Greenstone used the "carbon-climate response" model from Matthews et al. (2009, Nature) to convert cumulative carbon emissions into global mean temperature changes. It does not account for fossil fuel resources that are not available with current technologies, but does include those accessible with current technology but not profitable at current prices.
Greenstone wrote an article for the New York Times detailing how he arrived at his figures, a portion of which follows: I've tallied the projected warming from fossil fuels extracted so far and the projected warming capacity of various fossil fuels that can be extracted with today's technology. This accounting was done by taking the embedded carbon dioxide in each energy source and using a standard model for the relationship between cumulative carbon emissions and long-run temperature changes based on a 2009 Nature article. (More detail on the method is available here.)
For those who don't like suspense, here's the total: an astonishing 16.2 degrees. And here's how that breaks down. Since the industrial revolution, fossil fuels have warmed the planet by about 1.7 degrees. We are already experiencing the consequences of this warming. In recent weeks, we have learned that the world had its warmest winter on record and that Arctic sea ice hit a new low, even as intense storms continue to inflict harm on communities globally.
Next, look at fossil fuel reserves, the deposits we know to be recoverable under today's prices and technology. That is, they are inexpensive to access. If we were to use all of this coal, natural gas and petroleum, the planet would warm by an additional 2.8 degrees. Add the heat from those reserves to the 1.7 degrees from what has already been emitted, and you get a world that is 4.5 degrees warmer since the industrial revolution; this is beyond scientists' recommended 3.6-degree threshold.
The next set of fossil fuels in line is referred to as resources, rather than reserves. The difference is that they are recoverable with today's technology, but not at current prices. There is 3.1 degrees' worth of warming if the oil and natural gas in this category are utilized, which would lead to a total increase in global temperatures of 7.6 degrees.
This warming does not even consider our coal resources. A middle-of-the-road estimate of the coal that qualifies as resources indicates that its use would lead to an additional increase of 8.6 degrees. Thus, the use of all reserves and resources would lead to a total increase of 16.2 degrees. Today's climate and planet would very likely be unrecognizable.
Scientists predict global disaster at 3.6 degrees Fahrenheit over pre-industrial temperatures; there is enough fossil fuel extracted and within reach to raise temperatures 16.2 degrees.
Without pricing carbon to reflect expected climate damages, all of this coal, oil and natural gas is worth many trillions of dollars, so keeping it in the ground would mean passing up economic opportunities that are waiting to be taken and turning our backs on a long history of going to great lengths to recover these energy sources. A January study in Nature developed estimates of which fuels would have to be abandoned to stay below the 3.6-degree threshold. It found that most Canadian tar sands; all Arctic oil and gas; and a significant share of potential shale gas would need to stay locked up. It also found that major coal producers like the United States would need to keep 90 percent of their reserves in the ground.
There are essentially only three long-run solutions to the climate challenge. The first is to price carbon emissions to reflect the damages from climate change. In practice, this means pricing carbon in as many parts of the world as possible - and ideally, globally - so that there is a level playing field for all energy sources. There has been important progress in this area, including in the European Union, individual American states and regions (for example, California and the Northeast's Regional Greenhouse Gas Initiative), and parts of China.
And there are several ways to introduce carbon pricing, as a New York Times Op-Ed by David Hayes and James Stock underscored. But we are a long way from a global price on carbon, and the prices in existing carbon markets are lower than the projected damages from increased carbon emissions.
The second way to disrupt the energy market is to have low-carbon energy sources like nuclear, wind and solar become cheaper than their fossil fuel competition. Although there has been much progress in reducing the costs of wind and solar recently, they generally remain more expensive than fossil fuels. Further, the fracking revolution makes it clear that there will be continued technical advances that reduce the costs of recovering fossil fuels.
Indeed, it is well known that there are ample supplies of coal deeper beneath the Earth's surface that do not yet qualify as resources, and there is increasing evidence that energy from methane hydrates may become relevant commercially. In other words, it seems unlikely that today's low carbon energy sources will play a major role in the solution without significant public investment in research, development and test deployments of new technologies.
The third approach is to continue using those fuels, but capture and store the carbon before it is released or pull it out of the atmosphere after its release. Neither approach has yet been proved to work at scale, and costs remain high. Even if costs come down, it will very likely remain more expensive than using fossil fuels without capture and storage, so a carbon price would be necessary for it to be applied broadly. A related idea is to reflect sunlight away from the earth so temperatures do not rise as much. This approach does not reduce the buildup of carbon dioxide in the atmosphere, and there is agreement that further research is necessary.
If we use all of the fossil fuels in the ground, the planet will warm in a way that is difficult to imagine. Unless the economics of energy markets change, we are poised to use them.
Follow Will Hector: @WriteCompassion
(Source: New York Times)