The climate negotiations here in Lima, Peru (COP20) are a crucial staging post along the road to Paris in December 2015, where the parties to the UN Framework Convention on Climate Change (UNFCCC) are expected to sign a new climate agreement to come into effect in 2020.

The Lima negotiations opened on a slightly more optimistic note than usual, buoyed by the US-China announcement of post-2020 targets, which signaled an effort by the G2 to head off the possibility of 'another Copenhagen'. However, it is the EU that leads in ambition with its announcement to reduce emissions by at least 40% from 1990 levels by 2030. India, the world's third-largest aggregate emitter, has yet to make any announcement. President Obama is planning a trip to India in early 2015 so it is possible that we might see another joint announcement.

Yet despite these new notes of optimism, the negotiations quickly reverted to their usual tug-of-war.

The co-chairs of the Durban Platform for Enhanced Action (ADP) had prepared a twelve-page draft negotiating text containing all the required elements of the new 2015 agreement (mitigation, adaptation, finance, technology transfer, transparency of action and capacity building). By Wednesday of the second week of negotiations, a revised compilation of this text had blown out to 37 pages, reflecting multiple and conflicting formulations. The negotiations on this text have now closed, and it will remain a work in progress during the inter-sessional meetings leading to Paris at the end of 2015. It will take a Herculean and high-level effort to whittle this text down into a much shorter and more manageable form that might induce parties to sign at Paris.

So what role has Australia played? Despite the last minute decision this week to contribute $200 million to the Green Climate Fund, Australia has struggled to convince negotiators and observers that it is serious about joining the collective effort to prevent dangerous climate change.

Australia's 2020 targets are among the lowest in the developed world and few observers regard the Abbott Government's Direct Action Plan as credible. Nor has Australia ratified the Doha Amendment to the Kyoto Protocol, which introduced a second commitment period (2013-2020). Instead, Australia has been trying to change the accounting rules under the Kyoto Protocol that would effectively weaken its already meager 2020 target, although these highly technical negotiations are not yet concluded. Australia has also delayed any declaration of its post-2020 targets until mid-2015, pending the findings of a newly established Prime Ministerial taskforce.

However, the most unhelpful intervention has come from Trade Minister Andrew Robb, who has remained by the side of Foreign Minister Julie Bishop throughout the negotiations. During a meeting with business groups earlier in the week, he declared that the Government would not sign a Paris Agreement in 2015 if it disadvantaged Australia vis-à-vis its major trading competitors, and that Australia would not 'cop it in the neck'.

The Trade Minister's comments run deeply against the grain of expectations at Lima, where many developed and developing countries are going out of their way to showcase their domestic efforts and announce new, unconditional, measures. To remove any doubt about the sincerity of Washington's commitment, US Secretary of State John Kerry delivered a firebrand speech to a packed press gallery on Thursday afternoon to demonstrate that the US was now playing a leadership role. While Australia's key ally has gone out of its way to set an example in these negotiations, never before has Australia been so isolated and criticised.

The legal form of the 2015 agreement remains unclear. Everyone knows that the US Senate will not ratify a new climate treaty. The challenge for the negotiators is to craft an agreement that the US can sign and which President Obama (and his successors, if they are so inclined) can implement without Senate approval. President Obama has already demonstrated that this is possible by using his executive power (most notably by regulating CO2 emissions as a pollutant under the existing Clean Air Act).

China and India, for different reasons, are also reluctant to sign an agreement that would include internationally legally binding emissions reductions commitments. Last year's COP in Warsaw stepped around these problems by inviting all parties to 'to initiate or intensify domestic preparations for their intended nationally determined contributions' (INDCs). This confirmed what everyone was expecting: a flexible bottom-up process that avoided the fraught business of reaching an agreement on the distribution of mitigation responsibility. The latest versions of the sprawling negotiating text and the shorter draft COP decision are careful not to prejudice future negotiations on the vexed and intriguing issue of legal form.

However, new disagreement has emerged in Lima over the form and content of INDCs, such as how much information is to be provided by each party, whether it they should focus only on mitigation or also include adaptation, what kind of review process should apply and when. On the eve of the final day of COP20 the parties remain locked in negotiations that are likely to continue for at least another 24 hours.

It will take a great deal of skill from the COP president, Manuel Pulgar-Vidal, to bring these negotiations to a successful resolution.