Sampdoria midfielder Morten Thorsby will wear the No. 2 shirt this season to raise awareness about climate change, with the digit representing a long-term global temperature goal of the Paris Agreement.
Under the Paris accord, nearly 200 countries have pledged to keep global warming to "well below" two degrees Celsius above preindustrial temperatures to strengthen the global response to climate change.
Thorsby, who wore the No. 18 jersey last season, said he wanted to "use my life to fight for what is important".
"I wanted to be better than everyone, but at the same time I had a side of me that said 'what are you doing?'," Thorsby told BroPod podcast this week.
"We have a huge environmental crisis going on and I'm playing football. This makes no sense at all.
"I spoke to my parents and we reached the conclusion I wanted to use my life to fight for what is important -- and the best thing I can do is to become as good at football as possible and keep on speaking about these important issues."
The Norway international has also founded the 'We Play Green' foundation, which encourages the football community to adopt environmentally friendly initiatives.