While literally killing messengers who bear bad news has gone by the wayside, the spirit of the practice appears alive and well.

Just ask James Hansen.

Hansen is director of NASA's Goodard Institute for Space Studies and is regarded by many as one of the nation's leading experts on climate change.

Hansen was recently ordered to run his lectures, papers, Internet postings and requests for interviews through NASA's public affairs staff. The new rules came after Hansen gave a lecture at the American Geophysical Union highlighting the need for prompt reductions in emissions that are linked to global warming.

The scientist said he was being censored for not being in sync with the administration's position on global warming, while NASA officials say they want to make sure that Hansen and other NASA scientists were not making policy statements.

Hansen is not the first expert who has been gagged for contradicting the prevailing wisdom of political leaders. The Food and Drug Administration, for example, attempted to block a report showing that rate of death and heart disease among Vioxx users was greater than originally stated.

The Intelligent Design-Evolution debate is rooted in a similar silence-the-messenger philosophy. In Utah, Sen. D. Chris Buttars is pushing legislation that would require science teachers to tell students that there are opposing scientific theories to evolution and the origin of life. Scientists say there are no credible alternatives to evolution and there are no scientific theories at all on the origins of life. In truth, Buttars simply wants his religious views to have a place in public school. In his ideal world, those pesky scientists would shut up.

Keeping people "on message" may be good public-relations strategy, but it is not how science works. Science is about following the evidence where it leads, not presenting a particular message that has been decided upon in advance. Scientists find truth through experimentation, observation and discussion.

Scientific findings may be rigorously cross-checked in the verification process. This quickly exposes flaws and allows false notions to be discarded. It allows for refinement of theories that are moving in the right direction.

Thus, science is a self-correcting discipline. Incorrect information, even when it's part of long-standing conventional wisdom, can be laid aside as soon as better data, which is closer to the truth, show up.

Even an incorrect theory has value in reinforcing truth through the scientific process undertaken to disprove the error.

For instance, the "theory" of BYU physics professor Steven E. Jones that explosives brought down one of the buildings in the World Trade Center complex forces other scientists to disprove it. Jones bases his ideas on religious precepts, so he's actually more like Sen. Buttars than Galileo. But the point remains that the process of examination should ultimately illuminate the truth, whatever it is.

The scientific process is essential in answering questions about global warming. Are current global conditions a temporary aberration or the harbinger of a long-lasting change in climate? It's a question upon which may rest the fate of the world.

We should let scientists find the answers. We should let them speak freely.

We should not make them carry the burden of public relations, which is often something less than honest.