How Much Could Sea Levels Rise By
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There are two main reasons why sea surface levels (SSL) can change as a result of global warming. The first is due to polar ice melting and the second is due to the oceans becoming warmer and expanding. Other factors can affect the SSL but they’re very minor and changes happen over long periods of time.
We can easily measure the mass of ice around the world using satellites, from this was can then calculate that if all of it were to melt sea-levels would rise by 80.42 metres (250 feet).
The majority of ice is in Antarctica and if all this melted then sea-levels would rise by 73.42 metres, the Greenlandic ice would be responsible for 6.55 metres of sea-level rise and the remaining 0.45 metres would come from snow-fields, mountain glaciers etc. Note that the Arctic ice does not affect SSL and this is because the ice here is floating on the oceans and is already displacing it’s own mass of water.
Such sea-level rises would only happen if ALL the ice melts and this isn’t going to happen.
How Much Are Sea Levels Rising By
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In recent years the rate of ice-loss has been in the order of half a trillion tonnes per year, roughly two-thirds from Greenland and the rest from Antarctica. Whilst this might sound like a huge amount, by the time this additional water is distributed throughout the seas and oceans it amounts to just 1.5mm per year.
The other factor I mentioned was thermal expansion caused by the warming of the ocean waters. As more heat is being trapped in the atmosphere by greenhouse gases, some of the heat is being absorbed by the seas and oceans causing them to warm up. As they do the overall result is one of expansion (in the polar seas which have temperatures of around 0°C, the absorption of heat energy is causing contraction and that’s because water is densest at 4°C). Each year thermal expansion is increasing SSL by 1.6mm.
There’s a further 0.1mm a year rise in SSL which is caused by other factors such as isostatic rebound (natural rising up of the land), so all in all we’re now at a point where SSL is increasing by 3.2mm per year or one inch every eight years.
What Could Happen in the Future
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What we’re likely to see in the future are sea-levels continuing to rise, it’s hard to be specific as to how much and numerous studies have been undertaken. The worst case scenario came from the Gravity Recovery And Climate Experiment (GRACE) satellite data which produced a figure of 1400mm by the year 2100. As I say, this is a worst case scenario and most estimates put the figure at around 600mm (two feet) by the end of the century.
The further into the future we go the harder it is to come up with a reliable figure and that’s because over time small variations can be compounded into larger ones. For example, if we knew sea-levels were rising by 10mm per year and that the amount could increase by no more than 1% per year, then after 100 years the rate of sea-level rise could be anywhere between 10mm and 30mm per year, after 200 years it could be between 10mm and 80mm per year.
The Effects of Rising Sea Levels
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The greatest danger is faced by people living in low-lying areas and we’re already seeing the effects of sea-level rises. For example, half a million people have been evacuated from Bhola Island as much of the land is now inundated by sea-water. This island is in the Ganges Delta and a further 40 million people in that region live on land less than 1m above sea-level. Elsewhere, the Carteret Islands are currently being evacuated and other island groups such as Kiribati, Tuvalu and the Maldives are at risk.
There are numerous other problems associated with rising sea-levels such as coastal erosion, habitat destruction, water contamination and salination of land.
Minimising the Risks
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Much of the developed world can mitigate against the worst effects of rising SSL through civil-engineering projects such as coastal defences, tidal barrages, flood barriers, the provision of flood plains, hydrological management schemes, etc. The Thames Barrier in London is one such example which, when raised, cuts off London from tidal waters in the River Thames and so protects the city.
Globally we’re seeing more and more of these projects being designed and not surprisingly it’s the Dutch that are leading the way.
These flood defence projects, together with emergency planning and greater communications ensure that the risks are minimised. We can look at Hurricane Sandy for a good example. Had the storm struck fifty years ago it’s likely the death toll would have been in the tens of thousands. Advances in forecasting together with mass communications meant those living in potentially affected areas had several days warning and were able to take preventative action.
there is no global warming. But the purveyors of the AGW scare would make you think that there would be massive rises in the ocean's level.
Quote by Noel Brown, UN official: "Entire nations could be wiped off the face of the Earth by rising sea levels if the global warming trend is not reversed by the year 2000. Coastal flooding and crop failures would create an exodus of "eco-refugees," threatening political chaos."
The truth of the matter is that there has been no significant ocean rise in three or four centuries. Take, for example, St. Augustine, Florida, USA, the oldest continuous city on the American continent.. The sea level has stayed the same. Another example is the Thames river. It is at sea level in London. There many artist conceptions dating back to the 1500s and the sea level is virtually the same. And you would think that with all this 'global warming' going on and all the disappearances if the ice caps there would be some rise and there obviously hasn't been.
Depends on which hysterical global warming alarmists you listen to. And it's even more difficult to get an answer these days because they keep changing their catastrophic predictions of dire global destruction due to rising sea levels every year. The earth's climate has been steady and even cooling slightly so they've adjusted their sea level rise prediction to a mere fraction of what the hysteria was several years ago several times in fact. The real science is trickling in with actual climate data with results that contradict the "proof" of anthropological global warming caused by CO2 as predicted by extremely flawed computer climate models have provided. Even Al Gore conceded to that inconvenient truth when one of the multi-million dollar mansions he bought perpetrating this global warming fraud is right smack in the middle of San Francisco where the map in his fairy tale movie promised would be flooded within a few decades.
You have to realize that the earth has warmed much warmer than it is now and cooled many times in the past. The climate is changing and has always been changing. The Earth's crust is dynamic and changes and even that affects climate. None of this happens rapidly like on a human scale of time such as within our lifetimes. Anyone who claims it is or does is lying. They are lying to spread fear and coerce people to adopt some agenda driven scheme for some kind of social change much in the way that religio evangelical fundamentalists do to coerce a society to conform to their ideology. Believe and do this or you're going to burn in hell for all eternity they say.
Even if the planet warmed up 10 degrees C overnight or even 20 C it would take many 1000s and 1000s of years for any significant ice melt from the polar regions to have any significant effect on global sea levels. It just will not happen within our lifetimes or even those for 10 generations. It can't. It's laughable that people make these kinds of claims. I put those kinds of people in the same catagory with street corner evangelicals and alarmists who predicted the catastrophies of Y2k, 12-21-2012 Mayan calendar, the rapture, etc. that never happened.
Regional and local factors will influence future relative sea level rise for specific coastlines around the world. For example, relative sea level rise depends on land elevation changes that occur as a result of subsidence (sinking) or uplift (rising). Assuming that these historical geological forces continue, a 2-foot rise in global sea level by 2100 would result in the following relative sea level rise.
2.3 feet at New York City
2.9 feet at Hampton Roads, Virginia
3.5 feet at Galveston, Texas
1 foot at Neah Bay in Washington state
Of course none of us are expected to be around by that time, although our grandchildren might be.
If all the land ice melts, over 200 feet but that is likely 150 years or more from now.
Supposedly 80 feet but honestly I don't really believe that that will happen.
No one really knows.....though a number of folks have come up with some 'seat of the pants', wild-a*s guesses.
And how far WILL the seas rise in the next few hundred years, say?
