The world is watching expectantly as the clock winds down towards the United Nations Climate Change Conference (COP15; http://en.cop15.dk/) to be held 7-18 December 2009 in Copenhagen. While most are now convinced of the need for a strong and concerted response to the climate challenge, the exact nature and extent of that response remains uncertain. There is evidence (Barnett 2009) that current estimates of emissions now exceed all but the most extreme emission scenarios developed by the Intergovernmental Panel on Climate Change (IPCC). If that increase in emissions persists then temperature increases of 4 °C by 2060 have been predicted (Barnett 2009). An inevitable result of the potential for such extreme climate change is to advance the need for multiple adaptation strategies to decision making about, for example, infrastructure, urban planning and forest management. These strategies need to do more than incremental adaptation (Barnett 2009); instead transformative approaches may be required to adapt. The timing of the response is also proving to be a critical determining factor in the effectiveness of global actions. Using a simple conceptual model of emissions, Vaughan and co-workers (Vaughan et al 2009) show that avoiding dangerous climate change is more effective if such action begins early. Early action is also more effective than acting more aggressively later (Vaughan et al 2009). Uncertainties, although reduced, are still significant in the science of climate change. The interactions between control of particulate air pollutants and climate change are particularly challenging (Arneth et al 2009, Shindell et al 2009) but many other uncertainties require continuing research. The scientific uncertainties are only one aspect of an intense interdisciplinary, political, economic and cultural dialogue. It is clear that political will, economic interest, target setting for emissions reductions, adaptation, technology and financing (Pan 2009) will all have a major influence on progress to an international agreement. It is important that the political challenges are not underestimated. Long-term observers of the negotiations necessary for global agreements (Inman 2009) are pessimistic about the chances for success at COP15, and argue that agreements between smaller groups of countries may be more effective. China and other developing countries clearly expect greater emission cuts by developed nations as a condition for a successful deal (Pan 2009). Conversely, the constraints on US climate policies are considerable, notably those imposed by fears that an international agreement that does not include equitable emission control measures for developing countries like China and India, will compromise the agreement and reduce its effectiveness (Skodvin and Andresen 2009). In this context the need for earlier, and more reliable, information on emissions is a high priority. Myhre and coworkers (Myhre et al 2009) provide an efficient method for calculating global carbon dioxide emissions from fossil fuel combustion by combining industry statistics with data from the Carbon Dioxide Information Analysis Center (CDIAC; http://cdiac.ornl.gov/). Recent analyses of carbon dioxide emission data show a worrying acceleration in emissions, beyond even the most extreme IPCC projections, but are based largely on the CDIAC which gives information about emissions released two to three years before real time (Canadell et al 2007, Raupach et al 2007). The approach used by Myhre et al (2009) uses BP annual statistics of fossil fuel consumption and has a much shorter lag, of the order of six months. Of significant concern is that their analysis of the data also reveals that the recent strong increase in fossil fuel CO2 is largely driven by an increase in emissions from coal, most significantly in China. By contrast, emissions from oil and gas continue to follow longer-term historical trends. Earlier and accurate data on CO2 emissions is important for a range of reasons. It allows comparison with the scenarios developed by the IPCC; uncertainties in emission scenarios are one of the major sources of uncertainties in temperature projections, particularly at longer time scales, where temperature projections are increasingly dependent on specific emission scenarios (IPCC 2007). There have also been recent suggestions (Le Quere et al 2007) of a weakening of the oceanic sink for CO2, and earlier information on emission pathways will be important for testing this hypothesis. Some observers (Levi 2009) believe that the best outcome from COP15 may be an agreement on measurement, reporting and verification. While this may seem like a modest ambition, progress in this area is essential to a successful climate change measure and to compliance with any international agreement. As Levi (2009) points out, 'such verification will help make it more politically feasible to undertake similar emissions-cutting actions elsewhere, including in the United States'. The approach of Myhre et al is a very useful tool in such independent verification.