NASA has played a key role in one of the greatest periods of scientific progress in history. It is uniquely positioned to collect the most comprehensive data on our biosphere.

For example, recently generated NASA data enabled scientists to finally understand the Gulf Stream warming mechanism and its effect on European weather. Such data will allow us to improve our models, resulting in better seasonal forecasts.

NASA's Aqua satellite is showing that water vapor, the dominant greenhouse gas, works to offset the effect of carbon dioxide (CO2). This information, contrary to the assumption used in all the warming models, is ignored by global warming alarmists.

Climate understanding and critical decision making require comprehensive data about our planet's land, sea, and atmosphere. Without an adequate satellite system to provide such data, policy efforts and monitoring international environmental agreements are doomed to failure. Our satellite monitoring capability is being crippled by interagency wrangling and federal budget issues. As much as a third of our satellites need replacing in the next couple of years.

NASA should be at the forefront in the collection of scientific evidence and debunking the current hysteria over human-caused, or Anthropogenic Global Warming (AGW). Unfortunately, it is becoming just another agency caught up in the politics of global warming, or worse, politicized science. Advocacy is replacing objective evaluation of data, while scientific data is being ignored in favor of emotions and politics.

There are excellent correlations between the regular fluctuations of the Sun and the Earth's temperature, while scientists cannot find a relationship between industrial activity, energy consumption, and global temperatures. But global warming is an issue no longer being decided in the scientific arena.

Saying the Earth is warming is to state the obvious. Since the end of the ice age, the Earth's temperature has increased approximately 16 degrees Fahrenheit and sea levels have risen a total of 300 feet. That is certain and measurable evidence of warming, but it is not evidence of AGW - human-caused warming.

We can track the temperature of the Earth back for millennia. Knowing the temperature of the Earth, past or present, is a matter of collecting data, analyzing it, and coming up with the best answer to account for the data. Collecting such data on a global basis is a NASA forte.

I believe in global climate change, but there is no way that humans can influence the temperature of our planet to any measurable degree with the tools currently at their disposal. Any human contribution to global temperature change is lost in the noise of terrestrial and cosmic factors.

Our beautiful home planet has been warming and cooling for the last 4.8 billion years. Most recently, it has been warming - be it ever so slightly - but there is nothing unusual about it! The changes and rates of change in the Earth's temperature, just since the Industrial Revolution, have occurred many times in our climatic history. While climate scientists generally agree that the Earth's temperature is always changing, not many of them would say that humans are responsible for those changes.

None of this is to say there are not legitimate reasons to restrict emissions of any number of chemicals into the atmosphere. We should just not fool ourselves into thinking we will change the temperature of the Earth by doing so.

In a December 2007 Senate report, 400 prominent scientists signed a letter pointing out that climate change was a well-known natural phenomenon, and that adapting to it is far more sensible than attempting to prevent it. Their ranks included experts in climatology, geology, oceanography, biology, glaciology, biogeography, meteorology, economics, chemistry, mathematics, environmental sciences, engineering, physics, and paleo-climatology. Their message: When changes are gradual, man has an almost infinite ability to adapt and evolve.

The fearmongers of global warming base their case on the correlation between CO2 and global temperature, even though we cannot be sure which is cause and which is effect. Historically, temperature increases have preceded high CO2 levels, and there have been periods when atmospheric CO2 levels were as much as 16 times what they are now, periods characterized not by warming but by glaciation. You might have to go back half a million years to match our current level of atmospheric CO2, but you only have to go back to the Medieval Warming Period, from the 10th to the 14th Century, to find an intense global warming episode, followed immediately by the drastic cooling of the Little Ice Age. Neither of these events were caused by variations in CO2 levels.

Even though CO2 is a relatively minor constituent of "greenhouse gases," alarmists have made it the whipping boy for global warming (probably because they know how fruitless it would be to propose controlling other principal constituents, H2O, CH4, and N2O). Since human activity does contribute a tiny portion of atmospheric CO2, they blame us for global warming.

Other inconvenient facts ignored by the activists: Carbon dioxide is a nonpolluting gas, essential for plant photosynthesis. Higher concentrations of CO2 in the atmosphere produce bigger harvests.

In spite of warnings of severe consequences from rising seas, droughts, severe weather, species extinction, and other disasters, the U.S. has not been stampeded into going along with the recommendations of the UN Panel on Climate Change - so far. Even though evidence supports the American position, we have begun to show signs of caving in to the alarmists.

With scientific evidence going out of style, emotional arguments and anecdotal data are ruling the day. The media subjects us to one frightening image of environmental nightmare after another, linking each to global warming. Journalists and activist scientists use hurricanes, wildfires, and starving polar bears to appeal to our emotions, not to our reason. They are far more concerned with anecdotal observations, such as the frozen sea ice inside the Arctic Circle, than they are with understanding why it is happening and how frequently it has occurred in the past.

After warnings that 2007 would be the hottest year on record and a record year for hurricanes, what we experienced was the coolest year since 2001 and, by some measures, the most benign hurricane season in the Northern Hemisphere in three decades.

Even though recent changes in our atmosphere are all within the bounds of the Earth's natural variability, a growing number of people are willing to throw away trillions of dollars on fruitless solutions. Why do we allow emotional appeals and anecdotal data to shape our conclusions and influence our expenditures with the science and technology we have available at our fingertips?

The situation is complex, but the sad state of scientific literacy in America today is partially to blame for belief in AGW. When a 2006 National Science Foundation survey found 25 percent of Americans not knowing the Earth revolves around the Sun, you know that science education is at a new low and society is vulnerable to the emotional appeal of AGW. And don't underestimate the role of politics and political correctness.

