The scientific viability of the Anthropogenic Global Warming Hypothesis (AGWH) has been evaluated in terms of the Causality Principle (CP) which is the foundation of scientific philosophy. Based on the available experimental data, the relationship that is expressed by the AGWH (that rising CO2 concentration in the atmosphere is responsible for global warming (GW) as reflected in the rise in temperature) is noncausal because the cause (the change in [CO2 ]) lags the change in the temperature in the experimental record, in violation of the CP, regardless of the source of the carbon dioxide. Since the AGWH represents the foundational hypothesis of current Climate Science (CS), it is concluded that CS and the models that have been developed, based on the AGWH, to predict future GW lack a valid scientific basis. Finally, because no causal relationship exists between atmospheric CO2 and temperature, the Equilibrium Climate Sensitivity (SCS) is zero rather than being 3 ºC/doubling [CO2 ] as adopted by the IPCC and as low as 1.54 ºC/doubling [CO2 ] estimated by others. All ECS values are estimated from unvalidated models, and no measured values currently exist.