Michael Mann’s “hockey stick graph” was constructed with computers (“garbage in, garbage out”) to “prove” that a wonderfully steady climate prevailed over the world for nearly a thousand years and then suddenly, in the twentieth century, Modern Industrial Man with his disgraceful appetite for material things that make his life longer, pleasanter and easier, started polluting the air and water and  earth with disgusting “emissions” that heated the planet, which is now set to become so hot that … Oh, all sorts of dire consequences will follow. And drastic, impoverishing remedies must be hastily applied world-wide by diktat. The population of the world must shrink, so have no children and die early. If you insist on surviving, go back to living hand to mouth like your primitive ancestors.

We may be exaggerating a little, but not diverging from the broad  truth.

A report by The Science and Environmental Policy Project points out:

The first two assessment reports of the UN IPCC included charts showing temperature change for the last 1000 years that included the Medieval Warm Period and the Little Ice Age. The Summary for Policymakers of the 2001 Third Assessment Report eliminated these temperature changes and substituted Mann’s now infamous “hockey stick” graph produced by statistical techniques that purport to show that temperatures were relatively stable for about 900 years then shot up in the 20th Century. The results of a computer model trumps physical evidence. The research was “peer reviewed” but not available for independent review. …

If Mr. Mann had been open with his research data and methods, and permitted their review by independent scientists, his errors may have been appropriately corrected in a scientific setting rather than in a political one. Instead, he chose to withhold the information. It is imperative to understand the full extent to which Mann’s now discredited study distorted the climate and energy policies of the US government – at great cost to the taxpayer and energy consumer.

Commenting on this, John Hinderaker writes at PowerLine:

It is a remarkable fact that warmists claim the right to keep their data secret and avoid any critical assessment of their work, while at the same time demanding that every country in the world fashion its energy policies on the basis of their alleged findings. No doubt there is a precedent, somewhere, for such arrogance. But I am not sure there is any precedent, anywhere, for governments being stupid enough to accede to such unreasonable demands.

Yes, it would be a far better, though probably harder, aim for the citizens of democracies to lower the level of stupidity in their governments, rather than the temperature of the earth.