Dumb Movies and Environmentalism

In the 2000 movie Red Planet , which I caught on DVD the other day for some reason, there is a brief prologue in which it is explained that some time in the future, climate change has occurred on Earth, and a combination of the ozone layer being gone and global warning has rendered the earth nearly uninhabitable. Therefore, astronauts go to Mars, and release genetically modified green algae as the starting process in a terraforming process that will warm Mars up, unfreeze the Martian ice caps, and eventually release oxygen from underground so that there will be a breathable atmosphere.

Now as this was revealed, one curious question unfolded in my mind. If technology has been developed that can terraform Mars, a hunk of rock with frozen ice caps and only a very thin non-oxygen atmosphere and change its atmosphere and climate into an inhabitable world, why can't the same technology be used on Earth to terraform its atmosphere and climate back to what it was before the crisis occurred? Surely this is somewhat easier than transforming a hunk of rock into an inhabitable world. Either I am missing something, or this is the dumbest movie plot point since the human batteries in the Matrix. And how is it possible for Hollywood to release a movie like this without anyone asking this one simple question. And why didn't anyone in the audience ask this question either? (The film got lots of bad reviews, but not for this).

I suppose one possibility is that a UN dominated by banana-starved Europeans has prevailed on earth, genetically modified algae are banned on the planet, and therefore although terraforming technology exists and climate change can be controlled, there are laws preventing this from actually being done because "GM is wrong". But this couldn't be. Nobody would allow huge numbers of people to die for reasons of Romantic Luddism, would they?

Seriously, though. The mental disconnect that led to this plot illustrates an interesting point. On earth, the question of environmental damage is often thought about in isolation. The damage is considered, but the question of how technological advance can help clean it up is not. However, when we look at something completely divorced from the everyday, such as the potential colonisation of Mars, we suddenly can once more think of the technology. Curious.