The recent revelation that the Sahara was humid and hospitable to human communities from 6,000 to 10,500-years ago and the new theory that climate change may have precipitated the fall of the ancient Cambodian city of Angkor sometime after 1200 also will contribute to public doubts.
While the new evidence suggests that scientists still have much to learn about the climate, it also indicates that the message that "the science on climate change is settled" likely is nothing more than a foolish and dishonest effort to shut off debate.
In fact, the scientific debate on the causes of global warming may be just beginning.
Scientists understand only very little about how our extremely complex climate mechanisms operate. Their understandings are so limited that they're still trying to devise methods to measure the Earth's current temperature accurately and to evaluate properly what data exist from the past.
Many scientists agree the earth experienced a "Medieval Warm Period" from the 10th to 14th centuries, and a cooler "Little Ice Age" from roughly 1650 to 1850. As these events pre-date the widespread burning of fossil fuels, it is assumed they were natural climate variations, but science can't say definitively why.
Without accurate temperature measurements, it is impossible to know recent climate trends, let alone what caused them or what will happen later.
And without understanding how natural forces affect climate, scientists can't eliminate the possibility of natural causes for any climate fluctuations, making it difficult to know which, if any, climate changes are definitively influenced by human activities.
Scientists probably won't fully understand climate during the lifetime of anyone alive today.
The global warming debate seems ripe for a big injection of honesty. Scientists should make clear when they are speaking as scientists and when they are merely sharing political opinions like any other citizen.
Scientists who make claims of a "fact" that can't be proved - through the scientific method rather than via "consensus" should be called on the carpet - especially when they're acting with government grant money or employed by a government agency. Scientists, after all, are tasked with discovering the truth, not inventing it.
Few environmental activists who embrace the global warming theory are supporting alternatives to oil, such as increased drilling for natural gas and expanded use of nuclear and hydroelectric power.
Even Al Gore, the leading doomsayer on global warming, is no prince of conservation. While Gore preaches that common citizens should deprive themselves to serve the anti-global warming cause, he skips much of his own advice. Gore uses private planes - to promote his anti-global warming movie, no less - apparently deeming the first-class commercial travel most Americans would consider luxurious too much a sacrifice for him to make for the planet.
And Gore's three homes don't use "green energy," although for just "a few extra pennies per kilowatt hour," a simple call to a utility company would be all it would take to supply at least some of Gore's homes with wind-generated energy.
Gore and the true believers who flock to his banner apparently are only willing to pay lip service to what they call "the single greatest danger facing the Earth."
Avid environmentalists open themselves to charges of hypocrisy when they call global warming "an inconvenient truth," yet rarely are spotted doing anything even remotely inconvenient to fight it.
Honesty should be one global warming policy we all can agree upon.
David Ridenour is vice president of The National Center for Public Policy Research (http://www.nationalcenter.org" Target="_BLANK">http://www.nationalcenter.org), a conservative, free-market think tank.