Global Cooling?

[Trido (Justin)]

From: http://www.news.com.au/story/0,23599...009760,00.html

Does anyone think this is actually possible? I dunno. I've been brought up hearing from everyone that the world is getting hotter. Such a conflicting view is a little strange. Gotta admit though, here in Toowoomba, we got into the 30s like 2 or 3 times this summer. Most of it was spent in the mid to highish 20s and we had a few weeks in the low 20s. Far beyond the norm where the week of christmas is usually 35-40.

[acropolite (Phil)]

There was an excellent program on SBS Sunday last which discussed the possibility of the Northern Hemisphere being plunged rapidly in to an Ice Age, global warming causing the polar and Greenland ice to melt resulting in changes to the Gulf Stream current. There's already evidence that the Gulf Stream current is slowing in agreeance with modelling. If that does happen as a civilisation we're probably in deeper trouble than we expect.

[erick (Eric)]

"Dr Chapman proposes preventive, or delaying, moves to slow the cooling, such as bulldozing Siberian and Canadian snow to make it dirty and less reflective."

[Trido (Justin)]

Originally Posted by erick

"Dr Chapman proposes preventive, or delaying, moves to slow the cooling, such as bulldozing Siberian and Canadian snow to make it dirty and less reflective."

If it was April 1st, I would of thought it'd be a joke because of that.

[jjjnettie (Jeanette)]

I don't know.
Global warming vs global cooling.
There seem to be good arguments for both.
It'll be my childrens generation that will find out for sure what our worlds fate will be.

"This is the way the world ends,
This is the way the world ends,
This is the way the world ends,
Not with a bang but a whimper."
T.S. Elliot

[Trido (Justin)]

Full story here: http://www.theaustralian.news.com.au...6-7583,00.html

[alan meehan (Alan)]

damn cooling in the northern hemisphere ,means more cloud in the southern doesn,t it might have to take up playing golf

[renormalised (Carl)]

It could very well happen. The problem with the warming of the planet is that there is an overall rise in precipitation and that is the big bugbear. The Atlantic Conveyor which brings warm water to the European coast fails because there's an influx of fresh water in the upper levels of the ocean. This prevents the warm, salty water of the conveyor from sinking down to the cold abyssal deep flow and returning to the Southern Ocean. The diluted ocean water stays at the surface and begins to cool. The flow slows down to a stop and no warm water reaches Europe, hence the continent begins to cool and harsh winters set in. If it continues for too long, you start to get an overall cooling of the planet and a possible ice age sets in. You'd think all the CO2 being dumped into the atmosphere would prevent this from happening but the catch is the CO2 is the main driving force to the cooling. If you look at the CO2 levels in pre-ice age ice cores from Antarctica and the isotope ratios present in ancient lake sediment cores, the amount of CO2 was high beforehand and the C isotope was heavy C13, but when the planet began to cool, the isotope C12 became more prevalent in the cores cf. C13 and atmospheric CO2 dropped dramatically. The optimum temp at which CO2 is absorbed by ocean water is around 16 degrees celcius, which is several degrees cooler than present ocean water average temperatures and once the CO2 dropped below a critical level, this created the conditions to drive further cooling. Along with the build up of the ice, increasing the planet's overall albedo. Also, the cooling began a drying of the planet overall, but especially in the mid latitudes and this caused an increase in atmospheric dust (due to an increase of windy conditions) ... further cooling the planet. It basically becomes a vicious cycle of cause and effect, until something breaks the cycle.

[AstralTraveller (David)]

I have some knowledge of palaeoclimates. I studied them at uni and I now work as a technician in a lab that mostly does palaeo work. I'm no great supporter of the anthropogenic global warming hypothesis but I do want to see fair and balanced appraisal of evidence. Reading through the article I noticed a few 'supporting' facts that don't gel.

"little ice age, similar to the one that lasted from 1100 to 1850"

The LIA was 1450 to 1850. The Medieval Warm Period was about 950 to 1250.

"This bitterly frigid climate is interrupted occasionally by brief warm interglacials, typically lasting less than 10,000 years."

I don't agree. The last interglacial was about 20,000 years, the one before that <10k, before that 15k and then 30k (roughly speaking).

"the Holocene, began 11,000 years ago, so the ice is overdue"

The Holocene began at 10,000 years ago (10ka) and its beginning is not based on climate. The warming at the end of the Last Glacial Maximum had begun by 18ka. Depending on the record you use you can say modern temperatures were reached between 14ka and 9ka. Certainly no significant cooling events occurred after 11ka,

"We also know that glaciation can occur quickly: the required decline in global temperature is about 12C and it can happen in 20 years."

