European Commission President José Manuel Barroso and Connie Hedegaard, commissioner for Climate Action, talked up the EU's contribution to the agreement in a written statement.

"Europe has worked throughout the year to save the United Nations process to tackle climate change and the prospect of a global climate deal […] The international community has now strengthened the international climate regime with new institutions and funds," they stated.

Describing the road to a legally-binding deal as "long and challenging," they pointed out that the EU had "succeeded in speaking with one voice" and is "willing to do its fair share of the global effort".

Flemish Environment Minister Joke Schauvliege, representing the Belgian Presidency of the European Council, said the EU had "worked tirelessly to be a bridge builder whilst advancing its positions" in Cancún.

"The EU has reported transparently on the progress it has made in mobilising the 7.2 billion euros of fast-start funding it has pledged over 2010-2012 and we will continue to do so on an annual basis," he promised.

European Parliament President Jerzy Buzek regretted that only "step-by-step" advances were being made in climate agreements.

German MEP Jo Leinen (Socialists & Democrats), chair of the European Parliament's delegation to COP 16, described Cancún as having "paved the way" for a global climate treaty.

"The building blocks of the Cancún agreement will secure better protection of forests and transfer of green technologies to support sustainable economies in developing countries," he said.

"It also formally establishes a climate fund, in which innovative financing and EU solidarity will be critical elements," he added, calling for the EU's CO2 reduction target to be increased to 30% at February's summit of EU energy ministers.

Green MEP Satu Hassi said that the agreement fell "far short" of what was necessary.

"The snail's pace at which the UN climate talks are progressing is extremely concerning given the urgency with which climate action is needed," she stated.

Pointing the finger at "serial offenders in blocking progress," she placed the blame "squarely with politicians and not the [UN] process".

German MEP Karl-Heinz Florenz, spokesman for the European People's Party (EPP) in Cancún, described the talks as a "litmus test for the UN process" and hailed the "happy ending".

The Mexican presidency succeeded in balancing "transparency with the need for progress," he said.

However, despite being "optimistic" that an agreement could be reached at the next round of COP talks, he regretted that an end date had not been introduced into current UN texts.

Bairbre de Brún, an Irish MEP in the GUE/NGL Group in the European Parliament, described the deal as "a base on which to build," but warned that "we should not fool ourselves that we are anywhere near where we need to be".

"Governments also need to take domestic action to alter the patterns that got us into this mess while supporting the most vulnerable countries to cope with increasing climate change damage," she said, calling on the EU to move to a 30% emissions target "in order to remain competitive".

Jennifer Morgan, director of climate and energy for the World Resources Institute (WRI), noted how "modest expectations" had given way to "promising results" in the deal.

"This agreement was a remarkable turnaround for a multilateral approach to address climate change, including commitments on emissions from all the world's major economies. By consensus, countries agreed to a 'balanced package' that includes targets and actions, increased transparency, the creation of a climate fund, and other important mechanisms to support developing countries," she said.

However, calling on countries to "build on the momentum" from the deal, Morgan stressed that global temperatures were still on track to exceed two degrees Celcius. 

The Climate Action Network's senior policy officer Ulriikka Aarnio welcomed how the EU had "reasserted itself as a key player" in climate talks, but called on the bloc to increase its climate ambitions.

"We were pleased to see the EU contributing positively on important issues like the continuation of the Kyoto Protocol as well as their push on overall ambition level […] but they were not willing to help close important loopholes, which are hollowing out their calls for more environmental integrity," she regretted.

Describing political will as not being strong enough to address "climate chaos", Aarnio pledged to support EU member states that decided to call on the EU to adopt a unilateral 30% emission reduction target.

Mark Kenber, deputy CEO of the Climate Group, described the agreement as a "major shot in the arm" of the international climate process and a "strong signal that a clean industrial revolution" is under way.

"Countries have recognised that tackling climate change is good for both their economies and the environment, and are vying to be at the forefront of a clean industrial revolution that will boost jobs and growth," he stated.

Less enthusiastic was Susann Scherbath, climate justice campaigner for Friends of the Earth, saying that "justice was not done in Copenhagen - and neither was it done in Cancún".

"Key provisions are still in doubt – the future legal framework is unclear, deep emission cuts for rich industrialised countries are missing, it brings in the pledge-and-review system from Copenhagen, the World Bank has a role in managing climate finance and the push for markets and for carbon trading is not acceptable," she summarised.

The EU "didn't fulfil its promise of playing a progressive role by hiding behind inaction from other countries and using the climate negotiations to push for the expansion of carbon markets," she lamented, describing the deal agreed as "a weak package".

The most encouraging outcome in Cancún was that "movements for climate justice are louder than ever, especially from developing countries," she said.

Wendel Trio, international climate policy director for Greenpeace, welcomed the fact that governments had chosen "hope over fear" on the path to a global climate deal.

"Cancún may have saved the process but it did not yet save the climate […] more would have been accomplished if it were not for the negative influence of the US, Russia and Japan," he claimed.

"In Durban we need a global deal that helps countries build a green economy and that holds polluters accountable," he stated.