We’ve Never Been Here Before: 400ppm of CO2 Measured in the Atmosphere at Mauna Loa

Melanie Fitzpatrick,
May 14, 2013

We’ve just crossed a sobering milestone. For the first time since humans have walked the planet, the amount of carbon dioxide in the atmosphere at Mauna Loa Observatory has reached 400 parts per million. On May 9, scientists from both the National Oceanic and Atmospheric Administration (NOAA) and the Scripps Institution of Oceanography measured the daily average concentration of carbon dioxide in air above this value. I don’t know about you, but when I heard this I wanted to cry. Let me put this in context for you.

I started my scientific life as a fresh-faced glaciologist drilling ice cores on the immense ice sheet of Antarctica. It was the early 1990s and my job (an amazing one, I’ll admit!) was to tirelessly process the ancient ice that we were bringing up from the deep drill hole. There was almost a mile of ice to analyze! This frozen archive is made from pure snow that fell on the continent tens of thousands of years ago and compressed into hard, cold ice. These ice cores, like many others since, reveal the secrets of ancient atmospheres from the air bubbles trapped within their lattice. They allow us to compare the modern atmosphere that is measured at Mauna Loa with what happened in the past.

Past atmospheres: the cycles of CO2 and temperature

I remember my excitement on seeing the cycles of ice ages pop out from our analysis. You’ve probably seen those graphs of wavy lines that show carbon dioxide dancing between a low level during an ice age and a high level in an interglacial (like the one we are in now).

For the last eight glacial cycles carbon dioxide has varied between 180 parts per million and 280 parts per million. Carbon dioxide has, in general, gone up and down hand in hand with global average temperature. When carbon dioxide is high, temperature is high; when carbon dioxide is low, temperature is low, with the leads and lags being well understood by the scientists studying these in detail. The ice core record shows this has been the natural cycle for at least 800,000 years. As a yardstick, homo sapiens has only been around for a mere 200,000 years at the very longest. Earth’s climate is very sensitive to the level of carbon dioxide in the atmosphere. But in the last two centuries of our short time on the planet we have altered the atmosphere drastically.

Continue reading at:  http://blog.ucsusa.org/weve-never-been-here-before-400ppm-of-co2-measured-in-the-atmosphere-at-mauna-loa-126