:::::How would that read if a synonym was used? Perhaps definitely. 

 ::::::Global warming is the temperature rise that is unequivocally underway in Earth's atmosphere and oceans. 

 ::::::Global warming is the temperature rise that is definitely underway in Earth's atmosphere and oceans. 

 :::::I just think that that sounds dumb. In my opinion, the following is better English. 

 ::::::Global warming is the current rise in the temperature of the Earth's atmosphere and oceans. 

 :::::Which, in my opinion, is simply an attempt to redefine a common phrase to have a politically different meaning. But that is not the point of this discussion. That said, current rise is not appropriate for an encyclopedia that will still be around in 100 years. Neither is underway. I am sure you can do better.