There are a few fallacies regarding the global warming debate... the main one being that planting more trees will reduce the amount of carbon dioxide in the atmosphere. This isn't exactly true. Anyone that has studied biology to O Level (sorry GCSE) level will know that although plants do absorb carbon dioxide during photosynthesis, they also need to respire in order to stay alive (the processes of photosynthesis and respiration are basically the opposite of each other, one producing carbohydrates and oxygen from carbon dioxide and water and the other producing carbon dioxide and water from carbohydrates and oxygen). This means that although the plants take carbon dioxide from the atmosphere and convert it into oxygen by photosynthesis during daylight hours, they are also taking in oxygen and converting it back into carbon dioxide by respiration both day and night. And so plants tend to be "carbon neutral" really, neither adding to, nor removing carbon dioxide to the atmosphere. There are many other reasons why we need to save trees - the wildlife that lives in the trees, the wide variation of flowers and leaves that produce many advantageous things for us to use - but reducing carbon dioxide is not one of them.
On the subject of electricity, it has long been possible for us to produce unlimited and free electricity for everyone by having solar panels in space which can beam down the energy they collect. However the energy companies keep this knowledge quiet because then they won't be able to make such huge profits.
The only people who are really denying that global warming is happening tend to be those people that are making lots of money by polluting the planet, and so if they have to stop polluting, they will lose money. It is quite significant that the only major country in the world that refuses to sign up to pollution control is the one run by someone who's family makes their money from the most polluting product available (oil).