I recently saw this link on a friend's facebook page. Summarized, the story was about sunspot activity on our sun, how this is decreasing in the past years; was this going to lead us into a period of cold weather? During the Little Ice Age, sunspot activity was also rather low.
During the discussion that followed the article, somebody asked about the relative importance of sunspots vs greenhouse gases, seeing as how we'd been dumping rather large quantities of these into the atmosphere recently, much more so than during the little ice age. Which prompted someone else to comment:
Does this guy know that volcanic ativity since the Earth has been around is responsible for the gases that make up the atmosphere not humans. One medium grade volcanic expolsion is more distruptive to all human contributions times 4.
First let's check that second statement; is it true? According to the USGS, it is not true; the yearly emissions of CO2 due to humans is around one hundred times that of volcanoes. So this is just wrong. The first statement, however, is the one with the faulty thinking.
On the face of it, it seems logical enough; volcanoes have been around a lot longer than cars, so even if we're pumping CO2 into the atmosphere at an amazing rate, this cannot compete with volcanoes that have had millions of years of head start on the cars. This sort of faulty thinking can be hard to spot and catch, as it's sandwiched in the middle of a technical discussion about a topic that we're not familiar with. Let me make a similar statement about a more familiar topic.
Joe says "you have to be careful with drinking so much water, it's poisonous in large quantities". Whereas Susan says "are you crazy? Think about all the water you've drank in your lifetime! What difference is one more gallon going to make!!" It's essentially the same statement.
If a person never sweated and never went to the toilet, then all that water would still be in her body (and she'd weigh about ten tons instead of 135 pounds), and then Susan would be right ... one more gallon would not make a difference. However, that's not the way it works. You drink about a pound of water per day and you pee or sweat about the same amount out every day. If you drink your gallon of water within a short period, it is poisonous --- look it up, people die like that.
Same deal with volcanoes and humans. The earth was perfectly capable of keeping the CO2 in balance with all the emissions due to volcanoes. The big question is, now we're dumping 100 times more CO2 into the atmosphere ... can the earth keep up, or will this prove to be poisonous, like too much water too fast for the body?
