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Source: BBC, Helen Briggs reporting, Dec. 1, 2007

50 years on: The Keeling Curve legacy

Excerpt below:
"It is a scientific icon, which belongs, some claim, alongside E=mc2 and the double helix.

Its name - the Keeling Curve - may be scarcely known outside scientific circles, but the jagged upward slope showing rising carbon dioxide (CO2) levels in the atmosphere has become one of the most famous graphs in science, and a potent symbol of our times.

Scientific uncertainty over the speed at which the Polar ice caps can/will melt is another feature of the current state of the science for climatologists. To melt ice actually takes energy, and the simple (drip-drip-drip) melting of an ice sheet the size of Greenland would take several hundred years. There is certainty in that simple model for Greenland's future. This is one reason why it was allowed into the recent IPCC report.

The San Francisco Chronicle (April 3, 2007) reports on the effects that this recent ruling might have on California's efforts to reduce the c02 emissions of automobiles:

"The campaign led by California to combat global warming at the state level took a giant step forward Monday when the U.S. Supreme Court rejected the Bush administration's hands-off approach to climate change and pushed the government toward regulation of greenhouse gases.

The National Geographic News reported on April 8, 2004, that research was forthcoming about the imact of global warming on the Greenland ice shelf. Reporting on a just published study in the journal Nature, the article points to a future where Greenland ice melts entirely in a thousand years:

"The study considered the climate sensitivity of a range of climate models and a range of carbon dioxide scenarios, from 450 parts per million, the lowest level considered by the United Nation's Intergovernmental Panel on Climate Change, to a thousand parts per million, or four times the pre-industrial carbon dioxide concentration.

Low probability, but high impact scenarios: Introducing the backgrounds of a “Dangerous Climate Change”

The balance of scientific evidence now suggests that anthropogenic greenhouse gas emissions are having a significant effect on the earth’s system and especially on the earth’s climate. Since the 1970s, there has been a significant increase of extreme weather events. Tropical and extra-tropical storm frequency and magnitude have considerably increased and so have the flood risks and heatwave occurrences along with very severe socio-economic and ecological impacts all over the globe. Even though the natural science of extreme weather events has progressed over the last decades, modelling climate scenarios still remains pretty speculative. However, it is now scientific consensus that if we continue to follow our “Business as usual”-path and if the greenhouse gas emissions weren’t cut drastically within the next decades, the impacts of a changing climate will intensify throughout the 21st century, with dangerous high impact scenarios becoming more likely to happen. A “dangerous climate change” with raising temperatures especially above 2°C (above pre-industrial levels) could tip certain ecological thresholds and trigger non-linear processes and feedback loops within the earth’s system, forcing the system rapidly into a totally new equilibrium. Dramatic changes within the carbon cycle, the eco- and hydrosphere and most obviously within the kryosphere would exceed our society’s ability to adapt to these changes. Unmanageable and most likely irreversible consequences could put our mankind on the edge of extinction. (1)

The model looks at sea level rise from thermal expansion only, noting that ice melt is too difficult to determine:

"In response to greenhouse gas warming, sea level is expected to rise due to the thermal expansion of sea water as the ocean warms. Because the deep ocean will warm much more slowly than the upper ocean, the thermally driven rise in sea level is expected to continue for centuries after atmospheric CO2 stops increasing. To illustrate, Fig. 4 shows the increase of global mean sea level in the GFDL 4xCO2 coupled climate model experiment. Even though CO2 no longer increases after year 140, sea level continues to rise steadily well beyond year 500. The final equilibrium sea level change in the model is 1.9 meters for a CO2 doubling (not shown) which is roughly the level attained in the CO2 quadrupling experiment after 500 years. The equilibrium rise for the quadrupling experiment has not yet been simulated."

From NOAA:

Climate Impact of Quadrupling CO2