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What will Earth's temperature be in 5000 years?

Significantly warmer than today (> +3C)
3 (60%)
Slightly warmer than today (+0.5C to 1C)
1 (20%)
About the same as today
0 (0%)
Slightly cooler than today (-0.5C to -1C)
0 (0%)
Significantly cooler than today (< -3C)
1 (20%)

Total Members Voted: 5

Author Topic: What will Earth's temperature be in 5000 years?  (Read 3112 times)

Offline CliffordK

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What will Earth's temperature be in 5000 years?
« on: 03/04/2012 07:00:45 »
What will Earth's temperature be in 5000 years?

By that time, I have no doubt that the majority of Earth's fossil fuel (coal, oil, natural gas) reserves will be long gone or deemed inaccessible.  Hopefully humanity will have found our next energy source, or perhaps we will have learned to capture more solar, wind, geo, and bio energy.


 

Offline Don_1

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Re: What will Earth's temperature be in 5000 years?
« Reply #1 on: 03/04/2012 10:59:23 »
I suppose it depends on how much we are prepared to pay for fossil fuels. If I remember correct, JB said that only around 10% of the oil in a well is actually extracted, the remainder being too expensive to extract. If that continues to be the case, then perhaps we won't do too much damage to the atmosphere. But if we are prepared, or forced, to pay the price due to a lack of a sustainable efficient alternative, we might put back into the atmosphere much of the original content which has been locked away for many 100's of millions of years. The result of that could be catastrophic.

The problem right now is that the alternatives which are available are insufficient to satisfy demand and the alternatives which could satisfy demand seem to be on a horizon which does not seem to be getting any closer.

If we were to reach a global increase in temperatures of >3o, I think it probable that even the most ardent of climate change deniers would be forced to admit they had got it wrong and come into line with popular opinion. Whether there would still be time to put things to right is debatable.

I would hope that good science will prevail over greedy economics before we reach such a critical point. But I'm not putting money on it!

As a result of my fears, I'm going to go for the 'Significantly warmer than today (> +3C)' option, but with the reservation that it would be a global average increase, with some parts (such as the most northerly parts of Europe and Asia) being significantly colder. Differences between the polar and temperate zones and the equatorial, tropical and sub tropical zones will become ever wider.
« Last Edit: 03/04/2012 12:22:16 by Don_1 »
 

Offline damocles

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Re: What will Earth's temperature be in 5000 years?
« Reply #2 on: 03/04/2012 12:50:49 »
A couple of points need clearing up: firstly, we can never come close to burning all fossil fuels. When a fuel burns, it combines with oxygen in the atmosphere to make carbon dioxide and water. Every bit of oxygen in our atmosphere has a biological origin, and therefore corresponds either to biomass or to fossil fuel. But we know that some of the oxygen that our green plants have so thoughtfully produced for us has gone into changing compounds like pyrite, FeS2, into red iron oxide Fe2O3. And we also know that, unlike the case with oxygen, some of our elemental carbon and methane are remnants from the early Earth, that is, they are non-biogenic. Therefore there is not enough oxygen to burn all of the fossil fuel reserves and biomass back to water and carbon dioxide.

So we cannot burn all of our fossil fuel reserves. When we got to perhaps about 80% there would be no oxygen left in the atmosphere. Mind you, a lot of the Earth's fossil fuel reserves are buried deep or spread thin and would be totally uneconomical and near impossible to mine. Obviously, the crisis would arise long before then -- if we were to burn about 10% of the total amount of reduced carbon on the planet, we would not only be worrying about carbon dioxide build up, we would be needing to think about a significant oxygen depletion that would have occurred by then.

The situation is even a bit worse than that, though, because a lot of the global atmospheric modelling is showing that at the level of 450 ppm carbon dioxide in the atmosphere (which is 0.045% by number of molecules, or 0.068% by mass), some of the earth's systems in the atmosphere & oceans go from a state of negative feedback (stable systems tending to damp out changes) to a state of positive feedback (systems where a small perturbation gets amplified, and which might race almost uncontrollably in any direction). In the ice core record, which covers the last half million years of the Earth's history, carbon dioxide levels have ranged between about 210 and 280 ppm. Since about 1850, though, the level has been increasing at an accelerating rate. The present carbon dioxide level is about 390 ppm, and it is increasing by about 1.5 ppm per year. That gives us about 40 years before we will check out whether these models are right or not! There are things that could be done to prevent or slow that build up, but they would be very painful for the human population, and it is almost certain that any action will be too little, too late.

