June 2009 - Climate Change: And so what's wrong with carbon dioxide anyway?
Every breath you take [remember that song by The Police?] is a brew of many different gases. The one we need for life is oxygen and the amount in this gas mixture is 20.9%. The other major component is nitrogen at a level of 78.1%. The remaining 1.0% of air consists of gases such as water vapor, argon, carbon dioxide, methane, helium and many others in small amounts. Just as the oxygen molecule contains two oxygen atoms in a tight embrace, the nitrogen molecule also has two nitrogen atoms bonded closely together.
However the carbon dioxide molecule is different; it contains one carbon atom and two oxygen atoms in a linear arrangement with some very interesting properties. One is as a solid called dry ice, which keeps our ice cream cold, and which when it 'melts', leaves as a gas with no liquid behind. Neat, yes? But another property, and this one is of more interest to climate scientists, is that the connections of the three atoms together are ideal for absorbing infrared radiation [heat] that the planet Earth emits.
Ice core records from drilling into ice caps, up to two miles deep in both Antarctica and Greenland, provide astonishing insight into past Earth climates. The ice cores cover six ice ages [about 120,000 years each] including the last one which just ended about 11,000 - 14,000 years ago. The research results published over the last several years look at the layers of ice deposited over that long period of time and the tiny gas bubbles trapped in them; basically fossil water and air. Analyses of those layers, and bubbles, for carbon dioxide, dust particles, pollen types, methane and many other components, give us information on our atmosphere, how windy it was, volcanic eruptions that occurred, and, our climate, in amazing detail.
Still with me? Great!!
The levels of carbon dioxide over that whole period of time ranged from 0.0190% [190ppm] during the depths of an ice age, to about 0.0290% [290ppm] during the interglacial warm periods like the one we are in now. However, since the beginning of the Industrial Age about 250 years ago, the levels of carbon dioxide have been increasing, significantly. Thus our planet, our home is on a new path.
The level today of 0.0387% [387ppm] is far higher than anything seen in the last 800,000 years. And those levels are rising every year as we continue to burn ever increasing amounts of fossil based fuels such as oil, coal and natural gas. Deforestation and desertification also contribute to these rising levels since this reduces the fixing of carbon dioxide via photosynthesis.
Should one think that this low level of carbon dioxide is inconsequential, consider that every grain of rice we consume, every piece of pasta and every kernal of corn we eat, was manufactured by plants using photosynthesis using the carbon dioxide in the atmosphere. Every steak, every piece of meat we eat, also results from the grasses and grains consumed by these animals. Every 2” x4” or other lumber we buy for our home projects also result from the photosynthesis occurring in the leaves of trees that ultimately produces the wood. So, it is like a spice, a little bit is good, but too much is bad.
And, so what is it with carbon dioxide? How does it weave its climate impact into a molecule that contains one carbon and two oxygen atoms? It struck a Swedish chemist, Svante Arrhenius in 1896 [and some English chemists before him] that carbon dioxide had some unusual properties. He looked at this molecule in a number of experiments in the laboratory, crude by today’s standards, but remarkably accurate and with straight forward scientific logic. These results have been further amplified and supported by current science and modern instrumentation.
Basically the carbon atom in the carbon dioxide molecule likes to vibrate, to wiggle. One of its steps is to first move closer to one oxygen atom, and then closer to the other oxygen atom, in the ballroom equivalent of some un-named dance. Some of these molecular vibrations are perfectly tuned to absorb infrared heat. And this it does with efficiency. The net effect is that carbon dioxide absorbs heat at the Earth – atmosphere interface that would normally be emitted into space.
It is trapped and that energy begins to go to work. It is absorbed into the oceans that cover 70% of our planet, and the land, and begins to warm them. This warmth causes an expansion of the water, which in part, accounts for the rise of sea levels in the last half century of almost one inch every 10 years. It also causes the melting of ice in our glaciers and ice caps which further add to the sea level rise.
While this global temperature rise of about 1 degree Fahrenheit [0.74 degrees centigrade] over the past century may seem modest, it in fact represents an enormous amount of “new” energy on our planet and its systems. Consider this.
Glacial melt per year today is estimated in the hundreds of billions of tons worldwide. Each ton of ice at zero degrees centigrade needs to absorb an enormous amount of energy in order for it to be converted into a ton of water also at zero degrees centigrade, the melting point. Note that there is no change in temperature here. There is only a phase change, from ice to water, but this phase change requires a large amount of energy. This extra energy has an impact on our weather systems and our climate. Eleven years of the twelve year period 1995 -2006 rank among the 12 warmest years in the instrumental record of global surface temperature. As we continue to emit large amounts of carbon dioxide into the atmosphere we can expect more changes in our daily weather and its’ impact on our warming climate.
The scientific career of Raymond N. Johnson, Ph.D., spanned 30 years in research and development as an organic/analytical chemist; he is currently founder and director of the Institute of Climate Studies USA (www.ICSUSA.org). Climate Science is published the first Sunday of every month.