This news to me and I can't imagine where it comes from. As far as I know no palaeoclimatic record has such fine time resolution.

[AstralTraveller (David)]

Originally Posted by renormalised

If you look at the CO2 levels in pre-ice age ice cores from Antarctica and the isotope ratios present in ancient lake sediment cores, the amount of CO2 was high beforehand and the C isotope was heavy C13, but when the planet began to cool, the isotope C12 became more prevalent in the cores cf. C13 and atmospheric CO2 dropped dramatically.

What has this got to do with whether the planet will cool? The 12C/13C ratio can certainly be used as an indicator of past environments but it is not a causal agent. The ratio of the two stable isotopes is pretty constant at about 1.11% 13C, give or take a few parts per thousand. That's why we need such fancy instruments to measure the differences.

BTW these days we can watch the 13C/12C ratio drop as the CO2 concentration increases. This is because we are burning fossilized plant remains and photosynthesis discriminates against 13C, meaning that fossil fuels are isotopically 'light'. The difference between the 13C concentration of the present atmosphere and plant remains is about 20 parts per thousand. So we are adding CO2 which has relatively little 13C to the atmosphere and so diluting the 13C.

[renormalised (Carl)]

Originally Posted by AstralTraveller

I have some knowledge of palaeoclimates. I studied them at uni ......

"We also know that glaciation can occur quickly: the required decline in global temperature is about 12C and it can happen in 20 years."

This news to me and I can't imagine where it comes from. As far as I know no palaeoclimatic record has such fine time resolution.

Same here...part of my course (Geology).

I would agree with their assessment that the onset can occur quickly, however a full blown glaciation takes many thousands of years to develop. You don't develop kilometre thick icecaps in 20-100 years, but you could certainly develop large accumulations of snow and ice in that time period, especially if your spring and summer periods never melted much of the ice, due to being colder than normal.

[AstralTraveller (David)]

Originally Posted by renormalised

Same here...part of my course (Geology).

Where at? I am at Wollongong

Originally Posted by renormalised

Same here...part of my course (Geology).

I would agree with their assessment that the onset can occur quickly,

He is talking about 12C in 20 years. That is more than the onset. Again, where is the record with that temporal resolution?

[renormalised (Carl)]

Originally Posted by AstralTraveller

What has this got to do with whether the planet will cool? The 12C/13C ratio can certainly be used as an indicator of past environments but it is not a causal agent. The ratio of the two stable isotopes is pretty constant at about 1.11% 13C, give or take a few parts per thousand. That's why we need such fancy instruments to measure the differences.

BTW these days we can watch the 13C/12C ratio drop as the CO2 concentration increases. This is because we are burning fossilized plant remains and photosynthesis discriminates against 13C, meaning that fossil fuels are isotopically 'light'. The difference between the 13C concentration of the present atmosphere and plant remains is about 20 parts per thousand. So we are adding CO2 which has relatively little 13C to the atmosphere and so diluting the 13C.

The ratio isn't the causal agent, just that it might point to a causal agent.

High CO2 concentrations in the atmosphere would dilute atmospheric C13, but that would leave a small, yet greater conc' of the heavier isotope in the ice core and lake sediment records. Remember, most natural CO2 comes from outgassing via volcanoes and the natural ratios of C13/C12 are set via geological processes, not biological ones (except in biogenic sediment deposition such as limestones etc). Yes, we are burning fossil fuels that are preferentially light isotopically and that explains the present isotope ratios. However, we are talking about isotopic ratios and CO2 levels that had next to nill human input. And that due to a warming event, the C13/C12 ratio in the cores was higher than it normally would be due to the fact that the heavier isotope is preferentially incorporated into the core because of it's higher weight. Then when the lighter isotope was being incorporated into the cores and the ratio of C12 was increasing, then a cooling must've been taking effect. The CO2 conc' was coming down in the atmosphere. In any event, C13 is a lot less common than C12 so the ratio difference, as you've mentioned, is quite small and takes careful measuring with complicated equipment.

What I was trying to get at, with the concentrations of CO2 and the isotopes was that before the onset of the cooling, there may have been higher than normal CO2 concentrations in the atmosphere, heating the planet and causing an increase in the input of freshwater into the upper levels of the ocean, thereby changing the current and temperature regimes in the North Atlantic and triggering an eventual decrease in temps on the continent.

