What is the best direct method for assessing global climate change over time?

Assessing global climate change effectively requires a direct measurement that reflects the overall warming trends of the Earth's climate system. Surface temperatures on Earth have been consistently monitored using a variety of methods, including ground-based weather stations, satellite observations, and ocean buoys. This data provides a clear, quantifiable way to track changes in temperature over time, which is a fundamental indicator of climate change.

Monitoring surface temperatures offers insight into warming patterns, seasonal variations, and long-term climate trends. The increase in average global temperatures is correlated with other climate change indicators, such as ice melt, sea level rise, and shifts in weather patterns.

While other options provide valuable information regarding aspects of climate change—like the frequency of extreme weather events or specific species behaviors, they do not offer the comprehensive, direct quantification of global climate patterns that surface temperature measurements do. Thus, surface temperatures are recognized as the most direct method for assessing global climate change over time.