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Subject:
Masked global warming increase
Category: Science > Earth Sciences Asked by: stenb-ga List Price: $20.00 |
Posted:
30 Dec 2002 06:21 PST
Expires: 29 Jan 2003 06:21 PST Question ID: 134903 |
Melting ice hidden temperature increase calculation required.... If we know how many million tonnes of ice melts per year, i.e. net total from one year to another, we can calculate how much heat we have moved into melting this ice. Then we also know that melting one tonne of molten ice requires the same amount of heat as heating 50 tonnes of water 1 degree.... So if we know both ocean water mass (OWM) and net molten ice mass per year(NMIM) in ice sheets, land ice, glaciers and molten permafrost, we can solve the equation below for corresponding temperature increase, dT: dT*OWM=NMIM*50; The dT we obtain can then be added to measured global warming, to get a better understanding of how much the melting is masking the current warming. It may be 0.0001 dgr/year, so we do not have to consider it. Or the masked increase may be a significant number. Awaiting your response, Best Regards Sten global |
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There is no answer at this time. |
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Subject:
Re: Masked global warming increase
From: neilzero-ga on 30 Dec 2002 11:24 PST |
It does not appear to me that the annual energy required to melt the ice which melts each year, is relevent unless we subtract the annual energy required to produce the ice. The difference is likely small and varies from year to year in an almost random maner. Is the ice that melts on the mountain peaks of Equador (near the Equator) just as relevant as the ice that melts inside the Arctic Cirle or near the South Pole where it often refreezes within hours even in January, which is the warmest month. Does it matter if the melt water enters an underground aquifer, evaporates or reaches the ocean? More important estimates are likely + or minus 10% or more. Also several % of the ice evaporates = sublinates and this energy is mostly recoverd elsewere when clouds, frost or dew is formed. Doesn't this complicate your calculation? In the case of clouds some of the energy of formation is radiated back into space. Neil |
Subject:
Re: Masked global warming increase
From: jigari-ga on 30 Dec 2002 13:07 PST |
The question precisely stressed NET melted ice, which already includes new ice formed minus melted. THis is valid question and correctly formulated question. However, I believe that heating ocean waters is immensely more potent masking of global warming due to very high heat capacity of water. Using the notation in the question, masking of global warming is dT=q*OWM, where dT is change in average temperate of OWM and q is heat capacity of water. |
Subject:
Re: Masked global warming increase
From: stenb-ga on 30 Dec 2002 14:12 PST |
Thank you for reply, Neil. With "net total from one year to another" I mean the difference. I.e. annually net molten, i.e. ice not refrozen the following year. Yes the difference is likely small. I want to know if it is small enough to ignore over 50 years. To eliminate the apparent randomness from year to year, please compare present ice volumes with past ice volumes 10, 50 and 100 years ago, as far as data is possible to obtain. It doesn't matter where the ice ends up, we are looking for how much heat the net melting of it consumes. Pls ignore evaporation combined with or following the melting. (That may be a further masking of temperature increase, since soft water evaporates faster than salt water, and each tonne cold water evaporated corresponds to the heating of some 600 tonnes water 1 degree C. - Another question! ) The question to be answered now by the calculation is "How much would the temperature increase per year if there was no ice left before the freezing season starts each year", considering only the latent heat of fusion.. Once that number is known as a function of "tonnes ice net molten per year", better predictions of future temperature rises are possible. At a scenario "no ice left", simply add the dT calculated. (worst case scenario..) Regarding mentioned potential scenarios "where the water ends up", we shall probably include heating of this water from zero to ocean mean temperature. If this is 10 dgr.C(?) and included, the factor 50 shall be changed to 60. The fact that the total volume of sea water increases year by year can be ignored now as it can easily be adjusted for afterwards in equation. Some interesting differential calculations can also be setup based on that only a small percentage "surface water" is prevented to heat up quicker from the effect . The time constant is some 100 years for the bulk of the water in the depths of oceans to be affected by surface water heating. That also buffers any surface warming, i.e. acts as another huge heat sink, but to be left out for now. With the constants in the basic equation asked for in the questions other equations can easily be set up. Please provide both "annualy average molten ice" and present total ice. The question was prompted by recently published predictions that "there will be no permanently frozen sea ice left around the north pole by 2080", accurate or not. Best Regards Sten |
Subject:
Re: Masked global warming increase
From: stenb-ga on 30 Dec 2002 14:25 PST |
Thank you jigari. The discussion raises the question of what the definition of global warming is? I thought it was the mean temperature of the ocean, but I may be wrong. Please advise. We need figures for both mean ocean surface temperatures and mean ocean temperatures, plus figures for mean atmosphere temperatures. Regards Sten |
Subject:
Re: Masked global warming increase
From: jigari-ga on 30 Dec 2002 23:08 PST |
If I only could define global warming... If changes in average temperatures of deep ocean are not accounted, then plenty of warming is masked in deep ocean, which is the bulk of world's water mass and has huge heating capacity. Considering that residence time of deep ocean waters can be 500 years, however, the uptake of heat can be slow but an inevitable process. But your question is on faster time scales (decades) so the question is how much of masking by deep ocean (if it is not already accounted) is relevant. |
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