This is most likely due to the fact that we are
uncertain of the sensitivity of the geosphere to small changes in ice thickness
and ocean loading (Tuffen 2010) and hence are still not totally convinced that future
climate change would be sufficient to affect patterns of volcanic eruptions and
earthquakes.
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This marks the last two categories of natural
disasters that I will be covering as part of this series. Phew, we have come a
long way! Check back next week as I do a wrap up for the project and look back
at what we have done these past few months!
Over the Christmas break this year, I
hopped onto the plane and headed down under, towards Australia! During the
trip, I visited the Blue Mountains, just west of Sydney, some parts of which were
recently ravaged by major
bushfires in October. While bushfires may not be as widely researched and
discussed as the other types of natural disasters that I have brought up in the
previous posts, it has nonetheless been a recurring phenomenon in Australia for
millions of years. As such, I will briefly touch on the impacts of climate
change on bushfires in Australia, particular the southeastern region, in this
post.
Bushfires on Blue Mountain in October 2013. Credits: AFP
Southeastern Australia is one the top 3 fire
prone regions in the world, together with southern California and southern
France. In the past century, bushfires have destroyed thousands of homes and
claimed hundreds of lives including the infamous Black Friday fires in 1939 and
Ash Wednesday fires in 1983. One of the driving factors that have caused
southeastern Australia to be particularly vulnerable to bushfires is its
climate – hot, dry summers and mild, wet winters. The precipitation received
during winter and spring allows fuel (the vegetation) to grow, while the dry
summers favour the development of bushfires (Lucas et al. 2007). Moreover,
periods of drought have exacerbated the dry conditions and fire risks in the
region. Over the past decade, it has been observed that temperatures of the
region have shifted towards higher temperatures, while rainfall has declined
below the 1961-1990 mean (Murphy and Timbal 2008). The extended period of dry
conditions have contributed to the large fires that burned with little control
in 2006/07.
Eucaplyptus trees that are commonly found in Australia. Credits: Joon Ting
Another factor that has been blamed for
the bushfires is the predominant type of vegetation that lines the landscape of
Australia – eucalypts. There are more than 800 endemic species found in
Australia and forms the main diet for koalas. These trees are highly
flammable as they contain oil, which gives them their distinct spicy
fragrance. During periods of dry and windy conditions, their flammable oil
can cause small fires to develop into huge firestorms very rapidly. Yet, these
trees are extremely
fire resistant themselves and tend to survive the bushfires, allowing for
the regeneration of the eucalyptus forest after the fire. Hence, they tend to
be naturally selected in regions prone to bushfires including Australia and
California, where they continue to dominate the landscape. As such, it seems inevitable that southeast Australia experiences such frequent bushfires.
Eucaplytus trees that cover the Blue Mountains. Credits: Joon Ting
It has already been projected that
southeast Australia will become hotter and drier under climate change (Suppiah et al. 2004). Modelling studies have been further carried out to
determine how this projected change in climate will affect the fire risks of
the region. The Forest Fire Danger Index (FFDI) has been used to quantify the
fire risks and is calculated based on observations of temperature, relative
humidity and wind speed. Modelling studies carried out by Hennessy et al. (2005) on 17 sites in southeast Australia have suggested that the combined
frequencies of days with very high and extreme FFDI rating are likely to
increase by 4-25% by 2020 and 15-70% by 2050. This corresponds with more recent
studies by Lucas et al. (2007) that show that the increase in annual cumulative
FFDI is generally 0-4% in the low scenarios and 0-10% in the high scenarios by
2020, and 0-8% in the low scenarios and 10-30% in the high scenarios by 2050.
Nonetheless, there is still large uncertainty in these studies given that much
of the climate of southeast Australia is dominated by interannual and
interdecadal variability that is influenced by complex systems including ENSO
and Southern Hemisphere Annular Mode (SAM). The evolution of these systems
under future climate change is still not fully understood thus it is difficult
to ascertain how fire weather and risks will change in future when such variability is taken into account (Lucas et al.
2007).
