Even assuming all countries makes goods on pledges to cut greenhouse gas emissions, there's still a gap between what scientists say is needed to prevent catastrophic effects of climate change and what's been promised.
The next 10 years could determine the planet's fate
For all the haggling in Cancun over finance, forestry, technology transfers and open accounting, very little has been said about climate targets.
The world's pledges to tackle climate change, all contained in last year's Copenhagen Accord, list voluntary cuts as well as a goal to limit global warming to below two degrees Celsius. But there's a gap - called the gigaton gap - between what governments have pledged and what climate researchers have said is needed.
"If the voluntary commitments in Copenhagen were to be implemented," said Achim Steiner, director of the United Nations Environment Program, at the Cancun summit, "And I put the conditional on because none of us have a guarantee at the moment that they will be implemented, then we would be 60 percent of the way of where we need to be by 2020 in addressing a climate change action program that would allow the world to still have an opportunity to stay within the two degree range."
More use of renewable energy sources could help cut the gigaton gap
Limiting global warming to two degrees will be crucial for avoiding its worst effects and may be the cut off point for us to have any chance of doing something about the problem of climate change, according to Joseph Alcamo, the United Nations Environment Program's chief scientist.
"Around two or two-and-a-half degrees would be roughly the level at which there would be an increasing frequency of extreme climate events, where there would be much higher risk of reaching tipping points in the climate system," he told Deutsche Welle.
To have a good chance of keeping warming below the two-degree level, the scientists behind a UN emissions report presented in Mexico said global emissions will need to peak at around 44 gigatonnes, or 44 billion tones, by the end of the decade.
If no action is taken there would be a 12-gigaton gap between actual emissions and what's needed to limit climate change to a two degree increase by 2020. That's the equivalent of about 25 percent of current emissions. But if countries fulfill their promises the gap would be seven gigatons, Alcamo said.
"We can go 60 percent of the way simply by fulfilling ambitions expressed in the Copenhagen accord," he said, pointing out that the most optimistic implementation of the Copenhagen Accord would leave the world five gigatons short of what researchers say is necessary.
More to negotiate
An increase of more than two degrees Celsius would have major effects on life on Earth
But even the current best-case scenario is pockmarked with caveats still up for negotiation. Issues including like an agreement on forestry, climate finance for developing countries as well as resisting tricky accounting rules that disguise increases in emissions as decreases are all yet to be decided on.
Policymakers will need to dig deeper and they'll need to do it sooner rather than later since all models for keeping warming below two degrees have one thing in common, according to Ramzi Elias of the European Climate Foundation.
"All of them that have a likely chance of limiting warming to two degrees have emissions levels that peaked and started to decline before 2020," he told Deutsche Welle. "Therefore, what we do over the next 10 years is really crucial."
Leaving the big investments needed for a transition to a low carbon economy until after 2020 would likely be too late because of the cumulative nature of greenhouse gases in the atmosphere, Elias said.
Some people are already suffering the effects of climate change
But if the costs seem steep now, closing the gap completely will likely be doubly expensive, according to Michel den Elzen of the Netherlands' Environmental Assessment Agency. He put the price tag for current Copenhagen promises at between $60 billion and $100 billion.
"To close the gap, I think it is in the order of 0.3 percent of the worldwide GDP," he told Deutsche Welle, adding that it would be equal to about $200 billion.
UK Climate Secretary Chris Huhne, however, said the costs of inaction were even higher, pointing out that the extreme weather events of 2010 were a taste of things to come.
"Anybody who is any doubt about that please go and talk to the big insurance companies, because they are paying out for this," he said.
"Just in the UK alone over the last 10 years, the payout for flooding was 4.5 billion pounds, whereas in the 10 years before that it was 1.5 billion pounds. This is hard business evidence of the costs that are being inflicted on our economies and we have to tackle this problem."
Author: Nathan Witkop, Cancun / sms
Editor: Cyrus Farivar