It doesn’t take much effort to see that a large and dangerous gap has opened up between the level of emission reduction pledges and the global carbon budget and emissions trajectory needed to maintain a high probability of keeping warming below 2o C, much less the 1.5o C limit demanded by highly vulnerable countries. This ‘Gigatonne Gap’ is at least 5 to 9 Gt CO2e, depending on whether countries achieve the low or high end of their 2020 pledges, according to the figures from Project Catalyst. And they rely on a 450 ppm scenario which itself is not a sure bet to keep the global temperature rise to below 2o C. At current emission rates, the remaining global carbon budget for a 2o C or less world will be eaten up by some time in the early 2020s. The gigatonne gap is one we can’t afford to fall into, and it’s coming on fast. For a true and adequate response to the climate crisis, there can be no sweeping of actual emissions under a rigged-accounting carpet. Measurement and accounting for ‘what the atmosphere sees’ is essential. Where did the gigatonne gap come from? There are several reasons for it: lack of ambition, loopholes in agreements (both existing and under negotiation), and the absence of some key sources and sectors. Most developed countries simply have levels of ambition that fall far short of any reasonable mark. In addition to general un- willingness by governments, a major reason for the lack of ambition is that the US continues to pollute far above the level any measure of equity would allow. The US lack of ambition will surely come back to bite it, as other countries seize the economic advantages of the low-carbon future. And there is growing concern about the level of financial resources to support adaptation, REDD and mitigation in the bill about to be introduced in the US Senate. If the US does not take on its fair share now to close the gap, then other developed countries will have to take up the slack both in mitigation and financing action in developing countries. Moreover, as the world waits for the US to stop hanging separately from the rest of the planet, the leadership already being shown by countries such as Costa Rica, the Maldives and Tuvalu to reduce their own emissions should inspire those with greater responsibility. The ambition deficit is a big part of the Gigatonne Gap, but there’s much more. Let’s highlight a few of the loopholes that Parties should consider closing. There are loopholes throughout the architecture of the existing agreements, especially the Kyoto Protocol. As one example, the shoddy and loophole-ridden LULUCF accounting rules do not, in fact, reflect what the atmosphere sees. Then there is the CDM, which hardly has a stellar record in achieving real and additional emissions reductions, as well as keeping the door propped open for emitting technologies and bad investment choices in developed countries. The banking of ‘hot air’ AAUs is also a live issue that urgently needs a clean-up. The EU Commission estimates that over 10 billion tonnes of greenhouse gas emission units will likely remain unused during the 2008 to 2012 commitment period – and where and when will they land? These all need to be addressed in the KP negotiations, and no new loopholes should be allowed into either the LCA or KP track for the future. Remember: it’s what the atmosphere sees that counts. New sources and sectors of emissions also contribute to the Gigatonne Gap. Glo- bal aviation and shipping emissions are still not subject to reduction targets and that undermines the integrity of honest efforts being made to reduce emissions. Industrial gases, including HFCs, NF3 and N2O, should be removed from the CDM and addressed outside the market through a fund approach. Black carbon is a forcing agent that remains outside any control, and reducing it will have substantial development and health co-benefits. Addressing fossil fuel subsidies, as agreed in the G20, not only will help close the gap but add directly to the low-carbon transformations of the global economy. While the Gigatonne Gap is an urgent agenda item for the UNFCCC in 2010, there are many entry points and options, and they can be mutually supportive. Suggestions include a series of workshops to frame the discussion, a secretariat technical paper, and placement as a new SBSTA agenda item in addition to the LCA and KP negotiations. Closing the Gigatonne Gap is an opportunity for all countries not only to avoid the costs of climate change, but also to help achieve sustainable development in a fair way that respects common but differentiated responsibilities while taking advantage of respective capabilities. The Gigatonne Gap must urgently be addressed, so that the atmosphere can breathe more easily.