What you don’t know can indeed hurt you.

It can hurt you a lot.

For example, as head of the Atlanta-based Centers for Disease Control and Prevention, the nation’s top public health agency, Dr. Julie Gerberding was supposed to brief Congress this week about the health implications of global warming.

But before she could testify, the guts of her prepared presentation - more than half its original 14 pages - were removed under orders from the Bush White House.

Now, President Bush had every right to change that testimony. Gerberding is a presidential appointee, and as such she is expected to toe the president’s line.

The problem is, altering Gerberding’s testimony does not alter the reality she was trying to describe. If global warming poses health risks to the American people, as she believes, those risks will continue even if expert warnings are muted or even silenced. You can’t change reality by refusing to acknowledge it. We’ve tried that; it doesn’t work.

Five years ago, Gen. Erik Shinseki tried to warn that occupying Iraq would require hundreds of thousands of troops. Administration officials responded by publicly berating and humiliating the Army chief of staff, and other officers got the message to stay silent.

But the facts hadn’t changed; we did need those hundreds of thousands of troops, and when the time came, we didn’t have them.

Likewise, when Mike Chertoff, secretary of Homeland Security, and Michael Brown, head of the Federal Emergency Management Agency, went on national television after Hurricane Katrina to deny that tens of thousands of our fellow Americans were trapped in New Orleans without food or clean water, their claims did not alter the fact that we could turn on our television sets and see for ourselves that they were wrong. Their denials did not alter reality, but they did delay needed assistance.

This week, Gerberding was ready to tell Congress that the CDC considers climate change “a serious public health concern.” According to a leaked copy of her original remarks, she was ready to warn of specific challenges the country might face, from longer heat waves to tropical diseases.

However, “with adequate notice and a vigorous response,” she wanted to tell Congress, “the ill health effects of many exposures from climate change can be dampened.”

All those words were stricken from her testimony. She was barred from delivering the adequate notice she thought we needed, although she later was able to respond to congressional questions.

According to a White House spokesman, Gerberding’s testimony was altered not because it contradicted the president’s ideology, but because it did not match science produced by the International Panel on Climate Change, the United Nations commission convened to produce scientific consensus on global warming.

Now, that’s a suspect defense from the get-go. The Bush White House defending the scientific integrity of the UN climate report? And sure enough, a comparison of Gerberding’s prepared testimony against the IPCC report shows no contradiction whatsoever.

For instance, the White House did not let Gerberding say that “catastrophic weather events such as heat waves and hurricanes are expected to become more frequent, severe and costly.”

What does the IPCC say? Warmer and more frequent hot days and nights are “virtually certain,” and it’s likely that “future tropical cyclones (typhoons and hurricanes) will become more intense.”

Gerberding also wanted to warn us that future hurricanes could disrupt sewage treatment plants and taint water supplies, exposing large numbers of Americans to deadly diseases.

And the U.N. report? It issues the very same warning, citing as examples the aftermath of hurricanes Katrina and Rita, “where contamination of water supplies with fecal bacteria led to many cases of diarrheal illness and some deaths.”

On every point, Gerberding’s testimony jibes with the IPCC report. It was censored not because it contradicted accepted science, but because it reflected that science. It’s a heckuva way to run a country.

Email Jay Bookman at jbookman@ajc.com

© 2007 The Atlanta Journal-Constitution