Terminale, No. 4 (2012-2013)

GLOBAL WARMING CONTROVERSY GREEN HOUSE EFFECT The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere. As a result, the temperature there is higher than it would be if direct heating by solar radiation were the only warming mechanism. Solar radiation at the high frequencies of visible light passes through the atmosphere to warm the planetary surface, which then emits this energy at the lower frequencies of infrared thermal radiation. Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and lower atmosphere. The mechanism is named after the effect of solar radiation passing through glass and warming a greenhouse, but the way it retains heat is fundamentally different as a greenhouse works by reducing airflow, isolating the warm air inside the structure so that heat is not lost by convection.

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-1-3.html

http://en.wikipedia.org/wiki/Greenhouse_effect

GREEN HOUSE EFFECT GASES A greenhouse gas (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. In the Solar System, the atmospheres of Venus, Mars, and Titan also contain gases that cause greenhouse effects. Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would be on average about 33 °C (59 °F) colder than at present. http://en.wikipedia.org/wiki/Greenhouse_gas

The relative contributions of atmospheric long-wave absorbers to the present-day global greenhouse effect are among the most misquoted statistics in public discussions of climate change. Much of the interest in these values is however due to an implicit assumption that these contributions are directly relevant for the question of climate sensitivity. With a straightforward scheme for allocating overlaps, we find that water vapour is the dominant contributor (~50% of the effect), followed by clouds (~25%) and then CO 2 with ~20%. All other absorbers play only minor roles. In a doubled CO 2 scenario, this allocation is essentially unchanged, even though the magnitude of the total greenhouse effect is significantly larger than the initial radiative forcing, underscoring the importance of feedbacks from water vapour and clouds to climate sensitivity. Schmidt et al., 2010: The attribution of the present-day total greenhouse effect. J. Geophys. Res., 115

ANTHROPOGENIC CARBON DIOXIDE Anthropogenic CO2 comes from fossil fuel combustion, changes in land use (e.g., forest clearing), and cement manufacture. Houghton and Hackler have estimated land-use changes from 1850-2000, so it is convenient to use 1850 as our starting point for the following discussion. Atmospheric CO 2 concentrations had not changed appreciably over the preceding 850 years (IPCC; The Scientific Basis) so it may be safely assumed that they would not have changed appreciably in the 150 years from 1850 to 2000 in the absence of human intervention. In the following calculations, we will express atmospheric concentrations of CO 2 in units of parts per million by volume (ppmv). Each ppmv represents 2.13 X1015 grams, or 2.13 petagrams of carbon (PgC) in the atmosphere. According to Houghton and Hackler, land-use changes from 1850-2000 resulted in a net transfer of 154 PgC to the atmosphere. During that same period, 282 PgC were released by combustion of fossil fuels, and 5.5 additional PgC were released to the atmosphere from cement manufacture. This adds up to 154 + 282 + 5.5 = 441.5 PgC, of which 282/444.1 = 64% is due to fossil-fuel combustion. Atmospheric CO2 concentrations rose from 288 ppmv in 1850 to 369.5 ppmv in 2000, for an increase of 81.5 ppmv, or 174 PgC. In other words, about 40% (174/441.5) of the additional carbon has

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remained in the atmosphere, while the remaining 60% has been transferred to the oceans and terrestrial biosphere. The 369.5 ppmv of carbon in the atmosphere, in the form of CO 2, translates into 787 PgC, of which 174 PgC has been added since 1850. From the second paragraph above, we see that 64% of that 174 PgC, or 111 PgC, can be attributed to fossil-fuel combustion. This represents about 14% (111/787) of the carbon in the atmosphere in the form of CO2.

http://cdiac.ornl.gov/pns/faq.html

CARBON DIOXIDE AND TEMPERATURE

Vostok ice core records for carbon dioxide concentration and temperature change (http://www.ianschumacher.com/global_warming.html)

Earth’s climate has varied widely over its history, from ice ages characterised by large ice sheets covering many land areas, to warm periods with no ice at the poles. Several factors have affected past climate change, including solar variability, volcanic activity and changes in the composition of the atmosphere. Data from Antarctic ice cores reveals an interesting story for the past 400,000 years. During this period, CO2 and temperatures are closely correlated, which means they rise and fall together. However, changes in CO2 follow changes in temperatures by about 600 to 1000 years, as illustrated in figure 1 below. This has led some to conclude that CO2 simply cannot be responsible for current global warming. This statement does not tell the whole story. The initial changes in temperature during this period are explained by changes in the Earth’s orbit around the sun, which affects the amount of seasonal sunlight reaching the Earth’s surface. In the case of warming, the lag between temperature and CO 2 is explained as follows: as ocean temperatures rise, oceans release CO 2 into the atmosphere. In turn, this release amplifies the warming trend, leading to yet more CO2 being released. In other words, increasing CO2 levels become both the cause and effect of further warming. http://www.skepticalscience.com/print.php?r=25

HOCKEY STICK CURVE The hockey stick was a term coined for a chart of temperature variation over the last 1,000 years, which suggested a recent sharp rise in temperature caused by human activities. The chart is relatively flat from the period AD 1000 to 1900, indicating that temperatures were relatively stable for this period of time. The flat part forms the stick's "shaft". But after 1900, temperatures appear to shoot up, forming the hockey stick's "blade". The data led the researchers to the inevitable conclusion that greenhouse gas emissions were the dominant factor influencing climate variability in the 20th Century, a standpoint that remains hotly contested by some scientists. http://news.bbc.co.uk/2/hi/3569604.stm

The first sign that something amiss with the “hockey stick” was published in 2003 by Harvard scientists Willie Soon and Sallie Baliunas. Soon and Baliunas performed a survey of the existing scientific literature concerning the climate of the past 1,000 years and compiled evidence for and against the existence of the MWP and the LIA. They found that overwhelmingly, within the scores of scientific articles that they reviewed, there was strong evidence to support the existence of these well-known climatic episodes that were largely absent from the “hockey stick” reconstruction. Apparently, the handle of the “hockey stick”—that part of it which represents natural variation—is too flat.

