"For everyone hoping that Greta Thunberg would win, let's look to the future. If they inspire real change then their odds will be better in future years," he said.
But critics of the activist said they were glad she didn't win the prize, saying she had only created "more panic and hysteria, not peace".
Greta had been a favourite to win the prestigious prize, with reports suggesting she'd be up against New Zealand's Prime Minister Jacinda Ardern and the young leaders of the Hong Kong protest movement.
But the Prime Minister of Ethiopia, Abiy Ahmed Ali, was awarded the prize for making peace with the country's bitter foe, Eritrea.
British TV star Piers Morgan poked fun at the controversy, tweeting: "How dare they actually give it to someone who forged peace".
Andrew Stroehlein, the European Media Director for Human Rights Watch, said Ahmed was good choice, but there was much more to be done.
"Good choice, both for peace efforts with Eritrea and important improvements in Ethiopia itself, where the government released thousands of political prisoners and committed to other reforms," he said.
"At the same time, there is much to do. There's been a significant break down in law and order in parts of Ethiopia amidst escalating ethnic tensions that has resulted in significant numbers of internally displaced persons."
The Ethiopian Prime Minister's Office described the honour as a "collective win for Ethiopians".
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"Since Prime Minister Abiy Ahmed assumed political leadership in April 2018, he has made peace, forgiveness and reconciliation key policy components of his administration," the statement read.
"This victory and recognition is a collective win for Ethiopians, and a call to strengthen our resolve in making Ethiopia — the New Horizon of Hope — a prosperous nation for all."
Past Nobel Peace Prize laureates include Martin Luther King Jr, Malala Yousafzai, Mother Teresa and Nelson Mandela.
