In December 2015, governments across the globe will gather for one of the biggest events intended to adopt a new universal agreement on climate change that will be applicable to all parties in addressing global annual emissions of greenhouse gases by 2020.

During the two week 20th Conference of the Parties on Climate Action, held from 14 December, 2014, in Lima Peru, delegates set out ground rules, scheduled to be agreed in Paris, on how all countries can submit contributions to the new agreement.

United Nations members, however, made significant progress where they reached an agreement on how countries should tackle climate change; of course, by elevating adaption onto the same level as action to cut and curb emissions.

Delegates approved a framework for setting national pledges to be submitted to the Paris summit. It was also agreed that such an ambitious agreement in December, 2015 must reflect the principle of common but differentiated responsibilities and respective capabilities, in light of different national circumstances.

This principle of common but differentiated responsibilities requires developed countries to bear a special burden of responsibility in reducing and eliminating unsustainable patterns of production and consumption and in contributing to capacity-building in developing countries, inter alia, by providing financial assistance and access to environmentally sound technology.

In particular, since the developed countries are the most polluters of the environment, they should similarly play a leading role and assume primary responsibility in matters of relevance to sustainable development.

The principle, however, does not exempt developing countries, including Rwanda, from any responsibility, it rather requires them to adopt their climate change mitigation measures with respect to the limited capabilities.

If a new 2015 universal agreement on climate change signed and subsequently ratified, will be a landmark international environmental agreement with legal force applicable to all parties. What a likely watershed moment in international environmental law! And most likely it will supersede the Kyoto Protocol, which was largely binding on some of the developed countries, whereby, contrary to all expectations, some of the developed countries such as USA and Australia did not assent to it and thus not being as successful as intended.

The 2015 Paris summit, however, will not be the first summit of world leaders that ended up without a legal deal, so what expectations can governments, civil society organizations, academics, lawyers and environmental activists have in the deal?

If an agreement is reached, will countries give it effect in good faith, contrary to the ineffective implementation of the United Nations Framework Convention on Climate Change as well as the Kyoto Protocol?

Here are some of the recent important environmental gatherings that became fruitless (where an international legal text was supposedly in place). First, the Copenhagen Conference of the Parties (COP), which met from December 7-19, 2009, had been intended as the deadline to resolve questions about the post-2012 climate regime – a view reflected in the unofficial slogan for the conference, "seal the deal.”

More than 40,000 people, including more than one hundred heads of state or government, attended the Copenhagen Conference which reached a mere political Accord rather than a legal document.

Among its long-term vision was to "recognise the need to limit global temperature increase to no more than 2° Celsius”. The Copenhagen Conference was one of the largest environmental meetings in history.

Second, the United Nations Climate Change Conference, held from November 29 to December 11, 2010, in Cancún, Mexico, relaunched the United Nation’s multilateral facilitation role. Delegates agreed to aspects of a global framework to help developing countries curb their carbon output and cope with the effects of climate change, but they postponed the harder question of precisely how industrialized and major emerging economies will share the task of making deeper greenhouse-gas emission cuts.

Third, the United Nations Climate Change Conference, Durban 2011, which was the second largest meeting of its kind, whose outcomes included a decision by Parties to adopt a universal legal agreement on climate change as soon as possible, and no later than 2015.

Fourth, Doha Climate Change Conference of 8-9 Dec, 2012, decided to amend Article 3 of the Kyoto Protocol to extend "Commitment Period from 2012-2020”. The first commitment period was from 2008-2012 under the Kyoto Protocol which ended in December 2012.

It is important to note, however, that Canada withdrew from the Protocol in November 2012. The United States and Australia never ratified it, and, as a consequence, Russia and Japan did not subscribe to the second commitment period.

This compromises the overall reductions expected of developed economies. The last conference, as earlier noted, was held in Lima on December 14, 2014, which finally adopted ground rules for December 2015 Paris Summit.

As Paris conference is around the corner, world leaders of developed and developing countries need to show a political will to save the planet from the adverse effects of climate change, many of which are already locked in.

As it goes without saying "pollution has no border”, means pollution generated from a particular state often has serious impact upon other states. The writer is a lecturer and international law expert