Period of Record

420,000 years BP-present

Methods

Because isotopic fractions of the heavier oxygen-18 (18O) and deuterium (D) in snowfall are temperature-dependent and a strong spatial correlation exists between the annual mean temperature and the mean isotopic ratio (18O or δD) of precipitation, it is possible to derive ice-core climate records. The record presented by Jouzel et al. (1987) was the first ice core record to span a full glacial-interglacial cycle. That record was based on an ice core drilled at the Russian Vostok station in central east Antarctica. The 2083-m ice core was obtained during a series of drillings in the early 1970s and 1980s and was the result of collaboration between French and former-Soviet scientists. Drilling continued at Vostok and was completed in January 1998, reaching a depth of 3623 m, the deepest ice core ever recovered (Petit et al. 1997, 1999). The resulting core allows the ice core record of climate properties at Vostok to be extended to ~420 kyr BP.

The first isotopic analysis of the Vostok ice core was described in Lorius et al. (1985). Sampling of ice for 18O and deuterium was done in the field during the 1982-83 austral summer by cutting a continuous slice from the length of ice after careful cleaning. Sampling was performed on 1.5- to 2-m increments of ice. Samples were sent in solid form to Grenoble, France, and then melted before isotopic analysis in Saclay, France. Two independent series of samples were obtained. For the discontinuous series, duplicated to check reproducibility, one sample was taken at each 25-m interval from the surface down to the bottom of the core. For the continuous series, samples were collected between 1406 and 2083 m. Oxygen-18 and deuterium determinations were simultaneously performed on all the samples, and the δ18O results were discussed in Lorius et al. (1985).

The 420-kyr Vostok temperature record presented here was reconstructed from the continuous deuterium profile measured along the core. The new measurements were taken along ice in increments between 0.5 and 2 m in length to a depth of 2080 m and then every 1 m for the remainder of the upper 3310-m of the ice core. Isotopic analysis was again performed by the Geochemistry team at LSCE at Saclay. A sudden decrease from interglacial-like δDice values to glacial-like-values, followed by an abrupt return to interglacial-like values, occurs between 3320 and 3330 m (Petit et al. 1999). This occurrence plus the presence of volcanic ash layers at 3311 m suggests that the Vostok climate records may be disturbed below 3311 m. Thus, discussion of the new data set is limited to the upper 3310 m of the ice core. Petit et al. (1999) reported an ice recovery rate of 85% or higher and a measurement accuracy of ± 0.5°/°° Surface Mean Ocean Water (SMOW). The temperature estimates are based on both experimental and theoretical arguments. One of the fundamental arguments used in deriving this temperature record is that the deuterium content distribution is well documented over East Antarctica and over a large range of temperatures (-20° to -55° C); thus, there is a linear relationship between the average annual surface temperature and the snow deuterium content. The slope of this δD/surface temperature relationship was found by Jouzel et al. (1993, 1996) and Petit et al. (1999) to be 9°/°° per °C. Further details on the methodology are presented in Jouzel et al. (1987), Lorius et al. (1985), and Petit et al. (1999).

Trends

The strong correlation between atmospheric greenhouse-gas concentrations and Antarctic temperature, previously described by Barnola et al. (1987), is confirmed by the extension of the Vostok ice-core record (Petit et al. 1999). From the extended Vostok record, Petit et al. (1999) concluded that present-day atmospheric burdens of carbon dioxide and methane seem to have been unprecedented during the past 420,000 years. Temperature variations estimated from deuterium were similar for the last two glacial periods (Jouzel et al. 1996), and the detailed δDice record confirms the main features of the third and fourth climate cycles described by Petit et al. (1997). The records also indicate both similarities and differences between successive interglacial periods. Although the third and fourth climate cycles are of shorter duration than the first two cycles in the Vostok record, all four climate cycles show a similar sequence of a warm interglacial, followed by colder glacial events, and ending with a rapid return to an interglacial period. Minimum temperatures are within 1°C for the four climate cycles. The overall amplitude of the glacial-interglacial temperature change is ~8°C for the temperature above the inversion level and ~12°C for surface temperatures. Climate cycles deduced from the Vostok ice core appear to be more uniform than those in deep-sea core records (Petit et al. 1999).

http://cdiac.ornl.gov/trends/temp/vostok/jouz_tem.htm

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Gus: this is a scientific summary of the original study at Vostok, Antarctica. When its trend/conclusion was made (1999), the greenhouse gas mix was "present-day atmospheric burdens of carbon dioxide and methane seem to have been unprecedented during the past 420,000 years".

Now, new scientific studies have pointed out that [since the Vostok study] the present-day atmospheric burdens of carbon dioxide and methane has climbed further and seem to have been unprecedented during the past 2 million years...

My own assessment is that by reintroducing the massive amount of carbon back into the carbon equation of the earth surface, by burning fossil fuel, we are driving the planet to behave like it did back in the early Cretaceous, about 120 million years ago, with sea level about 100 metres above present sea level — and NO ice-caps. 

My estimate is that one of our saving grace at present — delaying the full-blown process of warming, can be noted with the different behaviour of the Arctic and the Antarctic — is that Antarctica is a continent isolated by an uninterrupted sea around it. This enforces a greater stability of climatic condition in that region compared to the north pole.

As well the warming of sea-water is "energy intensive". Around 90 per cent of the global warming energy is absorbed by the sea, with temperature rising far slower that atmospheric erratic increments, adding to stronger differentials for the creation of more powerful storms. Warmer sea with colder air above or cool sea with warmer air above can increase storm activity and power.

The earth axis and orbital wobbles also influence the behaviour of climate on a regular basis. In the past a warmer clime induced by a "regular" axis/orbit wobble possibly bring the planet closer to the sun or a more intense sun may have induced a warming which in turn would have induced release of CO2 and methane. This release would have invariably compounded the warming until the following cooling. What would induce cooling? Mostly a change in the photosynthetic equation in which say the heat intensifies the water vapour which in turn intensifies the absorption of CO2 in plants, leading to release of O2, a cooling gas as well as the cloudy water vapour which act as an albedo blanket during the day. 

The earth axis and orbital wobbles ARE NOT presently INFLUENCING  the amount of greenhouse gases in the atmosphere, nor are they influencing climate to a noticeable extent. 

Humans are.

We are burning fossil fuels, releasing CO2 in the atmosphere and letting methane add-on in the process. At the same time we have reduced the "green" equation of photosynthesis by cutting rain-forest, by cultivation and other forms of land modification — as well as increasing the acidification of the sea. Note that photosynthesis, from land and sea, represents about 6 times the amount of energy that humans use/ release on a yearly basis.

The "natural" equilibrium within the range, as measured in the Vostok up and lower levels, of CO2 has been BLOWN OUT by our adding about 200 ppm of CO2 since the industrial revolution, into the atmosphere gaseous mix. 

Please note also that YEARLY CHANGES ARE NOT LINEAR though the LONG trend is quite linear: up. The planet surface is warming up. When one does the comparative sums with the Vostok record at hand, we can expect a rise of 15 degrees Celsius by 2150. By then the average temperature of the planet could be 30 degrees Celsius, with varied temperature banding with the poles showing the biggest increase in temperature and the equatorial region with less increase in temperature.

Gus — a friend of this little planet.