Official May Tournament Final: Global Warming

C1) Positive feedbacks dominate climate Carbon dioxide has a significant influence on global land-sea mean temperature. All scientists agree that CO2 has some direct effect, increasing temperature by 1.1 degrees Celsius per doubling of CO2 concentration in the atmosphere. David Evans argues, “Most serious skeptical scientists have always agreed with the government climate scientists about the direct effect of CO2. The argument is entirely about the feedbacks.” [1] Climate sensitivity is the key point in all of climate science. The term ‘climate sensitivity’ refers to -- in this context -- the rise in equilibrium global land-sea mean temperature per doubling of the concentration of carbon dioxide in the atmosphere [2]. A 2005 study by Nir Joseph Shaviv confirms that the climate sensitivity, without any amplification, is 1.1 degrees Celsius [3]. Most serious scientists agree. The argument, as Evans argues, is about the feedbacks. What is a feedback? A feedback is a climate process that amplifies or dampens the effect of a climate forcing. A climate forcing is any factor that influences temperature increase, in this case referring to CO2. So, a feedback is anything that amplifies or dampens the effect of CO2 on climate. Feedbacks that amplify it are called positive feedbacks, while those that dampen it are negative ones [4]. I argue that positive feedbacks dominate climate, and therefore, increase the overall effect of CO2 on temperature. Various studies report positive feedbacks as more likely. Soden and Held report a 2 degree celsius climate sensitivity due to positive feedbacks. The study reports very few negative feedbacks. “Water vapor is found to provide the largest positive feedback in all models and its strength is consistent with that expected from constant relative humidity changes in the water vapor mixing ratio. The feedbacks from clouds and surface albedo are also found to be positive in all models, while the only stabilizing (negative) feedback comes from the temperature response.” [5] A 2003 study by Colman reports a feedback of nearly 3 degrees celsius, and the paper is cited by Soden and Held. In the study, “[a] comparison is performed for water vapour, cloud, albedo and lapse rate feedbacks taken from published results of ‘offline’ feedback calculations for general circulation models (GCMs) with mixed layer oceans performing 2 x CO2 and solar perturbation experiments.” [6] There is much evidence outside climate models as well. Wigley, et al. report a possible sensitivity of greater than 4.5 degrees celsius due to volcanic forcings, and supports an average sensitivity of 3.5 degrees. The study says, “After the maximum cooling for low-latitude eruptions, the temperature relaxes back toward the initial state with an e-folding time of 29–43 months for sensitivities of 1–4 degrees C equilibrium warming for CO2 doubling.” [7] A 2005 study by Forster and Gregory also uses volcanic forcings and feedbacks, and finds a climate sensitivity range of 1 - 4.1 degrees Celsius [8]. Even in a hypothetical scenario where negative feedbacks cancel out positive feedbacks to a climate sensitivity of 1 degree C, research by Ziskin and Shaviv (2011) has predicted that “the largest contribution to the 20th century warming comes from anthropogenic sources.” [9] They find that of the ~0.7 degree C temperature rise in the 20th century (some estimates slightly higher), about 0.4 degrees of that are due to anthropogenic forgings, or about 57% of the warming. Nonetheless, climate sensitivity is likely much higher than that. Research by Patrick Michaels, a CATO scholar, found that the amplifier was 1.6 degrees C [10]. This means that human activity causing global warming is much greater than 57%, even under these low estimates. I still maintain that sensitivity is somewhere around 2 - 3 degrees C. A study by leading climatologist JD Annan -- using the Bayesian statistical approach -- found a mean sensitivity of 3 degrees Celsius [11]. The following graph describes the consensus in the literature on climate sensitivity [12]. The following picture portrays the evidence regarding climate sensitivity. As such, I conclude that the effect of the rise in CO2 on climate is huge. C2) Evidence from paleoclimatology The paleoclimatological record is clear that CO2 has become the chief climate forcing in the Cenozoic Era (which began after the Cretaceous mass-extinction event 65.5 million years ago). Overall, solar activity has increased by 40% in this period. James E. Hansen and Makiko Sato argue, “The sun’s brightness increased steadily through the Cenozoic, by about 0.4 percent according to solar physics models (Sackmann et al., 1993). Because Earth absorbs about 240 W/m^2 of solar energy, that brightness increase is a forcing of about 1 W/m^2 . This small linear increase of forcing, by itself, would have caused a modest global warming through the Cenozoic Era.” [13] It’s clear that “CO2 was the dominant forcing in the Cenozoic.” [13] The temperature changes correspond to the changes in CO2 levels. Take the example of the Vostok ice cores. A study by French and Russian institutes says, “There is a close correlation between Antarctic temperature and atmospheric concentrations of CO2 (Barnola et al. 1987). The extension of the Vostok CO2 record shows that the main trends of CO2 are similar for each glacial cycle. Major transitions from the lowest to the highest values are associated with glacial-interglacial transitions. During these transitions, the atmospheric concentrations of CO2 rises from 180 to 280-300 ppmv (Petit et al. 1999). The extension of the Vostok CO2 record shows the present-day levels of CO2 are unprecedented during the past 420 kyr.” [14] This graph shows the correlations between CO2 and temperature over the past 200,000 years. There is proof that it is warmer now than since the Medieval Warm Period. In fact, it is warmer now than any year since 1400 [15]. Another study that replicated previous ‘hockey stick’ studies shows the following data [16]. Thus, paleoclimatology confirms that CO2 influences climate at huge levels. C3) Human activity I have now established that CO2 is responsible for much more that 57% of global warming, somewhere around 75%. Now, I must establish that humans are responsible for much of CO2 generation. First, a simple correlation -- CO2 levels rose with the beginning of industrial activity [17]. The following graph shows CO2 concentrations over the last 10,000 years. If the ratio between C-14 and C-12 decline, the observation would virtually confirm that human activity is responsible for increase in CO2 concentration. This is because the CO2 emissions humans make come from fossil fuels [18]. This has been observed [19]. Thus, human activity has influenced CO2 decline and CO2 is a driving force of climate. Therefore, I affirm. 1. https://mises.org... 2. http://www.pik-potsdam.de... 3. http://onlinelibrary.wiley.com... 4. http://www.ipcc.ch... 5. http://www.gfdl.noaa.gov... 6. http://link.springer.com... 7. http://onlinelibrary.wiley.com... 8. http://homepages.see.leeds.ac.uk... 9. http://www.phys.huji.ac.il... 10. http://www.int-res.com... 11. http://www.jamstec.go.jp... 12. http://www.skepticalscience.com... 13. http://www.columbia.edu... 14. http://cdiac.ornl.gov... 15. http://www.atmosp.physics.utoronto.ca... 16. http://www.skepticalscience.com... 17. http://www.skepticalscience.com... 18. http://www.skepticalscience.com... 19. http://www.bgc.mpg.de...