Huge sea level rises are coming
– unless we act now.

Professor James Hansen, Head of NASA's Goddard Institute for Space Studies in New York.
New Scientist 25 July 2007

- but, please, check first with a
world expert on sea level rise

I find it almost inconceivable that "business as usual" climate change will not result in a rise in sea level measured in metres within a century.

While the growth of great ice sheets takes millennia, the disintegration of ice sheets is a wet process that can proceed rapidly.

Once well under way, such a collapse might be impossible to stop, because there are multiple positive feedbacks. In my opinion, if the world warms by 2 °C to 3 °C, such massive sea level rise is inevitable, and a substantial fraction of the rise would occur within a century.

Business-as-usual global warming would almost surely send the planet beyond a tipping point, guaranteeing a disastrous degree of sea level rise. There is not a sufficiently widespread appreciation of the implications of putting back into the air a large fraction of the carbon stored in the ground over epochs of geologic time. The climate forcing caused by these greenhouse gases would dwarf the climate forcing for any time in the past several hundred thousand years.

Models based on the business-as-usual scenarios of the Intergovernmental Panel on Climate Change (IPCC) predict a global warming of at least 3 °C by the end of this century. What many people do not realise is that these models generally include only fast feedback processes: changes in sea ice, clouds, water vapour and aerosols. Actual global warming would be greater as slow feedbacks come into play: increased vegetation at high latitudes, ice sheet shrinkage and further greenhouse gas emissions from the land and sea in response to global warming.

The IPCC's latest projection for sea level rise this century is 18 to 59 centimetres. Though it explicitly notes that it was unable to include possible dynamical responses of the ice sheets in its calculations, the provision of such specific numbers encourages a predictable public belief that the projected sea level change is moderate.

However, if these IPCC numbers are taken as predictions of actual sea level rise, as they have been by the public, they imply that the ice sheets can miraculously survive a business-as-usual climate forcing assault for a millennium or longer.

However, about 14,000 years ago, sea level rose approximately 20 metres in 400 years, or about 1 metre every 20 years.

There is growing evidence that the global warming already under way could bring a comparably rapid rise in sea level. This planetary energy imbalance is sufficient to melt ice corresponding to 1 metre of sea level rise per decade, if the extra energy were used entirely for that purpose - and the energy imbalance could double if emissions keep growing.

Most of the resulting meltwater burrows through the ice sheet, lubricating its base and speeding up the discharge of icebergs to the ocean.

Ocean warming and thus melting of ice shelves will continue even if CO2 levels are stabilised, because the ocean response time is long and the temperature at depth is far from equilibrium for current forcing. Ice sheets also have inertia and are far from equilibrium. There is also inertia in human systems: even if it is decided that changes must be made, it may take decades to replace infrastructure.

Such scenarios require almost immediate changes to get energy and greenhouse gas emissions onto a fundamentally different path.

There is enough information now, in my opinion, to make it a near certainty that business-as-usual scenarios will lead to disastrous multi-metre sea level rise on the century time scale.

If sea level rises by 5 metres...

Viewed from space, Earth will not look that different: there will be surprisingly little loss of land. The trouble is, there are an awful lot of people on the land that will go.

While a mere 2 per cent of the world's land is less than 10 metres above the mid-tide sea level, it is home to 10% of the world's population – 630 million and counting - and much valuable property and vital infrastructure.

Without mega-engineering projects to protect them, a 5-metre rise would inundate large parts of many cities - including London, New York, Sydney, Vancouver, Mumbai and Tokyo - and leave surrounding areas vulnerable to storm surges. In Florida, Louisiana, the Netherlands, Bangladesh and elsewhere, whole regions and cities may vanish. China's economic powerhouse, Shanghai, has an average elevation of just 4 metres.

The Stern Report warned that climate change could mean up to a fifth of global wealth might be lost. A 5-metre rise in sea level would make the impact far greater. Worst of all, the sea may keep rising.

This summary is based on a report which in turn was based on a paper in the open-access journal Environmental Research Letters (DOI: 10.1088/1748-9326/2/2/024002) New Scientist magazine, 25 July 2007

Global warming of two to three degrees above the present temperature, Hansen warns, would produce a planet without Arctic sea ice, a super-drought in the American west, southern Europe, the Middle East and parts of Africa, and a catastrophic sea level rise which could be over 20 metres (see above). The incongruity of the IPCC’s sea-level projection for 2100 can be seen in the figure below which illustrates mean global temperature and sea level (relative to today) at different times in earth’s history, and the IPCC projection for 2100 (blue outline circle). "Such a scenario threatens even greater calamity, because it could unleash positive feedbacks such as melting of frozen methane in the Arctic, as occurred 55 million years ago, when more than ninety per cent of species on Earth went extinct" (Hansen, 2006b)."

Its other key findings from its executive summary are:

• Climate change impacts are happening at lower temperature increases and more quickly than projected.
• The Arctic’s floating sea ice is headed towards rapid summer disintegration as early as 2013, a century ahead of the International Panel on Climate Change (IPCC) projections.
• The rapid loss of Arctic sea ice will speed up the disintegration of the Greenland ice sheet, and a rise in sea levels by as much as 5 metres or more by the turn of this century is possible.
• The Antarctic ice shelf reacts far more sensitively to warming temperatures than previously believed.
• Long-term climate sensitivity (including “slow” feedbacks

