The increasing use of fossil fuels and changes in agriculture have contributed to global changes in temperature through two primary mechanisms: the greenhouse effect and land use changes.
1. Greenhouse effect: The burning of fossil fuels releases large amounts of carbon dioxide and other greenhouse gases into the atmosphere. These gases trap heat from the sun, which prevents it from escaping back into space. This causes the Earth's atmosphere to warm up, which leads to changes in climate patterns and rising global temperatures.
2. Land use changes: Changes in agriculture, such as deforestation and the expansion of croplands, can also contribute to rising global temperatures. Trees and other vegetation absorb carbon dioxide from the atmosphere, which helps to regulate the Earth's climate. However, when forests are cleared or burned, the carbon that was stored in the trees is released into the atmosphere, increasing greenhouse gas concentrations and contributing to global warming.
In addition, changes in agriculture can also lead to changes in the reflectivity of the Earth's surface (albedo), which can further contribute to warming. For example, replacing forests with croplands or urban areas can lead to a decrease in albedo, which means that more sunlight is absorbed by the Earth's surface, contributing to warming.
Overall, the increasing use of fossil fuels and changes in agriculture have contributed to global changes in temperature primarily through the greenhouse effect and land use changes.