Perhaps you should do your research and write the body first, then come up with introduction afterward. Until you know exactly what you are going to say, it will be hard to summarize your essay effectively. For instance, you apparently plan to talk about "hurricanes, tsunamis, and heatwaves" as part of the global warming phenomenon. However, once you have done some research, you will learn that tsunamis are caused by earthquakes with epicenters underneath the world's oceans, and that therefore they have absolutely nothing to do with global warming. At some point, you will probably also do a search in google for "global warming past ten years," at which point you will realize that, since 2002, the global temperature has held steady, and that since 1998 the Earth has actually cooled slightly. This will make it difficult to blame any of the natural disasters of the past decade, such as hurricanes and heatwaves, that actually could be affected by global warming, on global warming. So, do your research, write up your findings, then write your introduction once you know what you plan to introduce.
Sean, EssayForum.com