The inconvenient truth is that Al Gore's movie is way off base. The film has lost enough of its credibility that a British court recently ruled that it cannot be shown in schools without a disclaimer detailing its political bias.
The most damning scientific flaw in Gore's movie is his claim that of a link between global temperatures and carbon dioxide levels. There is a link, but, unfortunately for Gore's believers, it is not as he suggests. In truth, increased carbon dioxide levels come about 800 years after increases in temperature. If the temperature changes first, then how can CO2 be the cause of the temperature change?
In fact, carbon dioxide isn't even the most prevalent greenhouse gas in our atmosphere. Water vapor actually causes from 36-70% of the earth's greenhouse effect.
Gore's claims that the earth is hotter than ever before also do not bear scrutiny. Environmentalists have cited NASA data that showed that 1998 was the warmest year on record, but that was recently revealed to be untrue. Steven McIntyre, of the Climateaudit blog, determined that NASA's algorithm used to determine the hottest year had been corrupted by the Y2K bug. NASA corrected their figures (without a press release of any kind) and 1934 is now officially the hottest year on record. Five of the ten hottest years are now known to be before WWII.
Further giving lie to Gore's claims is the Medieval Warm Period. The Medieval Warm Period occurred from AD 800-1300. In this era, the glaciers shrank enough that the Vikings were able cultivate parts of Greenland. Parts of North America suffered severe droughts. Radiocarbon dating from the Sargasso Sea showed sea temperatures 1 degree celsius warmer than today. Alaska has been through three separate warm periods in the last two thousand years.
Following the Medieval Warm Period, the world entered the Little Ice Age. During the Little Ice Age, the Sargasso Sea was about 1 degree celsius cooler than today. This ice age lasted until the middle of the 19th century when the world entered a warming cycle, which we are still in today.
Gore also ignores the scientific advances of the last fifty years. Certainly there are more cars and factories operating today than in past decades, but today's technology makes them burn more cleanly than the fewer cars of old.
If man made carbon dioxide emissions are not causing the earth's warming, then what is? The answer may be the sun. A 2001 article in Nature describes the relationship between the sun and the ratio of oxygen-18 to the more common oxygen-16 molecule. Over a period of 3000 years, the authors of the study found a direct correlation between the intensity of cosmic rays striking the earth's atmosphere and the earth's temperature (http://www.hillsdale.edu/news/imprimis/archive/issu e.asp?year=2007&month=08). It would seem that the sun is responsible for the cyclical heating and cooling of the earth's climate.
When considering climate change, ask yourself several questions. Based on what we can see locally, the earth is getting warmer, but is it a true global change? Data from surfacestations.org casts doubts on data from improperly located automated weather stations. Stations located in urban areas may falsely report higher than actual temperatures.
If so, is the warming caused by man? As stated earlier, carbon dioxide cannot cause temperature change because carbon dioxide levels change 800 years after the temperature.
If so, is it reversible? Even if global warming were caused by man, it is highly unlikely that the whole world would agree to the draconian cuts on CO2 emissions that Gore and the environmentalists want. The US is not the problem. China and other developing countries have lax environmental standards and are set to pass the US in CO2 emissions in the next few years.
Is global warming bad? The earth is constantly changing. Warm periods in our history have typically been prosperous due to longer growing seasons for crops and require less energy for heating homes. Some areas would benefit and some would not. Even the UN report on climate change does not support the more hysterical environmental claims of catastrophe. Even if all of the ice caps melted, for instance, sea levels would rise less than two feet. Rising seas would not flood all low lying areas as Gore and company claim.
Finally, if the environmentalists are so concerned about greenhouse gas emissions, then why don't they support nuclear power? The French have proved that nuclear power can be a safe, clean, cheap source of electricity. Why not promote its use worldwide as an alternative to carbon based sources of energy?
The jury is still out, but the science used by the environmentalists is seriously in question. It is always a good idea care for the environment, but not at the cost of destroying our economy.