Global warming. Why if the sea levels are rising due to the aforementioned are mountains the same height above

Question

sea level as they were 30 years ago?

Answer 1

Because we established a base line level from average "sea level" over a century ago and have used that for all the measurements instead of the fluctuating sea level from tides, warming, cooling, local drought, etc. Effectively we said, "If the earth were a perfect sphere, it would be this diameter, but since it isn't, we will add or subtract to get the oblate spheroid and measure density under the surface to determine how plumb bobs hang off vertical and measure locations more precisely.
You didn't think we were going to republish all the heights like Mount Everest because the ocean 1000 miles away rose a foot?

Answer 2

Some good answers above.

The key point is that mountain heights are not stated relevant to sea levels. I'll explain...

Until fairly recently the heights of mountains were measured using a process called triangulation. This was a land based system of surveying which involved overlaying an imaginary grid of traingles over the landscape. The different angles would allow heights to be calculated from a known height. The further from ordnance datum (start point) the more calculations were involved and the greater the possibility of error. The heights of mountains were often out by as much as 0.1% and occasionally by as much as 1% - this could mean an error of 50m either way for a 5000m mountain.

So, the first important point is that we don't have very precise heights for the mountains. Modern surveying uses satellites and this provides more accurate heights but resurveying is a long and slow process. In countries such as the UK which is a small country, has no particularly high mountains and leads the world in surveying it's usually a matter of decades between surveys, in more remote places it could be centuries.

The second point is that each country uses it's own bench mark - an arbitary point above which all heights are given. This point is static even if sea levels aren't. For example, in the UK all heights are given Above Ordnance Datum (AOD) which is nothing more than a while line painted on the harbour wall at Newlyn in Cornwall (it's also called Newlyn Datum). Irrespective of sea level rises or falls the bench mark is still the same.

Thirdly, there is no consistency between one country and the next because each has defined it's own bench mark. For example, if the heights of mountains in the US were given relevant to the Canadian bench mark thay may all be a metre or two higher or lower. There is an international convention determining what the height of sea level is because shipping is international so there needs to be consistency.

Fourthly, the rises in sea level over the last 30 years have averaged about 100mm across the globe, mountains heights are generally stated in metres so even if heights were stated relevant to sea levels the diffrercence would only be 0.1 metres.

Because of movements in the tectonic plates which make up the Earth's crust there is a folding process which pushes mountains upwards - ranges such as the Greater Himal (Himalayas), Alps and Andes are created this way. The higher mountains are subject to seasonal variation depending how much snow fall is lying at the summit. Summits heights are changing all the time.

Answer 3

Land masses shift as the tectonic plates move against each other. Even though sea levels have been rising, some mountains are continuing to rise. Others are 'shrinking' It has recently been recorded that Mt. Everest is 'falling back'.
This is part of the natural process, even if sea levels were not rising in general some Islands would 'sink' back below sea level.
The debate is about whether we can slow rising sea levels because some of the rise is allegedly caused by CO2 that we have produced and this avoidable etc.

I am not a scientist but I think most of this is rubbish.

I accept the planet is getting warmer, I accept this has consequences but so many people are making money out of persuading people to 'go green' you can smell the rotten meat.

It is true we need to redirect resources but I don't think we can stop global warming and I don't think puny little mankind has the power to control nature.
What I do think is we need to anticipate the consequences of change and adapt.

If that means using less electricty etc then fine lets find ways of doing that.
Perhaps we should end computerisation?

Answer 4

You are misinformed. Mountains are not the same height above mean sea level.
The sea level rise, compared to 30 years ago, at the moment is very small, a matter of centimetres, but it is still a rise.
Mountains are not surveyed on a regular basis and may be subject to seismic movements (For example mountains in the West of Scotland are going up - getting higher, whereas the South Downs in England are going down - getting lower, because of a tilting of the Earth's crust under the British Isles.).
It is only when surveys are made over long intervals that any perceptible difference is seen, but that difference means that mountains are in fact getting lower, relative to the mean sea level.

Answer 5

There is considerable disagreement as to whether sea rise is really a concern among those who believe in global warming. That is one of the reasons the IPCC has backed off of any mention of catastrophic sea rise. They are now saying that it may rise as little as 8 inches and as much as 2 feet OVER THE NEXT 100 YEARS. Hardly catastrophic. And this is from the panel that presents Global Warming from a worst case scenario.

There are many scientists who have shown sea level decrease - especially in the Southern Hemisphere.

I think your observation might be applicable to elevations as reported on topographic maps. How have these changed in coastal areas? How have the actual coast lines changed in terms of elevation over the last 3 decades?

Answer 6

The sea levels are constantly rising and falling in different regions. The Indian Ocean has fallen by 20-30cm in the last 30 years.

Answer 7

Because most mountains are growing at about the same height that sea level is rising. Also, the changes are a matter of inches, so statistics are not changed for the small variations.

Answer 8

From what point on what day are the seas the same as 30 years ago? From what I know of science and the moon's effect on oceans, what you are suggesting is something that could only occur every so many years.

They use an average sea level, not the actual.

Answer 9

whatever the effects of global warming - and I don't dispute the fact that there is such a thing, only not as bad as Governments make out - the world is constantly in a state of flux, dinosaurs, ice age, etc. etc. it's just the way of things. However, I'm sure that we humans have greatly contributed to hastening whatever is sure to happen. As regards mountains being the same height - no, they are constantly on the move too, as is everything on the planet. Think of how much goes on deep, deep down under the earth's surface, plates colliding etc. etc.

Answer 10

are mountains not measured from their base ?
few mountains are on the beach

besides 1 inch in sea level means thousands of hectares of Arable lands lost
we are talking in millimetes when we talk about rising sea levels due to global warming
and after hundreds of years a few meters

But who knows with every going so fast now things will happens a lot faster
humanity has stopped global warming from being just a natural process