Nobody denies that there is such a thing as a greenhouse effect. If there were not, the side of the planet facing away from the sun would be freezing every night.
There is not even a lot of controversy over temperature readings. What is fundamentally at issue are the explanations, implications and extrapolations of these temperature readings.
The party line of those who say that we are heading for a global warming crisis of epic proportions is that human activities generating carbon dioxide are key factors responsible for the warming that has taken place in recent times.
The problem with this reasoning is that the temperatures rose first and then the carbon dioxide levels rose. Some scientists say that the warming created the increased carbon dioxide, rather than vice versa.
Many natural factors, including variations in the amount of heat put out by the sun, can cause the earth to heat or cool.
The bigger problem is that this has long since become a crusade rather than an exercise in evidence or logic. Too many people are too committed to risk it all on a roll of the dice, which is what turning to empirical evidence is.
Those who have a big stake in global warming hysteria are unlikely to show up at the conference in New York, and unfortunately that includes much of the media.