Even though some
people are still in denial, I think it is almost safe to say that Global
Warming and Climate Change are accepted by the majority nowadays. I remember
the cover of Bloomberg Businessweek after Hurricane Sandy hit New York City in
2012. The cover showed a flooded street with a title of “IT’S GLOBAL WARMING,
STUPID”. As an Environmental Engineering student at that time, I really
liked the blunt title -still do. You can have a look at it HERE.
Figure 1-Bloomberg magazine cover after Hurricane Sandy
When it comes to Climate Change, Intergovernmental Panel on
Climate Change (IPCC) is one of the well-known international bodies that
publishes different reports, assessments and technical papers that are widely
used as references.
In the IPCC
Technical Paper VI - June 2008 , the observed changes of climate and how
they are linked to water are categorized into precipitation, snow and land ice,
sea level, evapotranspiration, soil moisture, runoff and river discharge, and
patterns of large-scale variability. In this post we are going to look into some of the
named categories.
In order to better understand how one thing can influence
another thing when it comes to water cycle, I made the below diagram simplifying and summarizing some of the papers I read - sometimes
visualization aid is quite useful (maybe a mini model?). Now let’s go over the
diagram.
Global warming and rising temperature of the oceans have
acted as a driving force to change our climate. Hydrological cycle is closely
linked to atmospheric changes of temperature as well as climatic changes. Hence
we see GW and CC as the main change initiatives in the diagram. However, other
contributing factors to water availability and changes of water cycle should
not be overlooked. Other non-climatic factors such as population growth,
land-use change- affecting the local water cycle, changes in population
location(e.g. people moving to urban areas and hence changes to patterns of
water use ), water pollution (Grafton and
Hussey,2011), and changing lifestyles (Ludwig,
Slobbe, and Cofino, 2013) also have an influence on water resources. These
factors are shown by colored circles in the diagram.
Looking at the diagram we see that GW has caused increased
evaporation which means more atmospheric water vapor, hence more cloud
formation and more precipitation for some regions. Evaporation and changes in
precipitation patterns can also bring droughts for some areas.
Alteration in precipitation pattern has an impact on river flow regime
and river discharge , thus the surface water availability gets affected as
well. These changes differ for each region . For instance for regions in higher
latitudes there has been an increase in river flow while some parts of west
Africa , southern Europe, and southern America have been experiencing a
decrease (Babel,Agarwal,and
Shinde, 2014). And that does not end there, changes in river flow regime
can change seasonality and cause more extreme conditions. For example in Asia , while
the maximum monthly flow for the Mekong is expected to increase
by 35%-41%. For the years 2010-2038, the minimum monthly flows are projected to
decrease by 17%-24% in the basin. This suggests that there is a risk of
flooding during wet season and possibility of water shortage during dry season (IPCC,2008).
Ground water is an important water resource that has served
humans for centuries. This awesome resource of water gets affected by GW and
CC. Factors such as increased evapotranspiration and reduced rainfall will
reduce the aquifer recharge. On the other hand, increased
flooding results in increased aquifer recharge. Another important factor
regarding aquifer recharge is how the timing of the recharge is influenced by the volume of snow-melt and distribution of
rainfall(Babel,Agarwal,and
Shinde, 2014).
Lastly, lets talk about sea level rise- a serious risk for both humanity and
ecosystems. The fact that 60% of the world’s 39 metropolises with a population
of over 5 million are located within 100 km of the coastal region , including 12
of the world’s 16 cities with populations greater than 10 million (IPCC,2007) , makes it even scarier.
Even from the simple diagram in this post ,it can be seen how
far the impacts of Climate Change on water can go and how intertwined the system is. And hopefully we now know why
it is a big deal. In the coming posts we try to investigate the challenges of managing water resources considering the mechanisms discussed today.
Sometimes we are told not to make a big deal out of
something, well today is your lucky day cause you are allowed to make a big
deal out of this as much as you like! or better said you SHOULD make a big deal out of this...
