Sure, we have studies of ice cores, tree rings, geologic rock studies, anthropological studies, and a lot more. The problem is that the only people that can judge the validity of the study is other scientist in that field. The general public is often left perplexed. Temperature data is easily understood and there is really not much room for argument. Of course one can always claim that whatever climate change occurs is part of a natural cycle.Climate change is a very long term phenomena. You can't look at what the weather was last year or even the last decade to validate global climate change. For concrete proof, you would need reliable climate data for hundreds of years. We have good data for only about 130 years. We do have a lot of scientific evidence form many branches of science that the planet is warming, however none of this evidence will ever be as convincing as actual long term recorded climate data. Unfortunately, by the time we have that data, it won't be needed to validate climate change.
I am very pessimistic about our ability to do anything about climate change for several reasons:
1. The impact on life styles and world economics are huge. Most people are not willing to make the sacrifices today to avert some poorly defined world wide disaster that may occur in a hundred or so years from now. No matter how strong the evidence, many will still claim that this is a natural phenomenon and nothing can be done.
2. Any plan to deal with global climate change would require support from most of the nations on earth. This seems very unlikely.
3. We have never been very good at forming lone term plans and sticking to them. Look at the wars we have engaged in, 8 or 10 years and we are ready to call it quits. The time frame of putting a man on the moon in 10 years was based on the belief that American support would dwindle if the program lasted longer. Plans to deal with global climate change would need public support for much longer 10 years.
Faced with the above problems, political leaders have given mostly lip service to the problem. Our best shot at dealing with global climate change is to push programs for energy independence with cleaner forms of energy, not as a solution for climate change but as a solution to a host of other problems in which we would see results in a short time period.
I thought the Vostok ice cores showed an 800 year lag between the warming and then a subsequent rise in CO2.
Do you feel that modern CO2 is somehow different, more sensitive?