In the democracies, it would be political suicide for any government to take the harsh measures that would really be necessary; most dictators are old, and have little concern beyond themselves and perhaps a dynasty.

So, as I see it, we are on the Titanic. We have the choice of continuing to dance and ignoring the crisis, or rearranging the deck chairs to deal with it.
 

Offline Nizzle

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Re: What will Earth's temperature be in 5000 years?
« Reply #3 on: 10/04/2012 10:51:30 »
I didn't vote since there's no "I have no idea" option.
Anyway, in 5000 years humanity has evolved from biological to mechanical lifeform and agricultural lands will have switched to solar power or wind power farms since all we need for sustainability is electricity.
We'll still be drilling oil but we won't be using it as fuel anymore. We'll use it as motor oil or lubricating oil to maintain our robot bodies :P

I'm just saying, 5000 years is a long way ahead of us and who knows what'll happen in the mean time..
 

Offline CliffordK

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Re: What will Earth's temperature be in 5000 years?
« Reply #4 on: 12/04/2012 22:24:46 »
Ok,
A couple of points that I would like to suggest for the long-term climate prognosis.

At this point, the ocean and biosphere are absorbing about half of the excess CO2 that we generate.  If we could cease new production of fossil CO2, then over a few centuries the levels would return to an asymptote, somewhat above the levels at the beginning of the Holocene, but significantly less than the peak, at which point further reduction of the CO2 would depend almost entirely on organic processes and would be slow.  But, perhaps 90% of the excess CO2 would rapidly be reabsorbed.

Over the last few million years, Earth has been cycling through glacial/interglacial cycles.  The temperature cycles are likely caused a complex feedback system including Solar Output, Milkanovich cycles, Greenhouse Gases, Ocean Currents, Albedo, Insulation by the ice and glaciers, & etc.  However, without humanity, one might expect a new glacial cycle to begin sometime between now, and 5000 years into the future. 

I am just not convinced that we have, and we will inadvertently be making large enough changes in the planet to completely miss the next ice age, although it is possible that our high CO2 output will help reduce the impact of the glacial cycle, at least initially when we maintain high levels of CO2.  Undoubtedly we will not be able to, or may not wish to maintain high levels of CO2 for hundreds of thousands of years.

Obviously 5000 years is a long time in the future, and humanity will be tempted to intentionally directly modify our global climate.  Perhaps warming the poles, or attempting to decrease the annual seasonal temperature fluctuations.
 

Offline Nizzle

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Re: What will Earth's temperature be in 5000 years?
« Reply #5 on: 20/04/2012 06:40:50 »
However, without humanity, one might expect a new glacial cycle to begin sometime between now, and 5000 years into the future. 

So mankind did a good job burning all those fuels and possibly delaying the onset of the next glacial era, seeing as how a glacial era could, and probably would, be quite devastating for the best developed regions on earth. Now we're buying ourselves some extra time to solve this Cycle problem permanently ;)

Obviously 5000 years is a long time in the future, and humanity will be tempted to intentionally directly modify our global climate.  Perhaps warming the poles, or attempting to decrease the annual seasonal temperature fluctuations.

On this, I can only agree. I predict that in the future there will be some curriculum on the university called "Climate Engineering" as mankind will be more and more able to manipulate it.
 

Offline yor_on

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Re: What will Earth's temperature be in 5000 years?
« Reply #6 on: 23/04/2012 01:47:16 »
Hmm.

There are two recent studies. One that looked at the mid-Pliocene where we had a similar temperature that is expected in a medium scenario which as for now comes to about 3.6 degrees F (2 degrees C) above current global mean temperatures. This is a very optimistic estimate as I see it :) but never the less.

