Some scientists emphasize the contribution of natural climate change to todays warming temperatures. A study of climate published in the magazine Nature on February 10, 2005, for example, showed a significant temperature swing between the twelfth and twentieth centuries and a cooling period that ended around 1800. The study, conducted by scientists at Stockholm University, also showed that temperatures in the twentieth century were similar to those in the eleventh and twelfth centuries, but temperatures in the last fifteen years appear to be warmer than during any previous time. These results appear to track a thousand-year-long climate simulation undertaken by another research group that included two natural forces—solar radiation and volcanic dust—believed to affect global temperatures. Experts say these studies suggest that the Earths climate is naturally variable and that changes in the sun's radiation and volcanic eruptions may be the cause. However, the increased warming during the past fifteen years still supports the idea that humans, too, are contributing to global warming.
Science Daily, "Natural Climate Change May Be Larger than Commonly Thought," February 17, 2005. www.science daily.com/releases/2005/02/050212195414.htm.
such as the Medieval Warm Period and the Little Ice Age. Since the Medieval Warm Period produced temperatures much warmer than those the Earth is experiencing today, critics argue that the Earth today may simply be experiencing a similar natural warming cycle following the end of the Little Ice Age.
In addition, skeptics question the accuracy of another important piece of evidence relied upon by global warming advocates—climate models, many of which predict the possibility of skyrocketing heat before the end of this century. In truth, some critics say, global temperatures may be turning out to be milder than these models predicted. Climate scientist John Christy, for example, coauthored a 2006 report that found that global temperatures increased only about 0.22 degree Fahrenheit (0.12 degree Celsius) per decade since 1958 and only about 0.29 degree Fahrenheit (0.16 degree Celsius) per decade since 1979—far less than most climate models predicted. Christy concludes that the Earth is not heating up rapidly and that "the rate of change is rather modest."13
Skeptics also note that while parts of the planet are warming, such as much of the Northern Hemisphere and the Arctic, the Southern Hemisphere and Antarctica are not experiencing any statistically significant warming. In fact, researchers agree that although the Antarctic Peninsula—a sliver of land that projects into the ocean toward the southern tip of South America—is seeing a rapid rise in temperatures that is causing the melting of glacier ice, most of Antarctica has not registered any warming trend in the last fifty years, basically the period for which data is available. And some researchers have reported that over the past twenty years, temperatures in Antarctica have actually cooled slightly, accompanied by increasing snowfall and thickening ice. As atmospheric scientist David Bromwich explains, "It's hard to see a global warming signal from the mainland of Antarctica right now. . . . The best we can say right now is that the climate models are somewhat inconsistent with the evidence that we have for the last 50 years from continental Antarctica."14
These and other criticisms of the global warming science continue to create a seed of doubt among the public and policy makers about whether climate change is truly a threat.
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.