What does 'global warming' refer to?

The term 'global warming' specifically refers to the long-term increase in average temperatures of the Earth's atmosphere and oceans, particularly due to human activities such as the burning of fossil fuels, deforestation, and other practices that release greenhouse gases. These gases trap heat in the atmosphere, leading to a gradual rise in temperatures across the globe.

In this context, the correct answer highlights that global warming encompasses not only the rising surface temperatures on land but also the warming of the oceans. This dual increase has significant implications for climate systems, weather patterns, and ecosystems around the world.

Understanding global warming as an increase in both land and sea temperatures is essential because it helps to clarify the broader implications of climate change, including more extreme weather events, rising sea levels, and shifts in biodiversity. The other options, while related to environmental issues, do not capture the specific nature of global warming as it is widely understood in climate science.