The subject of climate change has returned to news headlines lately because of the president's speech at Georgetown U. However, the response by the broader population was not enthusiastic endorsement, but rather, intensification of the controversy. It's helpful to inquire how the transition came about.

It was 25 years ago this July that a Congressional hearing was staged to promote the idea that CO2 emitted by mankind burning fossil fuels is causing the globe to heat up excessively. Then-senator Al Gore was a major booster of the idea, which was subsequently emphasized in his book Earth in the Balance.

About 8 years ago, the belief was near-universal that global warming was real and dangerous. Since then, new scientific data has emerged showing it isn't so. Moreover, people have learned that the cost of complying with proposals to eliminate CO2 will be very high.

The foremost scientific observation is that there has been no warming for 15 years. Meanwhile, CO2 in the atmosphere has been steadily increasing, and recently crossed the "milestone" of 400 parts-per-million (ppm) in the atmosphere. The computer models, which have built-in the assumption that CO2 will cause temperature to rise, have predicted temperature-rise numbers that are totally and obviously in disagreement with observations. As a result, the models have lost credibility.

A series of satellites has been monitoring temperatures over the entire globe for 1/3 of a century by now, and no net global warming has been observed. When Al Gore began his promotion, that satellite data had accumulated for only about 7 years, too short a period to detect a trend.

Starting around 2006, investigators found that a high percentage of official temperature measurement stations were not reading accurately, due to problems of positioning or maintenance, along with the "urban heat island" effect. Therefore the land-based temperatures reported became suspect.

Somewhere in the 1990s, a small community of scientists began to affiliate (mostly via the internet) who didn't accept the "common wisdom" that CO2 causes global warming. They were at first ignored, but when their numbers grew to significant size, they were denounced as "climate deniers" -- an epithet meant to sound like "Holocaust deniers." Their preferred name is "climate skeptics."

Meanwhile, the large majority of scientists, and certainly the nonscientific public, went along with the prevailing belief that CO2 causes global warming. The scientific leaders fostering that position became known as the "climate establishment." They controlled the funding, the conferences, the journal editorial policies, etc. Until quite recently, there was a very solid wall known as "the consensus" defending that establishment policy.

But that has all crumbled now. The major "ClimateGate" scandal of 2009 revealed the deceit that the leading theorists had been practicing, and showed that scientists can be just as conniving and disingenuous as ordinary mortals. Thereafter, increasing numbers of competent scientists looked more closely at the data, and switched to the "climate skeptic" position.

The appeal to "consensus" dissolved when people remembered that Galileo and Einstein were certainly opposed to the establishment view. Actually, consensus has no place at all in science. Facts -- measurements and observations -- drive the progress of science, and data trumps theory.

Plus, people recalled from third-grade science class that animals and plants exchange CO2 and O2, and both are necessary for life.

Today, the assertion that CO2 is about to cause catastrophic change is categorized as "global warming alarmism." For several decades, the media have been uniformly aligned with the position of the global warming alarmists, and anyone who spoke against the theory was ridiculed. But because of the pre-eminence of data, among scientists there has been a gradual erosion of support for the global warming hypothesis.

Meanwhile, the public lost interest in the entire topic. The media were far behind the public. Only in late 2012 and 2013 have most of the major media players acknowledged that there is disagreement on the subject. Here's a typical snippet from the New York Times:

This January, as President Obama began his second term, the Pew Research Center asked Americans to list their policy priorities for 2013. Huge majorities cited jobs and the economy; sizable majorities cited health care costs and entitlement reform; more modest majorities cited fighting poverty and reforming the tax code. Down at the bottom of the list, with less than 40 percent support in each case, were gun control, immigration and climate change.

                                                                                                    Ross Douthat, "The Great Disconnect"

Lately, over in Europe, a new type of alarm is occurring as people in Germany and England look at their electric bills. The policies put in place by their governments to limit CO2 output have turned out to be terribly expensive, and the people want to stop funding "green energy" projects.

Meanwhile, in the USA, the administration (especially the EPA) is planning a new offensive against CO2, introducing various new taxes and regulations. Colloquially, that's termed the "War on Coal." The incumbent government is so ideologically committed to opposing CO2, and so inattentive to scientific data, that it is oblivious to the costs that will be incurred. Learning anything from the Europeans is out of fashion in Washington these days.

Summarizing where the scientific situation stands today:

1. There is NO consensus about the effect of CO2 on temperature.

2. There is agreement that natural causes of climate change have always played a role.

3. There is disagreement about the relative importance of natural vs man-made influences on climate. Professor Richard Lindzen of MIT stated the "climate skeptics" position succinctly: "That mankind has an effect on climate is trivially true and numerically insignificant." Others (Al Gore, etc.) invoke the computer models and predict catastrophic sea-level rise.

4. Our response to changing climate should be adaptation; efforts at mitigation are futile (and expensive!).

5. The debate is whether we have centuries or only decades to prepare for changes in climate.

Despite the full support of the scientific, political, and meda establishments, global warming/climate change was unable to gain traction as an exploitable, ongoing crisis for one simple reason: it contradicted the real world. What other current agendas are due to be trumped by the data?