The Arguments For and Against Man-Made Climate Change

The projections and theory of climate change are considered to be very sound in their scientific basis. Numerous scientists agree that anthropogenic atmospheric carbon emissions are positively correlated with average global temperatures. Although there seems to be a growing consensus on numerous aspects of global warming, there are still refutations that should be considered and evaluated. Ian Plimer is one scientist who has argued against man-made global warming and has claimed that the problem with the IPCC report is that there is no input from geologists and if scientists with an understanding of the geological record were involved then the idea of anthropogenic warning would soon be refuted. While Plimer's belief may contradict what appears to be solid scientific proof of anthropogenic climate warming, it is important to explore both sides of the global warming debate, including the claims and evidence that both sides present.

The Refutations of Anthropogenic Global Warming:

Plimer states, "The past is the key to the present." He explains that this concept is proven through geologic records that show the Earth's numerous and non-CO2-induced cooling and warming periods and that they emphasize drastic changes that occurred during these periods. These changes include massive temperature increases and decreases, as well as enormous fluctuations in sea level. Plimer insists that we can apply these detailed past records to what is occurring today regarding our warming climate, specifically that CO2 was not the culprit in the past and that it certainly is not the culprit now (Tracinski et al., 2009). Richard Lindzen is another so-called "skeptic" of global warming. Lindzen (2009) uses a variety of different theories to explain why global warming may be false. He specifically mentions that numerous climate models disregard or neglect the role the water vapor feedback system (which humans have a negligent impact over), including regional fluctuations and differences in atmospheric water vapor concentrations. Lindzen is particularly critical of climate models and general circulation models (GCMs), emphasizing the fact that these models are not capable of convincingly showing that small changes in top of atmosphere energy flow associated with increases in atmospheric CO2 concentrations lead to significant climate warming. Lindzen also refers to the non-linearity of changes in CO2 concentrations in correlation with temperature increases, specifically citing that climate sensitivity may only be 0.3-0.5 °C for a doubling of atmospheric CO2 levels, which is within natural changeability. Finally, Lindzen expresses that the scientific belief that small fluctuations in average temperatures can cause large transformations in climate is completely false. Over all, Plimer and Lindzen seem to agree that the main reason to refute the theory of global warming is because scientists overlook certain variables and evidence. But in order to assess these refutations, it is still crucial to examine the arguments that support anthropogenic climate change.

The Supporting Evidence for Anthropogenic Global Warming:

The Intergovernmental Panel on Climate Change (IPCC) was created for the purpose of assessing and reviewing a variety of different scientific findings and reports regarding climate change. The IPCC makes their collective findings clear in the sense that they support the evidence for anthropogenic climate change. In the Paleoclimate Chapter of the 2007 Fourth Assessment Report, the IPCC cites numerous evidence in support of anthropogenic global warming specifically emphasizing the findings of ice core data. Ice cores help scientists determine the atmospheric CO2 concentrations of a specific time period through isotopic ratio analyses. The report states ice core data over the last 650,000 years indicates that the previous natural variation of CO2 concentrations of 180 ppm to 300 ppm in the Antarctic region correlates with changes in temperature over this time period. Contrary to Plimer's claim that extremely high CO2 concentrations were associated with major glaciations (Tracinski et al., 2009), the IPCC report explains that it is likely that past periods with higher than the current CO2 concentrations were marked by warmer temperatures as well. The report also makes some very solid points that help recognize the atmospheric factors that have dramatically changed since the industrial period. According to the IPCC report, it is very likely that the average rates of increase for CO2 CH4 and N2O have been at least five times faster over the last 40 years of the 20th century than over any other 40-year interval during the past 2,000 years prior to the start of the industrial revolution. Finally, the IPCC report directly refutes Lindzen's climate sensitivity claim, namely that the actual number may be 2.3°C to 3.7°C for the doubling of atmospheric CO2 concentrations-which is as much as six times higher than Lindzen's estimate (Jansen et al., 2009.)

An Evaluation of the Claims:

By presenting the major claims and evidence made by both sides to theory of anthropogenic global warming, it is easier to make a conclusive assessment. Firstly, it is fairly straightforward to see the issue with Plimer's claims that geological evidence could disprove anthropogenic climate change and that CO2 was not correlated with warming in the past and it not associated with warming in the present. The most obvious error in Plimer's reasoning is that the present is unlike any other period in history in the sense that the Earth currently has a mass population of humans. The IPCC report contains solid data and evidence from ice cores and climate models that show we have changed the composition of our atmosphere over the past 100 years or so. Plimer emphasizes and insists that the information is in ancient geological records, but the research collected by the IPCC shows that ice core data is evidence enough to made conclusions for the past 800,000 years. Similarly, the IPCC report seems to accurately refute Lindzen's claims regarding a low level of climate sensitivity. Although Lindzen is particularly critical of the dependability of GCMs, the IPCC report shows that there is still credibility in the use of GCMs despite their limits. While no GCM is perfect, they do take numerous variables into account and are accurate based on the capabilities of our scientific knowledge.

To say that Plimer's claim that "the past is key to the present" is completely false seems a bit unfair. While Plimer's reasoning behind the statement seems to be easily refuted with sound scientific evidence, we can still use the basic idea of it and apply it to the support of anthropogenic global warming. It is evident that we can use data recorded throughout the past and apply it to our current climate change situation. The only condition is that we can't completely depend on the past to pave the way for our understanding of the present and future. Instead we must use past information in conjunction with our scientific knowledge of current climate and climate trends.

Bibliography

Jansen, E., et al. (2007). IPCC Fourth Assessment Report: Climate Change 2007. IPCC. Retrieved from http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch6.html

Lindzen, R. S. (1997 August). Can increasing carbon dioxide cause climate change? Proceedings of the National Academy of Sciences (PNAS). (94), 8335-8342.

Tracinski, R., & Minchin, T. (2009 August 5). Interview with Ian Plimer. Retrieved from http://www.intellectualactivist.com/php-bin/news/showArticle.php?id=1120