Footprint Calculator is a website which can show you how many Earths it would take to sustain the life of all humans, if everybody on Earth were to live like you do. It then gives you information on how to lower your carbon footprint. This is a really helpful starting point if you have just started getting interested in the issues of climate change and global warming, and you would like to find out a way to help.climate.nasa.gov
NASA: Climate Change and Global Warming is a website with many facts and statistics about climate change. There are also many interesting articles for further reading.globalclimatestrike.net
The Global Climate Strike and Fridays for Future websites have information about climate strikes around the world, resources for starting a strike, and imformation about what else you can do.350.org
350.org is the website for 350, an organization whose goal is to help the world transition away from fossil fuels to clean energy. It also has information about how you can get take action against climate change.