Dr. Jeff Masters' WunderBlog

Global cooling

Posted by: Dr. Jeff Masters, 00:24 GMT le 15 janvier 2007

Global temperatures in 2006 were the third coldest on record in the lower stratosphere, according to the National Climatic Data Center. Only 1997 and 2000 had colder temperatures since record keeping began in 1979 (Figure 1). Why is this important? Well, the stratosphere is that layer of the upper atmosphere approximately 14-22 km (9-14 miles) above the surface that contains our protective ozone layer. The main reason for the recent stratospheric cooling is due to the destruction of ozone by human-emitted CFC gases. Ozone absorbs solar UV radiation, which heats the surrounding air in the stratosphere. Loss of ozone means that less UV light gets absorbed, resulting in cooling of the stratosphere. Cooling of the stratosphere results in the formation of more polar stratospheric clouds, which require very cold temperatures to form. The presence of these clouds allows even more ozone destruction to occur, since the reactions responsible for ozone destruction occur much faster in clouds than in dry air. Thus, the recent cooling of the stratosphere allows high levels of harmful UV light to reach the surface. As CFC gases begin to decline in coming years thanks to banning of these substances in 1987, the stratosphere should start to warm, and ozone levels will recover.

Figure 1. Global lower stratospheric departure of temperature from average since 1979, as measured by satellites. The large spikes in 1982 and 1991 are due to the eruptions of El Chicon and Mt. Pinatubo, respectively. These volcanos ejected huge quantities of sulphuric acid dust into the stratosphere. This dust absorbed large quantities of solar radiation, heating the stratosphere. Image credit: National Climatic Data Center.

Greenhouse gases also cause stratospheric cooling
However, this recovery of the ozone layer is being delayed. A significant portion of the observed stratospheric cooling is also due to human-emitted greenhouse gases like carbon dioxide and methane. Climate models predict that if greenhouse gases are to blame for heating at the surface, compensating cooling must occur in the upper atmosphere. We need only look as far as our sister planet, Venus, to see the truth of this theory. Venus's atmosphere is 96.5% carbon dioxide, which has triggered a run-away greenhouse effect of truly hellish proportions. The average surface temperature on Venus is a very toasty 894°F! However, Venus's upper atmosphere is a startling 4-5 times colder than Earth's upper atmosphere. The explanation of this greenhouse gas-caused surface heating and upper air cooling is not simple, but good discussions can be found at Max Planck Institute for Chemistry and realclimate.org for those unafraid of radiative transfer theory. One way to think about the problem is that the amount of infrared heat energy radiated out to space by a planet is roughly equal to the amount of solar energy it receives from the sun. If the surface atmosphere warms, there must be compensating cooling elsewhere in the atmosphere in order to keep the amount of heat given off by the planet the same. As emissions of greenhouse gases continue to rise, their cooling effect on the stratosphere will increase. This will make recovery of the stratospheric ozone layer much slower.

Greenhouse gases cause cooling higher up, too
Greenhouse gases have also led to the cooling of the atmosphere at levels higher than the stratosphere. Over the past 30 years, the Earth's surface temperature has increased 0.2-0.4°C, while the temperature in the mesosphere, about 50-80 km above ground, has cooled 5-10°C (Beig et al., 2006). There is no appreciable cooling due to ozone destruction at these altitudes, so nearly all of this dramatic cooling is due to the addition of greenhouse gases to the atmosphere. Even greater cooling of 17°C per decade has been observed high in the ionosphere, at 350 km altitude. This has affected the orbits of orbiting satellites, due to decreased drag, since the upper atmosphere has shrunk and moved closer to the surface (Lastovicka et al., 2006). The density of the air has declined 2-3% per decade the past 30 years at 350 km altitude. So, in a sense, the sky IS falling!

What about global warming being caused by the sun?
Some scientists have theorized that increases in solar output are responsible for a significant portion of the observed global warming. For instance, Scafetta & West (2006) estimated that 25-35% of the global warming in the 1980-2000 period was attributable to solar variability. Other scientists disagree, finding no evidence of global warming due to solar activity changes since the 1940s. Since any increase in solar radiation would heat both the lower and upper atmosphere, the observed drop in upper atmospheric temperatures in the past 30 years argues against a large portion of the observed greenhouse effect being caused by solar variability. The observed cooling of the upper atmosphere in recent decades is strong evidence that the warming at Earth's surface is due to human-emitted greenhouse gases. It should also give us additional confidence in the climate models, since they predicted that this upper atmospheric cooling would occur.

