Confused about Global Warming

Okay. So I'm writing an argumentative essay about global warming and human activity. Because of the nature of this essay, I have to argue about something, which in this case is that global warming is caused by human activity. The following is the basic understandings of this issue.

Just what is it?

Global warming, the increase in the surface temperature on Earth.

Who or what caused it?

Human activity vs. the natural cycle of cooling and heating.

Is the debate settled?

Most scientists and authorities believe it is settled, as they have reach consensus, while the deniers insist on continuing the debate.

The problem of the debate bugs me. As I'm trying to argue that global warming is mainly caused by human activities, I'm arguing against professors, scientists, and politicians like these guys:

( Source: Wikipedia )

I'm not sure if I can be more confident or smarter than these people. If these people, with all their knowledge and experience in the field, still believe that global warming is not mainly caused by human activity, who am I to say otherwise.

Maybe I should draw on the facts first. What is the major human activities that cause global warming?

• Burning of fossil fuel, causing the increase of greenhouse gases in the atmosphere.

• Deforestation, causing the inability of the earth to absorb carbon dioxide

Secondly, what are the data and evidence that show the correlation between human impact and global warming.

Lastly, I need to find out what the majority of scientists agree on, and compare the mainstream view with the opposing view.

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