Its often because they are either stupid or have financial interests.

Adapting to climate change and finding a sustainable way of life implicates a couple things.

It means ending the use of fossil fuels for renewable everywhere. An oil or a gas company can't let that happen even if their resource is running out!!

Better use of existing resources and protection of the environment. Currently its cheaper to do stuff which produces waste than the opposite.

While climate change itself may mean a radical change or shift in society which may go against the believe of climate deniers.

So despite the proof we are held back by a few selfish bastards who would rather make some money than think about the future.

We need to adapt but also i think the climate itself is more complex than we make it out to be. The thing with science is we can't possible know everything their is too know 

At a weather report people can not claim that it will rain tomorow for 100% but they are 100% sure that the weather will be warmer in 100 years..

40-50 years people believed in global cooling and people who did not believe in it were mostly called stupid or idiots..

Anyway Global warmin is on a break like they reported some days ago..

https://www.ethz.ch/en/news-and-events/eth-news/news/2014/08/why-global-warming-is-taking-a-break.html

Hmm... A lot of people would say the same thing above "green" companies. They are feeding everyone with these new studies on warming but really they are just in it for the money as well. 

Also you seemed to contradict yourself saying "proof" followed by "we can't possibly know everything".

it's cold mother nature. weather happens in cycles.