International negotiators meeting in Kigali, Rwanda agreed on 15th October on amendments to the Montreal Protocol that will require replacing hydrofluorocarbons (HFCs) used in refrigeration and air conditioning with substitutes that are not greenhouse gases. The 1987 Montreal Protocol to the Vienna Convention on Protecting the Ozone Layer of 1985 phased out the use of chlorofluorocarbons (CFCs), which generally-accepted scientific research concluded was depleting the stratospheric ozone layer.
The most common replacements for CFCs have been HFCs, which are a very potent greenhouse gas. Thus the Kigali agreement turns the Montreal Protocol from a treaty to shrink the “ozone hole” into a treaty to slow global warming.
It has been claimed that banning HFCs will avert a one-half degree Celsius rise in the global mean temperature by 2100. That figure is highly dubious even if you believe that the global mean temperature can be calculated from atmospheric concentrations of greenhouse gases. Since the current possible replacements for HFCs are less efficient than HFCs, more electricity will be required to achieve the same levels of cooling. If much of that additional electricity is generated from fossil fuels, then carbon dioxide emissions will increase. Thus the total reduction in greenhouse gas emissions may not be nearly as large as predicted.
It is not clear whether the Obama Administration thinks that the Kigali amendment requires ratification by the Senate. Their argument for why the Paris Climate Treaty is not a treaty—because it does not include mandatory targets and timetables and has no enforcement mechanism—and therefore does not require ratification, does not apply to Kigali. Of course, whatever the Obama Administration decides could be changed by the next President.