What has been the main cause of climate change over the past 100 years? how do we know humans are causing the climate to change, rather than natural causes?

The main cause of climate change over the past 100 years has been global warming that has occurred due to increased levels of greenhouse gases.

Explanation:

Nowadays, the human's dependence on fossil fuels has increased to its highest. The climate change that we are getting to witness lately is a result of a continued increase in the levels of greenhouse gases that are released from the burning of fossil fuels. The greenhouse gases trap the heat received from Solar insolation and that released from various human activities and contribute to the rising of temperature. The increase in the global mean temperature has caused the climate to change substantially over the past 100 years.

Magma forms by partial melting of upper mantle and crust. partial melt means that only a fraction of the available material forms a melt, and that the remainder stays solid. the partial melt rises because of its lower density and ascends through he crust. this is so conclusive mean the answer would be magma igneous rocks or balistic magma.