Last year, I wrote about the challenges of finding current data on greenhouse gas emissions. Lately, I've been looking into the numbers on the global carbon budget. My conclusion: while there are many good pieces written, most of the graphics are poor, and, while most generally agree on the numbers (+/- 30%), there is a lot of confusion because people don't use consistent units. Some people use GtC (giga tonnes of carbon) or a million, million metric tonnes of carbon. Others use GtCO2. Sometimes people will use GtCO2eq. And there is the not-so-occasional use of simply Gt (presumably we're supposed to just know whether its carbon or carbon dioxide).
Here is my graphic, depicting what I understand to be a fairly widely held view of the numbers.
The next picture gets into a little more detail. In the IPCC's 2014 AR5 report, they used 2011 data and, assuming a 66% chance of staying under 2 degrees Celsius, noted we had a remaining carbon budget of about 1000 GtCO2. As of 2014 we've used about 150 GtCO2 of this, the remainder is 850 GtCO2 or about 230 GtC.
Another well-known writing on this topic is Bill McKibben's piece in Rolling Stone from 2012. He also used 2011 numbers, but took the numbers from Carbon Tracker, which used an 80% confidence level of staying under 2 degrees Celsius. His number was 565 GtCO2 or 155 GtC. Again, since 2011 we've used about 25% of this remaining budget, leaving only about 440 GtCO2 or 120GtC.
There are other numbers in other places. Rob Jackson and colleagues in The Bridge came up with a remaining budget of 900 GtCO2 or 245 GtC with a 66% certainty level of staying below 2 degrees Celsius.
Of course all these numbers depend on our understanding of the climate system, what policies we come up with to mitigate land-use drivers, and the accuracy of the emissions data.
But the general story told is that, if we think about the Earth's fossil fuels, we've used about 40% of what we know to be recoverable, and we can use perhaps one-sixth to one-third of of what remains, depending on how much we are willing to risk going over two degrees Celsius. Of course, two degree Celsius is not a magic number. There's no way to know if there are tipping points below two degrees Celsius.
I searched for data on global greenhouse gas emissions by country and was disappointed with what I found. Data in AR5 WG3 are from 2010. The Wikipedia site’s data are from 2010. It says they are from World Resources Institute (WRI), but WRI just gets their data from the UNFCCC. By the way, WRI’s new Climate Data Explore (CAIT), provides some interesting graphic output. However, it uses 2012 data.
Under the United Nations’s Framework Convention for Climate Change (UNFCCC) treaty (which was ratified by the US Senate), Annex I countries to the treaty (the more industrialized nations) are required to report their annual emissions of greenhouse gasses. The UNFCCC established and maintains the technical guidelines for doing this, and compiles the data. However, this process is disappointingly slow. While a note on the homepage reports that the data have been updated with 2013 numbers, all the downloads on the Annex I time-series data page only extend only to 2012. The same goes for the country GHG profiles (which are very useful). The only place I could find 2013 data on the UNFCCC site was in the national reports, which are here. Apparently the 2013 have not been organized by UNFCCC, or at least, I could not find it on their website.
UNFCCC exports data to numerous sites and that list is available here. It includes the USEPA, but the most current data on the USEPA site is from 2012. It also includes the Netherlands Environmental Assessment Agency. The best report on that site was the Trends in Global CO2 Emissions. This is a 2014 report that includes 2013 data. It notes in the report that the data are somewhat preliminary, however they have good confidence in the overall accuracy. If you are concerned about the high accuracy numbers for an individual country, you will have difficulty finding data that are newer than 2012.
The Carbon Dioxide Information Analysis Center at Oak Ridge National Lab (US Department of Energy), also estimates CO2 emissions. The estimates for 2011-2013 are preliminary. It is these estimates that are used by the Global Carbon Atlas. It's important to realize that the Atlas is using DOE estimates rather than UNFCCC data.
It’s incredible to me that, in an age when we are so used to having data quickly available, that it would be so difficult to get current data on an issue of this importance.
directs research at the Energy Trans Lab