There is cause and there is correlation. Science tells us that rising CO2 is causing rising global temperatures. The underlying theory isn't that difficult to understand. A simple thermodynamic model of global temperatures sans CO2 tells us that the earth should be a frozen snowball. However, the presence of balanced, naturally occurring CO2, as well as other greenhouse gases, gives us a nice 50 deg F baseline for the seasons to operate on. The simple theory tells us that as CO2 in the atmosphere increases, the global average temperature will also increase. A little knowledge about the vibrational modes of the CO2 molecule, the emission of infrared radiation from the planet's surface, and the coincidental absorption and emission of this energy at various altitudes is all you really need to generate a decent model capable of approximating warming effects to the 1st order. NASA's Jet Propulsion Laboratory (JPL) has started a new Global Climate Change website. There you can find the following chart which shows the dramatic increase in CO2 since the dawn of the industrial revolution:
Theory tells us that CO2 causes warming. Observation attempts to correlate rising temperatures with rising CO2 to validate the theory. This is where the bulk of the noise surrounding the global warming debate has come from. Again, a few years of data is insufficient to confirm or deny the effects of global warming. However, trends can be seen in a 5 year running average temperature profile and, so far, the data confirms predictions. A running average is needed to minimize the random effects of changes in the various ocean oscillations, solar cycles, volcanic activity, etc. One of the best non-partisan references on the web is Dr. Spencer Weart's The Discovery of Global Warming.
While the many variables inherent in the earth climate system make accurate modeling of the climate profoundly difficult, the theory itself is nonetheless straightforward. That's why articles like the following irk me to no end:
Global Warming Alarmists Have Their Theories Questioned from Beyond the GraveAside from the fact that Lord Nelson's and Captain Cook's logs fall outside the time period in question, this sensationalist headline gives the impression that the theory behind global warming is so weak that a study of 17th century logs (when thermometers were rarely, if ever, carried to sea) can easily rip holes into it. The study relies on the common language referring to storms in the 17th century and is, for one, necessarily subjective. The only hard science here is the statistics employed by the researchers sifting through the logs, and not from the romantic vision of some swarthy Captain on a brigantine faithfully annotating wind speeds, ocean currents, and air temperatures. Furthermore, one can easily come away from this article thinking that the consensus believes that every storm and every drought is due in some way to global warming. Not true. No scientist worth her salt will claim that yesterday's shower is directly attributable to global warming.
The ship logs of Lord Nelson, Captain Cook, and other British sailors are casting more doubt on the theory that global warming is man-made.
The Telegraph newspaper reports that a group of British academics and scientists has examined more than 6,000 logs which describe an increasing number of storms over Britain in the late 17th century.
The Register similarly provides a banal portrait of global warming:
Old ships' logs show temporary global warming in 1730sRight...specific weather events can't be traced back to CO2 emissions. This does not mean that the frequency of storms and their intensity is not increasing with CO2. We need data to establish that. Fortunately, the National Climatic Data Center (NCDC) has developed the Climate Extremes Index (CEI) that they use to quantify these events over time. While little can be said about hurricanes, other indices used indicate that the weather over the past 10-15 years is tending to more frequent and more intense events due mainly to increased humidity, a direct correspondence to higher global temperatures.
A climate prof noted for data mining of archived ships' logs has produced further insights into global warming. Dr Dennis Wheeler of Sunderland Uni says his latest analysis shows sudden warming of the North Atlantic and Europe - much like that seen in recent times - during the 1730s.
This, Wheeler believes, shows that widespread rises in temperature of the kind recorded lately can be caused naturally. He thinks that human-caused carbon emissions are contributing to climate change now, but says it is unwise to link human emissions to specific events unless evidence is very strong.
The lesson learned here is not to believe what the headlines say, especially from partisan media websites. Don't believe what I say either. Do a little research, develop your own argument, and then look at it from the other side - I mean seriously look at it from the other point of view, and see if you can shoot holes into it. So far, the deniers are holding the swiss cheese.