Conventional wisdom has it that our planet is at risk of "Global Warming", due to the industrial age's emission of CO2 and other greenhouse gases. CO2 emissions are expected to affect atmospheric, and oceanic warming, and there is strong evidence that this is occurring.
The historical record shows that atmospheric CO2 levels do indeed correlate with increases in global temperature, but also with THE ONSET OF ICE-AGES, which closely follow the spike in CO2 levels and global temperatures (graph)
One possible explanation is that increased global temperature, caused by rising CO2 levels, leads to increased evaporation, thus an increase in cloud cover, particularly over the poles, which eventually reduces the amount of sunlight reaching the Earth's surface. The resultant atmospheric cooling leads to increased precipitation, which scrubs CO2 from the atmosphere (as carbonic acid) further accelerating the decline in global temperatures. The end result would be dramatically-increased snowfall in cold regions leading to expansion of the ice-sheets. Note that current CO2 levels (red trace, extreme right) are higher than at ANY time during the historical record.
The Vostok (Antarctica) Ice Core Data and related references
The Oxygen isotope ratio (O18/O16) provides a measure of historical global temperatures. During colder periods, there is relatively little evaporation of O18, the "heavier" isotope compared to O16, leaving an elevated O18/O16 ratio in the oceans. Evaporated O16 is deposited in polar regions during snowfalls. In warmers times, melting of the ice returns O16 to the oceans and the O18/O16 ratio returns to "normal" values . The record of oxygen isotope fluctuations can be detected in ocean bottom, and ice cores. The record shows that the current ratios have already dropped to levels (extreme right) that preceded all previous ice-ages.
Taking these two pieces of information together, the indications are that an ice age is imminent - unless perhaps mankind's release of huge amounts of Greenhouse gases in the past 150 years is sufficient to overcome the historical trends. Another possibility is that temperature increases (perhaps due to Orbital Forcing) precede, and CAUSE, elevated CO2 levels.
Explanation of O18/O16 ratios
See Article - The Case for Global Cooling |
