The message of the United Nations Secretary-General on the 2014 International Day for the Preservation of the Ozone Layer - 16 September 2014 .

The Earth's protective ozone layer is well on track to recovery in the next few decades thanks to concerted international action against ozone depleting substances, according to a new assessment by 300 scientists. The Assessment for Decision-Makers, a summary document of the Scientific Assessment of Ozone Depletion 2014, is being published by the UNEP and the WMO, and is the first comprehensive update in four years. The stratospheric ozone layer, a fragile shield of gas, protects the Earth from harmful ultraviolet rays of the sun. Without the Montreal Protocol and associated agreements, atmospheric levels of ozone depleting substances could have increased tenfold by 2050. According to global models, the Protocol will have prevented 2 million cases of skin cancer annually by 2030, averted damage to human eyes and immune systems, and protected wildlife and agriculture, according to UNEP.

Fast action under the Montreal Protocol can limit growth of HFCs, prevent 100 to 200 billion tonnes of CO2-equivalent emissions by 2050, and avoid up to 0.5°C of warming by 2100.

The aim of this paper is to explore what a flexible and durable climate change agreement could look like and propose pragmatic options for the design of such an agreement.