A few years ago I was pretty convinced that the basic line on global warming was absolutely true. I really saw no reason to doubt that CO2 emissions were heating up the Earth and that failure to prevent this disaster might doom us all. I no longer believe that. There are a number of reasons for my change of mind, but let me lay out a few things first.
-The temperature records of the Earth over the last century show a substantial increase in average temperature. No one of any credibility denies this.
-The Earth has been drastically hotter and colder than it is now many times over its history.
-There is a substantial correlation between CO2 levels and average world temperature over a huge timeframe in the past that is well supported by scientific evidence.
-The vast majority of the models used by scientists to model Earth weather patterns assume that increases in atmospheric CO2 will increase the temperature of the Earth.
None of this proves that CO2 is actually increasing the Earth's temperature. The ice core evidence showing correlation *does not* imply causation, and in fact it may well show causality the other way. This is supported by the accepted fact that an increase in temperature will cause an increase in CO2 levels due to CO2 coming out of the oceans.
Another intriguing fact is that there are many times that temperature spikes up or down with no relationship to CO2. As an example, during the period from WW2 to the 1970s the temperature of the Earth dropped despite this period being one where CO2 levels rose drastically. This is only one of many similar issues, as most climate models also have absolutely no explanation for why if CO2 causes high temperatures and high temperatures cause CO2 why the Earth has had such a fluctuating temperature instead of a steady, inexorable increase due to a the feedback loop described above.
I started doing a little looking into this after seeing a video on the internet called The Great Global Warming Swindle a few years back. This video was really interesting because it combined a lot of political mumbo jumbo and somewhat sketchy science with some really hard questions that I was unable to find good answers to. I spent some time looking at the firestorm of debate that followed the video and came to the conclusions that the video itself should not be taken at all as an example of good science and that many people on both sides of the debate are pundits with no credibility. However, it did seem to me that CO2 deniers often made points that simply could not be addressed by their opposition.
People that claim that the Earth is not going through a noticeable warming period are either delusional, badly misinformed or straight up lying. However, from all the data I could locate the evidence that CO2 actually does what most models say it does seems sketchy at best. Our models cannot explain most of the Earth's climactic history so the idea that we are able to make accurate predictions about the future is pretty laughable - in science it is well known that it is usually easy to make a model that fits known facts but the real test is making a model that makes accurate future predictions. If your model can't even manage the practice round how can you rely on it for the real test?
None of this changes my stance on emissions though. I am very much for reduced emissions whether that be by carbon trading, tightened standards for vehicles, changes to renewable resources or other options to reduce our use of fossil fuels. However, I heartily dislike scientific models that simply aren't nearly as good as they are proclaimed to be being used as a giant stick to enforce political change. Using sketchy science and scare tactics to get changes you want may work once but it undermines the faith people have in scientists and the scientific method. Losing that credibility means that next time you need to convince people to change you will have a much harder time doing so.