Answer:
Yes, human activity is responsible for global warming. Global warming is largely caused by an increase in carbon in the atmosphere. Carbon is a greenhouse gas, which means it holds on to heat from the sun.
Carbon is released when fossil fuels (oil, coal, etc.) are burnt. Fossil fuels are burnt in order to create electricity. Ever since the Industrial Revolution, humans have burnt more and more fossil fuels, leading to an increase of carbon in the atmosphere. Therefore, yes, humans and their resource usage are responsible for global warming.