To stay with the example above, note that it might be ok to challenge the premise in the question: you might argue that global temperatures cannot be affected much at all by human action. Your startling thesis might be, "Since I have come to believe that global temperature change is an entirely natural process and almost nothing can be done about it, I am convinced that the United States has no significant role in global warming." But would this essay topic be advisable? It all depends on which organization asked you to write the essay. What does the institution value, and what beliefs do its members hold? Would the institution be proud to put your essay on its web site?
It is essential to learn what the institution values and then to demonstrate in your essay that you support those values. An essay about you should show that you either exemplify those values already or aspire to achieve them through some aspect of your life and work. An essay about the values themselves can interrogate those values a little, but ultimately must come out in favor of the institution's central values (if not also the secondary values).
If you do not genuinely share those values or at least tolerate them, consider carefully whether you really want to enter the contest. If you are a committed capitalist and win an award from a strongly communist organization (or vice versa) and put the award on your resume, what will this award suggest to potential employers? Maybe the $500 prize will come back to haunt you and you will lose a $50,000 job offer.
Note that in many scholarship and award contests, the organization is a billion-dollar foundation with very general central values. It is hard to go against the value of "education" or "science" broadly speaking, and the organization will not expect you to address those kinds of values in a general way. Instead, the organization often values and honors the same kinds of values that you would demonstrate in an admission essay: academic excellence and strong academic character; potential for success; strong social skills; strong communication skills; or personal virtues. These values and virtues are explained in detail under Admission Essays. Indeed, some of these characteristics might be explicitly mentioned as criteria for the award. Read the scholarship or award announcement carefully to see if certain personal criteria are given explicitly or implicitly.
Remember that even when you are writing about a topic other than yourself, your essay instructs the reader about you, both directly and indirectly: this is what I find interesting or valuable; this is how I solve problems and withstand challenges; this is why the institution should establish a relationship with me by supporting me. Most programs already expect that the essays of the top candidates will be written very well. What they are looking for is the winning essayist as well as the winning essay.