Answer: Scotland's carbon emissions. At least, that was the impression given by yesterday's exchange of views on the subject at Holyrood.
The Scottish Government's delayed second report on proposals and policies (RPP2) to meet climate change targets praises itself for a world-beating low carbon action plan and boasts that "by 2010 we were more than halfway to meeting the 2020 target of cutting greenhouse gas emissions by 42%".
That sounds very impressive. However, as opposition parties were quick to point out, appearances can be deceptive. The 42% target takes 1990 emissions as its baseline and in the last two decades Scotland has experienced ongoing deindustrialisation and the export of much manufacturing to the Far East. Recent figures show that, even during an economic downturn and despite continuing reliance on nuclear power, Scotland's carbon emissions since 2010 failed to fall by the modest target of 0.6%. In fact, they rose by 1.9% after taking emissions trading into account. Emissions from the housing and transport sectors are actually higher now than in 1990 and ministers have blamed the cold weather. All this would not have been evident from listening to Scottish Government minister Paul Wheelhouse presenting yesterday's report.
Instead of explaining how the Scottish Government proposes to get back on track, RPP2 is largely a restatement of RRP1. The only additions are a modest domestic heating strategy, some proposals for peatland restoration and a 2030 decarbonisation target, a measure SNP MSPs voted against being included in the Energy Bill.
Meanwhile Alex Salmond was in Aberdeen, talking up the potential of offshore wind. The First Minister hardly can be blamed for putting an optimistic gloss on the sector. (After all, it was partly Coalition ministers' pessimism in 2010 that lies behind the UK current economic woes.)
However, there is a huge gulf between producing big numbers in identifying capacity for offshore wind energy and actually producing the stuff. As Mr Salmond admits, without expensive port facilities, 30% lower production costs and far better grid infrastructure, investors will not take the bait and the sector will not deliver. The deep water around Scotland may even make offshore wind a non-starter. Meanwhile, the rest of the grid has to fill the fluctuating gap between supply and demand, a tricky task that could actually raise total carbon emissions according to some experts.
The reality is that the Scottish Government's energy strategy relies on considerable quantities of wishful thinking and seems to contain inherent contradictions. Environmental groups admire the SNP's green energy ambitions but observe that it continues to follow high and low carbon policies simultaneously. For instance, opencast mining has increased sharply, with more than 30m tonnes approved for extraction, even though carbon capture and storage on a commercial scale remains a pipe dream.
Renewable energy helps reduce carbon emissions only if it is balanced by reduction in fossil fuel use. Scotland is not only failing to do that but the SNP's economic case for independence in part rests on extracting every last drop of oil from the North Sea and exporting it for other countries to burn, producing up to 10bn tonnes of carbon dioxide.
Generation from renewables needs to be matched by a step change in improving domestic energy efficiency and much more effort to tackle transport emissions. The Scottish public would have more faith in future targets if existing ones were met. Political rhetoric on this issue needs to be matched by action on the ground.