lightblueline

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)

An obvious increase of extreme weather events such as heatwaves, floods and tropical storms during the last decades has given raise to worldwide concerns and indicates most likely the potential impacts of a global warming in the future. Besides these temporarily restricted events other impacts which emerge only gradually, such as rising sea levels are at least as serious.

Due to the high concentration of natural and socio-economic values located especially around coastal zones, rising sea levels raise significant concern. More than 1.2 billion people, representing 23 percent of the world’s population live on coastal plains at densities about three times higher than the global mean. (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

Here is Alex Tingle's global sea level rise layers on Google Maps. These data are derived from the NASA SRTM (Space Shuttle radar) mission.

Dynamic maps of sea level rise. Does global warming matter to you?

This is a Quicktime VR movie. Drag up and down to change sea level, drag side to side to rotate the Earth. As sea level rises, major population centers are affected. Two-thirds of the world's population lives within 500 km of a coastline. 90% of the world's population lives north of the equator, and 80% of the world's population lives below 500 m elevation. This places an overwhelming majority of people at risk when sea levels rise.

Download and enjoy!

Credit: Paul Morin and Kent Kirkby, Department of Geology and Geophysics, University of Minnesota

ORIGINAL website:

The EPA's website follows the IPCC 2001 report, which looks at increasing sea-level change over the next 96 years, but nothing close to 7 meters by the year 2100 :

Future Sea Level Changes

Here is the IPCC 2001 report:

Climate Change 2001: Working Group I: The Scientific Basis

Here is the table about future sea level change:

Sea Level Rise Projections to 2100

The BBC has released a report entitled "Earth - melting in the heat?" which outlines current studies about global climate change. While the lightblueline has been looking at ice melting in Greenland, the BBC also gives some very interesting information about the Antarctic.
"Huge, pristine, dramatic, unforgiving; the Antarctic is where the biggest of all global changes could begin.

There is so much ice here that if it all melted, sea levels globally would rise hugely - perhaps as much as 80m. Say goodbye to London, New York, Sydney, Bangkok, Rio... in fact, the majority of the world's major cities.