What Halted Global Warming in Mid-20th Century?

A comparison of a primary source vs. a secondary source.

A primary source is some kind of published material, such as a journal, that was written during the time under study and is subject to peer review.. Experts on the topic that is published will read through and review the article for accuracy, clarity and quality. Secondary sources analyze and interpret primary sources. The writer of the secondary sources takes out the main points and presents them to a more general audience in a simplified way. Both primary and secondary sources present the basic information but the primary source goes more in depth and complex.

The articles, ‘Ocean Cooling, Not Pollution, Halted Global Warming in Mid-20th Century’ and ‘An abrupt drop in Northern Hemisphere sea surface temperature around 1970.’ both explain what caused the halt of rising global temperatures around 1970. The secondary article, which is the one that is listed first above, states that instead of the steady increase of air pollution causing the sudden halt in global warming it was the surprising cooling down of the oceans between 1968-1972 that put global warming on hold. The most area that experienced the greatest cooling was the North Atlantic but there were decline in temperatures recorded throughout the oceans in the Northern Hemisphere. The secondary source has very limited information in it and only has a couple key points, but its message is still clearly stated. The recent discovery that ocean cooling was the reason for the drop in temperatures replaces the old thought that it was aerosol pollution causing the decline in temperatures.


The reason aerosols were previously suspected is that some types of aerosol pollution (sulfates from coal burning being an example) reflect sunlight, counteracting the greenhouse effect and masking warming that would otherwise happen due to greenhouse gas accumulation alone (McDermott, 2010).



This statement is one of the strong claims the author is trying to get the audience to understand. It was not aerosol pollution reflecting the suns rays but actually the abrupt cooling of the oceans that caused the temperatures to decline between 1968 and 1972.
The primary article, which the secondary article was based on, goes into more detail and shows lots of statistics and graphs that the author refers upon. The primary source is directed to more scientifically inclined people and people who are interested in global warming. The article is much more complex and detailed. Unlike the secondary source, the primary source shows all the studies and stats to back up the authors research. It is also much longer and contains a lot of dry, boring material. David W. J. Thompson, the author was obviously using all of his research and statistics he had collected to prove his claims.

In the primary source one of the main points the author is trying to relay to the audience is that the global temperature does not increase every year. There are times when the global temperature decreases.
The twentieth-century trend in global-mean surface temperature was not monotonic: temperatures rose from the start of the century to the 1940's, fell slightly during the middle part of the century and rose rapidly from the mid-1970's onwards. The warming-cooling-warming pattern of twentieth-century temperatures is typically interpreted as the superposition of long-term warming due to increasing greenhouse gases and either cooling due to a mid-twentieth century increase of sulfate aerosols in the troposphere or changes in the climate of the world’s oceans that evolve over decades, (Thompson1, 2010).


It is now proven though that the decrease in temperature was too rapid around the 1970's that it could not of been caused by aerosol pollution, but was caused by the decrease in ocean’s surface temperatures. Even though the world’s average temperature is on the rise, there are time periods when the temperature does not rise but actually drops.


The sudden drop in oceanic surface temperatures experienced between 1968 and 1972 was not an isolated event. It was widespread mainly through the northern hemisphere.
The drop is not concentrated in any discrete region of the Northern Hemisphere oceans, but its amplitude is largest over the northern North Atlantic (Thompson2, 2010).


The widespread drop of ocean temperatures in the Northern Hemisphere oceans was the cause of the global warming halt. In the primary source these were the main claims that the author was trying to express. The limitations of the article is that not everyone will understand all of the statistics and graphs that are posted. The audience is the limitation. The secondary source gets rid of that limitation by presenting the material from the primary source in an easy to rid and straight to the point fashion.


The primary and secondary sources both explain the main points of the issue. The primary source goes into a lot more detail compared to the secondary source. The secondary source is a quick and easy way to get informed on an issue and get the main points and arguments quickly. My primary source can be found by clicking on the following link:
http://www.nature.com/nature/journal/v467/n7314/full/nature09394.html,


and my secondary source can be found by clicking on the following link


http://www.treehugger.com/files/2010/09/ocean-cooling-not-pollution-halted-global-warming-mid-20th-century.php?campaign=top_news


My Visual:
http://www.treehugger.com/galleries/2010/01/thought-jaws-was-scary-10-more-fish-to-inspire-nightmares.php ...... a link of a slideshow of some sea creatures





References
McDermott, M. (2010, September 22). Ocean cooling, not pollution, halted global warming in mid-20th century. Retrieved from http://www.treehugger.com/files/2010/09/ocean-cooling-not-pollution-halted-global-warming-mid-20th-century.php?campaign=top_news


Thompson1, D. (2010, July 20). An abrupt drop in northern hemisphere sea surface temperature around 1970. Retrieved from http://www.nature.com/nature/journal/v467/n7314/full/nature09394.html


Thompson2, D. (2010, July 20). An abrupt drop in northern hemisphere sea surface temperature around 1970. Retrieved from http://www.nature.com/nature/journal/v467/n7314/full/nature09394.html