Definitions:
Temperature signal: A change in photosynthesis or respiration solely attributable to changes in temperature, i.e., the signal excludes other climatic effects such as water availability and sunlight.
Tipping point: This denotes the temperature threshold at which the global land surface will switch from a carbon sink to a carbon source when—due solely to temperature—photosynthesis is in exponential decline while respiration is in exponential increase.
Thermal maxima: The thermal maximum (Tmax) represents the peak of the temperature dependence curve where any additional increase in temperature will decrease the metabolic rate of either photosynthesis or respiration.
Warmest Quarter: Mean temperature of warmest quarter (3-month period)