How could human activities be responsible for the change in temperature between 1970 and 1995?

Yes.

We know that greenhouse gases absorb heat.

We know that carbon dioxide (CO2) is a greenhouse gas.

We know that burning fossil fuels releases CO2 that has been hidden away for millions of years.

We know that this raises levels of CO2 in the atmosphere.

That is how human activities are responsible for the rise in temperatures between 1970 and 1995.