by Syun-Ichi Akasofu
International Arctic Research Center
University of Alaska Fairbanks
The purpose of this note is to point out that the method of study adopted by the International Panel of Climate Change (IPCC) is fundamentally flawed, resulting in a baseless conclusion:
Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.
Contrary to this statement on page 10 of the IPCC âSummary for Policy Makersâ? (2007), there is so far no definitive evidence that âmostâ? of the present warming is due to the greenhouse effect. I believe that this baseless conclusion results from the scientific composition of the IPCC study group.
The IPCC study of the present global warming has fallen into a scientific gap between the meteorological approach and the climatological approach. A study of climate change, including a study of the present warming, should belong to climatology, as the name of the IPCC indicates.
One of the most important research areas for climatologists is past climate changes, from the time of the Earthâs beginning. Geologists are also interested in past climate change. Climatology has an element of archeology that is naturally not the main concern of most meteorologists, who are basically physicists. Thus, there is a fundamental difference in how meteorologists and climatologists seek to understand the present global warming, even if both are concerned about it.
Although the media often reports that the IPCC conclusion is based on the âconsensus of 2500 world experts,â? there are perhaps not more than a few hundred genuine climatologists in the world. A large number of the participating IPCC scientists are basically meteorologists, whose study areas are physical processes of weather phenomena, not necessarily weather forecasting; their main scientific interests do not include understanding climate change that has occurred in the past. There is also a large group of scientists in the IPCC study group whose primary expertise is in computer modeling.
Meteorologists identify and provide to the modeling groups the presently known climate forcing functions, such as the greenhouse effect, effects of solar output changes, and volcanic effects. Based on this input, modelers attempt to simulate climate change during the last 100 years. They simulate climate change based on the known forcing functions under the assumption that the computer is programmed to accommodate all the basic elements of weather/climate processes. For this particular reason, they also run their models without the known forcing functions and interpret what the computer output gives as ânatural changeâ?. However, this interpretation of the computer output is doubtful and is perhaps incorrect.
Following this methodology, since none of the known forcing functions are able to accurately reproduce the observed temperature rise (0.6°-0.7°C/100 years), the modelers âtuneâ? parameters associated with the greenhouse effect (with some justification) and claim that their models can reproduce reasonably well the observed temperature rise of about 0.6°-0.7°C during the last 100 years in terms of the greenhouse effect. An important point here is that the answer (0.6°-0.7°C/100 years) is given at the start. In the past, much of the criticism of climate modeling has focused on this âtuningâ? procedure.
However, there is a more fundamental problem inherent in the IPCC approach. If natural changes with unknown causes are occurring, they obviously cannot be included among the known forcing functions in the modeling. This is a more serious problem than the âtuning.â?
In the present modeling, natural changes of unknown causes, including the Big Ice Ages, the interglacial periods, Medieval warming, the Little Ice Age and some multi-decadal changes, are mostly beyond the consideration of many participating meteorologists and modelers. Even if they knew all the forcing functions, their positive or negative feedback processes may be too complex to comprehend in applying them to the Earth system.
I am aware that many climatologists and geologists are deeply concerned about the present trend in the study of global warming, since they are aware of many known climate changes with unknown causes. However, they can contribute little to the discussion of present warming, because they cannot offer concrete forcing functions, other than changes in the Earthâs orbital path around the sun, so that many remain as a silent minority. Further, their main interests seem to be focused on climate change that occurred before the present interglacial period, such as the Dansgaard-Oeschger cycles and the Younger Dryas period.
As mentioned earlier, it is important to recognize that studying any period of climate change, including the present warming, belongs to climatology, more than meteorology. A serious defect of the present IPCC approach is that it does not pay much attention to the possible presence of natural changes, which are so obvious as one examines climate changes even during the last several hundred years. This is simply because, by training, the participating meteorologists do not know how to deal with forcing functions of unknown natural causes; some of them may believe that all the forcing functions are well understood. Nature is far more complex than they seem to be willing to admit.
Unfortunately, most meteorologists and modelers tend to concentrate only on details of the known forcing functions. Indeed, most of them are concerned only with the greenhouse effect during the last 100 years, since the physics of the greenhouse effect is well established and aerosol effects may be dealt with. As a result, they do not examine previous climate change, even as recently as during the last several hundred years. They are also afraid of dealing with âlow qualityâ data in the past or of taking too much effort to gather them (compared with satellite data). However, these are what climatologists have to face. This is why I mentioned earlier that climatology has an element of archeology. In some sense, âlow qualityâ data are more valuable in studying the present climate change than accurate satellite data of the last 20-30 years.
If the IPCC had paid careful attention to the view of genuine climatologists about climate change during the last several hundred years, they should have recognized that the range of observed natural changes should not be ignored, and thus their conclusion should be very tentative. The term âmostâ? in their conclusion is baseless. Actually, it seems that the IPCC report attempts to make the case that the present warming is extremely unusual. It seems that the IPCC is still influenced by the so-called âhockey stickâ? figure that was prominently displayed in their 2001 report, even though it was discredited and is not in the 2007 report.
Even a casual study of climate change during the last few hundred years, based on the well-known literature, shows that there is a possibility that the Earth is still recovering from the Little Ice Age. This recovery may explain much warming due to unknown causes that has occurred even during the present interglacial period; the warming rate of this recovery may be as much as 0.5°C/100 years from about 1700 to the present*. This is comparable with the rate of 0.6°-0.7°C/100 years, which the IPCC claims to be due to the greenhouse effect. The cause of the Little Ice Age is not known; in consequence, the cause of the temperature rebound is also not known. Therefore, it cannot be included as a forcing function. Nevertheless, it exists. Many glaciers in the world began to recede starting about 1700, and sea ice in the Arctic Ocean began to recede starting in 1800, so these phenomena began long before 1940 when CO2 began to increase rapidly.
Thus, it seems that the IPCC study of the present global warming has fallen into the gap between the meteorological approach and the climatological approach.
In addition, there was one obvious temperature rise from 1920 to 1940, and even a decrease from 1940 to 1975, at the same time as CO2 began to increase rapidly. It is inconceivable that the IPCC did not carefully examine the rise between 1920 and 1940. The rate and magnitude of the increase was similar to those after 1975; note that there is the superposed linear increase associated with the rebounding from the Little Ice Age and others, two together making the temperature rise highest in recent years. Their conclusion âmostâ? should be very tentative until the causes of the 1920-1940 rise can be identified. There is no conclusive evidence that the rise after 1975 is different from the 1920-1940 rise.
The computers are âtaughtâ? that the temperature rise during the last hundred years is due mostly to the greenhouse effect. If the truth is that only about 10% of the present warming is caused by the greenhouse effect*, the computer code must be rewritten. If the rebounding from the Little Ice Age should continue during the next hundred years, it will contribute a temperature rise of about 0.5°C by 2100. In addition, the greenhouse effect may contribute an additional rise of about 0.5°C by 2100, so the expected temperature rise is about 1°C by 2100. In addition, the multi-decadal oscillation might be either positive or negative in 2100. For these reasons, it may be said that the present state of global warming study is not advanced enough to become the basis of global policy-making based on the temperature rise by 2100 that is predicted by the IPCC.
There are many clear and serious reasons to reduce the usage of energy in the future, completely aside from the IPCCâs incomplete and alarming reasons. It is also very curious that so little has been done to reduce the release of CO2, in spite of the great outcry about global warming and the countless numbers of national and international conferences and negotiations.
Climate Science: Roger Pielke Sr. 