thf24 asked in EnvironmentGlobal Warming · 1 decade ago

How are rising sea levels at the present time evidence of global warming?

Please read my entire post before answering; and no offense, but please don't answer if you can't provide scientific detail at least equal to the small, basic amount I've used.

First of all, I just want to say I don't consider myself a global warming denier. I don't think there's enough evidence to definitively say that Earth is either warming or not warming at an abnormal rate. It's fact that Earth's average temperature has risen between one and two degrees Fahrenheit since 1900. However, it's also fact that Earth is in a continuous cycle of natural warming and cooling, and fossil evidence indicates that Earth has been both many times warmer and cooler than it is now during its existence, long before the mass emission of greenhouse gasses. And while the Greenhouse Effect is a plausible theory and likely occurring, it remains unproven because it's impossible to construct a scientific experiment on a scale large enough to produce reliable data. So, I don't think it's possible to absolutely confirm or deny that Earth is warming faster than it should. I just wanted to make it clear that I'm not a blind denier.

Now, my question. Many say that sea levels have already risen as a result of global warming due to melting ice sheets at and near the poles. I'm curious as to how this can occur universally if the temperatures in these areas are still minus forty to minus eighty degrees Fahrenheit during the warmest part of the year. I understand that climate change causes changes in the direction of ocean currents, which in turn cause sea ice to melt. However, anyone who's had a little chemistry knows that the melting of any amount of floating ice wouldn't cause sea levels to rise significantly (negligible increase would result from factors such as thermal expansion), because its displacement is roughly the same whether in the solid or liquid state. The significant rise in sea level would come from the melting of ice sheets currently resting on land. But as I previously mentioned, none of the largest land ice formations have been exposed to temperatures anywhere near freezing long enough for noticeable melting during the last century despite the rise in average world temperature, and land ice for the most part wouldn't be subject to direct influence from ocean currents.

So if melting sea ice doesn't contribute to sea level rise and land ice can't be significantly melting yet, how can a recorded rise in sea level already be linked to the one-two degree increase?

Again, no offense, but if my reasoning is incorrect, I welcome your corrections but please be able to provide some basic scientific reasoning of your own. "Common sense" reasoning as I've heard it used in the past on this subject isn't valid and is usually wrong by nature.

11 Answers

  • 1 decade ago
    Favorite Answer

    The answer is quite simple, for a start the -40 or -80 you mention is an inland temperature for Antarctica or Greenland. At both, temperature's at the coast can and are much warmer with temperature at the peak of Summer (for short periods) getting to 5 to 10c in a number of regions.

    Glacial ice has what is called an Ice Mass Balance, snow builds a glacier and under the sheer mass it flows like water (but in slow motion), even at -80 the mass of the ice is to strong and the glacier flows. It is always gaining mass from snow fall and always losing mass by carving of icebergs at the edges. Warming of the Southern Ocean over the last few decades has increased snow fall over the Antarctic but the increase in mass has also increased the flow rate of many of the glaciers as have the warming conditions seen in Summer around the coast over the last several decades.

    The above link has the numbers for the current contribution of glacial melt to sea level rise 0.2mm for Antarctica and 0.3mm for Greenland (0.5mm) per year, actual sea level rise is around 3.2mm per year the balance is caused by thermal expansion. Prior to the early 1990s sea level rise going back ~ a century was ~1.7mm per year.

    On questions like yours deniers will usually try the "this has been happening since the last ice age ended" story this is simply not true, the record of sea level rise shows that sea level did rise (sharply) but it slowed ~8000 years ago

    Since ~2000 years ago, sea level rise flat lined, if as (bob) tries to claim the current rise was a continuation even at the slower 1.7mm per year over the 2000 years that would have been a rise of 3.4m.

    What the record shows is that sea level started to rise again ~100 years ago almost 20 years ago that rate increased and as temperatures continue to rise the rate will also continue to grow.

    Antarctica holds enough water to cause the global sea level to rise over 65m so only 1 or 2% of it has to be added to the global oceans to raise sea level up to 0.6 m or 1m. Even 0.6m would have a major effect on us all coastal communities around the world will be affected.

    0.6m would be the end for all those island that deniers say won't be affected.

    A number of these have no landmass that is 0.6m above sea level.

    Source(s): I have worked for the Australian Antarctic Program for over 20 years
  • Anonymous
    4 years ago

