Mankind Is the Main Cause of Global Warming

C1) Climate Sensitivity & Feedbacks My first contention is to demonstrate CO2 has effects in rising the mean land-sea temperature. Climate sensitivity is the level of hypothetical temperature rise if the concentration of atmospheric CO2 would double. [1] It is not a much debated fact that the temperature rise would be by 1 degrees C. This, though, can be amplified by feedbacks. Positive feedbacks amplify the temperature rise, and negative feedbacks diminish the temperature rise. A study published in Climate Research proved that the mean climate sensitivity is approximately 1 to 1.6 degrees Celsius due to the level of positive feedbacks. [2] Another significant body of research notes that climate sensitivity is likely much higher. A review of the evidence in 2008 finds that mean climate sensitivity is 3 degrees C, with a range of 2 – 4.5 degrees C. Nearly every study taken discovers the average climate sensitivity is 3 degrees C. [3] The above graph demonstrates the effect of upper fluctuations in equilibrium temperature via. feedbacks. [4] The graph shown above was from a 2007 research that places approximate mean climate sensitivity to double CO2 concentration at around 2.5 - 3. [5] It is a well known fact that industrial emissions have major impact on the concentration levels of carbon dioxide in the atmosphere. “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. ” [6] Thus, human-caused amplified climate sensitivity affects mean land-sea temperature. C2) Human-Emitted Greenhouse Gases There is a documented rise in CO2 concentrations in the atmosphere over the last 250 years, with a 100 ppm increase in industrial times *alone*, versus a 50 ppm increase from 9,750 years prior. Below is a graph showing the rise in atmospheric CO2 concentrations. [7-8] It is a well-known fact that majority of increase in atmospheric CO2 concentrations is caused by humans. This is because of the sudden hike during industrial times alone. [6] CO2 is known to form an atmospheric layer and trap heat within the atmosphere, thus increasing the mean temperature via. the greenhouse effect, wherein insolation and terrestrial radiation are both trapped within the atmosphere. [9-10] Below is a graph showing a correlation in the rise in temperature and rise in atmospheric CO2 concentrations. “[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. ” [11] The CO2-temperature correlation is also influenced by CO2’s impact on solar radiation itself. In the Cenozoic era, there was a rise in solar activity due to CO2. “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. " The CO2 levels caused a much higher forcing. In contrast, atmospheric CO2 during the Cenozoic changed from at least 1000 ppm in the early Cenozoic to as small as 170 ppm during recent ice ages. The resulting climate forcing, as can be computed accurately for this CO2 range using formulae in Table 1 of Hansen et al. (2000), exceeds 10 W/m^2. It is clear that CO2 was the dominant climate forcing in the Cenozoic. ” [12] There is proof that it is warmer now than any year of human life since 1400. This is depicted in the graph below. [13] Conclusion Thus, I have presented two valid contentions as to why global warming is man-made. Con must present contentions of their own in the next round and defend theirs in the round after. The resolution is resoundingly affirmed. Sources 1. . http://tinyurl.com... 2. . http://tinyurl.com... 3. . http://tinyurl.com... 4. . http://tinyurl.com... 5. . http://tinyurl.com... 6. . http://tinyurl.com... 7. . http://tinyurl.com... 8. . http://tinyurl.com... 9. . http://tinyurl.com... 10. . http://tinyurl.com... 11. . http://tinyurl.com... 12. . http://tinyurl.com...