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Climate Change

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Table of Contents

Climate Change

Climate Change

A major issue with the sustainability of our current energy portfolio is the effect on our climate. Pollutants created by burning fossil fuels are collecting in our atmosphere and trapping solar radiation, thus heating the earth. This phenomenon is known as the greenhouse effect. The greenhouse effect occurs naturally, but anthropogenic greenhouse gases, those created by human activity other than breathing, have significantly increased the size of the effect, and this is the basis for climate change. The sun is currently in a warming cycle, but this is believed to be responsible for only 10% of the observed warming.

The Human Link

The most significant anthropogenic greenhouse gas is carbon dioxide (CO₂). Combustion and agriculture are the most significant sources of CO₂, which remains in the atmosphere for about seven years. The plot below shows how temperature and CO₂ concentration are correlated with each other. This plot has been named the 'hockey stick graph' by Michael Mann, who was the first to produce a plot of temperature versus time, due to the relatively flat period followed by a sharp increase in the past 100 years.

Figure 1: The correlation between temperature and carbon dioxide concentration.

Source: ACIA Impacts of a Warming Arctic: Arctic Climate Impact Assessment (2004)

In addition to greenhouse gases, combustion and other human activities emit particulate matter into the atmosphere. Particulate matter, also known as aerosols, may cool the earth and only remain in the atmosphere for a few days after emission, but they are associated with many health problems and a significant number of deaths all over the world.

Effects from both greenhouse gases and particulate emissions are spread unevenly throughout the globe. For example, pollutants tend to be concentrated around cities, and the northern hemisphere has higher concentrations of pollutants than the southern.

The effects of climate change can be difficult for the average person to detect because we perceive climate through weather. Put glibly, the weather determines what you wear on any given day, while the climate determines what is in your closet. The combination of greenhouse gases and cooling aerosols may contribute to extreme weather.

The effects of increased temperature on the earth's climate may be devastating. Melting snow and ice will cause sea levels to rise, displacing millions of people from low lying areas. Warmer oceans may lead to larger and more powerful hurricanes and typhoons, and increasing acidity kills coral reefs. Furthermore, global warming is occuring unevenly; for example, Alaska has already experienced dramatic climatic changes. Some regions are experiencing increased droughts, while others suffer from stronger storms. To combat increasing temperature, we must move toward a sustainable energy system that does not increase the temperature of the earth.

Updated Chart on Global CO2 Concentration

* Global gas concentrations for CO₂ can be found in the following website : EarthTrends

The IPCC, Dramatic Mechanical Lifts and Climategate

In 2007, the largest group of scientists ever to convene on the topic of climate concluded that human activities had indeed led to increased CO2 in the atmosphere resulting in increased temperature. This group, Intergovernmental Panel on Climate Change (IPCC), was awarded the Nobel Peace Prize in 2007 for its work.

Al Gore's movie... watch the trailer here.

An email leak (or rather server hacking) in November 2009 spurred a controversy, now dubbed 'climategate', over the validity of climate science. The emails revealed misconduct within the climate science community including deleted and manipulated data. Decide for yourself: http://en.wikipedia.org/wiki/Climatic_Research_Unit_email_controversy

Areas of Uncertainty

Trends in population, how the economy responds to increases in petroleum prices, and governmental environmental policies are three examples of variables which effect the predictions of the future effects of climate change. There are other areas of uncertainty which our text lists as:

Uncertainties about how 'carbon sinks' (oceans and forests) will respond to increased concentration of carbon dioxide in the atmosphere. Wirth et. at provides an interesting review of the current state of terrestrial carbon sinks stating that the "terrestrial biosphere was largely neutral with respect to net carbon exchange during the 1980s but became a net carbon sink in the 1990s."http://www.nature.com/nature/journal/v414/n6860/abs/414169a0.html
The distinct relationship between carbon dioxide concentrations and temperature is uncertain. Thus far (since climate change has been considered) the two have been correlated but there is not enough hard data to say with great certainty how they will be related in the future. The atmosphere-ocean-cryosphere-biosphere is extremely complex and nonlinear. However, recent estimates suggest that changes in atmospheric concentration (namely carbon dioxide) should dominate the effects of climate change over any variability in solar irradiation. http://www.springerlink.com/content/6316w11nm5514576/fulltext.html This is still a subject of debate however as it is known that fluctuations in the sun's heat can cause climate changes on the time scales of decades and centuries.
Extreme climate changes in some regions of the world and modest changes in others result in accelerated change in some places but only a small change in the worldwide average.

Models for Climate Change

Modeling climate change is a very complex matter. Our text (Energy Systems Engineering by Vanek and Albright) takes us through some of the basics, highlighted below.