There seems to be a lot of enthusiasm around this announcement that the US would rejoin the Paris Agreement if Joe Biden were to be elected president. I don't want to be a killjoy, but I'd be a bit more cautious. Here's why. #thread #UnpopularOpinion https://twitter.com/JoeBiden/status/1324158992877154310

1. First, the Paris Agreement seeks to provide a stable, long-term framework for cooperation, which is also a signal sent to companies and markets. A return of the US would be a signal that countries can exit and rejoin the agreement depending on their election results.

If the participation of a country (and especially the US) depends on its elections, it creates a form of instability in the agreement. What if Ivanka Trump is elected president in 2024? The US would exit the Agreement again?

2. A return of the US into the Paris Agreement would be mostly symbolic. Symbols are important for sure, but Republicans in the US Senate are likely to kill any mechanism that would be legally binding. Furthermore, you don't need the Paris Agreement to curb your emissions.

3. One has to admit that the US has always tried to tone down the international ambitions on #climatechange, even when a Democratic president was in office. At a moment when COP26 needs more ambition than ever, is it a good time to bring back the US? Not so sure.

4. Finally, even if the US eventually rejoins the Paris Agreement, one cannot act as if nothing had happened between 2017 and 2021. This brilliant piece in @nature, with comments by @ClimateOpp, sheds some light on this aspect. https://www.nature.com/articles/d41586-020-03066-x