The 1970’s were the decade of research on global warming. This was not necessarily a delaying tactic on the part of the fossil fuel companies—although later on, when they knew the scope of the problem and understood its probable implications for their business model and revenue stream, continually insisting on the need for more research, and downplaying the urgency of taking action to reduce emissions, became a common ploy, although not a very successful one.
There was still a lot of genuine uncertainty. Emissions from coal-fired plants contain water vapour which might produce more clouds which could have a cooling effect. Other emissions like sulfur dioxide could also produce cooling. And what about the natural sinks: the oceans, trees, agriculture, soils and forests? Maybe more carbon dioxide was good for growing plants and would increase agricultural productivity? You couldn’t rule it out.
What about the oceans? The oceans are an enormous potential reservoir of dissolved carbon dioxide. Could the oceans absorb the excess CO2 in the air and keep atmospheric concentrations more or less constant? If they did, oceans would become more acidic. Was this a problem or not? Computers were becoming more powerful, and the first computer models of the atmosphere were being developed and tested against historical data.
As the research intensified, the warnings grew louder. But then they were side-lined by what was perceived as a more imminent threat.
The 1973 oil embargo against the USA by the Organisation of Petroleum Exporting Countries, OPEC, caused huge disruption in energy markets and the US economy. Oil prices went through the roof, and since the embargo coincided with a devaluation of the US dollar, a global recession seemed certain. In November 1973, the Nixon administration announced Project Independence to promote domestic energy independence. The embargo triggered measures in the US that focused on energy conservation and the development of domestic energy sources—including the creation of the Strategic Petroleum Reserve, a 55 mph speed limit on US Highways, and the imposition of fuel economy standards.
Energy independence was now a top priority in Washington DC. Congress put checks in place to curb the use of oil and natural gas in power plants. This was good news for coal and nuclear power, and the electric power companies soon went on the offensive. In 1976, American Electric Power, an investor-owned utility, placed an advertisement in the New York Times. Under a large tableau which showed US proven reserves of coal being 20 times larger than oil and gas reserves combined, the ad warned ominously in boldface type:
If every Politician hung this on his office wall, he’d soon see the severity of our energy problem. And its solution.
The solution evidently was coal.
The ad is also notable because it is one of the first put out by one of the major energy companies to attack people who were opposed to coal. The ad proclaimed : The problems generally associated with the mining and burning of coal have been solved. Except—the destructive, regressive actions of a small minority…the fanatical environmentalists.” .
Of course it wasn’t true that the problems with coal had been solved. If anything, they would only get worse.
The Electric Power Research Institute continued to provide a fair and balanced view of the global warming issue without deliberately emphasizing the uncertainties. In 1978, an article appeared in the EPRI Journal entitled: CO2 and spaceship Earth, which included extensive quotes and analysis from climate change experts. The article accurately noted : The most widely accepted theory holds that man-induced influences on the atmosphere—mainly the generation of CO2 from fossil fuel combustion—will cause a significant rise in global temperatures over the next 25-200 years.
The same year, President Carter signed the National Climate Act. The Act established a National Climate Program intended to “enable the United States and other nations to understand and respond to natural and man-induced climate processes and their implications.”
The NAS takes notice
By now, the US National Academy of Sciences (NAS) was focused on the problem. Its first report, published in 1979, concluded that “If carbon dioxide continues to increase, the study finds no reason to doubt that climate changes will result and no reason to believe that these changes will be negligible.”. In plain English: climate change will occur and it will be significant. But how soon would these changes occur and how large would they be? Those were the big questions.
There were two more NAS reports: in 1980 and 1983. The first of these reports was almost dismissive of the issue: recommending more research and saying that the problem was not that urgent. Many scientists didn’t agree—but it was clear that there were still serious uncertainties surrounding the issue—particularly the question of the sensitivity of global temperatures to a doubling of atmospheric carbon dioxide levels.
The third report: Changing Climate : Report of the Carbon Dioxide Assessment Committee was really two reports in one: with the scientists sounding the alarm, and the economists essentially saying it was still too early to decide what to do.
