<Student’s name>
<Professor’s name>
Global cooling is a process of gradual cooling of the Earth. Hypothesis, which postulates a global cooling of the Earth's surface and its atmosphere until its glaciation.
Hypothesis never had significant scientific support, but in its favor say some publications in scientific and popular scientific press about the cyclical ice ages and the trend decline in average temperature, observed from the 1940s to the 1970s.
Now more common in academic circles is the hypothesis of global warming is increasing the earth's temperature, due to man-made human activities.
According to researchers, the annual temperature on Earth will drop a few degrees. This phenomenon was observed in the period between 1650 and 1850 years.
Approximately 3000 years ago in the North-Western Europe established a cold and wet weather. Valley of the Alps were covered by glaciers, the water level in the lake rose, there were extensive marshes. Sahara became a desert.
For information on changing weather conditions over the past 2,000 years, scientists draw from historical documents at 0,2-0,3 ° C. Along with this there were also changes in global precipitation patterns that are visible on the movement of climate zones in the direction of "North - South". For example, a slight shift of the subtropical high pressure areas (called "horse latitudes") obviously has caused more and more severe droughts in the Sahel. Since this was due to an increase in precipitation and in the countries of sub-Saharan Africa. Thus, the water level in Lake Victoria has begun to rise, flooding coastal communities.
Reid Bryson
In 1972, on a scientific conference, the famous climate explorer Reid Bryson has presented his research work. He believed that the gradual climate change leading to a decrease in temperature in recent years due to the increase of aerosol loadings. This event caused a huge stir among the world's media. The idea of global cooling has gained immense popularity.
Reid Bryson was one of the world's most famous scientists, who remained committed to the trend of global cooling. In 1948, he founded the Department of Meteorology in 1963 - the center of climate research. His idea was that at the present time, the Earth passes in the early stages of a new ice age. It was assumed that she began to cool around 2000 years ago, and after about another 400 years, global sea level will be significantly reduced due to the increase of glaciers.
Bryson believed that the accumulation of greenhouse gases will not lead to long-term global warming. He believed that air pollution has the potential for global cooling in the short term. He was criticized after a scientific consensus in the 1970s, but the perceived criticism calmly. He defended his views on lifelong learning.
In the mid-1970s., Based on the observed global cooling, the scientists came to the conclusion about the impending new ice age. They believed that the last 10 years, LTD could be interglacial.
Ice age predicted in the 70s. The media are spreading warnings about global cooling since the 1950s, alarms grew louder in 1970. In 1975 cold snap of" one of the most important problems "has become a pre-eminent threat" of death and suffering. "Statements global catastrophe were remarkably similar to what the media are spreading now about global warming. Forecasts ice age of the 1970s were mainly based on media reports. Most of the peer-reviewed scientific publications in the time predicted warming due to increased carbon dioxide levels.
The study of the greenhouse effect goes back to the French mathematician and physicist J. Fourier, who discovered this phenomenon in 1824. In 1860. British physicist John Tyndall found that CO2, like water vapor escapes the infrared radiation from the earth. Finally, at the end of the XIX century. S. Arrhenius, a Swedish chemist, pointed to the possibility of climate change due to the increased amount of heat to the atmosphere, and the accumulation of CO2 in it as a result of human activities, and in 1922. English geologist R. Sherlock noted that this activity is already affecting the climate
What was the scientific consensus in the 1970s about the future of climate change? The most frequently cited example of the predictions of cooling the 1970s - an article in 1975 in Newsweek "The cooling world" in which it was suggested that the cold snap "could herald a sharp decline in food production. Meteorologists disagree about the cause and force cooling trend. But they are almost unanimous in the opinion that it will reduce agricultural productivity to the end of the century.
1974 article in the Journal of Time "New Ice Age?" paints a bleak picture of the same:
"When meteorologists calculate the average temperature around the globe, they find that the atmosphere is gradually getting colder over the past three decades. Trend shows no signs of reversing. Climatological Cassandras are becoming increasingly concerned about the fact that the weather anomalies that they are studying may be harbingers of a new ice age. "
Peer-reviewed scientific publications
However, this article in the media, rather than scientific research. Review of peer-reviewed scientific papers from 1965 to 1979 shows that there were several papers predicting global cooling (7 in total). Much more work (of 42) predicted global warming (Peterson 2008). The vast majority of climate research in the 1970s predicted that the Earth will heat up due to carbon dioxide. Contrary to the belief that the scientists of the 1970s predicted the cold snap, the situation is just the opposite.
