Which factor has contributed to the increase in Earth's surface temperature since the 20th century?

The increase in Earth's surface temperature since the 20th century can be primarily attributed to climate change, particularly the anthropogenic (human-induced) climate change resulting from the significant increase in greenhouse gas emissions. This process involves the accumulation of gases such as carbon dioxide and methane in the atmosphere, which trap heat and lead to a rise in global temperatures.

The overall understanding of climate change encompasses various factors, including industrialization, deforestation, and the burning of fossil fuels, all of which have accelerated the greenhouse effect and contributed to global warming. This is evident in scientific studies that demonstrate a clear correlation between human activities and the rising levels of atmospheric CO2, as well as the observable impacts on weather patterns, polar ice melt, and sea level rise.

Other choices like solar activity, natural geological processes, and ocean currents, while they play roles in Earth's climate systems, do not account for the pronounced and accelerated warming noticed since the 20th century, which has largely been driven by human-induced changes rather than natural factors alone. Understanding these distinctions is critical for grasping the broader implications and urgency of addressing climate change.