On Tue, Feb 8, 2011 at 12:04 PM, Scott Stroz <[email protected]> wrote: > > I have yet to hear anyone explain how the climate changed so much > before man had machines. > > Look at the graph here, > http://www.daviesand.com/Choices/Precautionary_Planning/New_Data/ > > How do you explain the climate change from several hundred thousand years ago? > > I am really not trying to be a prick, I am trying to understand. Over > the last few hundred thousand years the climate has changed a lot and > drastically, why is it that we think the current climate change is > anthropogenic, but not at other times?
I don't think you are a prick at all for asking that and it is really one of the big things that Paleoclimatologists spend their time asking. I am not one, obviously, but I'll do my best to explain as far as I understand it. There are two major things to consider. One is how things are changing and the other is how rapidly they are changing. The graph you link to shows variations in temperature and CO2 concentration. First thing to notice is that most of the graph area is in the negative region, meaning that it was colder than now and there was less CO2 in the atmosphere. So we are in a very warm period, near the maximum of the previous spikes. Yet our current trends are toward drastic increase in temperature and CO2 levels, which if you do your basic calculus, would indicate that we are not near the local maximum for our current spike. You'll also notice that the horizontal ticks on that graph are marked off in 10,000 year increments. The current major spike we are seeing in CO2 concentrations and temperature increases are happening in *decades*. It can be difficult to measure ice core ages down to years, so we cannot be certain that there were no similar spikes that happened in just a couple of decades in the pre-human period but circumstantial evidence would seem to make it unlikely. As far as I know, however, that is still an open question though. As to what the causes of the previous variation were, there are a number of factors that have been put out there to consider. Orbital variation, variation in the suns energy output. fluctuation in the ocean's current and volcanism are all elements that are thought to contribute to the feedback loops that make up the historic patterns of climate change. Obviously, all of those things are still at work. However, we can look at those and see the effects of some of them currently (like the change in atmospheric composition and weather patterns after Mount Pinatubo exploded) and they are insufficient to explain the historically unprecedented rapid increase in atmospheric CO2 concentrations and global temperature. On the other hand, we can see a precise increase in the amount of CO2 that humans have been pumping into the atmosphere in the last couple decades. So, to summarize, we know some of the factors that have historically influenced global climate change. Those factors are still at play now. However, they are insufficient to explain the sudden and drastic change in the atmospheric composition and global temperatures that we are currently seeing. There is a possibility that there is another factor at play that is not related to human activity that we are currently totally unaware of, however, the direct link between the post-industrial revolution change in human activity and the subsequent changes in atmospheric composition seem compelling and broadly substantiated. Hope that helps, Judah ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Order the Adobe Coldfusion Anthology now! http://www.amazon.com/Adobe-Coldfusion-Anthology/dp/1430272155/?tag=houseoffusion Archive: http://www.houseoffusion.com/groups/cf-community/message.cfm/messageid:334109 Subscription: http://www.houseoffusion.com/groups/cf-community/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/groups/cf-community/unsubscribe.cfm
