I’ve heard that we can alreadly have an ice age with our current tempetures, all we need is a bit more percipation. If so I assume we could have one if the temps got a tad warmer, not much but just a tad. Also if it got a tad warmer wouldn’t this lead to more evaporation of the sea? leadihng to more rain/snow? Could an increase of global temp (either by man (if you are so politically inclined) or natural causes) actually be causing an ice age?
It’s difficult to predict effects on climate, because there are so many factors. The Earth has a way of mediating itself, but as geologic history shows it also has a way of radically changing climate. Even though ice ages and warm periods are very gradual, it’s still difficult to spot one until it’s well underway.
The ice age through global warming theory is actually based on ocean currents.
In the theory, it is believed that the salinity (salt content) of the ocean affects the jet stream. As the salinity decreases, the flow of the current/jet stream decreases. The jet stream is a major factor in weather to keeping North America and Europe warm, so a decrease in the jet stream would make it much cooler for us.
Now the tie in to global warming is actually greater melting of the polar ice caps. As the ice caps melt, the salinity of the ocean decreases (more water to hold an equal amount of salt.)
The affect of greater precipitation is actually tied to the fact that water vapor is also a heat-trapping greenhouse gas. The evaporation therefore actually aids in melting the ice caps further.
Here’s a couple links that might provide better explanations of the theory:
http://www.commondreams.org/views04/0130-11.htm
http://www.whoi.edu/institutes/occi/currenttopics/abruptclimate_rcurry_pr.html
The second link discuss the affect of greater evaporation.
Basically this is only a theory right now, but more and more evidence is being produced to strengthen the theory. If it is correct, then global warming can cause an ice age. So to answer your last question: Yes, global warming possibly can cause an ice age.
I’ve read the ocean current theories as well.
Basically the oceans act like a thermostat. If it gets too warm it will turn on the AC on a planetary scale.
As the warm current from the equator go up the US east coast and by Greenland it cools off and drops. If the ice cap on greenland melts too much it could seriously affect that current and bring on an ice age.
I think this is the plot of the upcoming The Day After Tomorrow movie due out this summer.
This is not quite correct. The jet stream does not play a major role in warming anything, and there is no direct tie between ocean salinity per se, the speed of ocean circulation, and the speed of the jet stream. Warming of higher latitudes is accomplished by meridional ocean heat transports from the equator (think poleward direction, roughly paralleling lines of longitude), whereas the jet stream has a greater zonal impact on the distribution of energy in the climate system (think west to east in the northern latitudes, roughly parallel to lines of latitude).
A reduction in the Gulf Stream would cause cooling in northern Europe, but because the ocean itself was no longer transporting heat to the same degree. The change in heat transport itself would produce atmospheric effects, to be sure, but these are not so simple to project.
The issue here boils down to the principle driver of ocean circulation: the formation of North Atlantic Deep Water (NADW) in, well, the north Atlantic. As the Gulf Stream moves northward along the east coast of North America and curls around past Greenland, Ireland, etc., the water sheds its heat and becomes more dense. The increase in density, combined with a relative increase in salinity, causes this mass of water to sink from the surface to the bottom of the ocean. It is this sinking that is the driving force behind the ocean “conveyor belt” on a global scale.
With global warming, the melting of the Greenland ice sheet would inject a great deal of fresh water into the surface ocean, decreasing the density of surface waters by a significant amount. With the decrease in density, the water can no longer sink to great depth, the ocean conveyor is weakened, and weather patterns patterns are subject to change.
What sort of changes? Well, for one, you could reasonably expect northern Europe to cool off considerably. And yes, if heat is not being transferred poleward as it is now, one would expect increased evaporation in warmer equatorial regions that would require an increase in precipitation somewhere else. Whether that increased precipitation would fall as snow at higher latitudes and persist on an annual basis (necessary for a true return to ice age glacial conditions) is unclear. Short-term (i.e., significant on human timescales) climatic disruptions are a practically a given, but it is very difficult to predict how, exactly, regional patterns will change.
Nitpick: it’s only a hypothesis right now. A theory would have a considerable body of evidence to support it; this concept is still young, with little data as yet to support it.
The first link is a rather sensationalized and somewhat inaccurate portrayal of the issue; I suspect a journalist whose specialty is not science. The second link is a press release that points out some interesting observations have been made that may indicate a change in ocean circulation is going to take place sooner rather than later, but otherwise it expands a bit on the same points I made above.
Technically we are still in an ice age; after all, we have significant ice caps in both Antarctica and Greenland. Ice ages do swing back and forth between very cold intervals, during which ice sheets advance, and “interglacials” during which there is relative climate warming and retreat of the ice. The $64,000 question is: what will global warming do? Will it wreak havoc with ocean circulation and thus allow the return of ice-age like conditions at higher latitudes in just a few years’ time? (Note “ice-age like” - a full blown return to glacial conditions requires the regrowth of ice sheets over Scandinavia and North America, which would take thousands of years to accomplish.) Or will the warming drive us completely out of “cool climate” mode into a new state in which total absence of ice sheets is the norm?
There are a lot of very bright people are working very hard to understand what the probabilities are, but the bottom line is… no one really knows. Yet.