As a CIA senior economic analyst I worked on environmental issues in the early 90s and thought there was no reasonable doubt that CO2 emissions from burning fossil fuels were causing the planet to warm, with potentially catastrophic consequences within a few decades. Scientists in the 19th century already knew that CO2 was a heat-trapping gas but thought that it wouldn't cause major problems for centuries since they didn't anticipate the huge increase in fossil fuel use in the 20th century.

The 1992 book that convinced me was "The Economics of Global Warming", by William Cline, a respected economist at the Institute for International Economics. Like a good economist (or CIA analyst) he looked the data and the arguments on both sides, and concluded that the case for human-caused warming was very strong, and the likely consequences very bad, so the logical response was to begin taking remedial action. 

Since essentially all economists believe in free markets, he pointed out that the reason they don't work in this case is that the users of fossil fuels don't pay the full cost of using them because they don't pay for the environmental damage they do. The obvious policy solution is a "carbon tax", phased in gradually over a period of years so that businesses and consumers would have time to adjust. And while the demand for fossil fuels is not price-sensitive in the short term (demand is "inelastic" in economics jargon), it becomes much more sensitive when the price increase is sustained for years or decades.

Cline wrote a follow-up book in 2011,  "Carbon Abatement Costs and Climate Change Finance", which concluded that the costs are actually quite modest, in comparison with the magnitude of the problem--about 0.25 percent of global GDP in 2030, rising to 1.2 percent in 2050. 

Since 2011 the magnitude of the problem has become much more obvious--droughts,  wildfires, crop failures, rising sea levels, and shrinking of both polar ice caps and most of the world's glaciers.

The time to act is NOW!