My views on Global Warming and especially on the man-made hype
Ever since I read in 1991 about the correlation between the length of the solar cycle and global temperature (actually the variation in the average annual European temperature) presented by Egil Friis-Christensen and Knut Lassen (reference) , my attitude towards the views presented by the Intergovernmental Panel on Climate Change (IPCC) have become increasingly sceptical.
Especially the views presented in the Summary for Policy Makers on WG I "Climate Change
2001: The Scientific Basis" and in the Summary for Policy Makers on the Synthesis report
contain views that I can not as a marine geologist accept. Probably the most questionable
reference is the merging of temperature reconstruction for the past 1000 years, with weather
station temperature data and extended with GCM scenarios, as shown in Figure SPM-10b:
Variations of the Earth’s surface temperature: years 1000 to 2100. . This curve has been used
indiscriminately by Robert Watson (previous chairman of IPCC) as an example of where we are
heading due to man-made increase in greenhouse gases. The millennial curve (Mann, M.E., R.S.
Bradley, and M.K. Hughes. 1999. Northern hemisphere temperatures during the past
millennium: Inferences, uncertainties, and limitations, Geophysical Research Letters
26:759-762.) is a proxy temperature curve for the northern hemisphere based mainly on tree ring
data. It does not show any of the well known climatic excursions, e.g. the Medieval Warm Period
(http://www.skepticism.net/articles/2002/000033.html), the Little Ice Age
This question of global temperature is beautifully covered by Willie Soon et al. in a draft paper titled: Reconstructing Climatic and Environmental Changes of the Past 1000 Years: A Reappraisal written for Energy & Environment
Questions and answers:
It is said that atmospheric carbon dioxide (CO2) is steadily rising due to increasing use of fossil fuels. It is also implied that the gas is evenly distributed and furthermore that the residence time of CO2 in the atmosphere is very long. On this issue Dr Minze Stuiver’s answer to my question as to residence time.
The variations in atmospheric CO2 is well exemplified in data collected by a ship travelling between Kingston, Jamaica and Portsmout, UK.
The following is from U.S. Global Change Information Office:
Why Do Human-made Greenhouse Gases Matter When Water Vapor Is the Most Potent Greenhouse Gas?
The Earth's surface temperature would be about 34̊C (61̊F) colder than it is now if it were not for the natural heat trapping effect of greenhouse gases like carbon dioxide, methane, nitrous oxide, and water vapor. Indeed, water vapor is the most abundant and important of these naturally occurring greenhouse gases. In addition to its direct effect as a greenhouse gas, clouds formed from atmospheric water vapor also affect the heat balance of the Earth by reflecting sunlight (a cooling effect), and trapping infrared radiation (a heating effect).
However, just because water vapor is the most important gas (bolded by BW) in creating the natural greenhouse effect does not mean that human- made greenhouse gases are unimportant.Over the past ten thousand years, the amounts of the various greenhouse gases in the Earth's atmosphere remained relatively stable (my italics) until a few centuries ago, when the concentrations of many of these gases began to increase due to industrialization, increasing demand for energy, rising population, and changing land use and human settlement patterns. Accumulations of most of the human-made greenhouse gases are expected to continue to increase, so that, over the next 50 to 100 years, without control measures, they will produce a heat-trapping effect equivalent to more than a doubling of the pre-industrial carbon dioxide level.
Increasing amounts of human-made greenhouse gases would lead to an increase in the globally averaged surface temperature. However, as the temperature increases, other aspects of the climate will alter, including the amount of water vapor in the atmosphere. While human activities do not directly add significant amounts of water vapor to the atmosphere, warmer air contains more water vapor. Since water vapor is itself a greenhouse gas, global warming will be further enhanced by the increased amounts of water vapor. This sort of indirect effect is called a positive feedback.
It has been suggested that as greenhouse gases accumulate, the atmospheric events that generate cumulus clouds in tropical areas would cause a drying rather than moistening of the upper layers of the troposphere (the lowest region of the atmosphere). However, observations of the current atmosphere provide evidence for the conclusion that on a global scale, a warmed atmosphere will moisten and this will enhance greenhouse warming.
Clouds are another important factor in determining climate. The increased levels of water vapor in the atmosphere, as well as changes in temperatures and winds, will also cause changes in clouds that will alter the amount of energy from the sun that is absorbed and reflected by the Earth, at some locations enhancing and at others diminishing the warming due to greenhouse gases. The response of clouds to global warming is a major uncertainty in determining the magnitude and distribution of climate change.
The above question and answer leads to an important question. If the greenhouse gases have been rather constant for the past 10000 years, how come Earth has experienced very large climatic fluctuation as e.g. the Holocene climatic optimum, the Medieval Warm Period and finally the Little Ice Age 18-19th century?
This page is to be continued