Final answer:
The least likely explanation for global warming is normal variations in the earth's temperature. The main culprits are human activities, particularly burning fossil fuels, which increase greenhouse gases, deforestation, and ozone layer depletion. However, a combination of these factors is resulting in the global warming we see today.
Step-by-step explanation:
The least likely explanation for global warming is that it is solely due to normal variations in the earth's temperature. While Earth's climate has naturally fluctuated over millennia, the rapid warming we're currently witnessing far exceeds natural variation rates.
Global warming largely results from anthropogenic activities, particularly the burning of fossil fuels since the Industrial revolution, contributing to an increase in greenhouse gases that trap heat in the atmosphere. Concurrently, widespread deforestation and the depletion of the ozone layer resulted in less CO2 being absorbed and more harmful UV rays reaching the Earth's surface.
It's critical to note, however, that not one but a combination of these factors is causing the current unprecedented rates of global warming. The issue is complex and multidimensional, so pinning it down to one sole cause is unrealistic and mitigates the extent of human-induced change.
Learn more about Global Warming Causes