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Answering “Questions about climate changes” from Barry and Kay Hartman (letter, Sept. 21):

A sample of 14,000 years doesn’t tell the whole story of climate change (Antarctic ice cores go back 800,000 years). This period is known as the interglacial, and glaciers grew and receded. While there were no cars and factories, carbon dioxide (CO2) in the atmosphere ranged from about 180-280 parts per million (ppm). CO2 is produced and taken up naturally. The variation in atmospheric CO2 levels depends on many factors, including volcanic activity, fires and many other natural processes.

Today’s fossil fuel consumption is outcompeting the earth’s ability to take up the CO2. The balance is out of whack. We now have CO2 levels consistently above 400ppm. Modern humans have never lived in an atmosphere with 400ppm CO2. Our ice core records tell us that. The dangerous part of being out of balance is we will find tipping points that cause a runaway warming effect. For instance, as the permafrost melts methane releases, which is another greenhouse gas contributing to warming.

On Michael Moore and Al Gore: CO2 stays in the atmosphere for upwards of 200 years, so we are actually the biggest polluters; China and India are still catching up.

Cameron Best,

Missoula

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