How to start a formal essay?

How to start a formal essay?
How can I start off my formal essay about global warming? I cant use a question… i need it to be catching… THANKS!

Something like:

Many people in the world wonder what the causes of climate change are. Different people have different opinions, but nobody really knows the truth. There are people all over the world ready to criticize every word you have to say about the worlds greatest threat. And is none other than the fatal global warming. We are experiencing global warming day and night without even knowing it. Our ozone layer is already ripped open.It is very similar to an open cut. We would immediately put a bandage on to prevent it from getting infected. If it gets infected, it will harm your body. The ozone layer is the protective skin for our world. We cannot put a bandage on it, this open cut on the ozone layer will harm us. The ozone layer is also protection from the heat for us. We would burn without it. But when we get further into global warming, when exactly did it start, and how?

That could be your first paragraph, i hope it helps!!!