Scientists' Explanation for Exploration 3

A Comparison of Regional Temperature Anomalies

Local or regional temperatures show much greater natural variability than larger geographic-scale temperatures. For example, in Boulder, Colorado, the monthly temperature anomaly may vary by 7°C; while in the United States it may vary by 3.9°C and globally, by 0.8°C.

Temperature varies less on a global scale. Global mean temperature is ruled by the simple energy balance. You learned previously that the best way to determine if greenhouse gases are having the effect predicted by the physics of the greenhouse effect is to calculate the Earth’s energy balance. Natural variations are much smaller on a global scale than on a regional or local scale because the many natural variations cancel out when averaged over the entire globe. The natural variations in temperature over a larger geographic scale is canceled out, and therefore, it is easier to detect longer-term temperature trends when comparing global mean temperature (GMT).