Mankind Is the Main Cause of Global Warming

Overviews OV1: I *did* define ‘global warming’ in R1, thus Con’s objection regarding there being no definition of global warming is invalid. OV2: The first round was supposed to be *only* for acceptance--thus, I request Con to pass the final round to equalize the # of rounds. OV3: I shall only present my own case in this round, and rebut Con’s case in the next. C1) Climate sensitivity is likely high CO2 climate sensitivity is the rise in equilibrium temperature with rise in CO2 concentration in the Earth’s atmosphere [1], especially calculated with a 2x rise in CO2 levels and its correlation with atmospheric temperature levels. Idso (1998) and Shaviv (2005) predict that non-amplified mean CO2 sensitivity is 1 degree celsius [2][3], thus there would be a 1 degree celsius rise in temperature with doubling CO2 concentration. But the effects of CO2 on equilibrium atmospheric temperature is amplified by climate feedbacks. A feedback is something that causes a variation in sensitivity via. generally environmental means [4], and can be positive or negative in nature. A positive feedback is a feedback that causes a rise in overall climate sensitivity, while a negative feedback causes a drop in climate sensitivity [5]. Various studies report positive feedbacks as more likely. Soden and Held (2005) reported a 2 degree celsius climate sensitivity due to positive feedbacks [6]. 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.” [7] Colman (2003) 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.” [8] There is much evidence outside climate models as well. Wigley, et al. (2005) reports a possible sensitivity of greater than 4.5 degrees celsius due to extremely high positive feedback levels, and supports an average sensitivity of 3.5 degrees [9]. 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.” [10] Additionally, using volcanic activity, Forster and Gregory (2005) predict an amplified climate sensitivity of around 1 to 4.1 degrees C [11]. 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.” [12] 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. A significant body of research notes that climate sensitivity is probably much higher, approximately 3 degrees C with a range of 2 to 4.5 degrees C. Their findings can be seen in the graph below [13]. Thus, I have demonstrated that climate sensitivity is high and the climate system is predominated by positive feedback mechanisms. C2) Paleoclimate In the Cenozoic era (the last 65 million years), overall solar activity has risen 0.4%. “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.” [14] The study reports that carbon dioxide is the dominant force behind temperature rise and rise in solar activity in the Cenozoic. Royer, et al. (2004) notes that CO2 drives Phanerozoic temperature, and writes, “Atmospheric CO2 is an important greenhouse gas, and because of its short residence time (~4 yr) and numerous sources and sinks, it has the potential to regulate climate over a vast range of timescales, from years to millions of years.” [15] The temperature changes of the Cenozoic correspond to CO2 changes. “[T]here 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.” [16] Harries, et al. (2001) finds that CO2 traps solar radiation, thus increasing solar radiation’s interaction with the Earth’s atmospheric temperatures [17]. Satellites have reportedly found “direct experimental evidence for a significant increase in the Earth's greenhouse effect [because of CO2].” [18] It is known that CO2 levels are increasing. “In pre-industrial times over the last 10,000 years, CO2 was relatively stable at around 275 to 285 parts per million. Over the last 250 years, atmospheric CO2 levels have increased by about 100 parts per million.” [19] The graph below illustrates increasing CO2 levels [20]. It is well known that carbon dioxide is the primary greenhouse gas emitted through human activity. “Human activities are altering the carbon cycle—both by adding more CO2 to the atmosphere and by influencing the ability of natural sinks, like forests, to remove CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.” [21] It is, according to most paleoclimatological studies, warmer now than the Roman warm period or the medieval warm period, primarily because of human-caused CO2 influence [22]. Thus, I affirm. Over to Con. 1. http://www.pik-potsdam.de... 2. http://www.int-res.com... 3. http://onlinelibrary.wiley.com... 4. http://www.scribd.com... 5. http://www.ipcc.ch... 6. http://www.gfdl.noaa.gov... 7. Ibid. 8. http://link.springer.com... 9. http://onlinelibrary.wiley.com... 10. Ibid. 11. http://homepages.see.leeds.ac.uk... 12. http://www.phys.huji.ac.il... 13. http://www.iac.ethz.ch... 14. http://www.columbia.edu... 15. http://droyer.web.wesleyan.edu... 16. http://cdiac.ornl.gov... 17. http://www.nature.com... 18. Ibid. 19. http://www.skepticalscience.com... 20. http://www.esrl.noaa.gov... 21. http://www.epa.gov... 22. http://www.atmosp.physics.utoronto.ca...