How to remove clouds in game?

[Atis One]

I heard that CIV IV runs faster once you remove the clouds. And since my game runs so slow my question is how to remove the clouds in the game. I'd appreciate it. Thanks.

 

[Artosoft]

I use "Graphic Scaling Tools" to change the amount of cloud:
http://www.civfanatics.net/~bluemarble/content/index.php

Regards,
Arto.