What has been one of the key drivers of climate variability in the last century?

Changes in greenhouse gas concentrations have been a key driver of climate variability over the last century due to their significant role in influencing the Earth's energy balance. Greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, trap heat in the atmosphere, leading to an increase in global temperatures and resultant changes in climate patterns.

The substantial increase in these gases since the Industrial Revolution, primarily due to human activities like fossil fuel combustion, deforestation, and industrial processes, has intensified the greenhouse effect. This rise in concentrations correlates strongly with observed climate changes, including shifts in weather patterns, increased frequency of extreme weather events, and long-term alterations in ecosystems.

While increased natural disasters, the position of tectonic plates, and solar flares can affect local or short-term climate conditions, they do not compare to the extensive and systemic influence of escalating greenhouse gas concentrations as a driver of climate variability on a global scale over the last century.