Global CO2 levels are one piece of data that is pretty indisputable, even amongst the deniers. What is the effect of global CO2 levels? When was the last time that there were global CO2 levels at the current one? What was the evidence of climate at the time that CO2 levels were at these numbers (oh gosh, it was warmer on a global scale the last time this happened, imagine that)? What is the effect of these CO2 levels upon people, plants, animals, oceans, etc.? Isn't this important? Isn't this worthwhile to determine these effects? Is the globe and its climate something of value to research?
The idea that man, while spewing enormous amounts of various gasses and particulates at rates that are far in excess of what has ever historically been produced into our common atmosphere, has no overall effect upon global climate is pretty far fetched at this point. Deniers for the most part are true believers and have little respect or understanding of science or the scientific method. While science is sometimes wrong, when there is sufficient research, it is usually right. Do we have enough research? Maybe, or maybe not. But deniers are often trying to cut or discredit research into global climate effects. This suggests that there are other reasons for such denier claims beyond any potential scientific dispute. An example of this is typically based upon financial reasons such as when Exxon (of which I am a stockholder) specifically funds 'directed research' to debunk and politically slander less directed research. Then hires political/infotainment groups to push its less than rigorous findings as an equal counterpoint (when in actuality it is far from equal) into the public discourse when the vast majority of the public has no clue or background (and why would they when its just a struggle to pay the mortgage). We have seen this behavior before, time and time again when findings and solutions may be in conflict with profit (the tobacco industry is the prototypical example).
Unfortunately we live in a era where public policy discourse is more a matter of who shouts the loudest, longest, and pays for the most airtime using the most convincing actors. Developing a body of evidence based upon rigorous scientific research and deriving findings (either positive or negative) based upon such evidence and then cooperatively developing policies that will address such findings is where we should be going vs developing belief/political systems to dispute science and research. It is ultimately destructive to ignore the power of science (the method is its most valuable contribution to society, even if most of society could not come close to articulating it).
There are global effects of human activity. Who really knows if there is a tipping point or not, until we have hindsight. The issue is certain human activity over the long term can be /has been affecting global climate, based upon the HUGE, VAST, OVERWHELMING SUPER-MAJORITY of scientific evidence. There is little credible scientific evidence showing that emissions has had no effect upon overall climate.
Given evidence, should we not have discourse on how to mitigate human impacts to minimize negative outcomes? Climate change is undeniably happening (not just supported by science, but also by the insurance industry), and it will have pretty far-reaching consequences (sea level rise is just one of the effects, and farcically stating that you live 50M over current sea level is just childish as a counterpoint).
Climate change is happening. Human activity is either a contributor or a significant factor (this is where deniers' belief system comes into conflict with evidence). We should be discussing how to minimize human effects, not the belief (against a preponderance of evidence) that humans have no effect.