Scientific consensus
The most comprehensive review of the problem of climate change in the 1970s (and the closest to the scientific consensus at the time) is contained in the report of 1975, published by the U.S. National Academy of Sciences / National Research Council. Their main conclusion: " we do not have a good quantitative understanding of our climate machine and what determines its course. Without this fundamental understanding is not possible to predict climate " This contrasts sharply with the current position of the National Academy of Sciences of the United States: " at the present time there is strong evidence that significant global warming is happening It is likely that most of the warming in recent decades can be attributed to the result of human activity Scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action in the world. "This is a quote from their joint statement with the science academies of Brazil, France, Canada, China, Germany, India, Italy, Japan, Russia and the United Kingdom. In contrast to the 1970s, are now a number of scientific organizations issued statements confirming anthropogenic global warming.
What these forecasts was based on?
Quite often, the base number of predictions of global cooling in the 1970s overlooked. Perhaps the most famous of these predictions were Rasool and Schneider (1971):
"Increases in global aerosol background concentration is only 4 times may be sufficient to reduce the surface temperature by as much as 3,5 ° C."
Yes, their global forecast cold snap was based on four-fold increase in the atmospheric concentration of aerosols. It cannot be called completely unrealistic scenario - after all, the emission of sulfur dioxide has been growing quite rapidly until the early 1970s (Figure 2). These emissions cause a variety of environmental problems, and as a result, a number of countries, including the U.S., have established limits for sulfur dioxide, by the adoption of the Clean Air Act. As a result, the concentration of atmospheric aerosols has not increased four times, they have started to decline since the late 1970s:
Similarly, if we now introduce a limit on carbon dioxide emissions, we can finally take control of global warming.
Summary
So, predictions of global cooling in the 70's based largely on media reports and only a few independent scientific studies. A small number of studies, forecast cold snap is outweighed by a much larger number of works who predicted global warming due to increased carbon dioxide. Today we are dealing with an avalanche of peer-reviewed studies and overwhelming scientific consensus on man-made global warming. Compare forecasts cooling in the 70's to the present situation is inappropriate and misleading. In addition, we have reduced emissions of sulfur dioxide, which could cause global cooling. It remains an open question whether we will reduce carbon emissions, the engine of global warming.
Earth's climate in the XX century, as earlier, affect many processes. Human-induced enhanced greenhouse effect has become the leading factor of only around 1975. Prior to this, with the mid-XIX century to 1960, the concentration of CO2 in the atmosphere has increased by 35 ppm (parts per million), and after that - already at 70 ppm.
Human influence - it is also the smallest air pollution Particulate matter, which began to "work" before the enhanced greenhouse effect, just in the 40's. This cooling effect («global dimming»). It is weaker than the greenhouse effect, but write off is also impossible. Sometimes the cause of the cold 1945-1960 gg. called nuclear explosions. But this is just a coincidence. The explosions did not have such a strong influence on the atmosphere, while other factors both qualitatively and quantitatively well explain everything that happened during all periods of the XX century.
The main factor in the warmer of the 1930s and 1950s, cold called the Sun. Interestingly, in the 30 years to increase the temperature and the lower and upper atmosphere - the troposphere and stratosphere, ie, "light" warmed stronger. Then a stronger and then weaker "light bulb" was enough for the global variations of temperature. But now, apart from the relatively weak influence of the Sun, a new, more powerful factor. Now anthropogenic enhanced greenhouse effect is about 10 times stronger than the factor of solar radiation.
In recent decades, temperature trends in the troposphere and stratosphere are different: the greenhouse layer - a layer of CO2 and methane - has become thicker. Under it, in the troposphere is warming, and above it, in the stratosphere - colder. This observation shows around the globe.
Sources
- http://journals.ametsoc.org/doi/pdf/10.1175/2008BAMS2370.1
