Human Responsibility Questionable
While it seems obvious that by generating and releasing CO2 into the atmosphere, humans have some impact on CO2 levels. However, the connection between human CO2 output and climate is not nearly so simple. Following are two demonstrations of this.
The Climate Changed Before Industrialization
- According to Wikipedia, a period of time known as the Medieval Warm Period (800-1300 AD) was characterized by relatively high temperatures across at least Europe. During this time, Greenland was green enough to be settled by the Vikings.
- This period was followed by the Little Ice Age (~1300-1850 AD) during which glaciers advanced in Greenland and the Thames froze over during the winter in England.
Changes in Extraterrestrial Climates Indicate at Least an Extraterrestrial Factor
As TH Barb notes here, data indicates that Mars is enduring climate warming as well. Thus, it seems reasonable to conclude that at least part of the warming currently occuring on earth is not related to human emission of CO2.
Furthermore, almost all discussions of Global Warming seem to dwell on horrible catastrophes that seem like they came out of some Hollywood Catastrophe film. Almost none of the discussion observes that the previously mentioned Medieval Warm Period is associated with a relatively prosperous period of European history, not numerous climatological and geological catastrophes.
Additionally, it is well known that plants rely on CO2 in a manner similar to our reliance on oxygen. Thus, increased CO2 levels tend to lead to increased plant growth, certainly a boon to farmers needing to stave off the horrible famine supposedly looming in our future as a result of global population growth. This article provides some details on the effects of CO2 on plant growth. A more recent study, despite the misleading headline, comes to a similar conclusion. Although the headline is "High carbon dioxide levels can retard plant growth" a careful reading of the article itself reveals that a depletion of other resources, not high levels of CO2, resulted in decreased plant growth in the 3rd year. In other words, the first 2 years demonstrated high growth, but depleted other resources required for plant growth that were not resupplied, resulting in a poor 3rd year. Armed with fertilizers and other tools, I seriously doubt this will be a major problem for farmers.
Drastic Plans Yield Minor Results
Even if we assume that human CO2 emissions are a major factor in global warming AND global warming will drastically and negatively influence the world, there seems to be little reason to change our emissions unless there is good reason to believe that such changes will have a significant impact on reversing global warming. In the few cases where I have heard the impacts discussed, it seemed to me that the benefits were ridiculously small in comparison to the probably massive economic impact of such changes. If the world as we know it really IS doomed to end within the next 50 years, I see little reason to intentionally make the remaining time we have worse before it gets worse anyway.