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Well, there's a big difference between weather and climate. So today, here's a quick lesson in exactly how global warming, which is attached to global climate, actually works.
Global warming is defined as a significant increase in the Earth's climatic temperature over a relatively short period of time as a result of the activities of humans. Specifically, it can be recognized as an increase of 1 or more degrees Celsius in a period of 100 to 200 years. Even within a single century, an increase of just .4 degrees Celsius would be significant.
Here's how global warming occurs: Earth turns the sun's visible light energy into infrared light energy. That energy leaves Earth slowly because it is absorbed by greenhouse gases. This in turn warms the earth. When people produce greenhouse gases, energy leaves Earth even more slowly. The temperature on Earth therefore rises which, over the course of several hundred years, changes the earth's climate.
The Intergovernmental Panel on Climate Change (IPCC), a group of more than 2,500 scientists worldwide, met for a February 2007 Parisian convention to compare and advance climate research. The IPCC determined that the Earth has warmed .6 degrees Celsius between 1901 and 2000. When the time frame advanced by five years, from 1906 to 2006, the same scientists found the temperature increase was .74 degrees Celsius.
In other words, significant.
Weather is local and short-term. If it's -11 degrees Fahrenheit in your town right now (like it is here), well, that's weather. Climate is long-term and doesn't relate to one small location. The climate of a specific area, like the Northeast, is the average weather conditions in a region over a long period of time, say, over 30 years. If the part of the world you live in has cold winters with lots of snow every year, that would be part of the climate for the region you live in. The winters there have been cold and snowy for as long as weather has been recorded, so we know generally what to expect.
Very, very important here is the understanding that any mention of climate relates to very long-term weather calculations. When we talk about a change in climate, that can only be charted by tracking weather over at least 100 years. Climatic changes often take tens of thousands of years. If you stumble upon a winter that is much colder than usual, with a ton of snow—even if that lasts several winters in a row—that isn't a change in climate. That's just an anomaly—an event that falls outside of the usual statistical range but doesn't represent any permanent, long-term change.
Clear enough so far? Here's another layer to the whole discussion. Even a slight difference in climate (that is, a sustained temperature and weather difference over 100 to several hundred years) can have significant effects. Take the Ice Age, for example. When you think of that era, you likely envision the world frozen over and covered in snow. But actually, during the last age (ice ages recur roughly every 50,000 to 100,000 years), NASA reports that the earth's average temperature was only 5 Celsius degrees cooler than it is today.
So based on science, this records-breaking cold winter is, unfortunately, not a sign that global warming is a hoax. Most recently, NASA's Goddard Institute for Space Studies confirmed there is a global warming trend occuring; noting that 2013 tied with 2006 and 2009 for the warmest year since 1880.
Here are some other findings from the IPCC (as gathered by Phys.org):
- Of the last 12 years, 11 have ranked among the warmest years since 1850.
- The warming trend of the last 50 years is nearly double that of the last 100 years, meaning that the rate of warming is increasing.
- The ocean's temperature has increased at least to depths of 3,000 meters (over 9,800 feet); the ocean absorbs more than 80 percent of all heat added to the climate system.
- Glaciers and snow cover have decreased in regions both in the Northern and Southern hemispheres, which has contributed to the rise of sea levels.
- Average Arctic temperatures increased by nearly twice the global average rate over the last 100 years (the IPCC also noted that Arctic temperatures have are highly variable from decade to decade).
- The area covered by frozen ground in the Arctic has decreased by approximately 7 percent since 1900, with seasonal decreases of up to 15 percent.
- Precipitation has increased in eastern regions of the Americas, northern Europe and parts of Asia; other regions such as the Mediterranean and southern Africa have experienced drying trends.
- Westerly winds have been growing stronger.
- Droughts are more intense, have lasted longer and covered larger areas than in the past.
- There have been significant changes in extreme temperatures -- hot days and heat waves have become more frequent while cold days and nights have become less frequent.
- While scientists have not observed an increase in the number of tropical storms, they have observed an increase in the intensity of such storms in the Atlantic correlated with a rise in ocean surface temperatures.