When a group of Chinese researchers used public energy data to calculate the CO2 emissions of each of China’s provinces from 1997 to 2010, and then added them all together, they came up with an amount larger than the number reported for the whole country—by 1.4 gigatons. That’s about the same as one year of CO2 emissions by Japan. According to the group, differences in reported coal consumption for “coal washing and heating for energy transformation processes” and manufacturing are the main reasons for the discrepancy. Their findings were published in Nature Climate Change.

But just two days after that study was published, the director of the climate change research center at the Chinese Academy of Sciences in Beijing told Reuters that his organization’s preliminary findings indicate China has actually been emitting a lot less than has been reported. He said the IPCC’s standard method for counting emissions fails to address the “big differences in calorific content of China’s many grades of coal.”

As Brad Plumer wrote on Tuesday:

Let’s go ahead and state the obvious: It will be impossible to hash out any sort of global agreement on climate change if we can’t even agree on how much carbon-dioxide different countries are actually putting into the air.

And I think we can expect this type of uncertainty, whether or not it’s directly related to CO2 emissions, to be amplified as countries argue over how much each should have to pay toward geopolitical efforts to mitigate climate change.

But I almost forgot about my question: So how many gigatons is it, China?