Given the complexity of climate, no confident prediction about future global mean temperature or its impact can be made

See Climate Change: What Do Scientists Say? by Richard Lindzen, emeritus professor of atmospheric sciences at MIT.

"I’m an atmospheric physicist. I’ve published more than 200 scientific papers. For 30 years I taught at MIT, during which time the climate has changed remarkably little. But the cry of “global warming” has grown ever more shrill. In fact, it seems that the less the climate changes, the louder the voices of the climate alarmists get. So, let’s clear the air and create a more accurate picture of where we really stand on the issue of global warming or, as it is now called—“climate change.”

There are basically three groups of people dealing with this issue. Groups one and two are scientists. Group three consists mostly, at its core, of politicians, environmentalists and the media.

Group one is associated with the scientific part of the United Nation’s International Panel on Climate Change or IPCC (Working Group 1). These are scientists who mostly believe that recent climate change is primarily due to man’s burning of fossil fuels—oil, coal and natural gas. This releases C02, carbon dioxide, into the atmosphere and, they believe, this might eventually dangerously heat the planet.

Group two is made up of scientists who don’t see this as an especially serious problem. This is the group I belong to. We’re usually referred to as skeptics.

We note that there are many reasons why the climate changes—the sun, clouds, oceans, the orbital variations of the earth, as well as a myriad of other inputs. None of these is fully understood, and there is no evidence that CO2 emissions are the dominant factor.

But actually there is much agreement between both groups of scientists. The following are such points of agreement:
1) The climate is always changing.

2) CO2 is a greenhouse gas without which life on earth is not possible, but adding it to the atmosphere should lead to some warming.

3) Atmospheric levels of CO2 have been increasing since the end of the Little Ice Age in the 19th century.

4) Over this period (the past two centuries), the global mean temperature has increased slightly and erratically by about 1.8 degrees Fahrenheit or one degree Celsius; but only since the 1960’s have man’s greenhouse emissions been sufficient to play a role.

5) Given the complexity of climate, no confident prediction about future global mean temperature or its impact can be made. The IPCC acknowledged in its own 2007 report that “The long-term prediction of future climate states is not possible.”

Most importantly, the scenario that the burning of fossil fuel leads to catastrophe isn’t part of what either group asserts. So why are so many people worried, indeed, panic stricken about this issue. Here’s where Group Three comes in—the politicians, environmentalists, and media.

Global warming alarmism provides them, more than any other issue, with the things they most want: For politicians it’s money and power. For environmentalists it’s money for their organizations and confirmation of their near religious devotion to the idea that man is a destructive force acting upon nature. And for the media it’s ideology, money, and headlines. Doomsday scenarios sell.

Meanwhile, over the last decade, scientists outside of climate physics have jumped on the bandwagon, publishing papers blaming global warming for everything from acne to the Syrian civil war. And crony capitalists have eagerly grabbed for the subsidies that governments have so lavishly provided.

Unfortunately, group three is winning the argument because they have drowned out the serious debate that should be going on. But while politicians, environmentalists and media types can waste a lot of money and scare a lot of people, they won’t be able to bury the truth. The climate will have the final word on that."