Even the local weatherman, whose main job is to give a consensus five day forecast, feels the need to rail against "climate change skeptics" and talk about melting polar ice. Thanks for the intellectual stimulation. It is good, once in a while, to remind one's self what a good, measured and circumspect approach to science has to say about climate cycles. Professor Judith Curry, Chair of the Department of Earth and Atmospheric Sciences at the Georgia Institute of Technology, is a scientist whose writings I've come to enjoy.
Starting from the beginning, she notes the large number of degrees of freedom in a complex natural system that encompasses immense atmospheric and oceanic systems. These in turn, are driven by a number of complex sub-systems with innumerable inter-linkages. Finally, these systems are non-linear and regularly feature large scale perturbations. It sounds simple, but look how different it is to situations in which traditional mathematical models do well.
Modelers like to characterize systems with an economy of sub-systems, and these in turn are preferably characterized by limited numbers of well defined linkages. Even if the system is thought to be non-linear, it's nice to use linear approximations. It's also nice to have the system converge quickly to a new equilibrium after a small perturbation. Whether it's a model of an ocean fishery or a model of central bank monetary intervention, modelers don't like to begin with the complexity of natural systems because of the need for circumspection about any theoretical results.
High priests of climate change have no doubts, qualms, or reservations. Thus for example, the American Meteorological Society, of which Dr. Curry is a former member of the Executive Council, writes,
- "Warming of the climate system now is unequivocal, according to many different kinds of evidence.
- Climate is always changing. However, many of the observed changes noted above are beyond what can be explained by the natural variability of the climate. It is clear from extensive scientific evidence that the dominant cause of the rapid change in climate of the past half century is human-induced increases in the amount of atmospheric greenhouse gases, including carbon dioxide (CO2), chlorofluorocarbons, methane, and nitrous oxide.
- Geologic research proves irrefutably that the permanent change is the fundamental characteristic of the Earth's climate as throughout its entire history, and the changes occur in cycles of varied length - from several thousand to just a few years.
- Not all reasons for climate change or their phenomena are fully known yet.
- Although in the history of the Earth, a considerably warmer climate than today had dominated, there had been repeated occurrences when the Earth experienced massive global cooling which always resulted in vast ice sheets that sometimes even reached the subtropics.
- Over the past 400 thousand years - even without human intervention - the level of CO2 in the air, based on the Antarctic ice cores, has already been similar 4 times, and even higher than the current value. At the end of the last ice age, within a time of a few hundred years, the average annual temperature changed over the globe several times; in total, it has gone up by almost 10 °C in the northern hemisphere, therefore the changes mentioned above were incomparably more dramatic than the changes reported today.
- Detailed monitoring of climate parameters has been carried out for slightly over 200 years; it only covers parts of the continents, which constitute only 28% of the world. Some of the older measuring stations established - as a result of progressive urbanization, in the peripheries of the cities, are now within them. This factor, among other things, is the reason for the rise of the measured values of temperature. The research of the vast areas of the oceans has only been launched 40 years ago. Measurements taken for this kind of short periods of time can not be considered as a firm basis for creating fully reliable models of thermal changes on the surface of the Earth, and their accuracy is difficult to verify. That is why far reaching restraint needs to be kept regarding blaming, or even giving the biggest credit to man for the increased level of emissions of greenhouse gases, for such a theory has not been proven.
- There is no doubt that a certain part of the rise of the level of greenhouse gases, specifically CO2, is associated with human activity therefore, steps should be taken to reduce the amount on the basis of the principles of sustainable development, a cease (sic.) of extensive deforestation, particularly in tropical regions.