This article, It’s Not About Feedback by Willis Eschenbach, is critical to understanding the nature of climate variability and the mistaken direction taken by political organizations, such as the IPCC and others, in interpreting observations based on a preconceived misunderstanding of climate dynamics.
In our shared mechanistic world, we operate on the common sense principle that "If you push something hard enough, it will fall over." This is the linear world of everyday expectations, in which a given action always results in the same outcome, and it works pretty well in most situations, such as getting out of bed, drinking a cup of hot coffee or stepping off the front stoop.
However, when we deal with complex systems such as weather, atmosphere, oceans and climate, this principle serves us poorly. In the world of complex and chaotic systems, when you push something hard enough, sometimes it does indeed fall over. Other times, when you push that same something with the same force, it stands resolutely unmoving. And even other times, the same push results in the object flying off into a corner of the room and whining piteously to itself.
This is because in the complex world, there are far more variable and unpredictable factors than one's simple push acting on the object and affecting the outcome.
This is the case with climate variability. The IPCC, and other political and science organizations, operate as if climate changes in reaction to one simple push, the total amount of CO2 in the atmosphere. They have put together a body of observations: increasing average temperature at many surface temperature measuring stations; a decline in extent and thickness of Arctic ice; melting of glaciers and ice fields in some parts of the world; and increasing atmospheric concentration of CO2 (and other "greenhouse" gases). They have entered these data into their computers and the computer ground on them a bit and spit out a Douglas Adams answer: 42. Unfortunately, just as in Hitchhiker's Guide to the Galaxy, they neglected to formulate the appropriate question to the ultimate answer.
The basic assumption in these computations, well refuted by Eschenbach, is that there is a linear relationship between the total concentration of CO2 in the atmosphere and average surface temperature, and further, that human production of CO2 is responsible for the observed increase in atmospheric CO2 concentration. In other words, if humans continue to push up CO2, temperatures will continue to rise, glaciers will continue to melt, and, in short, the global Popsicle will be no longer lickable.
As Eschenbach points out, this turns out not to be the case.
The Earth's biosphere, including the oceans, landmasses, atmosphere and all the biological and geophysical bits that hang about within them, is a pretty clever place. Over unimaginable millennia, the biosphere has developed a homeostatic system that works to keep conditions on the Earth within a narrow range of temperature, humidity and atmospheric gas concentrations, hovering around the freezing point of water. Even odder, this range of conditions is uniquely maintained at just the right combination for the establishment and maintenance of life, as we know it, as it has been fruitful and multiplied across the face of the earth, in pursuit of its own unique form of happiness.
This has caused a great many philosophers to scratch their thinning pates in consternation. Is the Earth and this Universe designed just so, for Life and human beings to evolve and contemplate the wonder of its creation? Or, on the other hand, paw or various appendages, if the Universe were not so ordered would there be anyone around to scratch their thinning pates wondering about it?
This is known as the Anthropic Principle, over which much ink and dead trees have been sacrificed in sorting it all out.
What's important for those of us getting out of bed in our mechanistic world, contemplating steaming cups of coffee and slippery front stoops, is this: Climate variability has no constant rate of change or direction; climate changes constantly, as it has since there first were oceans and atmosphere; and global warming is a misperception of cause and effect caused by overdependance on computer models and insufficient attention to the complexity of global climate systems.