PDS APES 5th Period 2009-10

At the end of class on Friday Mr Willard left us with 5 questions regarding global climate change. These questions were as follows:

1. Is the Earth warming?

2. If so, is this warming unnatural?

3. If it is unnatural, is it anthropogenic (human-caused)?

4. What might happen as a result of this climate change?

5. What can and should we do to fix this?

Then in class on Monday we discussed the views of the Intergovernmental Panel on Climate Change (IPCC) on this subject and tried to answer some of these questions. So is the Earth warming?  According to the IPCC yes, the global average temperature has increased by 0.74 degrees Celsius, which is approximately1.3 degrees Fahrenheit, over the past 100 years.  This may not seem like a drastic change but this number is only a global average. It is important to note that in some places the climate is changing very little and in other there is a much more rapid climate shift.  For example arctic temperatures have risen twice as fast as the rest of the world over the past 50 years. Another fact that is evidence of global warming is the temperature records as of recent.  Since  1861, when temperatures were first recorded, the 5 hottest year are record were 2005, 1998, 2002, 2003, and 2006.

Ok so there is definitely evidence supporting that the Earth is warming, but is this warming unnatural?  According to the IPCC temperature and carbon dioxide levels in the troposphere are “beyond normal range” and paleoclimatic records show an “unnatural increase in temperature and carbon dioxide over the past 50 years”.  This graph illustrates Carbon Dioxide levels in the atmosphere and Global Temperature over the past 1000 years.

The next question regarding global warming is, Is this unnatural climate change our fault?  Once again the  IPCC says that global climate change is indeed anthropogenic.  Since the Industrial Revolution there has been a drastic increase in 3 of the 4 major greenhouse gases, and these are Carbon Dioxide (CO2), Nitrous Oxide (N2O), and Methane gas.  All of these gases have increased due to human activity.  The main causes of CO2 increase is the burning of fossil fuels and land use change.  Land use change in this situation most directly means deforestation.  Deforestation is a major problem because it destroys one of the planets natural carbon sinks.  A carbon sink is is a place that stores carbon such as CO2.  When you cut trees that usually store carbon more carbon in the form of CO2 is released into the atmosphere. Another acticity  that we as humans do to cause an increase in greenhouse gases is agriculture, and this causes increases in methane and N2O levels in the atmosphere.

For those of you who were not in class on Thursday February 25th we discussed the first portion of Chapter 11, which was about water shortages.

If 71 percent of the earth is covered by water many would ask how could water shortage be an environmental issue? Well the fact is that only 2.6 percent of the worlds water is fresh water, and of that 2.6 percent almost three quarters of fresh water is frozen in either polar ice caps or glaciers. This leaves us with only 0.6 percent of the worlds water as a usable resource.  In other words usable fresh water is scarce on our planet.  The world population uses water for the following things:

• Agriculture (69 %)
• Industry/power (23%)
• Domestic uses (8%)

As fresh water moves throughout the hydrologic cycle we obtain it either from runoff or from aquifers. An aquifer is an area underground where fresh water is stored  in permeable soil or rock. The amount of water in an aquifer is determined by the water table, which is the top level of water in an aquifer. To help visualize how an aquifer works picture water being poured into a glass.  When the water hits the bottom of the glass, which would be bedrock in the aquifers case,  the liquid level begins to rise thus raising the water table. To take this analogy a step further now picture a straw being placed in the glass in order to extract the water from the top layer. Every time you take a sip the “water table”  in the glass decreases causing you to push your straw deeper into the glass. This analogy explains the way that well drilling works with aquifers.  However what makes this process an environmental issue the the fact that often times we are draining aquifers faster than they can replenish resulting in a water shortage.

There are four major causes for water shortages on our planet

1. Dry climate
2. Drought
3. Dessication – This is when soil dries out do to overgrazing or  too much plowing in a certain area
4. Water Stress – This is the demand for fresh water by humans

There are four major “solutions” to solving water shortages as well and these are

1. Dams
2. Water Transfer
3. Deslinization
4. Conservation

The problem is that none of these methods are true solutions, meaning that they all have pros and cons. For example  transering water from a large river or lake to a place with an arid climate has major implications.  Often times the body of water shrinks drastically making it an unreliable source of water in the future.  An example of this is the Aral Sea in the middle east.  Due to water transfer what was once the worlds fourth largest lake  shrunk to about half of its size. Another example that deals more with conservation is Xeriscaping in desert climates.

Satillite photos showing the depletion of the Aral Sea

I hope this help clarify water shortages for those of you who missed the lecture!