<a href=showthread.php?s=&postid=7727857#post7727857 target=_blank>Originally posted</a> by eckrynock
I'm getting tired of weak examples (cat in oven, breed restrictions) etc. Please tell me you have something other than the fact that we know it gets hot in summer allows us to forecast a 1000 years into the future.
aks and you shall recieve, and sorry this is a bit lengthy, but it's fairly complex, and it's been a busy day in the lab.
this is from the paper that i linked earlier, sorry about referencing something from science, as most people don't have access to it. i will provide a few exerps for you guys though, specifically to address the climactic oscillations that are present at almost any temporal level you look at.
to help simplify things because i know it took me a long time to wrap my brain around isotopic theory (have to say theory because, like continental drift, it's just an idea that has been proven a few times, not reproduced in a lab)
so isotopes work as such: there are stable and instable isotopes of almost every atom. stable isotopes do not degrade into another element/and or isotope of the original element, unstable ones do. the common proxies for ice core/sediment core work are the isotopes of oxygen, hydrogen, and carbon. oxygen 18(denoted as O18 or d18O,(d=delta)), deuterium (heavy hydrogen, dH, or 2H), and carbon 13 (13C, C13, or d13C).
these isotopes are found naturally in nature at a fraction of the "common" isotopes of the same elements. the common ones being those on the periodic table, i.e. oxygen 16, hydrogen (without a neutron), and carbon 12.
in seawater, there is a standard (Vienna Standard Mean Ocean Water, or VSMOW) that was collected from the middle of the atlantic. the previous SMOW was off the end of the Scripps pier in the 60's. The International Atomic Energy Agency decided that something more remote would probably be more homogeneous. as a result of the VSMOW, one can look at the O18 and dH of water anywhere on the planet and determine certain things from the numbers.
the numbers differ for a few reasons, such as: the stable isotopes such as O18 are heavier than the normal O16 and therefore require more energy to cause a change in phase. so if you have 10 molecules of h2o in the ocean and one of those has a dH, a different one has an 18O, and a third has one of each, the following will happen.
the normal 7 molecules will require X amount of energy to evaporate,
the one with a dH will require X+1,
the one with an 18O will require X+2,
and the one with both will require X+3.
these fractionation events as they are called, happen at known rates due to temp, DP, RH...etc. so from this we can determine where water came from. a rain drop in a place like santa barbara will have an 18O value of something like -8%, while a rain drop in Colorado could have a value more like -80%.
it is from these known fractionation events that formulas can be derived that work for the whole globe. by reconstructing ice and sediment cores from around the globe, (these include Norther hemisphere cores like greenland, Antarctic cores like Vostok, and sediment cores from around the world courtesy of the Ocean Drilling Program, and the Deep Sea Drilling Program)
when the data is compiled, one can look back into the past climate and observe patterns and oscillations over time.
these three figures do just that:
notice in the last one they talk about aberrations and their role in the changing biosphere. look at the rate of change in temp during the Late Paleocene Thermal Maximum. This is a 5-6 degree C rise in deep sea temperature over ~8-10ky. this rapid change should be noted, since the earth's temp is currently changing at an even faster rate, which can at least in part be attributed to anthropogenic sources.
for more info on rapid climate change, there is a book by James P. Kennett titled: Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis
it is a pretty good read and gives alternate theories as to these rapid climactic aberrations.
sorry for the long-winded post, but i hope this gives everyone some insight into the natural and anthropogenic sources for climate change.
