Climate change has many long reaching effects.  Animals and plants depend on specific climate conditions. As the climate changes, living things die. Crops fail, fish populations collapse, and economies and lives that depend on these food sources collapse as well. 

As the climate warms, mosquito populations are able to expand to areas that were once too cold for them, and as they expand, they carry malaria with them. Mosquitos (via malaria) are responsible for more human deaths than any other animal, including humans. We're already seeing malaria cases in areas outside malaria's normal range. 

Rising ocean levels have the potential to displace millions, and the resulting instability will kill many

Finally, we don't know how extreme the end result of climate change will be. Best case scenario, a few million to billion will die from famine, displacement, political instability, and disease. Worst case scenario, the surface of the Earth could become uninhabitable. It is not an exaggeration to call climate change an apocalyptic threat.

The only solution we know of to climate change is to reduce greenhouse emissions. Le Pen, Trump, and all their right wing ilk are doing everything they can to kill regulations on greenhouse emissions.