    I took this from a website: "Sea level rise is due to a number of causes, some of which may exert a more regional influence than others. These include: Thermal expansion – As seawater becomes warmer it expands. Heat in the upper layer of the ocean is released quickly into the atmosphere. However, heat absorbed by the deeper layers of the ocean will take much longer to be released and therefore, be stored in the ocean much longer and have significant impacts on future ocean warming. An increase in freshwater inputs from mountain glaciers, ice sheets, ice caps, and sea ice, as well as other atmospheric and hydrologic cycles due to rising global surface and ocean temperatures Physical forces – Subsidence and lifting are associated with tectonic activity and the extraction of water and resources such as gas and oil. These types of forces don't actually change the volume of the ocean, only the relative sea level. However, these changes do affect movement over land, as well as estimates from satellite altimetry. For example, in Scandinavia's Gulf of Bothnia, the weight of glaciers had caused the land beneath it to compress and sink. Now that glaciers are melting and the pressure has been released, the region is lifting at a rate of as much as 11 mm per year. This rebound makes it seem like sea level is dropping even though it is actually rising by 2.1 mm per year (Milne et al., 2001). Ocean current variations – Large, regional ocean currents which move large quantities of water from one location to another also affect relative sea level without changing the actual volume of the ocean. For example, el Niño moves water from one side of the Pacific to the other every three or four years. These large-scale variations also affect the relative sea level of certain areas. In normal conditions, trade winds blow across the Pacific toward the west. According to NOAA, the trade winds push warm surface water to the west Pacific, so the sea level is roughly 1/2 meter higher in Indonesia than it is in Ecuador. During el Niño years, this warm water is pushed over to the eastern Pacific. Atmospheric pressure - influences sea level by impacting the surface itself. This also only affects relative sea level as the water pushed out of one place will move to another." The sea level is rising due to global warming, there is no doubt about that. That's not what the debate is about though. The debate is whether global warming is caused by man-made carbon dioxide or not. I wouldn't mind a little global warming since I live in Canada. (: As for Kiribati being doomed I wouldn't be so sure of that. 2050 is a long way away. Just remember when all this global warming talk started, it was only maybe 20 years ago at most.

  • A Guy
    Lv 7
    1 decade ago

    ??? YOu want "scientific detail at least equal to the small, basic amount I've used" and then

    just write "it's a fact" that "average temperature has risen between one and two degrees Fahrenheit since 1900. However, it's also fact that Earth is in a continuous cycle of natural warming and cooling, and fossil evidence indicates that Earth has been both many times warmer and cooler than it is now during its existence". SOME scientists might provide a reference (or link) to what established these facts, and your argument seems to be the sort of "fair and balanced" stuff that made me stop watching television.

  • Noah H
    Lv 7
    1 decade ago

    The equation isn't simple. It has a whale of a lot of moving parts. Certainly temperatures rose and fell in 'geological time', but for different reasons than we''re currently experiencing in 'historical time'. 'Warming' in geological time took hundreds of thousands and even millions of years. The current warming has taken place in less then 200 years. Discounting the effect of burning billions of tons of coal and billions of gallons of oil leaves a major gap in the claim that all this is 'natural'. Dismissing 'two degrees' as nothing is also a major gap in scientific thinking. Ice freezes at 32 degrees F. It melts at 32.1 degrees F. The data shows slightly longer summers and slightly shorter winters. Freezing is less robust and melting is a bit more...over time and area it makes a difference. Thermal expansion actually does make a difference particularly if that expansion acts on millions or billions of more ice turned liquid in addition to the water that already exists. While it's possible to have doubts as to the extent of the problem, the data is more than enough to define the problem. All of the other data...the north moving treeline into the tundra areas of the world, the migration of birds, animals and fish, rising acidity of oceans can't be discounted. The main tell is the ever growing strength of the 'greenhouse effect. Less incoming solar radiation is outgoing in the form of infrared radiation and that's absolutely related to to the rise of CO2 from 284ppm in the early 19th century to the close to 400ppm in the early 21st century. True, so far the increase in the heat index has been slow, but that's because the extra heat is slowly melting ice and warming sea water....given the extent of these two heat sinks a slow rise in temperature is to be expected. However we add 12 to 15ppm of CO2 every decade to our paper thin atmosphere and heat and atmospheric physics are clear that at 450ppm we can expect a far more rapid 'warming'. 'Warming' and climate change are as real as it gets. The data is firm and the science is real. Bummer for us!

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  • Bob
    Lv 6
    1 decade ago

    Well the globe has been warming since the end of the last ice age and the sea has been rising since the end of the last ice age. No surprise that the sea is rising at about 1.8mm per year. That rate fluctuates a little but the average has remained constant. There is no record sea level rise. That is created by cherry picking data points between a year when the rise was lower and graphing a line to a year where the rise was higher.

  • Jeff M
    Lv 7
    1 decade ago

    Karrack: Water does not expand as it cools. Water contracts as it cools up until the point of near freezing when it suddenly expands and freezes. This is because of the way the molecules are organized when frozen, they take on a 3D structure that contains lots of empty space.

  • 1 decade ago

    more CO2 = heat trapped = temp goes up = ice melts = H2O in liquid form = water level rises = low level islands sink = people move

  • BB
    Lv 7
    1 decade ago

    You stated: "It's fact that Earth's average temperature has risen between one and two degrees Fahrenheit since 1900."

    I beg to differ. The surface temperature data used as the foundation of the man-caused catastrophic global warming cause, is corrupted due to poor station siting and questionable data manipulation. The result has been a progressive false 'warming' of our climate.

    It IS a fact though, that we really don't know whether or not there has been some lesser degree of warming or even Cooling, since the data is so corrupt.

  • 1 decade ago

    <<First of all, I just want to say I don't consider myself a global warming denier. I don't think there's enough evidence to definitively say that Earth is either warming or not warming at an abnormal rate.>>

    I don't consider myself to be a non-flat Earth denier. I don't think there is enough evidence at present to establish whether or not the Earth is flat.

    One thing is for sure though--Al Gore is getting rich by convincing people that the Earth is not flat.

  • 1 decade ago

    The primary cause of sea level rise is thermal expansion - that is, water expands as it get's warmer.

    The secondary cause is the melting of ice on land.

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