Mankind Is the Main Cause of Global Warming

No Major CO2 IncreaseThis is true. CO2 levels have been higher. But what were the climactic conditions during those periods? "The last time carbon dioxide levels were apparently as high as they are today - and were sustained at those levels - global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland. " Clearly, the levels that CO2 is reaching are unsustainable. [1]The reason the CO2 rise is considered high is because the CO2 level is the highest in around 50 million years. And it only took 150 years to get that way. So, while the CO2 level is not as high as it has been, the climate was much warmer then, and the CO2 rise is large in the large scale. CO2/Temperature CorrelationCO2 does not correlate exactly with temperature. However, if we consider CO2 and the sun, the correlation is almost perfect. The sun has not caused the most recent spurt of global warming, so it must be concluded that the rising CO2 levels are causing global warming. [2][3]The graph below shows the two forcings plotted against temperature: Further, my opponent's correlation graph is inaccurate. It forgets the huge uncertainty early on. This graph shows the uncertainty: With this uncertainty, Robert Berner (the author of the study and graph), said himself, "Eexact values of CO2. .. should not be taken literally. " That correlation graph should not be taken seriously. The better one is the first graph above, that shows that CO2 has a big effect on the climate. Berner also said in the same study, ". .. over the long term there is indeed a correlation between CO2 and paleotemperature. .. "[4][5]The Earth's Current Climactic TrendMy opponent's studies are based on faulty data sets and misunderstandings about how the climate works. Different data sets show the Earth is warming, and the Earth's climactic indicators show that the Earth is still warming. For one thing, my opponent's temperature graphs are based off of RSS data. UAH and HADCRUT4 data both show that the Earth has been continuing to warm throughout the last 15 years. [6][7] For another, it was found that the heat content of the Earth is increasing. "This new research combines measurements of oceanheat, land and atmosphere warming and ice melting to find that our climate system continued to accumulate heat through to 2008. .. Since 1970, the Earth's heat content has been rising at a rate of 6 x 10^21 Joules per year. " If you look back to my first round, you'll see my point that excess CO2 traps heat, and this is exactly what we're seeing[8][9]: Further, if we focus on surface and lower troposphere temperatures (just where we'd expect there to be warming), we see that the warming trend continues. "Foster and Rahmstorf (2011) used multiple linear regression to filter out the effects of the El Niño Southern Oscillation (ENSO), and solar and volcanic activity (Figure 2), and found that the underlying global surface and lower atmospherewarming trends have remained very steady in recent years. "[8][10]: The hockey stick continues to stick because there's no evidence that there were any periods for at least the last 2500 years that indicate that the climate was warmer then than it is now. The hockey stick was been replicated numerous times. This graph still appears to be the real story when it comes to the recent climate[11]: Interestingly, my opponent's "Greenland GISP2 Ice Core - Temperature last 10,000 years" graph cuts off at 1850. [12]Water VaporMy opponent is correct that water vapor is the most important greenhouse gas. However, water vapor only acts as an amplifier of other warming. Water vapor levels can't be raised. However, since CO2 levels can, the warming that follows is amplified by water vapor in the atmosphere. In other words, it's a positive feedback (see my first argument), not a cause of warming in and of itself. [13]Arctic Ice LevelsThe claim that the arctic sea ice would be completely gone was an apocalyptic one that did not turn out to be true. However, it is still known that the levels of sea ice are decreasing. See the below graph: "The blue line represents the trend calculated from January 1 1979 to the most recent date indicated on the figure. Monthly averaged ice volume for September 2014 was 6,970 km. This value is 40% lower than the mean over this period, 59% lower than the maximum in 1979, and 0.7 standard deviations above the 1979-2013 trend. " The arctic sea ice levels are decreasing. [14]As for the Antarctic sea ice claim, while the sea ice is gaining in extent, it is decreasing in mass. This is the result of a complex set of scenarios. [15]This graph shows the loss in Antarctic ice mass: [16]The claim that the temperature are warming at the same rate doesn't change the fact that increasing CO2 levels are behind the warming. As for the claim that arctic sea ice levels are rising at the same level, this is blatantly false, as the graph below shows: [17]Sea LevelsIt is true that the sea ice melting portends rising sea levels. However, the sea level is actually increasing. Looking at the sea level for an eight year period hardly shows a long-term trend, especially when there's variation in the climate. The sea level rise in French Guiana would not have inundated the country. Further, there's also variation in the sea level rise in different places. When the global data is analyzed, a clear trend of sea level rise is seen. "To construct a global historical record of sea levels, tide gauge records are taken from locations away from plate boundaries and subject to little isostatic rebound. This has been done in A 20th century acceleration in global sea-level rise (Church 2006) which reconstructs global sea level rise from tide gauges across the globe. "[18][19]: What can be seen is that the sea levels are rising, and that the increase is accelerating. Relying on isolated events and short-term trends does not answer the question of whether sea levels are rising as a whole globally. The WeatherThe correlation between global warming and weather is much more complex than my opponent gives the anthropogenic global warming theory credit for. For one thing, storms rely on many more variables than just temperature, especially tornadoes. "Then there are problems unique to tornadoes. Beyond knowing that they require a certain type of wind shear, meteorologists just don’t know much about why some thunderstorms generate tornadoes and others don’t. " If we don't understand why certain thunderstorms create tornadoes, then we are in no place to analyze the correlation between tornadoes and one variable. We simply just don't know enough yet here. [20]Hurricanes can be better analyzed, because they are more dependent on ocean temperatures than tornadoes are on land temperatures. Higher temperatures won't necessarily lead to more hurricanes, but they will lead to stronger hurricanes. "The Power Dissipation Index is found to increase since the mid-1970s, due to both longer and more intense storms. Hurricane intensity is also highly correlated with sea surface temperature. This suggests that future warming will lead to an increase in the destructive potential of tropical hurricanes. "[21][22]The below graph shows this: The correlation is clear here. Further, it was found that while the number of lower-intensity hurricanes has stayed about the same, the number of higher-intensity hurricanes has increased for this very reason. The greater number of hurricanes seen would be small, considering most hurricanes are lower-intensity. [23]SourcesSources in comments.