I would've been better dealing with oxygen isotope records as they chart temp increase and decrease better than the carbon isotope record.

[renormalised (Carl)]

Originally Posted by AstralTraveller

Where at? I am at Wollongong



He is talking about 12C in 20 years. That is more than the onset. Again, where is the record with that temporal resolution?

JCU.

I do know of recent studies that show the warming occurring at a pace pretty much in line with that sort of pace, but I don't recall one with a cooling at that rate....not offhand anyway. Whether there is or not, I don't know. I haven't kept up with the literature for quite awhile.

Anyway, regardless of the pros and cons of this argument in particular, I'm like you. I don't particularly follow without question the anthropogenic cause for global warming. Too many variables to deal with to be fully convinced as such. Considering they have a hard time trying to model mesoscale climatic effects, how in the hell do you then say we have a good fix on the global climate models. Things just aren't that simple. However, that's not to say we shouldn't be cautious about what we do w.r.t. gaseous emissions into the atmosphere. They must have some effect, but to what extent that effect is, can still be open to debate (despite what they might say, or believe).

[OMEGA DAWN]

THERE IS A "CAUSE AND EFFECT" OF ALL MATTER WHICH CREATES A CHAIN REACTION IN FORM. MATTER IN IT'S VARIOUS DEGREES OF FORM ACCORDING TO IT'S OUTSIDE INFLUENCES MAY RESHAPE ITSELF FROM SOLID TO LIQUID TO GAS TO LIQUID TO SOLID AGAIN. CONSIDER THE ICE CUBE: TAKE IT OUT OF THE FREEZER, PUT IT ON A SAUCER AND LET IT MELT UNTIL THE SOLID CUBE TURNS INTO A LIQUID CALLED WATER. WITHIN PERHAPS 2 DAYS THIS LIQUID TURNS INTO A GAS AS IT BECOMES EVAPORATED INTO VAPOR TO ADD MORE HUMIDITY TO YOUR AIR IN THE ROOM. HUMIDITY IN THE AIR CAN CAUSE CONDENSATION (CONSIDER THE DRAINING OF STREAMS OF COLLECTED PARTICLES OF MOISURE ON THE WINDOW WITH THE AIR CONDITION ON HIGH). NOW HERE IS YOUR REFERENCE OF CAUSE AND EFFECT OF GLOBAL WARMING LEADING TO AN ICE AGE( WHICH IS ALWAYS AFTERWARDS).NOW, CONSIDER THE POLAR CAPS, WITH THEIR PARTIAL TOP LAYER MELTING DUE TO INCREASE OF HIGHER TEMPERATURE. THE TOP PART OF THE ICE DRAINS DOWN THE SLOPES AS LIQUID SPREADING MORE ICE AS IT GOES. FOR IT REFREEZES AGAIN DUE TO BEING ON ICE, HAVING MORE SNOW &/OR HAVING TEMP. DROP. ADD WITH IT REPETITION OF THIS PATTERN. THIS WILL SPREAD THE CIRCUMFERENCE OF THE FROZEN LAND TO EXPAND IT'S ORIGINAL AREA. AN EXCELLENT EXAMPLE OF THIS IS TO GO BACK TO THE CUBE OF ICE ON THE SAUCER, BUT THIS TIME PLACE IT ON A PLATE(YOU ARE GOING TO NEED THE EXTRA SPACE FOR EXPLANDING CIRCUMFERENCE). LET THE CUBE MELT A LITTLE, THEN PUT IT BACK INTO THE FREEZER TO REFREEZE.THE ICE GETS WIDER. REPEAT THE PATTERN BUT LET IT MELT A LITTLE MORE, THEN REFREEZE IT. IT WILL CONTINUE TO GROW IN WIDTH. IF YOU ADD A TILT OF IT'S AXIS THIS LIVING BREATHING ORGANISM CALLED EARTH, SHE MIGHT EVEN PRODUCE "ICE CREAM". AS IN BASEBALL, "YOUR TEAM WAS CREAMED, BUDDY!"

[iceman (Mike)]

argh all capitals! So hard to read.

Can you please post in lower case?

[OMEGA DAWN]

SURE, My letters r melting...but obviously not these- Thought a little humor might enlighten the subject;HOWEVER, SOME SUBJECTS AREN'T EASILY HUMORED. So be it.