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What rebuttal does the Human Driven Global Warming theorist have for the 800-1200 year lag in the Carbon Dioxide vs. Temperature graph?
Andy C
Professor Mitchell: Over the several hundred thousand years covered by the ice core record, the mainstream view is that temperature changes were primarily driven by changes in the earth's orbit around the sun. During this period, when carbon dioxide concentrations varied between 180 and 300 parts per million, it is likely that changes in increased temperature (due to orbital changes) did drive increases in carbon dioxide. Decreases in temperature would have increased the solubility of carbon dioxide in the oceans, leading to absorption of carbon dioxide in the oceans and lower concentrations in the atmosphere.
However, concentrations are now higher than ever before and increasing much faster than at any time in at least the last 600,000 years. This should be a warning that what is happening now may be very different to what happened in the past. In fact, over the last 100 years, carbon dioxide concentrations have increased by 30% to 380 parts per million due mainly to human induced emissions from fossil fuel burning. There are independent lines of evidence that point to the increase in carbon dioxide over the last 100 years being caused by human activities, e.g. carbon dioxide from fossil fuel burning has a particular chemical signature which is detectable in the atmosphere. Because carbon dioxide is a greenhouse gas, the increased concentrations have contributed to the recent warming, and probably most of the warming over the last 50 years.
The underlying physics is that temperature and carbon dioxide concentrations are linked so that a change in one will be amplified by the resulting change in the other – giving what is known as a positive feedback. For example, in recent ice ages, the fall in carbon dioxide due to the cooling by orbital changes produced a further cooling through a weaker greenhouse effect.
The underlying physics is that temperature and carbon dioxide concentrations are linked so that a change in one will be amplified by the resulting change in the other – giving what is known as a positive feedback. For example, in recent ice ages, the fall in carbon dioxide due to the cooling by orbital changes produced a further cooling through a weaker greenhouse effect.