The public debate should focus on the real cause of global temperature change and whether we can do anything about it. Is global warming a natural inevitability, or is it AGW - human caused?

The conflict over AGW has deteriorated into a religious war; a war between true believers in human-caused global warming and nonbelievers; between those who accept AGW on faith and those who consider themselves more sensible and better informed. "True believers" are beyond being interested in evidence; it is impossible to reason a person out of positions they have not been reasoned into.

It doesn't help that NASA scientist James Hansen was one of the early alarmists claiming humans caused global warming. Hansen is a political activist who spreads fear even when NASA's own data contradict him.

Warming in the upper atmosphere should occur before any surface warming effect, but NASA's own data show that has not been happening. Global temperature readings - accurate to 0.1 degree Celsius - are gathered by orbiting satellites. Interestingly, in the 18 years those satellites have been recording global temperatures, they have actually shown a slight decrease in average temperatures.

Hansen is currently calling for a reduction of atmospheric CO2 by 10 percent and a moratorium on coal-fired power plants, while claiming the Bush administration is censoring him. Other so-called scientists are saying the world must bring carbon emissions to near zero to keep temperatures from rising.

In today's politically correct environment, many are reluctant to dispute the popular wisdom; when they do, they are frequently ignored. When NASA Administrator Michael Griffin, Hansen's boss and a distinguished scientist in his own right, attempted to draw a distinction between Hansen's personal and political views and the science conducted by his agency, he was soon forced to back off.

It is the true believers who, when they have no facts on their side, try to silence their critics. When former NASA mathematician Ferenc Miskolczi pointed out that "greenhouse warming" may be mathematically impossible, NASA would not allow him to publish his work. Miskolczi dared to question the simplifying assumption in the warming model that the atmosphere is infinitely thick. He pointed out that when you use the correct thickness - about 65 miles - the greenhouse effect disappears! Ergo: no AGW. Miskolczi resigned in disgust and published his proof in the peerreviewed Hungarian journal Weather.

For nearly a decade now, there has been no global warming. Even though atmospheric CO2 has continued to accumulate - up about 4 percent in the last 10 years - the global mean temperature has remained flat. That should raise obvious questions about CO2 being the cause of climate change.

Instead, AGW enthusiasts are embracing more regulation, greater government spending, and higher taxes in a futile attempt to control what is beyond our control - the Earth's temperature. One of their political objectives, unstated of course, is the transfer of wealth from rich nations to poor nations or, as the social engineers put it, from the North to the South, which may be their real agenda.

At the Bali Conference on Climate Change in December 2007, the poor nations insisted that the costs of technology to limit emissions and other impacts of climate change on their countries be paid by the rich nations. Most anticipated a windfall of money flowing into their countries to develop technology or purchase carbon credits. In this scenario, selling allotments for CO2 emissions would provide a temporary boost to their own cash flow, while severely limiting the economic development of those countries purchasing the carbon credits.

In the face of overwhelming evidence for natural temperature variation, proponents of AGW are resorting to a precautionary argument: "We must do something just in case we are responsible, because the consequences are too terrible if we are to blame and do nothing." They hope to stampede government entities into committing huge amounts of money before their fraud is completely exposed - before science and truth save the day.

Politicians think they can reverse global warming by stabilizing CO2 emissions with a cockamamie scheme of "cap and trade." A government entity would sell CO2 allocations to those industries producing it. The trillions of dollars in new taxes and devastation to the economy would be justified by claiming it will lower the temperature of the Earth. This rationalization is dependent on two assumptions: (1) that CO2 is responsible for the cause of changes in the Earth's temperature, and (2) a warmer Earth would be bad for humanity.

The reality is that atmospheric CO2 has a minimal impact on greenhouse gases and world temperature. Water vapor is responsible for 95 percent of the greenhouse effect. CO2 contributes just 3.6 percent, with human activity responsible for only 3.2 percent of that. That is why some studies claim CO2 levels are largely irrelevant to global warming.

Without the greenhouse effect to keep our world warm, the planet would have an average temperature of minus 18 degrees Celsius. Because we do have it, the temperature is a comfortable plus 15 degrees Celsius. Based on the seasonal and geographic distribution of any projected warming, a good case can be made that a warmer average temperature would be even more beneficial for humans.

For a tiny fraction of the trillions of dollars a cap-and-trade system would eventually cost the United States, we could pay for development of clean coal, oil-shale recovery systems, and nuclear power, and have enough left over to pay for exploration of our solar system.

By law, NASA cannot involve itself in politics, but it can surely champion the role of science to inform politicians. With so many uninformed and misguided politicians ignoring the available science, NASA should fill the void. NASA is synonymous with science. Allowing our priorities to drift away from hard science is tantamount to embracing decadence. NASA will surely suffer; and politicizing science is killing it.

I do see hopeful signs that some true believers are beginning to harbor doubts about AGW. Let's hope that NASA can focus the global warming discussion back on scientific evidence before we perpetrate an economic disaster on ourselves.

Physicist Walter Cunningham, an award-winning NASA Apollo 7 Astronaut, was the recipient of the NASA Exceptional Service Medal and Navy Astronaut Wings, the 1969 Haley Astronautics Award and named to Named to the International Space Hall of Fame. Cunningham is a member of the American Geophysical Union and fellow of the American Astronautical Society. He also worked as a scientist for the RAND Corporation prior to joining NASA. While with RAND, he worked on classified defense studies and problems of the earth's magnetosphere. He has accumulated more than 4,500 hours of flying time, including more than 3,400 in jet aircraft and 263 hours in space.