I used to be a global warming doubter. When the theories of greenhouse gas build up began appearing in the late 1960s and early 1970s, they were hypothetical speculations with little evidence to back them up.
Throughout the 1970s and 1980s, many prominent environmentalists were saying that the world would run out of oil with supplies peaking in 1990. When we were still awash in oil, the same environmentalists embraced the threat of global warming as the reason to cut back on our use of fossil fuels. There are plenty of good reasons for eliminating our carbon habit. But when people embrace the same end for different reasons it raises my level of suspicion.
But science proceeds by trying to prove or disprove hypotheses and today's report from the National Academy of Sciences [LINK] destroys as much doubt as science ever can with its conclusion that the past few decades have been the warmest in 400 years. And all the evidence points to human activity –- that is, burning carbon fuels -– as the main driver of this warming.
The political reason for today's report -– which is a consensus of top experts -- was a 1999 study [LINK] that got a lot of popular and political attention. It claimed that the 90s was the hottest decade in 1,000 years and 1998 was the hottest ever.
That paper and its famous "hockey stick" chart of temperature elevation made up a significant part of the Intergovernmental Panel on Climate Change's (IPCC) reports, which tried to form a consensus on climate change.
Today's report says that 1,000 years may be a bit much. But it concludes that since 1600 the record is powerful and the world is getting hotter.
A lot of powerful interests do not want to believe the world is getting warmer due to human activity. And there are still significant unknowns. No one can say yet what the specifics effects of global warming will be. But the scientific evidence shows we are entering a period of massive human-induced climate change. There will be doubters about today's report. There will always be a scientist to say the Earth is flat, but there is not much doubt now the Earth is getting warmer.