One of the main problems with the “theory” of anthropogenic global warming is its reliance on rising atmospheric CO2 levels to force a global rise in temperature. This is predicted by climate change proponents by running large, complex computer models that imperfectly simulate the physics of Earths biosphere: ocean, land and atmosphere. Central to tuning these general circulation models (GCM) is a parameter called climate sensitivity, a value that purports to capture in a single number the response of global climate to a doubling of atmospheric carbon dioxide. But it has long been known that the Earth system is constantly changing—interactions shifting and factors waxing and waning—so how can a simple linear approximation capture the response of nature? The answer is, it can not, as a new perspective article in the journal Science reports.The climate is so complex and our understanding is so simplistic and ignorant that it is extraordinary hubris to think we can reduce the whole system to a single number. The evidence demonstrates that climate response is different for different circumstances. And we don't know many of the circumstances or the reasons why.
When it comes to Earth's climate, new factors are constantly being discovered. A new, and as of yet unidentified chemical substance is involved in driving sulfuric acid formation over forests, making all cloud formation models obsolete. A more direct example of how changing climate can change the climate system's response is the discovery that absorption of CO2 has more than doubled over the past half century. These, and other discoveries indicate that a more general measure of the Earth system's ability to maintain its prevailing state when subject to forcings is required.
As we said in The Resilient Earth, the complexity of Earth's climate system far exceeds current day climate science's abilities to understand. Basing future predictions on CO2 by trying to capture the planet's climate response in a single value called “sensitivity” is a feeble attempt to explain climate change by an immature science. What is needed is more sense about climate sensitivity, for clearly, trying to find a single value to explain climate change is a fool's game.