Alaska Science Forum

This article is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Guest author Tom Gosink is a Research Associate in Chemistry at the Geophysical Institute.

There are about a dozen trace chemical components of the atmosphere which affect the heat balance of the earth's surface. Carbon dioxide (CO₂) is the most important of these trace constituents because of its ability to behave in a manner similar to a greenhouse. Both convert light energy into heat energy and trap it. Most of the atmospheric CO₂ exists below the higher clouds; thus the energy it converts to heat is temporarily trapped near the earth's surface. If the average global air temperature increases by even 2°C for a few years, drastic changes in weather patterns will occur, partly in a natural attempt to shift the climate back to the status quo. Glaciers will begin to melt faster than they are formed, and sea level will rise several to tens of meters over a period of about a century. It has happened in the past. On the other hand, if world average air temperatures decrease about 2°C, the climate will revert to an ice age. Repeated volcanic activity such as the recent eruption of E1 Chichon in Mexico could cause such cooling due to the scattering of light by particulates high in the atmosphere. The 1980 eruption of Mt. St. Helen's was not strong enough to be significant in this respect.

Carbon dioxide is a natural and essential component of all living systems. Our exhaled breath contains a closely regulated 4.7% of CO₂. Resuscitator oxygen has 0.5% CO₂ added to it to stimulate involuntary breathing. Large commercial greenhouses add smaller quantities of CO₂ to the enclosed air to enhance harvests. The latter use of CO₂ is for plant nutrition, and not for the purpose of warming. Nature seeks to establish a balance of less than 0.003% (300 parts per million or ppm) of CO₂ in the atmosphere. Atmospheric concentrations of CO₂ have been rising for the past century, clearly linked to man's increased use of combustion. Average air in clean regions such as the Arctic now contain about 350 ppm CO₂. Carbon dioxide concentrations continue to rise 1 to 2 ppm per year due to nature's inability to cope with about half of the nearly 6 billion tons of CO₂ per year being added to the air by all of man's activities. When the concentration reaches about 400 ppm in the next 20 to 40 years, the global warming due to carbon dioxide is calculated to begin.

Oceans absorb and release about 30 billion tons of CO₂ per year as part of the natural cycle. Between 2 and 3 billion tons of CO₂ per year of the extra CO₂ added to the system by man is absorbed by lower latitude oceans.

The Arctic, about 4% of the earth's surface, is neither an insignificant participant to the CO₂ balance nor a passive ice-sealed region. Research has shown that summer Arctic sea waters are highly undersaturated in CO₂ and draw down over 2 billion tons of the gas, but that during winter the water becomes highly oversaturated. The sea ice cover retards, but does not stop, the release of CO₂ back into the air. Tundra and taiga regions of the Arctic and subarctic are another important depository for about 2 billion tons of CO₂ in the form of peat. The decay rate of the dead plant material is retarded by low temperatures, which, in turn slows the release of the gas.

The critical question for research in the Arctic is, will warmer temperatures accelerate or retard the greenhouse effect? Uncovering winter Arctic seas as they now are would definitely promote a warming trend by releasing trapped CO₂. If the ice is removed, it is questionable what the resultant increased penetration of light and wave action will do to the Arctic sea water. Will it absorb even more CO₂, or will it continue to release CO₂ ? On land, will the increased vegetation growth, and consequent insulation of the surface provide a CO₂ depository sufficiently large to counteract that produced by hastened decomposition?