Every euro not invested in climate protection will cause 10-100 euros more in debt in 10 years.
No, your time scale is off. Yes, climate change is real; and yes, climate change will have bad effects; but climate change is a slow catastrophe. Think 20, 30, 50, a hundred years down the road. The "climate protection" needed is primarily negative actions: stop investing money into assets that are in locations that will be vulnerable to climate change.
But the main mitigation is to stop putting carbon dioxide into the air now that will continue to be warming the climate in 20, 30, 50, and a hundred years from now.
And nuclear is not "way too late", because those people living 10, 20, 50, and a hundred years in the future will also need to not put carbon dioxide into the air.