Mr Castro described President Obama's admission that the US had been too slow to act on climate change as a brave gesture.
But he added that the American capitalist system was incompatible with a clean planet.
Mr Castro has long been a fierce critic of US presidents.
In his latest editorial, published in all the state media, Mr Castro quoted widely from Mr Obama's address to the UN.
'Aggressive foreign policy'
He praised the American president for saying that the US had been slow to act on climate change and that richer countries had to take the lead since they had caused much of the damage.
No other US president, he said, would have had the courage to make such remarks.
But the 83-year-old revolutionary criticised what he called America's aggressive military foreign policy which threatened the survival of our species.
These comments come just a week after President Obama extended the decades old US trade embargo for another year. BBC