the periodic review largely drew on information outside the unfccc making use of a structured expert dialogue technical workshops and meetings for open and substantive discussions between fccc delegates and external experts the structured expert dialogue concluded among other things that already climate change impacts are hitting home and the guardrail concept in which up to c of warming is considered safe is inadequate and would therefore be better seen as an upper limit a defence line that needs to be stringently defended while less warming would be preferable unfccc e the emphasis on national inventory reports in the enhanced transparency framework is important for filling what is currently a major information gap and providing a sound basis for tracking progress towards a diverse range of ndcs