I think you could start off by giving a brief history of how we have developed into what Tim Flannery calls "the weather makers". It wasn't always this way. Our progress has led to this point, and now "the future of biodiversity and civilizations hangs on our actions." That could be one way to approach an introduction, by briefly describing the past. Then slowly, you could move on to the present, talking about what are the latest trends in Unnatural weather changes and climate variations. You could maybe look up various practices and methods or tools used in weather-affecting systems and processes, and then out of all these methods, you could take a select few and talk a bit about them in your essay. Depending on what side you ultimately pick (For weather change or against, example) you should start off with the side you DON'T agree with. So for example, if you take a weather-affecting practice such as cloud seeding, which affects clouds and precipitation, and you are AGAINST weather change, then what you can do is start by talking about evidences or instances where this practice worked/was introduced. From there, you can move on to actually speaking against it, providing details about how cloud seeding is just another misguided laboratory experiment which in reality leads to the "extinction of precipitation" where it is used, causing more problems such as a high risk of drought, crop damage due to lack of rain..etc.
It could provide a nice transition where you speak about why others maybe support the opposite point of view, then moving onto why you support YOUR point of view.
Hope this helps :)