Global Waming

Global Warming


Introduction

The current fear is that increasing CO2
levels will raise the Earth's mean temperature and/or affect weather
patterns. But before we tackle this issue we must first understand what
factors control the global environment. I'm not going to address all of
them because I could easily write a 50 page paper on that, but I hope
to cover enough of the essential ones that you can have a firm grasp on
the fundamentals of the issue at hand. I am also going to ignore the
detailed methods of observations (including but not limited to fossil
evidence, snowfall accumulation, and isotopic analysis)

The Global Environment

Firstly, you have to understand that the global environment has been
changing since the Earth's creation. A full understanding of the
subject would require an in-depth look at the creation of phenomenon
like the oceans and our atmosphere (specifically, the makeup of the
atmosphere), but I’m afraid that we will have to take those as given
and fairly constant. That is, except for Carbon Dioxide – its
concentration in the atmosphere has been rising steadily for the past
500,000 years.

The Earth's temperature fluctuates naturally on three observed cycles.
These cycles can be tracked in sediments as old as 200 million years.

• The 20,000 year cycle originates in the precession of the Earth’s rotation. Like a spinning top that is losing speed, the Earth wobbles on its rotational axis to a period of roughly 20,000 years. This wobble is significant (approximately 47 degrees). Wobble one way and the southern hemisphere receives more sunlight. Wobble the other and the northern hemisphere is warmed. As the north has proportionally more continents than the south, a variety of processes (many involving life) cause a more sunlit north to warm the planet as a whole (for more information, research "fertilization of the oceans")
  
• The 40,000 year cycle is also based on our planet's rotation, but I don’t understand it. I do know, however, that it is more powerful than the 20,000 year cycle.
  
• Then there is a 100,000 year cycle that is possibly due to
  fluctuations between a circular and elliptical orbit (although many
  scientists say that this would not cause such drastic effects as have
  been observed). It may also coincide with a variety of natural
  terrestrial fluctuations. Maybe even in the life cycle. This is by far
  the most dominant force of environment change. Until, that is, us.
  

Here you can see these cycles as recorded in the Vostok ice core.
Lake Vostok is fascinating, by the way. If you have the time, I highly
recommend looking into it. It is a lake created by the massive pressure
of Antarctica glaciers melting their bottom layers. This effect can
create a 'slick' for glaciers to slide suddenly and rapidly into the
ocean.

The Earth is a very complicated system. Into its many sub-systems are
built levels of equilibrium. If you tweak any one thing just a little
bit, the system can probably account for it in a manner similar to
homeostasis. However, occasionally a system cannot handle a change. Now
we come to a very spectacular example of a tweak not being handled
gently, and resulting in violent global environment change, almost to
the level of that terrible movie "The Day After Tomorrow".

About 8,200 years ago the most recent ice age was ending. The massive
glacier covering most of North America was melting. Hudson Bay was open
to the Atlantic. On the southern edge of Hudson Bay was the remaining
portion of this massive glacier. Behind the glacier was trapped a
massive amount of water – the largest lake in known history. It was
huge, dwarfing the great lakes, and held back from Hudson Bay by this
melting glacier. Of course one summer the glacier gave way (about 8,200
years ago) and this lake rushed into the ocean. In this one summer, 2 x
1014 m3
of fresh water rushed out. To put that in perspective, it was roughly
25 times as much water as the Amazon. To understand the consequences,
we once again need a little more background information:

The North Atlantic Ocean does not freeze in the winter. It is
moderately salty, and as it cools, salt water becomes denser. This
denser water sinks (creating the North Atlantic Deep Water current...
future lecture topic, perhaps?), and under pressure cannot freeze.

Our 'broken dam' flooding into the Hudson that summer, however, changed
that. It made the North Atlantic significantly fresher, such that the
next winter it froze. Ocean currents were disrupted, solar radiation
was reflected, and Greenland got really really cold. Then, a whole slew
of unforeseen events occurred. China dried out like you wouldn't
believe. Africa dried out. North America became cold. Europe became
phenomenally cold. In just one season the mean temperature in Europe
dropped as much as 12 degrees Celsius. All manner of disruption
occurred. Fortunately, this lasted no more than a couple of decades,
and the Earth moved back to its regular track.

Global Warming

When the Earth is in balance, everything moves fairly smoothly in
accordance with the natural fluctuations, but if the system experiences
a considerable change for whatever reason, its response can be entirely
unpredictable.

Today’s pressing concern is that rising levels of CO2 will disrupt the global environment and harm human life. Well there is no doubt about this in the scientific community. CO2 is a greenhouse gas (albeit a weak one), and the levels have increased by almost 30% in the last 150 years (http://www.gly.uga.edu/railsback/CO2...ntrations.jpeg). All estimates have CO2
levels rising by another 50% in the next couple of decades. The moral
of the story is that while global environment models do not agree on
what the result of this change will be, but they do agree that it will
be significant. We cannot force such a large and sudden change on our
planet and not expect it to react. Anyone who says otherwise is not
facing the facts.

For an interesting perspective on Global Warming, you may want to look
up the works of Professor Nordhouse. He is the world’s foremost expert
on coupling environment change with economics. Of course he agrees that
it is in our best interest to reduce CO2
emissions, but he also takes a fascinating look how an increase in
temperature of just a couple of degrees could stimulate the world’s
economies. Of course, it leaves countries like Bangladesh underwater
and thousands will die, but it's an interesting proposal.