Articles about the environment can be extremely demoralizing – see September's IPCC report and the collapse of proposals to create the world's largest wildlife reserve as cases in point. So it is refreshing to hear some good news.

The latest Scientific Assessment of Ozone Depletion report from the United Nations shows that action taken under the Montreal Protocol is working and has resulted in long-term decreases in the atmospheric abundance of controlled ozone-depleting substances (ODSs). It makes for an inspirational (and timely) reminder of how international co-operation and diplomacy can enforce significant positive change.

The Montreal Protocol was finalized in 1987 in response to the realization that many of the chemicals used in aerosols, air conditioning systems, refrigerators, and industrial solvents were eroding the planet's stratosphere, creating a hole and allowing harmful levels of ultraviolet radiation to seep through the ozone layer. The international agreement compelled the global community to begin the phasing out of ozone-depleting substances like chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and halons.

Every four years, a report like this one is released, documenting the recovery of the ozone layer. The 2018 edition shows that ozone levels in sections of the stratosphere have been recovering at rates of 1-3 percent since 2000. And if recovery rates continue as they are predicted to do, the report says the Northern Hemisphere and mid-latitude ozone should be fully recovered by the 2030s, the Southern Hemisphere ozone in the 2050s, and the polar regions before 2060.

This is despite the fact that there has been an unforeseen rise in global emissions of CFC-11 since 2012. As a result, declines in global concentrations between 2014 and 2016 was just two-thirds the speed it was between 2002 and 2012.

"The Montreal Protocol is one of the most successful multilateral agreements in history for a reason,” Erik Solheim, the head of UN Environment," said in the press release.

"The careful mix of authoritative science and collaborative action that has defined the Protocol for more than 30 years and was set to heal our ozone layer is precisely why the Kigali Amendment holds such promise for climate action in future."

If the Kigali Amendment is ratified in 2019,the revisions will add specific targets and timelines to find environmentally-friendly alternatives to hydrofluorocarbons (HFCs), restrict countries that have ratified the agreement from doing business in controlled substances with those that have not, and encourage richer countries to provide financial aid to poor countries transitioning to greener products.

This, experts say, could "be the single largest real contribution the world has made so far towards keeping the global temperature rise 'well below' 2 degrees Celsius" as set out by the Paris Agreement. According to the report, the world may be able to avoid up to 0.4 percent of global warming this century just by keeping to the Kigali Amendment.