There are, of course, two parts to this answer: the first is that businesses have realised that, sooner or later, politicians are going to legislate to compel them to do so (indeed, it is already happening). Businesses, being the forward-thinking entities that they are, have reckoned that if they join in voluntarily (or even merely appear to), the legislation will be less draconian and will thus do them less damage.
The second part of the answer is contained within this article highlighted by Tom Nelson. [Emphasis mine.]
Climate change represents the biggest opportunity for global giant General Electric over the coming decades, the company's Australian and New Zealand chief executive Steve Sargent says.
"For us, we look at this (climate change) as the biggest business opportunity of the century," Mr Sargent told an American Chamber of Commerce in Australia lunch in Melbourne.
And he is not even talking about the Carbon Emissions Allowances trading which has, in the EU, enabled energy businesses to make millions (if not billions) without even having to produce anything...