There was some basis for concern. If carbon dioxide emissions were the only factor affecting global climate, it is clear that increased emissions would tend to produce warmer temperatures over time. Those temperatures could create problems that rational societies would want to address.
But carbon dioxide emissions are not the only factor affecting global climate. Solar activity and water evaporation and countless other things do, too. Climate scientists do not fully understand those things and how they interact. It is rational for society to want to learn more.
Unfortunately, the cadre of climate scientists who have dominated public discussion and have controlled the IPCC have been demonstrated to be far, far less than trustworthy. Like the theorists who invented epicycles to explain away the failure of Ptolemaic theory to account for astronomical observations, they have distorted science in the interest of something that resembles religious dogma.
The secular religion of global warming has all the elements of a religious faith: original sin (we are polluting the planet), ritual (separate your waste for recycling), redemption (renounce economic growth) and the sale of indulgences (carbon offsets). We are told that we must have faith (all argument must end, as Al Gore likes to say) and must persecute heretics (global warming skeptics are like Holocaust deniers, we are told).
People in the grip of such a religious frenzy evidently feel justified in lying, concealing good evidence and plucking bad evidence from whatever flimsy source may be at hand.
The rest of us, and judging from polls that includes most of the American people, are free to follow a more rational path. In his State of the Union Address, Barack Obama alluded to "the overwhelming evidence on climate change." But he felt obliged to add, "even if you doubt the evidence" -- an admission that the evidence is less than overwhelming. On a par with, it seems, the claims of trial lawyers and the assurances of used car salesmen.