More than just a Google Map clone, EarthViewer (Android, iOS) allows users to explore the Earth's geological past, present and future. Users can explore interactive maps of the movements of the Earth's continents across millions of years, as well as temperature maps of the past century. Users can locate modern cities and landmarks and trace their positions across eons of continental drift, or even their expected future positions.
Skeptical Science (Android, iOS) is a quick guide to debunking climate change denial, listing and refuting the most commonly used arguments used to undermine climate change science, complete with links to scientific studies to debunking these claims. The app presents a top 10 list of arguments, searchable categories and a news feed. It's a great and informative resource for taking the fight against climate change to the streets.