"Sea levels were as much as 70 feet higher than they are now. Florida would have been a narrow strip instead of a broad peninsula, Washington, D.C., might have offered oceanfront views and much of Bangladesh would have been under water. Greenland, now covered in melting glaciers, had forests growing on its northern slope... Carbon dioxide levels in the atmosphere were between 350 and 400 parts per million (that is, between 350 and 400 carbon dioxide molecules for every million molecules of air), said Pagani, who called the estimates "a pretty good ballpark figure." ... Today, the carbon dioxide concentration is similar. An April 5 reading at Hawaii's Mauna Loa Observatory was over 394 parts per million. This figure has climbed from less than 320 ppm in 1960 and could be over 450 ppm by 2100. A graph is visible at the NOAA site http://co2now.org/... A study in the journal Nature Climate Change compared four existing climate models, and found all four are largely consistent with each other and with USGS data on the Pliocene.

But problems with simulating what could happen in the North Atlantic are significant, said Mark Chandler of NASA's Goddard Institute for Space Studies. The models show less North Atlantic warming than occurred during the Pliocene. "What happens to the North Atlantic in the future is going to dramatically affect the Western world," Chandler said."

The technique for extrapolating makes it difficult to be exact about where and how though. "paleoclimatologists who study ancient climate find clues in cores drilled in sediment layers on ocean bottoms and in some leaf remains. They then examine different isotopes (atomic weights, with varying numbers of neutrons) of non-radioactive, stable carbon.

Mark Pagani, a paleoclimatologist at Yale University, described how this works: When algae in the Pliocene sucked up carbon dioxide to perform photosynthesis, they produced organic carbon with distinct isotope signatures that were sensitive to the concentration of CO2 in seawater. These signatures are preserved in fossils that can help determine how much carbon dioxide was in the atmosphere back then. "We needed to figure out what was on the land, where the plants were growing, where the mountains were, where the sea level was, where the ice sheets were," Dowsett said. Using these techniques, scientists have estimated carbon dioxide levels at some locations going back as much as 150 million years, Pagani said."

And then we have another recent study discussing Antarctica.

"Sea levels have increased on average about 18 centimetres (7 inches) since 1900 and rapid global warming will accelerate the pace of the increase, experts say, putting coastlines at risk and forcing low-lying cities to build costly sea defenses. Scientists last month said that thinning glaciers and ice caps were pushing up sea levels by 1.5 millimetres a year, and experts forecast an increase of as much as two metres by 2100.

A very rapid sea level rise is thought to have occurred 14,650 years ago but details about the event have been unclear. Some past sea level records have suggested glacier melt led to a 20 metre increase in less than 500 years. But uncertainty lingered about the source of the melt, its force and its link to the changes in climate.

A team of scientists, including researchers from France's Aix-Marseille University and the University of Tokyo, claim to have solved the mystery which may shed light on climate change. They reconstructed sea level changes by analyzing samples of coral collected from reefs in Tahiti and dated them to determine the extent and timing of the sea level rise.

"Our results ... reveal that the increase in sea level in Tahiti was between 12 and 22 metres, with a most probable value between 14 and 18 metres, establishing a significant meltwater contribution from the southern hemisphere," said the authors of the study published in the journal Nature."

So? I don't know, but I expect a changed environment. And as we can't really use historical material, as there was no man made CO2 at those times? And no, we're not slowing down :) We're producing more CO2 for each year, as everyone wants to maintain their 'standard of living' with the newly industrialized Countries adding their contribution as they try to catch up to the western world. And they do more for minimizing their contributions than we do actually, but that doesn't really matter here. The net contribution of CO2 grows, each year, so any new prognosis will, as usual, have to be revised upwards as for what temperatures we will meet 2100.

And then we have the tundra that is melting, releasing both CO2 as well as Methane. We can't really assume that what we see historically describe what we will meet. What we can do is to assume that the effects of it might be similar though. It's a changing world, and what it will do the major ocean currents is anyones guess, as well as what acidity we will find in the oceans at that time.

 

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Re: What will Earth's temperature be in 5000 years?
« Reply #6 on: 23/04/2012 01:47:16 »

 

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