Friday, October 16, 2009

What is global cooling? Definition and meaning

If we define the global warming as the global increase in the average Earth's temperature due to increased levels of greenhouse gases in the atmosphere then the most simplest global cooling definition would be global decrease in Earth's average temperature. This global decrease in Earth's average temperature is mostly the result of aerosol effects which I will tell you more about later in the article.

To fully explain global cooling we need to go almost 40 years in the past, namely back in the 1970s when different inaccurate press reports did announcement that our planet is experiencing global cooling effect, and some even predicted new ice age to come in less than 100 years time. However, though the press in 1970s wrote a lot about the cooling of the Earth it has to be said that the term global cooling only became popular after global warming popularity, mainly as its counterpart.

First of all it has to be said that the temperatures in period from 1940s to 1970s indeed had slight downward trend though definitely not sufficient enough to imply global cooling of our planet. General scientific opinion about the whole 20th century is that Earth has not gone through some significant cooling trend but did the opposite, namely undergone global warming trend, especially in the last ten years of the 20th century due to heavily increased CO2 emissions.

But what was then the cause of the cooling trend that happened in the middle of the last century? Science tells us that the answer to this question lies in the aerosols. Aerosols (solid tiny particles or tiny liquid droplets in a gas) are  mostly created as the byproducts of fossil fuels combustion. If the number of aerosols in atmosphere is high they can have cooling effect on our planet by reducing the total amount of sunshine reaching the surface. There is increasing number of scientists and politicians that would use aerosols as the ultimate fighting method against climate change problem (see this article for more info Geoengineering against climate change ) Aerosols have with no doubt contributed to cooling tendency in the middle of the last century but once world started full industrialization on global scale in 80s their cooling effect was no match for excessive greenhouse gas emissions and ever-increasing warming effect.

Some scientists believe that global cooling trend is real possibility because of fresh water mixing into the North Atlantic due to Arctic glacial melting. However most scientists agree that chances for this are very low and Intergovernmental Panel on Climate Change (IPCC) stated that chances for global warming are much bigger compared to the chances for global cooling. Though it has to be said that nobody can be quite sure about the exact effect that is going to happen once this fresh water from Arctic mixes into the North Atlantic. Judging by the current melting rates at Arctic we could very soon see what this would mean to temperatures and climate on our planet.

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