A New Ice Age?

barakn writes "Scientists have savaged the new movie The Day After Tomorrow, which depicts global warming causing a new ice age and freezing New York solid. The movie follows on the heels of a report to the Department of Defense in February, written by two guys who are not climatologists, about the implications of global warming triggering the growth of ice sheets in the northern hemisphere. There is a plausible theory which suggests that melting ice may release enough fresh water to halt circulation of warm water from the Gulf Stream, thus significantly cooling Europe and the east coast of North America. Note that this theory depends on melting ice, not growing ice, which may be one reason scientists find the ice age scenario so hard to swallow. New satellite evidence suggests a part of this circulation may already be slowing down. Those on the North American west coast will not have to worry about ice sheets, but changes in Arctic ice could mean the western drought will be permanent. For those of you who would rather do something before it's too late, iron seems to work, but the long-term ecological implications are still unknown."

Comments

Aren't we still in an Ice Age?

[Anonymous Coward]

IIRC, the historic/geologic average temperature of the Earth over it's 5-billion or so years had been something like 72 degrees F.

Today, it's like 59 degreees F.

If that recollection is true, then we're still in an "Ice Age" and should expect the world to be getting warmer if the "Ice Age" is in fact coming to an end.

Sorry if this doesn't fit into the "human == BAD, all_natural == GOOD" paradigm, but getting struck by lightning or eaten by a lion does fall into the "all_natural" category too...

Re:Aren't we still in an Ice Age?

[sparks]

Absolutely correct, we are at present still in an ice age which has lasted for about four million years, with (geologically) brief "interglacials" of around 10,000 - 20,000 years every 140,000 years or so.

We are in one of one of those interglacials now, and in fact it has lasted 18,000 years so far - so it's not at all crazy to start looking for signs of the end of it.

This is not the first ice age; there one approx 600 million years ago; another 450 mya; another 300 mya. They each lasted at least a few tens of millions of years. This ice age is young and will likely exist for many millions more years. During this whole time, we can expect the glacial and interglacial cycle to continue.

There are some important points everyone who discusses climate should be aware of:

For most of the history of the Earth, it has been very much warmer than it is now.

For the last four million years, it has, on average, been very much colder than it is now.

A thousand years ago, there was a "medieval warm period" during which global temperatures were significantly warmer than today; to the extent that wine grapes were grown in Southern Scotland.

Five hundred years ago temperatures were significantly colder than today; "the little ice age". Opinions vary as to when the LIA ended; some say aruond 1900, others say it hasn't totally ended yet.

Note that both the MWP and the LIA occurred before the industrial revolution; they were not caused by man.

There is no "normal" temperature.

The current climate has not existed very long, and will not stay the same for very long (and this would be true even if there were no humans).

No it's not.

[Hittite Creosote]

All human activity since the industrial revolution is less than one small to moderate eruption

Uh... do you actually have a cite for that?

Because, for example, the eruption of Mount St Helens put 1 Million tonnes of sulfur aerosols into the stratosphere - these are the things that have the most effect on the worldwide climate, the ash from volcanos is local effect only.

Now, a million tonnes sounds absolutely huge. But it is still only just over five times what, say, the State of Louisiana emits as sulfur dioxide every year.

So in other words - the US easily produces as much sulfur dioxide, and more, every year than the explosion of Mount St Helens.

Or put it this way - you get sulfur dioxide from burning fossil fuels. We mine, worldwide, billions of tonnes of coal every year (the US alone produces just under a billion). How much sulfur dioxide do you think all that lot produces? The answer is that a typical small coal-fired power station (100 MW) may produce from 20 000 up to 30 000 tons of sulphur dioxide a year. In other words, Mt St Helens is worth a measly 40 small coal-fired power stations. How many of them are there in the US alone?

Re:No it's not.

[clifgriffin]

Mt. St Helens was a relatively small eruption.

I believe the poster you were responding to was citing the eruption of Mt. Pinatubo. This particular eruption in 1991 was at least 10 times as violent as Mt St. Helens.

It created an "aerosol cloud" that spanned the continents and even affected global weather.

Scientists estimated a 4 to 6 percent loss in ozone at the time. It was also said that the toxic output of this blast contained nearly a thousand times the ozone depleting chemicals that humans have created since the Industrial Revolution.

And here's the kicker: This was only the 2nd largest eruption of the 20th century!

Sometimes I think it is human pride that makes us want to be the most influential, and thus devestating, force on this planet.

Re:Wait... so you're telling me...

[Dirtside]

More accurately, the books the movie is based on were written by Bell and Strieber. They didn't write the screenplay (or at least they're not credited with it; Roland Emmerich and Jeffrey Nachmanoff are).