Science is based on fact, not opinion. "Fact" in a scientific context is a generally accepted reality (but still open to scientific inquiry, as opposed to an absolute truth, which is not, and hence not a part of science).

Opinions are neither fact nor theory. A person writing an essay, review, or opinion article is trying to persuade you to accept his or her views, which may conflict with science-based evidence. Opinions are not officially the domain of science (but don't think scientists don't have opinions — they are only human, and opinions often help to guide their research). Science cannot directly address opinion, although it can use scientific evidence to counter incorrect or misleading information supporting an opinion.

When it comes to the topic of climate science, you will encounter both fact and opinion, sometimes in the same article. It is important to know the difference and to be able to spot when the author is voicing an opinion. Obvious indicators of opinion are when sentences include words like: "Generally, it is thought" , “Many believe that", "It is a sad day when." Test Yourself Further

It took a long while to determine the best way to investigate the world. One way is to just talk about it (for example Aristotle, the Greek philosopher, stated that males and females have a different number of teeth, without bothering to check; he then provided long arguments as to why this is the way things ought to be). This method is unreliable: arguments cannot determine whether a statement is correct, this requires proofs.

Over time, we found a better approach: to do experiments and perform careful observations. The results of this approach are universal in the sense that they can be reproduced by any skeptic. It is from these ideas that the scientific method was developed. It consists of systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses. When it comes to studying nature, most of science is based on this procedure.

Conclusions arrived at through the scientific method are stronger than opinion-based conclusions.

Replication is also vital to good science — for the scientific community to accept a finding, other investigators must be able to duplicate the original investigator's findings. Thus, you cannot make up your data; other scientists must be able to follow the same methods you used (whether experimentation, mathematical calculations, formulating major concepts, measuring data, or whatever) and come up with the same results.

An example of non-science is the “unpublished hypothesis”. Wild, controversial hypotheses (often in the form of television "sound bites") are hungrily accepted by the public (who cannot be blamed for not knowing better). For ideas to become accepted in the scientific community, ideas must be published (undergoing the process of peer review) to separate the good science from the bad science. Even still, some not-so-good science still leaks into publications, so scientists must think critically when reviewing other's work.

Cherry-picked data draws on isolated papers or a limited range of data in a way that challenges the consensus view and purposely neglects the broader body of research supported by hundreds of papers.

The purpose is usually to persuade the reader to the authors point of view, which the full range of scientific data do not support. For example, a single paper (now discredited along with the physician who wrote it) suggested a connection between vaccination and autism. This unscientific paper contributed to people deciding not to vaccinate their children, which in turn has led to a rise in measles and other deadly diseases in the United States and elsewhere.

click the image below to see how cherry picking data can distort the truth.

Anybody with money can hire a “scientist” who will argue views inconsistent with established knowledge, often complemented by denigration of established experts, including questioning credentials, integrity, and motives.

The tobacco industry employed industry-sympathetic scientists to attack mainstream research. They were wrong, and many people suffered and died as a consequence. (For years, the scientific community recognized that the preponderance of data pointed to a link between the habit of smoking and cancer and heart disease.

And for years, the public rejected that conclusion, in large part because of money spent by the tobacco industry to confuse interpretation of the scientific evidence and to block a social and political consensus. But through a process of political, economic, social, and legal debate over values and beliefs, a social consensus emerged.

The public now accepts that cigarettes cause cancer and governments have set policies to address this.)

Sometimes articles you read will argue you cannot trust legitimate science because it is part of a complex and secretive conspiracy. For example, former South African President Thabo Mbeki based his denial of AIDS on conspiracy theories that appealed to legitimate historical perspectives. But he was wrong, and many people suffered and died as a consequence.