Science denialism is a barrier to a better world. Every country in the world faces huge social, ethical, and political challenges, and in each country the enemies of free, careful thought are preventing meaningful progress regarding those challenges.

Science denialists all share common methods and arguments. “There’s not enough data,” they say, and “scientists think they know everything,” and “researchers are playing god!” In the past, denialists have propped up the tobacco industry, sold faulty medical knowledge and equipment, and hastened the spread of HIV and AIDS by spreading misinformation and preventing good research. Here a few of the most dangerous groups of science denialists operating around the world today.

Climate Denialism

These people are probably some of the most dangerous human beings on the planet today. Scientists the world over agree that the earth’s temperature is rising, and that this rising temperature will almost certainly bring about some devastating effects. Scientists and nature enthusiasts on every corner of the planet have been reporting strange things regarding temperature and wildlife for decades now.

Climate denialists make a lot of money from industries that pollute. When people cite scientists who supposedly don’t believe in global warming,they’re almost certainly talking about scientists who earn their paychecks from coal and other polluting companies. Scientists and scientific communicators need to step up their promotional game and shut down the denialism they face.

Luckily, many of the the traditionals villains in this fight—multinational corporations, agri-businessmen, etc—are changing their tune. Big money is making its way into the fight for the earth, and the tide may be turning even as it rises.

Anti-Vaccine Activists

Vaccines are miracles of medical technology. They prevent millions of deaths worldwide every year, many of those are children. Vaccines are rigorously tested for safety and effectiveness, and probably save more lives a year than any other technology in the world.

Yet vaccines face many obstacles, and one of the most significant of those obstacles is people who spread misinformation about what vaccines do. Anti-vaxxers, as many health expert refer to them, ignore clinical research and choose to believe whatever it is they want to believe that they read on the internet. Anti-vaxxers are vocal. They spread their dangerous message to anyone who will listen to them. This message is especially insidious because it endangers not only its adherents, but also vaccinated people who are exposed to unvaccinated people.

Again, though, anti-vaccine activists are losing credibility with the general public. Recent outbreaks of the measles and other preventable diseases are helping alert the world’s people that vaccines are necessary to the health of the world’s public.

New Age Healers

People who believe that fighting medical knowledge and replacing it with crystals, herbs, and other untested remedies are putting themselves in harm’s way. Real medical science works by testing; if something works, doctors use it. New age, holistic, and various other alternative medicines do not go through testing.

New age and alternative medicine proponents are not nearly the menaces to the public that climate denialists and anti-vaccine activists are. Still, though, they represent a stubborn clinging to ignorance that is no good for the world.