|Basics of AGW
The basic science driving anthropogenic global warming (AGW) is not rocket science and can be easily understood. The essence of it is as follows:
The Conversion of Geological Carbon to Biological Carbon
The Earth can be viewed to contain two very different forms of carbon. We will call one of these "geological carbon" (GC). GC includes "inert" substances such as the fossil fuels (coal, oil, and natural gas) and various inorganic substances such a calcium carbonate (limestone). These forms of carbon stay put in or on the Earth essentially forever if they are left undisturbed.
The other basic type of carbon we will call "biological carbon" (BC). BC consists of all living plant and animal materials as well as the CO2 in our atmosphere and the CO2 that dissolves in our oceans, lakes and streams. The BC forms of carbon are "active" and continuously cycle through the atmosphere, oceans, plants and animals.
The present AGW problem has been caused by the exceedingly rapid rate with which man has been converting GC to BC by the combustion of fossil fuels. While the plants might like the EXTRA CO2 man has been adding to the BC cycle, both the atmosphere and the oceans do not.
In the atmosphere, this EXTRA CO2 increases the amount of infrared radiation (heat) that is absorbed as the Earth attempts to cool itself via its emission of infrared radiation. Therefore, just as you get warmer when you put on a heavier coat, the Earth also gets warmer as extra BC and atmospheric CO2 are made by the combustion of fossil fuels.
In the oceans, the extra dissolved CO2 is converted to carbonic acid (CO2 + H2O = H2CO3), which makes the oceans more acidic, thereby perturbing its ecosystems.
Now consider the rapid rate with which man is converting GC to BC. We began doing this on a significantly large scale in about 1850. We now estimate that we could use up the Earth's known reserves of oil in several decades and its know reserves of coal in about two centuries. If allowed, that would mean that man had accomplished this massive conversion of GC to BC in approximately three centuries, which is to say "instantly" if viewed on the geologic time scale.
Now consider the very slow rate with which this EXCESS CO2 will be removed from the BC cycle and returned to the inert forms of GC. First, it takes at least several million years to naturally convert plant material to the fossil fuels. Another means of BC to GC conversion is called the "weathering" of CO2 by which the CO2 dissolved in rain drops or in the oceans comes in contact with rocks that contain calcium oxide (CaO). A small portion of that dissolved CO2 will then be converted to limestone (CaCO3). Unfortunately this process is also quite slow and has a significant effect only over a time scale of several centuries to a few millennia. The other natural processes by which carbon is removed for BC cycle is by sequestion in the soil of the Earth via the roots of plants and trees. The rate of this removal process is limited, however, by the fixed size of the Earth and its decreasing fraction of forested land. It is thought that greately improved land use policies could result in the removal of no more than about 50 ppm CO2 from the atmosphere.
Therefore, as we convert GC to BC, that convertion is essentially permanent on a time scale of relevance to human beings (several centuries) and the concentration of CO2 in the Earth's atmosphere simply continues to rise. Every day with business as usual, we are racheting up the atmospheric CO2 level essentially forever on the human time scale. Today, the atmospheric CO2 level is 33% higher than it has ever been in at least 750,000 years and is increasing at a rate of 0.6% per year! As this rate is further increased by the rapid economic development other countries (especially China and India), we can expect to see a 50% increase in the pre-Industrial Age level of CO2 by the year 2025 or sooner.
Unfortunately, most models of the Earth's atmosphere indicate that if we reach this CO2 level by 2025, the probability of having reached a "game over" condition for future human civilizations will be extremely high. Because there is a time lag of about 20 years between the causes and full effects of the CO2 level we accumulate up to any point in time, we Baby Boomers might still enjoy relatively livable conditions in the year 2025. However, for our younger generations expecting to live into the second half of the current century, life will become exceedingly problematic. Just how bad those conditions will be depends largely by what we do in the next decade.