harvard historian naomi oreskes urged hundreds of scientists to step beyond the objectivity of their data and embrace the riskier role as “sentinels” for scientific facts.

“we do need to speak for the facts because the facts don’t speak for themselves,” oreskes said to an overflowing auditorium at the boston conference of the american association for the advancement of science. “we live in a world where many people are trying to silence facts,” said the author of “merchants of doubt.”

the book and documentary based on it show how the tobacco and sugar industries and climate change deniers cast doubt on scientific facts without ever needing to refute them.

among scientists today there is often a “fear of losing credibility” if a scientist speaks out in defense of science that has become politicized such as [science supporting] climate change, evolution, or vaccination, she said. but history doesn’t justify that fear and she offered ample examples of scientists taking important political and social positions, she said.

“i know of no evidence that the theory of relativity or the photoelectric effect or any of einstein’s work lost scientific credibility because he was an advocate of nuclear arms control,” she said. “the fear of losing credibility is exactly that: a fear.”

oreskes said scientists like to “let the facts speak for themselves” instead of getting involved. but a responsible scientist should find a “middle-ground” between activism and disengagement by speaking up for scientific truth, she said.

“u.s. scientists are known for being very timid. they’re not people who are boat rockers,” said speech attendee tom macginnis. in that way, scientists “have become part of the establishment, unfortunately.”

oreskes gave historical examples of scientists who stood up for truth when moral issues were at stake. climate scientists roger revelle, david keeling, wallace broecker, and harmon craig spoke out publicly on the dangerous warming effects of carbon dioxide in starting in the early 1960s.

“these leading scientists of a previous generation were acting as sentinels. they were calling attention to an issue that was not yet publicly recognized,” she said. “and as far as we can tell from the archival record, most of the political leaders to whom they reached out were at least receptive to being made aware of the issue.”

broecker, of columbia university, remains an active and leading climate researcher who continues to speak out.

with scientific issues such as climate change that require some form of government intervention for solutions to be adopted, the denial of facts is not an issue of scientific illiteracy, she said. it stems from political and ideological loyalties.

“actually among republicans, higher levels of education correlates with higher levels of rejection of climate science,” she said.

this rejection stems from a deeply-rooted belief in free market policies or fear that regulation might lead to a “restriction on freedoms,” she said.

“this explains why climate change denial is so much more prevalent in the united states than anywhere else in the world,” she said. “we have in the united states a deeply rooted belief that the government who governs best governs least.”

“our opponents are motivated by values, and that’s not necessarily wrong. and their arguments do work in part because they do resonate with the values of so many americans, i mean who doesn’t believe in freedom?” she said.

so oreskes urged scientists to speak to values that all of us share: “the value of fairness, which includes protecting innocent people from getting hurt; the value of accountability, that those who made a problem have an obligation to address it; and the value of realism, accepting the reality that markets can fail and sometimes there are problems that we have to address when the market doesn’t work efficiently, or doesn’t work at all; and the values of creativity and technological leadership  and hard work, of rolling up our sleeves and getting the job done.”

rising extremes of droughts, floods or food shortages can reduce a country’s political stability and cultural tolerance, warned scientists at the american association for the advancements of science conference in boston this weekend.

as global temperatures continue to rise, these and other environmental threats are expected to increase.

“what you have here is a model where different forms of ecological threat are producing stronger cultural institutions,” but stronger in the sense of more regimented, said joshua conrad jackson, a psychologist at the university of north carolina, chapel hill. “that could carry over into intergenerational changes in cultural institutions.”

if a parent raises a child in a time of high ecological threat, they are likely to raise that child with stricter rules and regulations and tightened cultural norms, jackson said.

a team of social scientists and climatologists presented their preliminary findings from surveys historical cultural and climate records. they found that higher rates of ecological threat generally lead to stricter, more intolerant cultural norms in a society and higher rates of violence.

jackson, with michele gelfand at the university of maryland, found that ecological threats like food deprivation,  pathogen prevalence, and natural disasters lead to higher pressures to marry, more moralizing religions, and autocratic leadership.

other researchers discussed the ability to detect the influence of past environmental changes on culture, and whether these changes affected a country’s political stability.

eric jones, an environmental anthropologist at the university of texas, found that after events such as a natural disaster, people tend to band together for at least a short period of time. but if the ecological event is chronic or repeated, like a drought that lasts for years, there is “less to give” and less sharing and redistribution within the community, he said.

in prehistoric societies, ecological changes led to periods of political upheaval and violence, said timothy kohler, an archaeologist at washington state university. after periods of extended drought in ancient communities like the pueblo in the southwestern united states, kohler found evidence of high rates of violent trauma on the bones and skeletal fragments in communities that had high rates of societal inequality.

it is especially difficult for communities to adapt to environmental change when their population grows because there are fewer available natural resources, he said. many historians point to more contemporary events such as the droughts that created the dust bowl during the 1930s, when an estimated 40 percent of the population fled oklahoma family farmsteads.

leadership can topple as well.

“climate events bring an end to regimes of relatively high inequality, but also are accompanied by violence. we need to be concerned with the degree of inequality as well as population density if we want to avoid violent outcomes,” kohler said.

kohler wrapped up the panel by discussing the implications for the future, where population and ecological threats are expected to increase.

“thinking ahead to a world with 25 percent more people than we have now in 30 years or so, you could borrow a term from the 1960s — is this going to be a more uptight world than the world we live in now?”