User:Milton Beychok/Scratchpad

Skepticism about global climate change and its anthropogenic origin

Although the national science academies of many countries accept the IPCC's conclusion that future man-made climate change is likely, a minority of skeptical scientists and others believe that the present climate change, if it exists at all, is not man-made and is unavoidable. The skeptics dispute any immediate danger and any need for large reductions of man-made CO₂ emissions. The skepticism is based on the complex problems associated with the underlying science and the uncertainty of the available climate data. The latter has been acknowledged and accounted for by the IPCC as much as possible.

There is a tendency to downplay the number of skeptical scientists or to ignore them. For example, when an FPS (Forum on Physics & Society) editor of the American Physical Society wrote: "There is a considerable presence within the scientific community of people who do not agree with the IPCC conclusion that anthropogenic CO₂ emissions are very probably likely to be primarily responsible for the global warming that has occurred since the Industrial Revolution", the FPS Executive Committee hastened to declare that his statement does not represent their views. Clearly, any suggestion of a "considerable presence" of scientists disagreeing with the IPCC is politically undesirable. None-the-less, over 400 prominent scientists from more than two dozen countries, testifying before a U.S. Senate committee in 2007, voiced objections to major aspects of the so-called "consensus" on man-made global warming. Many of those scientists were participants in the IPCC..

The complexities and problems of climate change science

All participants in the dispute, between those who agree with the IPPC's conclusions and those who do not agree, recognize that climate change science involves difficult problems. Some of the skeptical scientists believe that many of those problems are too difficult to be solvable. In the first place, it is an observational science (like astronomy), meaning that experiments cannot be performed or verify or disprove certain hypotheses.

In the second place, the Earth's climate is an extremely complex system, much more complex than physical scientists usually tackle. Most of the physical sciences is based on a reductionistic approach, in which systems are reduced to smaller ones that are easier to understand but still possess their essential characteristics. In climate science, such an approach is impossible because the atmosphere, the oceans, and the land masses are tightly coupled subsystems and consequently the energy and mass exchanges between those three major subsystems of the Earth must be studied simultaneously and cannot be be reduced to separate smaller systems. Further, the electromagnetic radiation balance (i.e., insolation of solar irradiation) between energy absorption and back radiation by the Earth plays a crucial role and cannot be omitted, which means that the Earth's climate system itself is not a closed system.

Third, there exists no encompassing theory that predicts the characteristics of the climate and which is accepted by all climatologists. Theories are ad-hoc and taken from many different areas of applied physics: turbulent and dissipative systems, convective and radiative transport phenomena, non-linear (chaotic) systems and their inherent sensitivity to initial conditions, and so on. Further, there is not enough reliable data to evaluate the existing climate models. Hence, even models trying to explain the present world climate are based on subjective choices open to criticism. The problems are compounded for predictions of world-wide climate changes. Thus, many climate scientists do not have much faith in the ability of climate models to predict the future. The validity of computer models predicting the climate a few decades ahead is questioned by those who refer to the inability of current computer models to predict the weather for more than 10 days in advance.

Another problem is the use of proxy data (i.e., indirect data such as tree rings and the isotopic content of arctic and antarctic ice) used to determine past temperatures of the Earth. Proxy data are used to construct historical temperature profiles, yielding, for instance, the hockey stick shaped graph. Some scientists question the reliability of temperature profiles based on proxy data and doubt that the present global warming is unique. They argue that the Earth, without human intervention, has had warm periods before and they refer to the discovery of Greenland by the Vikings around the year 1000 when Greenland was green, and the era of the dinosaurs when the Earth was green.

The majority of skeptical scientists admit a definite increase of CO₂ in the atmosphere, due to the growing use of fossil fuels, but doubt that the increase in CO₂ concentration will lead to a world-wide catastrophe.

Open letter to the UN Secretary-General from skeptical scientists

During the United Nations Climate Conference on the Indonesian island of Bali in December 2007, more than 100 scientists (climatologists, physicists, biologists, meteorologists, statisticians, and others) wrote an open letter to Ban Ki-Moon, the Secretary-General of the United Nations. The letter expressed their opinion that "the 2007 UN climate conference [is] taking the World in entirely the wrong direction". They recognized that a climate change is occurring but they state that it is a natural phenomenon which is impossible to stop and express their doubts that "it is possible to significantly alter global climate through cuts in human greenhouse gas emissions."

The open letter casts doubt on the procedure of writing the IPCC Assessment Reports of 2001 and 2007. The letter stated that "the reports are prepared by a relatively small core writing team with the final drafts approved line-by-line by ­government representatives". It further states that "the great ­majority of IPCC contributors and ­reviewers, and the tens of thousands of other scientists who are qualified to comment on these matters, are not involved in the preparation of these documents. The summaries therefore cannot properly be represented as a consensus view among experts".

Climate sensitivity

The concentration of CO₂ in the Earth's atmosphere at the beginning of the Industrial Age (1750) was about 278 ppm. It is currently (2008) about 385 ppm. The concept of climate sensitivity arose when the IPCC members asked themselves how much the temperature on Earth would change by an increase of CO₂ in the atmosphere. To answer that question, the IPCC adopted this definition:

Climate sensitivity is the equilibrium temperature change, $\scriptstyle \Delta T_{\lambda }$, in the surface temperature, TS, caused by the doubling of the pre-industrial CO₂ concentration.

More simply put, the IPCC defined climate sensitivity as the temperature change, in the Earth's surface temperature, $\scriptstyle \Delta T_{\lambda }$, that would be caused by doubling the pre-1750 atmospheric CO₂ concentration of 278 ppm to 556 ppm which is currently expected to incur later in this century.

The IPCC estimated the climate sensitivity to be 3.26 °C. In other words, when the atmospheric concentration of CO₂ reaches 556 ppm (expected later this century), the IPCC predicts that the Earth's surface temperature will be 3.26 °C higher than it was more than 150 years ago (1750).

In a contribution to the APS Forum on Physics & Society of July 2008, entitled "Climate sensitivity reconsidered", Christopher Monckton, a known critic of anthropogenic causes of global warming, takes issue with the 2007 IPCC report. Moncton is a British journalist and he acknowledges that he was assisted in various ways during the preparation of his APS Forum contribution by physicists, meteorologists and others at Harvard University and Massachusetts Institute of Technology (both in Cambridge, Massachusetts), Imperial College (London, England), St. Andrews University (Scotland) and other universities.

The major point made in Moncton's contribution in the APS Forum on Physics & Society is that the IPCC's estimated climate sensitivity of 3.26 °C is much too high. Using the same methodology and the same physical effect parameters as did the IPCC, but estimating his own values of those parameters, Moncton obains a climate sensitivity of 0.58 °C. In other words, Moncton predicts that the Earth's surface temperature will be only 0.58 °C higher than it was in 1750.

Moncton documents and references his calculations in much detail. Although Moncton is a journalist, his work should not be discounted simply because it has not been published in a peer-reviewed scientific journal.