Last February, I experienced "snowmageddon" on the East Coast. I recall during that time reading a news article about some conservative politicians' gleeful mocking of former Vice President Al Gore and the concept of global warming; they claimed that the blizzards and record snowfalls were evidence that global warming does not exist. Sen. Jim Inhofe of Oklahoma and his family built an igloo on the Washington Mall and placed in front of it a cardboard sign that read, "Al Gore's new home," and "honk if you [heart] global warming." Sen. Jim DeMint of South Carolina tweeted that day, "it's going to keep snowing in DC until Al Gore cries 'uncle.'" However, ignorance must truly be bliss for these senators. As Think Progress pointed out, "scientists have been warning for decades that global warming would increase the severity of winter storms." These Republican senators' actions further demonstrate their myopia in their focus on a single weather event (or 2 weather events) and slightly colder than normal temperatures over a short period for a very small geographic area (compared to the entire planet).
The bottom line is that no single weather event, including a hot spell or a cold spell are evidence supporting or contradicting the theory of global warming. Global warming adherents would be making a similarly flawed argument if they indicated that the recent heat wave in the East Coast, by itself, was evidence of the existence of global warming.
However, scientists have just reported that the first six months of 2010 have been the warmest on record, and that 2010 is on track to become the hottest year since global average temperature records were kept. In seeking evidence for or against global warming, scientists look at trends, not single data points. They examine global temperatures, not just the weather in the U.S. (as ethnocentrists Inhofe and DeMint apparently enjoy doing). The science of greenhouse gases is very well established, especially with respect to carbon dioxide. There is no significant dissent within the relevant scientific community of carbon dioxide's property as a heat-trapping gas.
Since I am not a climate scientist, or any type of scientist, I kindly refer you to the official statements and consensus opinions of the most distinguished and relevant scientific bodies in America:
Most US climate scientists belong to the American Geophysical Union. Their statement indicates that "the Earth's climate is now clearly out of balance and warming..." and that the warming is "best explained by the increased atmospheric abundances of greenhouse gases and aerosols generated by human activity during the 20th century."
The American Meteorological Society's statement also affirms that global warming is occurring and that it is due to human activity.
The US National Academy of Science, which was established by Congress to provide scientific advice to Congress and is comprised of the most distinguished scientists in the country, also published a statement affirming the existence of climate change. It concludes that "emissions of carbon dioxide from the burning of fossil fuels have ushered in a new epoch where human activities will largely determine the evolution of Earth's climate," and that "emissions reductions larger than about 80 [percent]... are required to approximately stabilize carbon dioxide concentrations for a century or so."
The American Association for the Advancement of Science has issued a number of statements, including this one, which indicates that,
The concentration of atmospheric carbon dioxide-- derived mostly from the human activities of fossil-fuel burning and deforestation... is higher than it has been for at least the past 650,000 years... Thousands of respected scientists at an array of institutions worldwide agree that major health and economic impacts are likely unless we act now to slow greenhouse gas emissions.
Finally, and perhaps most significantly, a joint statement of 18 different American scientific societies, whose scientists are involved in research relevant to climate change and its effects, produced this consensus statement, that "observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that greenhouse gases emitted by human activities are the primary driver."
Virtually every relevant authoritative scientific organization in the country has demonstrated its consensus with the global climate science community that global warming is occurring, that it is due to human activity, and that if we do not curtail our greenhouse gas emissions, we will probably experience drastic changes in our environment with adverse impacts on human health and prosperity. The mainstream media, which generally seeks to capitalize on any controversy by inflating it in order to increase their ratings, gives climate skeptics ample opportunity to confuse the public by allowing them to make statements unsubstantiated by climate scientists. The result has been a confounded and divided public on the issue, with politicians using it as a political football rather than focusing on the facts.
For those who are interested in seeing some of the data with their own eyes, the following are links to measurements of atmospheric carbon dioxide and global temperature:
Carbon Dioxide Measurements (the ice core records are particularly interesting)
Global Temperature Data
FAQ on Global Warming by the National Climate Data Center