A rise beyond 2C, the internationally agreed safety limit, may push the climate beyond tipping points and into dangerous instability. The expected pledges are likely to limit temperature rises to about 3C.

But those negotiating towards a global agreement due to be settled in Paris in December remain upbeat. The current pledges would avoid a catastrophic rise of 5C that would ensue if no emissions cuts were made, and the agreement is expected to contain measures to ratchet up emissions cuts in future years.

Nonetheless, significant disagreements remain to be overcome, including how much money poor nations will receive to cope with warming and how any deal is policed.
The UN’s climate chief, Christiana Figueres, said that so far 62 countries had submitted promises of emissions cuts ahead of the Paris meeting, covering about 70% of global emissions. UK government sources told the Guardian that pledges, called Intended Nationally Determined Contributions (INDCs), were expected from India, Brazil, Indonesia and other nations before Paris.

Available at: http://www.theguardian.com/environment/2015/sep/16/paris-climate-summit-pledges-wont-avoid-dangerous-warming-say-uk-and-un