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21 januari 2011

'Meters zeespiegelstijging per eeuw bij huidige beleid'


Illustratie: klimaatprojectie (PDF) NOAA (2007) voor het jaar 2050; dit model figureert overigens niet expliciet in het artikel van Hansen en Sato.

Door Joe Romm, Climate Progress, 20 januari 2011

Romm: (...) Right now, we’re headed towards an ice-free planet. That takes us through the Eemian interglacial period of about 130,000 years ago when sea levels were 15 to 20 feet higher, when temperatures had been thought to be about 1°C warmer than today. Then we go back to the “early Pliocene, when sea level was about 25 m [82 feet] higher than today,” as NASA’s James Hansen and Makiko Sato explain in a new draft paper, “Paleoclimate Implications for Human-Made Climate Change.”
The question is how much warmer was it in the Eemian and early Pliocene than today — and how fast can the great ice sheets disintegrate?

Hansen en Sato:

'IPCC BAU (business-as-usual) scenarios assume that greenhouse gas emissions will continue to increase, with the nations of the world burning most of the fossil fuels including unconventional fossil fuels such as tar sands.
An alternative extreme, one that places a substantial rising price on carbon emissions, would have CO2 emissions beginning to decrease within less than a decade, as the world moves on energy systems beyond fossil fuels, leaving most of the remaining coal and unconventional fossil fuels in the ground. In this extreme scenario, let’s call it fossil fuel phase-out (FFPO), CO2 would rise above 400 ppm but begin a long decline by mid-century (Hansen et al., 2008).
The European Union 2°C scenario, call it EU2C, falls in between these two extremes.

BAU [business as usual] scenarios result in global warming of the order of 3-6°C. It is this scenario for which we assert that multi-meter sea level rise on the century time scale are not only possible, but almost dead certain. Such a huge rapidly increasing climate forcing dwarfs anything in the paleoclimate record. Antarctic ice shelves would disappear and the lower reaches of the Antarctic ice sheets would experience summer melt comparable to that on Greenland today.

The other extreme scenario, FFPO [fossil fuel phase-out], does not eliminate the possibility of multi-meter sea level rise, but it leaves the time scale for ice sheet disintegration very uncertain, possibly very long. If the time scale is several centuries, then it may be possible to avoid large sea level rise by decreasing emissions fast enough to cause atmospheric greenhouse gases to decline in amount.

What about the intermediate scenario, EU2C [European Union 2°C scenario]? We have presented evidence in this paper that prior interglacial periods were less than 1°C warmer than the Holocene maximum. If we are correct in that conclusion, the EU2C scenario implies a sea level rise of many meters. It is difficult to predict a time scale for the sea level rise, but it would be dangerous and foolish to take such a global warming scenario as a goal.'

Romm:

'If Hansen and Sato are right, we will know within a decade or two. Unfortunately, continuing to do nothing while we wait to find out all but ensures we cross the tipping point and entire the realm of worst-case scenarios. Further delay is beyond immoral.'

Zie ook:

World Meteorological Organization: 2010 equals record for world’s hottest year and the “data confirm the Earth’s significant long-term warming trend.”
Door Joe Romm, Climate Progress, 21 januari 2011

2010 "characterized by a high number of extreme weather events".

Zie ook m'n blognotitie:
Impact CO2 op klimaat mogelijk twee keer sterker dan gedacht

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