The following steps per country needs to be taken:
1) which ISP's/hosting companies claim to be green?
2) Have they made their (mandatory) green energy certificate publicly available?

Per country a list is made of ISP's & Hosting Companies that claim to be green.

There are two ways to become a sustainable provider:
1) switch to sustainable energy
2) compensate the CO2 production by buying CO2-credits or planting trees.

It should be clear that the first option is a better and as well much cheaper road to take. But we know that in the datacenter world it can be quiet complicated to find out what kind of energy your racks are using, and even which company in what country the energy buys for you. The larger datacenters are clustered into sometimes very large international companies, and the wish of some of their customers to switch to (often less then 1% more expensive) sustainable energy is not taken very seriously - al least untill now. Sometimes they just claim to be green just to stop the discussion, but if they cannot show a sustainable energy or CO2-compensation certificate, they are not green.