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Then came the painstaking effort by Steven McIntyre and Ross McKitrick to simply attempt to reproduce the “hockey stick” using the data and procedures described by Mann and colleagues in their 1998 Nature publication. The resulting trials and tribulations of McIntyre and McKitrick make for a truly eye-opening look at the supposed “openness” of the scientific process. For years they toiled tirelessly in their task, working through countless roadblocks erected by the “hockey stick’s” original creators, and documenting an embarrassing number of errors in the original procedure including inaccurate data descriptions, insufficient methodological details, data compilation errors, data handling mistakes, and questionable statistical techniques. http://www.worldclimatereport.com/index.php/2005/03/03/hockey-stick-1998-2005-rip/

In the graph above the dotted line is the original Hockey Stick chart as published by Mann and as adopted and promoted by the IPCC. The solid line shows the past temperature reconstruction if the data used by Mann is averaged using the correct statistical analysis techniques rather than Mann’s unconventional ones. http://www.uoguelph.ca/~rmckitri/research/McKitrickhockeystick.pdf

CARBON DIOXIDE BENEFITS? A physicist from Colorado State University and his colleagues from the North American Carbon Program (NACP) have discerned and confirmed the unforeseen advantages of rising carbon dioxide levels. Through the processes of photosynthesis and respiration, scientists have been able to elucidate why plants are growing more rapidly than they are dying. Too much carbon dioxide can be a bad thing, but sometimes it can have a positive effect on plants and trees. The more carbon emissions we dump into the air, the faster forests and plants grow. http://www.sciencedaily.com/videos/2007/0603can_carbon_dioxide_be_a_good_thing.htm energybusinessdaily.com/

Far from being a pollutant, rising atmospheric CO 2 concentrations will never directly harm human health, but will indirectly benefit humans in a number of ways. Chief among these benefits is global food security. People must have sufficient food, simply to sustain themselves; and the rise in the atmosphere's CO2 concentration that has occurred since the inception of the Industrial Revolution (an increase of approximately 100 ppm) has done wonders for humanity in this regard. And, it will continue to work wonders in helping us meet the rising food consumption needs of a larger, future population. In addition to increasing the quantity of food available for human consumption, the rising atmospheric CO2 concentration is also increasing the quality of the foods we eat. It significantly increases the quantity and potency of the many beneficial substances found in their tissues (such as the vitamin C concentration of citrus fruit), which ultimately make their way onto our dinner tables and into many of the medicines we take, improving our health and helping us better contend with the multitude of diseases and other maladies that regularly afflict us. In just one species of spider lily, for example, enriching the air with CO2 has led to the production of higher concentrations of several substances that have been demonstrated to be effective in fighting a number of human maladies, including leukemia, ovary sarcoma, melanoma, and brain, colon, lung and renal cancers, as well as Japanese encephalitis and yellow, dengue, Punta Tora and Rift Valley fevers. http://www.plantsneedco2.org/default.aspx?menuitemid=252

A NEW SOLAR THEORY OF CLIMATE The current position of bodies like the IPCC and the broader climate alarmist lobby is that climate change in the industrial age is predominantly caused by anthropogenic greenhouse gases primarily CO 2, with relatively small natural contributions due to solar irradiance and volcanoes. However in the last decade a new theory, developed by Henrik Svensmark a physics professor at the Danish National Space Centre in Copenhagen, about how variations in the Sun’s magnetic activity may have a very profound impact on climate on earth has attracted growing interest in the scientific community. http://a-sceptical-mind.com/an-alternative-solar-theory

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The sun’s brightness may change too little to account for the big swings in the climate. But more than 10 years have passed since Henrik Svensmark in Copenhagen first pointed out a much more powerful mechanism. He saw from compilations of weather satellite data that cloudiness varies according to how many atomic particles are coming in from exploded stars. More cosmic rays, more clouds. The sun’s magnetic field bats away many of the cosmic rays, and its intensification during the 20th century meant fewer cosmic rays, fewer clouds, and a warmer world. On the other hand the Little Ice Age was chilly because the lazy sun let in more cosmic rays, leaving the world cloudier and gloomier. The only trouble with Svensmark’s idea — apart from its being politically incorrect — was that meteorologists denied that cosmic rays could be involved in cloud formation. After long delays in scraping together the funds for an experiment, Svensmark and his small team at the Danish National Space Center hit the jackpot in the summer of 2005. In a box of air in the basement, they were able to show that electrons set free by cosmic rays coming through the ceiling stitched together droplets of sulphuric acid and water. These are the building blocks for cloud condensation. But journal after journal declined to publish their report; the discovery finally appeared in the Proceedings of the Royal Society late last year. http://www.timesonline.co.uk/tol/news/uk/article1363818.ece

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