The Daily Item, Sunbury, PA

Letters

May 16, 2013

A signifcant milestone

It doesn't smell any different and it doesn't feel any different but we have changed the atmosphere. It has not been like this for about 3 million years. No humans have ever breathed air like this and we should be very worried about its implications.

Carbon dioxide (CO2) levels in the atmosphere have just passed the symbolic but significant milestone of 400 parts per million (ppm). A few hundred years ago, at the dawn of the industrial age, the CO2 concentration was only 280ppm but it has increased exponentially since then as a direct result of our burning of fossil fuels. When the concentration of this greenhouse gas was last at the current high, the arctic was completely ice free and the sea level was 120 feet higher. Average polar temperatures were more than 14 degrees Farenheit higher and overall, the world was 5 to 6 degrees warmer than today. These conditions are expected to return with incalculable costs unless we act soon.

As a result of industrialization, global temperatures are now rising 75 times faster than in prehistoric times and have increased by almost 2 degrees in recent history. While the world's governments supposedly agreed to limit the increase to approximately 3 degrees, little has been done to limit the emission of causative greenhouse gasses. While it is good to have some CO2 in the atmosphere, its natural ability to retain heat like a greenhouse stops the Earth from freezing, we now have too much of a good thing.

If we fail to limit future greenhouse gas emissions, the Earth is predicted to pass through a series of tipping points, temperatures at which runaway global warming will occur. Once the summer ice in the Arctic melts completely, all that solar heat energy will be absorbed by the oceans instead of being reflected back into space. As atmospheric temperatures reach a critical point, frozen tundra circling the Arctic will melt releasing immense quantities of methane, another greenhouse gas that traps 20 times more heat than CO2 thus leading to even greater warming.

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