PETM

56 Mio years ago, Global Warming fueled by greenhouse gases in abundance occurred once before! This event is called the Paleocene Eocene Thermal Maximum (PETM).

Due to an initial warming, maybe caused by exceeding volcanic eruptions, clathrate hydrates in oceans became unstable, releasing Methane, a potent greenhouse gas. A positive feedback started!

The global mean temperature on Earth rised from averaged 18°C up to 23°C, causing major changes in marine and terrestrial ecosystems. 

PETM is indicated by three proxies:

Indicators of PETM in the oceans (IPCC, 2007).

Global rise in temperature decreased O18/O16 ratio in oceans through enhanced evaporation of heavier isotope. There is a temperature-sensitive fractioning of oxygene isotopes via differential evaporation from oceans to atmosphere. 

Whereas the release of methane decreased C13/C12 ratio. Carbon isotope C13 is sparse in Methane, as this originates from microbes and life (on Earth) discriminates enzymatically against it. Hence a release of methane means a diminished C13/C12 isotope ratio.

Still in the oceans a part of released Methane was oxidated to CO2 or carbonic acid, dissolving carbonates (CO3) on the seefloor. 

Jens Christian Heuer

The Hockeystick – A Milestone in Climate Science

Prof. Michael E. Mann holding a tree grate with tree rings Source: Homepage Michael E. Mann

In 1999 climate scientist Michael E. Mann and his colleagues published a reconstruction of average temperatures last millenium-round on northern hemisphere  come to be known as “hockeystick”-curve (M.E.Mann,R.S.Bradley, M.K.Hughes: “Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations”, Geophysical Research Letters, 1999). This scientific paper was really a pioneering feat! It was the first reliable reconstruction of temperatures in global scale over such a long time.

The team of scientists used proxy data from tree rings, corals and ice cores on the one hand and instrumental temperature data on the other hand such as it was. The “hockeystick” demonstrated at first how extraordinary (human-made) global warming during 20th century really was! For that reason all climate skeptics dislike this curve up to the present day.

The Hockeystick-Curve. The graph resembles a hockeystick in shape: with a long part of curve declining slightly as the shaft and with a short part of curve upturning suddenly as the blade.   Source: Mann, Bradley und Hughes 1999

Assembling and evaluation of all data for “hockeystick” happened in a very sophisticated way. The proxy-data, mainly tree rings extending to 1980 were validated by instrumental data back to 1854, occasional to 18th century yet. Long proxy record and shorter instrumental record overlapped a good way. Using only instrumental data from time intervall 1902 to 1980 for calibration of proxy data, Mann and his collegues were able to use leftover intervall from 1854 to 1901 (and the rare earlier instrumental data from 18th century) to verify this calibration. Calibration and validation of proxy data  worked accurately, meaning that „hockeystick“ is correct in this regard.

CO2 is a greenhouse gas but it also acts as a fertilizer, especially for trees in high elevations. More CO2 let tree ring width and tree ring density (of summerly late wood) mimic an additional rise in temperature that does not really exist. Thus the tree ring data were readjusted.

Above: Records of two tree ring data series (ITRDB Millenial, North American Treeline), which diverged from 19th century on due to influence of CO2. ITRDB Millenial includes trees in high elevations much sensitive to dunging effect of CO2. Below: Variations in atmospheric CO2 and residual between the two data series, used for readjustment. Source: Mann, Bradley und Hughes, 1999

Two examples how carefully Mann and his team had gone about it! All that and then some you can read in original paper, downloadable on Mann´s homepage (see sources below). It´s worth it! Michael E. Mann was also a lead author of 3rd. IPCC-Report about global warming in 2001.

In the course of General Assembly of European Geosciences Union (EGU) in April 2012 Michael E. Mann received the Oeschger-Medal for his research! Hans Oeschger (1927) was a Swiss scientist, famous because of his ice core research. Together with Willi Dansgaard he discovered a series of abrupt climate changes (Dansgaard-Oeschger Events) during the last glacial period by analysis of Greenland ice cores. Also he measured first the glacial-interglacial change of atmospheric CO2 encased in ice core´s tiny air bubbles.

But also some climate sceptics tried again and again to discredit Mann scientifically and personally. Fortunately they failed yet.  I hope it stays that way!

Jens Christian Heuer

Sources: European Geosciences Union (EGU) , Homepage Michael E. Mann

Weather Situation September,14th 2012

Full Earth September, 14th 2012, 11.00 UTC Sourece: EUMETSAT

General Synopsis of North Atlantic and Europe: A Cut-Off Low over Mediterranian has detached from Jetstream further north. Mediterranian Cut-Off Low looks really beautiful! Jetstream at the North is decernible as a band of cloud.

Usually the pathways of low pressure weather systems are strongly controlled by current of the Jetstream. But sometimes the Jetstream  slows down or even breaks, so that weather systems can detach (Cut-Off). After that they move independently until they decay or are captured by a trough of a new established Jetstream.

Low pressure systems on Northern Hemisphere are spinning anticlockwise due to Coriolis force. Inside the system air is rising and cooling. If air-moisture is sufficient condensing water vapor starts to form clouds, made of tiny water droplets (or tiny ice crystals in higher altitudes). It might rain or snow. Bad Weather!

For comparison the model calculation chart for windspeed and Jetstream in the higher troposphere:

Windspeed and Jetstream in the higher Troposphere. Source: www.netweather.tv

The mathematic circulation model shows almost perfect all features of reality!

Jens Christian Heuer

New MeteoSat

First Picture of MeteoSat 3rd Generation. Full Earth from geosationary orbit. Source ESA

MeteoSat Weather satellites 3rd Generation are stabilized by three gyrating momentum-wheels orientated to the three directions in space. The precursor MeteoSats, 1rd and 2rd generation were stabilized by their own spin. With the new three-axle stabilization the instruments of weather satellite are pointed to Earth more exactly and for a longer time, most likely even to the end of orbit time.

MeteoSat 3rd Generation have a Flexible Combined Imager for visible and infrared channels (inclusive some additional ones) with better spatial resolution compared to old weather satellites.

Jens Christian Heuer

Jetstream


Nice Animation of a Jetstream Source: NASA – GISS

Jetstreams are driven by atmospherical differences in temperature and thus in air pressure. There are horizontal gradients in air-temperature of atmosphere, for example between polar regions and mid latitudes, but there are also vertical gradients leading to convection and to cloud formation if air moisture is sufficient.

A Jetstream forms Rossby waves, troughs and ridges traveling streamwise and also eddies, the weather-making high and low pressure systems. These eddies arise from turbulences in jetstream like the vortexes of a raging river do.

Jens Christian Heuer

A nice animation: