Climate Change due to Global Warming – a hoax?

[cbacba]

Originally Posted by Cthulhu

It's about 4, whether 3.9 or 4.1 it doesn't matter so much. And that's the direct forcing without feedbacks.

The figure I see most is about 1C warming given a 0.25C per 1wm-2 sensitivity (again without feedbacks)

The imbalance is at the tropopause, the Earth has to emit 4wm-2 more energy to counter the imbalance, and the only way the Earth as a planet can lose energy is by radiating more.

A temperature increase of the planet would be necessary to cause the Earth to emit more radiation, which it would have to do in order to get back to equillibrium.

A doubling from 1976 would probably be closer to 2.8 W/m^2. A doubling from 1750 would be more like 3.7W/m^2 estimated.

The .25 deg. is a bit high. Also, the act of putting in addition ghgs which cause additional absorption also increases the emissivity function of the radiation from the atmosphere meaning that it's going to radiate more even without a T increase. Go ahead and plug the numbers in for stefan's law using 288K surface temp - verify it's about 350-400w/m^2 and then add 4 to that and reverse the process to find T.

[Cthulhu]

Originally Posted by cbacba

A doubling from 1976 would probably be closer to 2.8 W/m^2. A doubling from 1750 would be more like 3.7W/m^2 estimated.

A doubling from any point (except very high or low concentrations) should give approximately the same forcing. 360ppm to 720ppm should be about 3.7W/m^2 too.

The .25 deg. is a bit high

Perhaps, or maybe a bit low. I am going by the 1.1K figure for direct effect of doubling co2.

Also, the act of putting in addition ghgs which cause additional absorption also increases the emissivity function of the radiation from the atmosphere meaning that it's going to radiate more even without a T increase.

The radiative forcing already takes everything into account. 3.7W/m^2 is the immediate drop in emitted radiation from the tropopause if co2 is doubled.

Go ahead and plug the numbers in for stefan's law using 288K surface temp - verify it's about 350-400w/m^2 and then add 4 to that and reverse the process to find T.

Unfortunately it's too complicated to use stefan-boltzmann. 288K is the surface temperature, but the radiative forcing of 3.7W/m^2 is at the tropopause. To calculate the effect of 3.7W/m^2 forcing on climate requires calculating the radiation change through much of the atmosphere.

[cbacba]

Cthula,

you're waffling a bit there.

I'm not sure why you think it's the tropopause where it's important, why not try the total edge of space. If you go out into the sun, at least the last time I saw it many cloudy days ago, you'll note a yellow colored disk in the sky. That disk is glowing at about 5780K and is gas that is at a rather good vacuum compared to what you're used to breathing. This is where the radiant heat is coming from that keeps the earth above the teens in kelvin temperature (ignoring geotherm). if our atmosphere above the tropopause where that hot and stayed that hot for just a little while, everything would cook quite well done.

The back of the envelope calc for stefan's law that gives a ballpark approximation is simply as I put it, if radiating 350 or 400 W/m^2 and you increase that by 4 W/m^2, then that would roughly overcome what was being absorbed. It shows you the magnitude of what's involved. If you want to get nitpicky over about precision, then double that as about half the radiation outbound is absorbed - but then it's not going to tell you anything additional because the very notion of an average temperature when it comes to a nonlinear equation is in gross error.

The numbers I used for a 1976 doubling is actually from a radiative model based on hitran and the 1976 std atmosphere. A doubling doesn't even make it to 3w/m^2.

However, as stated, this log effect of doublings changing the same increment is only approximate. Each doubling produces less incremental change than the previous.

The radiative model also has to assume the temperature distribution remains the same and that has to come from elsewhere. Conservation of energy indicates that any shell is going to assume the temperature where input = output for equilibrium. But input (further up) is only coming from below and output goes up and down. The improved emission will force a drop in T as the energy balance cannot support it.

[Tony Sebo]

"Do not expect us to compromise on European interests," he said. "Both our international credibility and credibility before European Union citizens depend on fulfilment of the targets."

this is now the main driver of MMGW. Many people's 'credibility' now depends on persisiting, dispite mounting eviddence that we have all been conned.
http://afp.google.com/article/ALeqM5...2-EnGZIHgY_MmA

[Tony Sebo]

Originally Posted by spot1234

If it was a hoax at some point the IPCC and almost everyone working in the field would have to have said to themselves "Hang on this Man made Global warming theory doesn't add up! What are we going to do for work? we will just have to make it up" This to me is silly.

but lots have.. they are instantly vilified, denied funding and have had their carreers destroyed!

[cbacba]

evidently, the fable (by O. Henry) of The Emperor's New Clothes is apparently not universally read.

[Besoeker]

Originally Posted by cbacba

However, it doesn't require a significant amount of T change because it's a T^4 relationship..

What is related to T^4?

[cbacba]

Originally Posted by Besoeker

What is related to T^4?

that would be power emission. you'll need to read a number of posts above to understand the exchange.

[Bored Wombat]

Originally Posted by Ross Welford

But that's not true is it? Between about 1940 and 1970 temperatures fell - giving rise to well-publicised fears of a "new ice age".

Reasonably well publicised in the press. The scientific community were less taken by it, which makes it different from the global warming revelations of the past 20 years.

Originally Posted by Ross Welford

This was a period that saw the post-war regeneration and a massive increase in industrial output and transport.

Also very high aerosol pollution and acid rain. The temperature drop in the 70s is in line with modelling.

Originally Posted by Ross Welford

Temperatures then started to climb again, but then stopped in 1998.

No. It's still climbing. Not as steeply as it was when solar irradiance was on the increasing phase of its 11 year cycle, but still increasing.


Predictions are that from 2009 we should be starting to see a strong increase again, with at least half the years 2009 to 2014 expected to exceed existing records. (source)

Originally Posted by Ross Welford

It's not such a close correlation as we are led to believe.

Its not supposed to be a correlation. The causality is on fairly solid ground though.

Originally Posted by Ross Welford

Furthermore, temperatures on earth have been much higher than they are today. It's reckoned that during the time of the Roman Empire, and again during the Middle Ages it was very warm indeed, long before cars, planes, industry etc.

Most temperature reconstructions don't put it as this warm. We're probably warmer than any time in human history.

And CO2 concentrations are higher than at any time in the last million, so there's more warming in the post.

Originally Posted by Ross Welford

Opportunity for a bunch of smug, sanctimonious busybodies to strut around telling us how to live "better" lives? Definitely.

How are you being asked to live a better life?

[cbacba]

the last million years is chosen because it's the only time in the last 550 million years+ where co2 levels have been anywhere close to as low a level as they are at present. Of course the vast majority of the last million years has been in horrible ice ages where the co2 levels appear to be substantantially less that they were even before man entered his industrial revolution and in fact, seldom reached such high levels as existed before the beginning of that revolution.