The Weather Channel Position Statement on Global Warming
Introduction The scientific issue of global warming can be broken down into three main questions: Is global warming a reality? Are human activities causing climate change? What are the prospects for the future?
Warming: Fact or Fiction? The climate of the earth is indeed warming, with an increase of approximately 1 - 1 1/2 degrees Fahrenheit in the past century. The warming has taken place as averaged globally and annually; significant regional and seasonal variations exist. The amount of warming in the upper atmosphere has been more difficult to quantify, but new research shows a trend similar to that near the surface.
Impacts can already be seen, especially in the Arctic, with melting glaciers, retreat and thinning of sea ice, and thawing permafrost affecting human populations as well as animals and vegetation. There and elsewhere, rising sea level is increasing coastal vulnerability.
Odds are now leaning toward increased frequency and intensity of heat waves in the warm season and warm spells in the cold season in parts of the world, as well as reduced frequency of low temperature extremes.
In some regions there has been a tendency for an increase in precipitation extremes, both wet (including floods) and dry (droughts). These observations over the past several decades are consistent with what theory and global climate models would suggest.
Global warming cannot be ruled out as a contributing factor to recent increased hurricane activity.
Human Influence To what extent the current warming is due to human activity is complicated because large and sometimes sudden climate changes have occurred throughout our planet's history - most of them before humans could possibly have been a factor. Furthermore, the sun/atmosphere/land/ocean "climate system" is extraordinarily complex.
However, it is known that burning of fossil fuels injects additional carbon dioxide and other so-called greenhouse gases into the atmosphere. This in turn increases the naturally occurring "greenhouse effect," a process in which our atmosphere keeps the earth's surface much warmer than it would otherwise be.
More than a century's worth of detailed climate observations show a sharp increase in both carbon dioxide and temperature. These observations, together with computer model simulations and historical climate reconstructions from ice cores, ocean sediments and tree rings all provide strong evidence that the majority of the warming over the past century is a result of human activities. This is also the conclusion drawn, nearly unanimously, by climate scientists. Any meaningful debate on the topic amongst climate experts is over.
Humans are also changing the climate on a more localized level. The replacement of vegetation by buildings and roads is causing temperature increases through what's known as the urban heat island effect. In addition, land use changes are affecting impacts from weather phenomena. For example, urbanization and deforestation can cause an increased tendency for flash floods and mudslides from heavy rain. Deforestation also produces a climate change "feedback" by depleting a source which absorbs carbon dioxide.
The Future The bottom line is that if greenhouse gas emissions continue to increase, a significant warming trend is expected to also continue. The ability to adapt will be crucial. Potential outcomes range from moderate and manageable to extreme and catastrophic, depending on a number of factors including location and type of effect, and amount of greenhouse gas emissions. Not every location and its inhabitants will be affected equally, but the more the planet warms, the fewer "winners" and the more "losers" there will be as a result of the changes in climate. The potential exists for the climate to reach a "tipping point," beyond which radical and irreversible changes occur.
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