only about 1 trillion tons of carbon can be burned and the resulting gas spewed into the atmosphere. Just over half that amount has already been emitted since the beginning of the Industrial Revolution, and at current rates of energy consumption, the trillionth ton will be released around 2040
Do they honestly believe there is some total quantity of emissions that can be tolerated? I mean as opposed to a rate of emissions - like annually. We know that the system recycles carbon taking it out of the atmosphere, and we know that the rate it's removed increases as the concentration increases. So if we assume there is a limit, it should be on the rate of carbon emissions and not the total emitted over time.
If you read the "Summary for Policymakers" PDF document linked in the summary, there is no talk of "total quantity of emissions tolerated" or any of this trillionth ton idea. Instead it appears to be talking about . In fact, it appears to reside solely in that New York Times article that very clearly says:
To stand the best chance of keeping the planetary warming below an internationally agreed target of 3.6 degrees Fahrenheit above preindustrial levels and thus avoiding the most dangerous effects of climate change, the panel found, only about 1 trillion tons of carbon can be burned and the resulting gas spewed into the atmosphere.
Just over half that amount has already been emitted since the beginning of the Industrial Revolution, and at current rates of energy consumption, the trillionth ton will be released around 2040, according to calculations by Myles R. Allen, a scientist at the University of Oxford and one of the authors of the new report.
(emphasis mine) So to answer your question: The trillion tons is an estimate of what we would need to burn in order to hit an internationally agreed limit that would likely produce the worst effects of climate change. The number of tons we burn is even an estimate. It's all estimates because we don't have parallel Earths where we can keep controls and change one variable to see what happens. If you don't accept the ability of making estimates with levels of certainty, there is no way to make any statements about the effects of putting carbon into our atmosphere on a global scale.
These guys are looking dumber all the time.
I suppose it would appear that way if you only get your information from The New York Times and throw away everything they're actually saying.