The research continued. The Electric Power Research Institute published a series of reports on the issue. The institute was not denying that carbon dioxide emissions would lead to higher global temperatures. Its main focus was on how this would affect business. The June 1986 edition of the EPRI Journal reported that a study was underway using Florida Power and Light as a case study. The results were published in 1988 and concluded that “climate changes possible over the next 30 years may significantly affect the electric utility industry.” One of the key takeaways from this study was that utilities would come out ahead if they incorporated climate change predictions in their long-term planning. This report mostly focused on the potential need to increase electricity generation capacity in order to meet rising electricity demand caused by higher temperatures—an approach that framed climate change adaptation more as a business opportunity. In other words, more coal-fired power plants were needed—not fewer.
But not all the reports were so ignorant of the global implications. In an article published by the Edison Electric Institute in 1987, the authors (all three were top scientists), noted that:
Twenty years ago, the “greenhouse effect” was only the subject of speculation among a few scientists. Today as evidence for it accumulates, the greenhouse issue is debated not only among scientists, but also in federal government reports. Congressional hearings, and major newspapers and magazines…One implication of that argument is that the global temperature rise…may be just the start of a much larger increase , irreversibly ordained by the stuff we’ve already put into the air. That argument implies that if we wait until we’re sure we’ve caused a real problem, the problem may already be much larger than we realize.
Exxon engineers it
But the most sophisticated research into carbon emissions and carbon chemistry was being conducted by the chemical engineers at Exxon. Through much of the 1980s, Exxon researchers worked with university and government scientists to produce models of the climate system that resulted in several papers in peer-reviewed journals. This was genuinely good scientific work. Exxon needed to know the science, and they had some of the best chemical engineers, chemists, and of course geologists in America already on the payroll. Their work confirmed the analysis and projections being made by mainstream climate scientists that emissions of carbon dioxide would definitely lead to global warming. By the early 1980s, Exxon scientists and managers were sufficiently informed about climate science to assert that anthropogenic global warming was a potential threat to the company’s business interests. Exxon knew it had a serious problem. 
In 1988, two landmark events dramatically changed the perception of the issue and the tone of the narrative. The first was the testimony before a Congressional committee by James Hansen, the Director of the Goddard Institute for Space Studies. In June 1988, Hansen testified before a Congressional hearing on climate, presenting research that showed that there had been a warming of about a half a degree Celsius relative to the 1950-1980 average. Hansen’s team had calculated that the probability that this could be explained by natural events was only 1 percent. In other words, global warming had started. 
This was major news. The New York Times put the story on its front page under the headline: Global Warming Has Begun, Expert Tells Senate. Hansen was quoted as testifying that: “Global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and observed warning. It’s already happening now.”.
The second event was the inauguration of the Intergovernmental Panel on Climate Change, the IPCC, by the World Meteorological Organisation (WMO) and the United Nations Environment Program (UNEP). The IPCC’s goal was to assess in a comprehensive manner all the evidence relevant to understanding human-induced climate change and its potential impacts.
It was now clear to the electric power utilities and the fossil fuel companies that the US government was likely to impose restrictions on the emissions of carbon dioxide from electricity generation and the petroleum industry, and that pressure was building internationally to take measures to tackle global warning. This was the year that the electric power utilities and the fossil fuel industries started to organize.
They began to take concerted and coordinated action to counter the evidence and undermine the science.
For more on the continuing attempts to deny the science, look here:/climatezone.org/climate-politics/the-decades-of-denial/
Check out these sources:
 The Office of the Historian: Milestones 1969-1976. Oil Embargo 1973-1974. Available at //history.state.gov/milestones/1969-1976/oil-embargo
2] The ad is shown on page 33 of the EPI report (Utilities Knew) cited above.
 EPI report. Op.cit.
 See: //www.govtrack.us/congress/bills/95/hr6669/summary
 See Merchants of Doubts. Op. cit. The NAS report is available at : //www.nap.edu/catalog/18714/changing-climate-report-of-the-carbon-dioxide-assessment-committee
 EPRI report. Op.cit.
 EPRI report. Op.cit.
 Banerjee N., Cushman J.H., Hasemeyer D., and Song L., Exxon: The road not taken. Inside Climate News, 2015.
 Merchants of Doubt. Op.cit. page 184.