This film explores how the world's climate has changed over time and how human activities have accelerated this natural process. People and places -Environmental awareness and care - Environmental changes Learning Points Global warming causes melting icecaps and rising sea levels. Global warming is mainly caused by carbon dioxide in the atmosphere. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.