There's a lot of really dumb people in this thread.
Look, our air quality is seeing effects from the 70's abuse of pollution. You know back when there were no regulations on what came out of a smoke pipe or what you dumped into the riverbeds.
The thing about global warming is it's such a recently publicized issue. People are finding a way to blame 2 bad years of snow on the east coast on a topic that the average North American household is extremely ignorant to. Science is great, but as Steph pointed out, data can be wrong. Unfortunately back when we believed the earth is flat, this was due to belief, and not even close to being based on any factual evidence. Modern science is not influenced by religion, but mistakes happen. The earth IS more than 3 billion years old. That has been proven and researched.
Now, human existence on this earth has been a minute on a timescale of a year. What I'm saying is, there is no possible way that we can tell what the earth's temperature was like a billion years ago. We can get estimates from geographic suggestions, but we can not determine the weather patterns other than the extremes (ice age etc). Obviously there are certain compounds and chemicals being mass produced by humans, but our earth is very sustainable of its own direction. What I'm saying is, it takes more abuse than you can imagine to shift the earth's climate a considerable amount. I am not saying it is impossible, but it takes a lot of time and a lot of consistent pollution. Unfortunately, we have been polluting for a long time and we are starting to see the effects of it. Mercury overloading in the rivers, much more potent acid rain, and other various forms of long-term polluting consequences.
It is unfair and incorrect to come out and make assumptions such as Hurricane Katrina being caused by global warming. Yes it was a very powerful storm, but it also hit in an area that never expects those types of storms. Gore sort of uses this as a guilt trip and an indirect approach to gain attention to his own publicity, which is very wrong. On his website, Al Gore confidently claims that in 25 years 300,000 people will be killed by global warming...Umm, so how exactly does global warming kill someone? If that means death by hurricanes and other natural disasters, that is not global warming.
If you look at the past 120 years, the 1880's were in a low temperature point ranging at about an average 13.8 celcius. Then it starts to increase as the industrial revolution takes part, but then significantly drops at the time of WW1. Then it increases at about the time of the Great depression. If you look at the actual numbers, and not the misleading graphs that have been shown to alter perception, the earth has recently been about .7 degrees warmer than in the previous early century.
Let's look at a volcano...Volcanoes spit out loads of sulfur dioxide which gets into the stratosphere. Now one of the last major volcano eruptions of the century Mount Katmai in AK erupted and had ash travel as far as Africa. Now a volcano actually produces a much harsher affect on the environment (although it is very short-term) because of the sulfur-dioxide it produces. The year of the Katmai eruption, the average temperature was far lower than what it is today. This could mean a variety of things, but I'll let you guys formulate your own opinion.
Now the earth is indeed getting warmer, but it was also getting warmer in the 40's. The consistency can be judged because the rate of increasing temperature since human industrialization has definitely been faster, but we don't have enough older evidence to determine a solid climate average.