Final answer:
The best authority to use in a persuasive essay on global warming is a scientist that studies global warming.
Step-by-step explanation:
In a persuasive essay on the topic of global warming, the best authority to use would be a scientist that studies global warming. Scientists who specialize in this field have the expertise and knowledge to provide factual and accurate information on the topic. They can offer scientific evidence and research findings to support their arguments, making their statements more credible.
While the other authorities mentioned -- an environmental studies professor, a farmer who has experienced drought, and a government official who has drafted laws about global warming -- may have valuable insights, a scientist studying global warming would have the most relevant expertise and up-to-date knowledge on the subject matter.
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