such as carbon cycle feedbacks which are starting to operate) may be double the IPCC standard.
• A doubling of climate sensitivity would mean we passed the widely accepted 2°C threshold of “dangerous anthropogenic interference” with the climate four decades ago, and would require us to find the means to engineer a rapid drawdown of current atmospheric greenhouse gas.
• Carbon dioxide (CO2) emissions are now growing more rapidly than the most pessimistic of the IPCC scenarios.
• Temperatures are now within ˜1°C of the maximum temperature of the past million years.
• We must choose targets and take actions that can actually solve the problem in a timely manner.
• The object of policy-relevant advice must be to avoid unacceptable outcomes and seemingly extreme or alarming possibilities, not to determine just the apparently most likely outcome.
• The 2°C warming cap is a political compromise; with the speed of change now in the climate system and the positive feedbacks that 2°C will trigger, it looms for perhaps billions of people and millions of species as a death sentence.
• To allow the reestablishment and long-term security of the Arctic summer sea ice it is likely to be necessary to bring global warming back to a level at or below 0.5°C (a long-term precautionary warming cap) and for the level of atmospheric greenhouse gases at equilibrium to be brought down to or below a long-term precautionary cap of 320 ppm CO2e.
• The IPCC suffers from a scientific reticence and in many key areas the IPCC process has been so deficient as to be an unreliable and dangerously misleading basis for policy-making.

Arctic summers ice-free 'by 2013'

[really? check data here and here]

The latest modelling studies by Californian Professor W. Maslowski indicate that summer Arctic sea ice could disappear within 5-6 years. This does not take account of summer melting this year which reduced the ice cover to the smallest
ever extent in modern times. This stunning low point was not even incorporated into the model. "So you can argue that our projection of 2013 is already too conservative," Maslowski explained to the BBC. Other teams have variously produced dates for an open summer ocean that, broadly speaking, go out from about 2040 to 2100.

But it is has become apparent in recent years that the real, observed rate of summer ice melting is now starting to run well ahead of the models.

Professor Peter Wadhams from Cambridge University, UK, is an expert on Arctic ice. He has used sonar data collected by Royal Navy submarines to show that the volume loss is outstripping even area withdrawal, which is in agreement with the model result of Professor Maslowski.

"The ice is thinning faster than it is shrinking; and some modellers have been assuming the ice was a rather thick slab.

He cited the ice-albedo feedback effect in which open water receives more solar radiation, which in turn leads to additional warming and further melting.

"In the end, it will just melt away quite suddenly. It might not be as early as 2013 but it will be soon, much earlier than 2040."

Former US Vice President Al Gore cited Professor Maslowski's analysis on Monday in his acceptance speech at the Nobel Peace Prize ceremony in Oslo.

APPENDIX 3 to A Vision for Somerset as a Sustainable Community (South Somerset Climate Action)

Jonathan.Amos-INTERNET@bbc.co.uk
Jonathan Amos, Science reporter,
BBC News, San Francisco
12 December 2007
Abbreviated from
http://news.bbc.co.uk/1/hi/sci/tech/7139797.stm

Scientists identify 'tipping points' of climate change
Independent – 5 Feb 2008

[but check here to question the science behind the "scare stories" of tipping-points. Dr Spencer was a scientist with NASA but left because he disliked NASA's hype and degradation of science.]

The Earth could be tipped into a potentially dangerous state that could last for many centuries if global average temperatures continue to rise.

"Society may be lulled into a false sense of security by smooth projections of global change,” scientists report in the journal Proceedings of the National Academy of Sciences.

They describe “tipping points,” where a small increase could trigger a disproportionately larger change in the future and global warming could run out of control.

“It is still possible to avoid them with cuts in greenhouse gases,” said Professor Lenton of the University of East Anglia, who led the study.

Irreversible dramatic changes that could occur within the next 100 years.

* Arctic sea ice: some scientists believe that the tipping point for the total loss of summer sea ice is imminent.

* Greenland ice sheet: total melting could take 300 years or more but the tipping point that could see irreversible change might occur within 50 years.

* West Antarctic ice sheet: scientists believe it could unexpectedly collapse if it slips into the sea at its warming edges.

* Gulf Stream: few scientists believe it could be switched off completely this century but its collapse is a possibility.

* El Niño: the southern Pacific current may be affected by warmer seas, resulting in far-reaching climate change.

* Indian monsoon: relies on temperature difference between land and sea, which could be tipped offbalance by pollutants that cause localised cooling. This could lead to widespread crop failures and famine. “Could occur within a few years.”

* West African monsoon: in the past it has changed, causing the greening of the Sahara, but in the future it could cause droughts.

* Amazon rainforest: a warmer world and further deforestation may cause a collapse of the rain supporting this ecosystem.

* Boreal forests: cold-adapted trees of Siberia and Canada are dying as temperatures rise.

APPENDIX 5 to A Vision for Somerset as a Sustainable Community (South Somerset Climate Action)

Original article by Steve Connor:
http://www.independent.co.uk/environment/climatechange/
scientists-identify-tipping-points-of-climatechange-
778027.html

Carbon Footprints - Worst Offenders

• Return airline flight London - New York wipes out a year's worth of "acceptable" carbon footprinting.
• But if you travel by ship, like the QE2, it wipes out seven years' worth.
• But airline CO2 only accounts for 2% of UK CO2
• Worldwide, forest logging and burning accounts for the single biggest human activities figure, 25% of the total world CO2.
• Biofuels are a non-solution
• Nobody's yet calculated the effect of increasing population on manmade CO2 increase

But is CO2 a problem or a precious resource?
• AGW science omits the far bigger quantities of CO2 that are "outgassing" and "sinking" naturally through the oceans, as consequence, not cause, of oceans warming and cooling - check the high correlation here
• CO2 acidification is a non-issue, a scare story
• It would be very good anyway to plant trees everywhere there's space, to absorb the extra CO2 nutrition now available through human effort.
• Deserts could be greened faster than people realize.