Am y tro cyntaf, cafodd rôl hanfodol llywodraethau is-genedlaethol – yr haenau o lywodraeth o dan y genedl-wladwriaeth - ei chydnabod trwy eu cynnwys yn nhrafodaethau ffurfiol yr uwchgynhadledd, gan gynnwys diwrnod penodol i gynrychiolwyr is-genedlaethol. Ar gyfer Cymru, mae hyn yn dilyn dros 10 mlynedd o waith a fu’n greiddiol i fudiad y Llywodraethau Taleithiol a Rhanbarthol.  Fel Is-Lywyddion y Rhwydwaith rhyngwladol o Lywodraethau Rhanbarthol dros Ddatblygu Cynaliadwy (nrg4SD), mae gennym rôl allweddol wrth ddod â phartneriaid ynghyd, sbarduno cydweithredu a chynrychioli'r rôl arweiniol allweddol y mae Llywodraethau Taleithiol a Rhanbarthol eisoes yn ei chwarae ar lefel fyd-eang. Gyda'n gilydd, rydym yn gallu sbarduno, dangos cyrhaeddiad ac arweiniad a chyflawni ar raddfa sy'n gwneud rôl y Llywodraethau Taleithiol a Rhanbarthol yn hanfodol i weithredu dros yr hinsawdd.  Er enghraifft, mae Cymru a Llywodraethau Taleithiol a Rhanbarthol eraill wedi gwneud ymrwymiad uchelgeisiol i liniaru newid hinsoddol, hynny drwy’r Memorandwm Cyd-ddealltwriaeth rhwng Arweinwyr Is-genedlaethol ar yr Hinsawdd Fyd-eang (y CM o dan 2 fel y’i gelwir), sy'n cynnwys 65 o awdurdodaethau o 20 o wledydd a phum cyfandir sydd ar y cyd yn cynrychioli mwy na $17.9 triliwn o GDP a 588 miliwn o bobl - mwy na'r Unol Daleithiau. Yn ogystal, rydym rhyngom fel Llywodraethau Taleithiol a Rhanbarthol wedi addunedu i leihau mwy o allyriadau na’r holl allyriadau y mae Tsieina’n eu cynhyrchu mewn blwyddyn.
For the first time, the crucial role played by subnational governments – those tiers of government beneath the nation state - was recognised as part of the formal UN summit proceedings, including a specific day dedicated to delivery at the subnational level. For Wales, this follows more than 10 years of work at the heart of the State and Regional Government movement. As Vice Presidents of the international Network of Regional Government for Sustainable Development (nrg4SD) we have a key role in binging partners together, driving collaboration and representing the key leadership role that State and Regional Government are already playing globally. Collectively we are able to demonstrate drive, reach, leadership and scale of delivery that makes the role of State and Regional Governments crucial to delivering climate action. For example, Wales and other State and Regional Government have made a commitment to ambitious mitigation through the Memorandum of Understanding on Subnational Global Climate Leadership (also known as the Under 2 MoU), which covers 65 jurisdictions from 20 countries and five continents and collectively represents more than $17.9 trillion in GDP and 588 million people – this is bigger than the United States of America. In addition the total emissions reduction pledges we have made as State and Regional Governments (and reported through the Compact of States and Regions) are now greater than the annual emissions of China.