Would legally binding commitments on adaptation in INDCs modify existing obligations under the Convention and how could this be avoided?
Under the UNFCCC developed country Parties have agreed to support the adaptation to climate change impacts in developing countries. However, there is no legal obligation on developing countries to adapt to the adverse (or other) effects of climate change.
If we assume that the ultimate agreement on INDCs requires or allows a country’s adaptation commitments to be in a legally binding form, then such commitments would modify the legal obligations of any country making such a commitment to the other parties in a legally binding form. For international lawyers, a “binding” commitment to another country or countries is a legal obligation to those countries. It would not matter that the country making the commitment had no such obligation under the Convention, since the commitment would be made later in time than the Convention.
To avoid incurring a new obligation, a developing country would have to avoid making any commitment in a form that constituted a binding commitment to other parties. If, for example, the climate negotiations concluded in 2015 with a new agreement binding on all parties with respect to adaptation commitments made thereunder, then countries wanting to avoid binding commitments would have to avoid scheduling them under that agreement.
This could be further clarified by a statement along the following lines: “The Government of [country X] declares its understanding that signature of the  Agreement shall, in no way, constitute a renunciation of the rights and obligations under the UNFCCC, that no provisions in the new Agreement can be interpreted as derogating from the provisions of the UNFCCC and create new obligations on adaptation [or any other matter] for developing countries.”
The current ADP negotiations do not contemplate that INDCs will initially be made in legally binding form, but rather without prejudice to the legal nature of the contributions. Thus INDCs would facilitate clarity, transparency and understanding of those contributions but not create legally binding obligations. If similar language were included in any final decision, then it would not be necessary for any party to take steps to avoid incurring new obligations to the other parties.
The scope or extent of developing countries’ commitments and their legal nature in respect of national adaptation efforts will depend on the wording of the relevant parts of any future agreement, together with the wording of any ‘savings clause’ which clarifies the relationship between such an agreement and the Convention (either generally and/or in relation to adaptation).