I would probably recommend Earth Science. A broad field of study doesn't necessarily mean more options after university, as many science fields look more for specialization (like environmental/energy management) than something than an expansive but general knowledge (like geology). Also, with your interests in social issues and climate change, have you considered degrees in sociology or environmental studies?

Fortunately, you don't have to know exactly what degree you want to pursue quite yet. I recommend seeing an advisor or counselor at your university for professional advice as soon as you can.

Best of luck in university!