Guest post by Steven Goddard
There are still people who insist that changes in CO2 can explain the pattern of glacial and interglacial periods. This article will present several arguments demonstrating that is incorrect, based on the ice core data below.
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The most obvious reason is that CO2 lags temperature. Changes in ocean temperature have driven the changes in atmospheric CO2, as explained here. CO2 is not the driver.
Now consider the earth 20,000 years ago. Temperatures were low – about 8C cooler than the present. Due to the cold ocean temperatures, levels of atmospheric H20 (the primary greenhouse gas) were low. CO2 levels were also low, at about one half current levels. The earth’s albedo was very high due to extensive ice cover which had much of North America and Europe buried in ice. Using the popular “CO2 and feedbacks explain everything” theory, all of these negative feedbacks should have driven earth further and further into an irrecoverable ice age. Cold ocean water should have continued to absorb more CO2 from the atmosphere.
Atmospheric H2O should have continued to decline due to lower vapor pressures over the cooling oceans. Albedo should have continued to increase due to expanding glaciers further from the poles. All of these negative feedbacks should have caused temperatures to decrease further, and the death spiral should have continued. But none of these things happened. Instead, the earth warmed very quickly. CO2 was absolutely not the driver, and positive/negative feedbacks had to be in balance.
Consider the earth 14,000 years ago. CO2 levels were around 200 ppm and temperatures, at 6C below present values, were rising fast. Now consider 30,000 years ago. CO2 levels were also around 200 ppm and temperatures were also about 6C below current levels, yet at that time the earth was cooling. Exactly the same CO2 and temperature levels as 14,000 years ago, but the opposite direction of temperature change. CO2 was not the driver.
Now consider 120,000 years ago. Temperatures were higher than today and CO2 levels were relatively high at 290 ppm. Atmospheric H20 was high, and albedo was low. According to the theorists, earth should have been warming quickly. But it wasn’t – quite the opposite with temperatures cooling very quickly at that time. CO2 was not the driver.
If CO2 levels and the claimed lockstep feedbacks controlled the climate, the climate would be unstable. We would either move to a permanent ice age or turn into Venus. Warmer temperatures generate more CO2. Increased CO2 raises temperatures. Warmer temperatures generate more CO2 …… etc. It would be impossible to reverse a warming or cooling trend without a major external event. Obviously this has not happened.
An exercise to get people thinking for themselves. If the temperature at some point in the past was 4C cooler than now and CO2 levels were 240 ppm, was the temperature going up or down? There are ten points on the graph that match those conditions. Half of them have rapidly rising temperatures and half have rapidly falling temperatures. It becomes abundantly clear that there has to be another degree of freedom which is dominant in controlling the glacial cycles.
In the ice core record, temperature drives CO2 – not the other way around. Sometimes the earth warms quickly at 180 ppm CO2. Other times it cools quickly at 280 ppm CO2. Again, CO2 is not the driver of glacial cycles – there has to be a different cause.
The use of the term “negative feedback” in this article is the commonly understood meaning – i.e. feedbacks that drive temperature down. Technically speaking, this usage is incorrect. From a viewpoint of semantics, a negative feedback would be one that works against the current trend. This semantic difference has no relevance to the logic being presented in the article.