Humanity is the main cause of global warming.

The word 'main' as used in the debate heading presents the position that humanity's contribution to global warming is greater in magnitude than any other factor. The definition of 'main' could be explained as: chief or principal in rank, importance, size, etc. Therefore, Pro must prove that the human portion is in fact the largest of factors. Of course, the human portion needn't be greater than 50% of the total effect if there are multiple elements/factors at play. I also agree that it is more than possible that human activities could affect, change or initiate natural processes, but again, that would have to be quantified (what portion of a natural system has been altered by human elements versus natural change). Natural and human effect can be intertwined and extremely complicated, if not impossible to differentiate and separate. This is referred to as the "attribution of recent climate change". I will reference the following scholarly article: https://gfdl.noaa.gov... "Detection and Attribution of Recent Climate Change: A Status Report". The authors make several important conclusions in this comprehensive study: "Greenhouse warming alone is insufficient to explain the observed pattern of climate change." and "The most probable cause of the observed warming is a combination of internally and externally forced natural variability and anthropogenic sources (see also Tett et al. 1999). But given the large model uncertainties and limited data, a reliable weighting of the different factors contributing to the observed climate change cannot currently be given. In short, we cannot attribute, at this time, with a high level of statistical significance, the observed changes in global and large-scale regional climate to anthropogenic forcing alone.". This research contradicts Pro's assertion that human causes are definitively more important than natural ones. In addition, to say that our current warming trend was caused solely by the industrial age based on the chart I presented (in round 3) would be to dismiss the fact that the sharp rebound from the Little Ice Age and commencement of our current warming trend (1600-) was initiated and occurred well before human activity was a relevant factor. I agree with much of the content contained within the two sites referenced by pro, but none of them contains information that establishes that human activity plays a greater role than natural variability. The CO2 now website asserts that "The human impact on climate during this era greatly exceeds that due to known changes in natural processes, such as solar changes and volcanic eruptions." and lists several of the unique contributions and circumstances associated with human activity and greenhouse gasses. It also states that "the radiative forcing from human activities is much more important for current and future climate change than the estimated radiative forcing from changes in natural processes." These are grand statements, but there is no attempt to quantify them unlike the formal research document I presented above (which contradicts these sites). There is also no mention on Pro's sites of the fact that our current warming period was initiated well before the industrial age and human influence by natural forces. Even the IPCC continues to protect its reputation by using vague terms such as "...likely" regarding the position of humanity's "...dominant role in global warming". I acknowledge that we currently are experiencing global warming. For those who lived in 1100 BC and 1300 AD, they also experienced global warming on a larger scale than we do today, even though human activity had little correlation to that warming. Thus, to say that Global Warming is unique to the industrial age is false. It is also very likely that scientists will one day be able to prove/quantify what portion of Human Activity is attributable to global warming. Presently, it is not possible as my opponent acknowledges. This is why no scientist(s) or scientific body has declared a victory on this issue (A quantified attribution of recent climate change). In fact, a very large amount of money and large amount of research continues to be spent on this very issue because it has yet to be proved or resolved. I also agree that the current warming period presented on the on the chart I referenced is abrupt and is likely a reflection of the influence of human activity. Being that this warming period has yet to exceed several recent warming periods in effect and duration, we need more time in order to be able to place our current warming period into the context of other prior larger warming periods. It is simply premature to state definitively that human activity is the main factor in global warming. My statement is reflected in the current feverish rate of research being performed into the Attribution of Recent Climate Change. If a definitive conclusion had been reached, this research would not be needed to such a degree. Keep in mind, that I am not advocating that humanity should not take responsibility towards reducing our greenhouse gas emissions; quite the contrary.