Ever since Prof. James Hansen's 1988 testimony before a Senate committee featuring Al Gore, Americans have been treated to a steady drumbeat of alarm over the Menace of Global Warming. Hansen, Gore, and a host of enviro organizations have proclaimed that human addiction to carbon combustion is causing global temperatures to rise alarmingly, and that governments must take unprecedented and desperate measures to reduce emissions.
The alarmists' central argument was, and is, that a doubling of the present atmospheric concentration of CO2 will produce global temperature increases of as much as 8.6 degrees C by the end of this century. This would produce unimaginable catastrophes: droughts, flood, hurricanes, drowned coastal cities, plague, species extinction, and more.
Skeptics noted that the Medieval Warm Period (900-1200 A.D.) brought better weather, improved nutrition, and a wonderful flowering of civilization. More atmospheric CO2 would spur plant growth, and warmer winters would help New Englanders by lengthening their growing seasons, reducing their heating bills, making their travels easier and safer, and disadvantaging the competing ski areas further south.
The warming zealots scorned such observations. Their technique was to spend billions of taxpayer dollars on computerized climate models. The scientists who controlled both the models and the input data churned out scary scenarios aimed at terrifying politicians into approving the taxes, rationing, subsidies and penalties needed to curb greenhouse gas production worldwide.
The fact that the models failed to reproduce the known temperature record of the past century gave them no pause whatever. The charlatans simply invented unobservable climactic effects that magically led to the positive feedback that assured the approach of Al Gore's Heat Death.
The United Nation's climate body, the IPCC, issued periodic reports attributed to "over 2,000 climate scientists", but actually produced by a very small number sucking up millions in research dollars, plus the ever-present political flacks who actually crafted the "summary for policymakers".