This last step causes a flaw, as too often instead of experts in the field, the calibration to temperature is done with Excel or Matlab instead of actual scientific method. Throwing hundreds of proxies together and seeing which ones are matching to current temperatures, creates the possibility that you have selected proxies at random. This has the effect of creating hockey sticks, as random data average to zero, while in current times, only the higher value proxies have been kept.
Prior to the beginning of the Industrial Revolution, usually said to have 'begun' in Hutterfield, England in 1830 with the invention of water powered machinery to make textiles the CO2 level stood at 286ppm. We know that because even in that day fairly accurate measurements were made. By the 20th century indirect methods determined that the 286ppm totals extended back to end of the last ice age and further data showed that for 65 million years prior.
By 1850 the use of coal began to power the industrial revolution. By 1870 the use of 'rock oil' for oil lamps began to pick up and by 1900 the use of gasoline began. By 1950 the CO2 level stood at 350ppm... the highest reading since the dinosaurs roamed....and the highest reading EVER for hundreds of millions of years.
Today readings as high as 400ppm have been recorded.... all of it attributed to burning fossil fuels. By 2030 the CO2 index will reach 450ppm...the foothills at least of a runaway greenhouse effect. By then there will be over 9 billion people in this world... this situation won't be good. It will be worse because the deniers seem to be able to hold up any plan to even begin to THINK about dealing with this. The ignorance is remarkable as illustrated by this 'question'. Even a casual investigation into the history of the science of climate and how we actually 'know things' is missing from their agenda. I don't have an answer for this anymore than the passengers on the Titanic had a plan for when the ship went down. They certainly knew it was going to sink at some point, though early on during this event I'm sure there were 'deniers' who called the folks preparing to abandon ship, 'alarmists'...so things never change!
Glaciers, some of which are millions of years old at the bottom (yeah, pretty amazing) hold trapped bubbles, so measuring CO2 is really easy. You only have to calculate the age of the layer that the bubble is trapped in, and they've gotten pretty good at that.
Air temp and water temp are pretty well coordinated, so if you know one, you have a pretty good idea of the other. Turns out that there are thousands of species of plankton, many of which are around today, pretty much unchanged. AND, those various species have varying preferences for temp, growing better when it's a temperature that each individual species needs. When they die, they sink to the ocean floor. There are now thousands of ocean core samples, many of which were looking for oil, but most of which can be analyzed to see what was in the ocean at the time. When you look at the relative proportions of the various species, you can have a pretty accurate indication of the temperature in which they grew. And, since they're plants, and need sunlight, and must grow near the surface, where the water temperature and the air temperature are pretty close.
Is that okay?
No one knows exactly what air temperature was hundreds of years ago. As you said, such measurements were never recorded. We would have little idea of what global temperatures were hundreds of years ago, except for such proxies as oxygen-18 in ice cores, tree rings and boreholes.
Carbon dioxide probably changed little prior to the industrial revolution, because, without people driving SUVs and using coal to produce electricity, there was little to change atmospheric carbon dioxide concentration. Nevertheless, carbon dioxide in air centuries ago may be determined using the following sequence.
1. Use berylium-10 proxies to determing cosmic ray flux.
2. Use the cosmic ray flux to determine the atmospheric concentration of carbon-14.
3. Use the carbon-14 in tree rings to determing the atmospheric concentration of carbon dioxide.
BULL= I proved to 350 million people and the 43000 scientists that bush hired to find the cause of Global Warming and the solution to end it in 2008 that all non solids that rise into the upper atmosphere separates into nothingness in 2008. On 11/28/2012 Global Warming ended. Mike
Well , all they need to do is get in Doc.1981 De Lorean and go 88 mph , Set the time for were they wish to go . and they can be the first to get the readings they clamed to know . Some clamed Tree rings , but come on ,that just shows a good growing year at best , and to save the Earth by cutting the trees down to see what happened .And ice ,were we not told it all melted .
They are recorded in tree ring and ice cores.
nobody was there either millions of years ago, but we know that coal came from dead plants. We do not need to have cameras taking pictures a million years ago to know that either.
look up dendrochronology and isotopic analysis.
isotopes: http://en.wikipedia.org/wiki/Isotope
Or molecular density, same diff.
explain how scientists are able to determine the air temperature and the amount of carbon dioxide in the atmosphere hundreds of thousands of years ago when such measurements were never recorded
