Countries will have to be far more ambitious in cutting greenhouse gas emissions if the world is to effectively curb a rise in global temperature at 2 degrees C or less.
This is the conclusion of a new greenhouse gas modeling study, based on the estimates of researchers at nine leading centres, compiled by the UN Environment Programme (UNEP).
The experts (see notes to editors) suggest that annual global greenhouse gas emissions should not be larger than 40 to 48.3 Gigatonnes (Gt) of equivalent C02 in 2020 and should peak sometime between 2015 and 2021.
They also estimate that between 2020 and 2050, global emissions need to fall by between 48 per cent and 72 per cent, indicating that an ambition to cut greenhouse gases by around three per cent a year over that 30 year period is also needed.
Such a path offers a 'medium' likelihood or at least a 50/50 chance of keeping a global temperature rise at below 2 degrees C, says the new report.
The new study, launched on the eve of UNEP's Governing Council/Global Ministerial Environment Forum taking place in Bali, Indonesia, has analyzed the pledges of 60 developed and developing economies.
They have been recently submitted to the UN Framework Convention on Climate Change (UNFCCC) following the UN climate convention meeting in Copenhagen in December.
The nine modeling centres have now estimated how far these pledges go towards meeting a reasonable 'peak' in emissions depending on whether the high or the low intentions are met.
'The expected emissions for 2020 range between 48.8 to 51.2 GT of CO2 equivalent based on whether high or low pledges will be fulfilled,' says the report.
The report, as noted earlier, says that in order to meet the 2 degree C aim in 2050, emissions in 2020 need to be between 40 Gt and 48.3 Gt.
Thus even with the best intentions there is a gap of between 0.5 and 8.8Gt of CO2 equivalent per year, amounting to an average shortfall in emission cuts of 4.7 Gt.
If the low end of the emission reduction pledges are fulfilled, the gap is even bigger-2.9 Gt to 11.2 Gt of CO2 equivalent per year, with an average gap of 7.1 Gt says the report How Close Are We to the Two Degree Limit?
Achim Steiner, UN Under-Secretary General and UNEP Executive Director, said: 'There are clearly a great deal of assumptions underlying these figures, but they do provide an indication of where countries are and perhaps more importantly where they need to aim.'
'There clearly is 'Gigatonne gap' which may be a significant one according some of the modelers. This needs to be bridged and bridged quickly if the international community is to pro-actively manage emissions down in a way that makes economic sense,' he added.
'There are multiple reasons for countries to make a transition to a low carbon, resource efficient Green Economy of which climate change is a key one. But energy security, cuts in air pollution and diversifying energy sources are also important drivers,' said Mr Steiner.
'This week at the UNEP GC/GMEF we will also shine a light on the opportunities ranging from accelerating clean tech and renewable energy enterprises to the climate, social and economic benefits of investing in terrestrial and marine ecosystems,' he added.
Some of those multiple opportunities for action are showcased in the UNEP Year Book 2010 which is being presented to ministers responsible for the environment who are attending the meeting.
These include Reduced Emissions from Deforestation and Forest Degradation (REDD) which gained political support at the Copenhagen climate change meeting.
REDD, which involves supporting developing countries to conserve rather than clear tropical forests, could make an important contribution not only to combating climate change but also to overcoming poverty and to a successful UN International Year of Biodiversity.
. The Year Book estimates that investing US$22 billion to US$29 billion in REDD could cut global deforestation by 25 per cent by 2015.
It also highlights a new and promising REDD project in Brazil, at the Juma Sustainable Development Reserve in Amazonas.
. Here each family receives USUS$28 a month if the forest remains uncut, one potential way of tipping the economic balance in favour of conservation versus continued deforestation.
Renewables are also gaining momentum: although still very low compared to the huge potential of renewable energy, the global installed wind generation capacity has grown at the rate of 25 per cent per year over the past five years.
. In China, for example installed capacity has nearly doubled every year since the end of 2004 - and the report notes that the wind energy potential under perfect conditions has been estimated at up to 72,000 GW, nearly five times total energy demand. Probably 20 per cent of this energy potential could be captured in the future, representing almost 15 000 GW.
Managing a response to climate change also echoes the challenge of International Environment Governance, a key theme at this week's GC/GMEF.
Governance also underpins the international response to other challenges highlighted in the UNEP Year Book 2010.