I'll be at the annual meeting of the American Meteorological Society in San Antonio this week, and plan to post a blog from there Wednesday.

Jeff Masters

Categories: Climate Change

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251. Thunderstorm2 20:22 GMT le 16 janvier 2007
well i got it off of WU Member Since: 22 décembre 2006 Posts: 129 Comments: 7608

252. LowerCal 20:32 GMT le 16 janvier 2007
Just the area is fine. I have some inlaws in that general area. I'll just type in their City, State. Thanks. Member Since: 26 juillet 2006 Posts: 58 Comments: 8972

254. weatherboykris 22:12 GMT le 16 janvier 2007
CB,see my blog. Member Since: 9 décembre 2006 Posts: 125 Comments: 11343

255. weatherboykris 22:12 GMT le 16 janvier 2007
And by the way,no one(or at least not me) is denying that warming is taking place and it is being caused mostly by human related processes. Member Since: 9 décembre 2006 Posts: 125 Comments: 11343

257. weatherboykris 22:18 GMT le 16 janvier 2007
STL,see my blog Member Since: 9 décembre 2006 Posts: 125 Comments: 11343

261. ryang 23:13 GMT le 16 janvier 2007
Cyclonebuster come to my blog! Member Since: 25 août 2006 Posts: 329 Comments: 12333

262. weatherboykris 23:31 GMT le 16 janvier 2007
Sadly, we are going to see more events such as this as the Arctic ice melts away! What kind of sense does that make?Maybe in the short term as polar airmasses become shallower,but in the long term they would descrease. Member Since: 9 décembre 2006 Posts: 125 Comments: 11343

263. ZRR 23:54 GMT le 16 janvier 2007
These cold polor stratospheric conditions form right along with warm zonal winter weather conditions, witch was definately the case in 1997-98. How do we know global atmopheric flow changes are not causing the cooling rather than ozon depletion. Durring a zonal flow there is much less mixing with air from the lower lattidudes and polar air. This causes the cold poles and the subsequent polar statospheric clouds. Member Since: 9 août 2006 Posts: 217 Comments: 332

265. bigtrucker 00:07 GMT le 17 janvier 2007
Skyepony at 10:02 AM EST on January 15, 2007. Bigtrucker~ any sites with form letter that eveyone can quickly send to their senators? I wrote to the Senator for any info he could send. im also working on a blog titled refrigerant and the atmosphere. And if the general public was made aware of, and acted by voicing their support, more legislation would take place Member Since: 9 janvier 2006 Posts: 79 Comments: 6111

267. KEEPEROFTHEGATE (Mod) 00:26 GMT le 17 janvier 2007
HERE IS SOMETHING TO PONDER WHY IS THAT THIS WINTER MORE PRECIP.WATER IN HIGH ARTIC IN UPPER LEVELS IS IN A LIQUID STATE RATHER THAN THE MORE NORMAL FROZEN STATE AS PER OBSERVATIONS BETWEEN OCT DEC 06 Member Since: 15 juillet 2006 Posts: 143 Comments: 40559

269. ZRR 00:44 GMT le 17 janvier 2007
Correction (Artic Ozone fluctuations) are directly realted )Ozone depletion is directly related to high lattitude flow patterns. The upper tropausphere is connected to the lower stratosphere in wind and temperature advection. High lattitude blocking and amplified flow patterns do mix warmer air into the statusphere. As for the surface record in both polar regions it is very limited compaired to the rest of the global land masses. Weather Stations in antartica have registered cooling in the last 20 years even Realclimate.org admits to this but is good at explaining it away. Fact global stratuspheric clouds are much more common in Antartica because of lack of land masses to disturb the polar circulation the south pole. So the flow is much more zonal. That fact combined with a land mass centered over the pole creates both a colder tropausphere and statusphere. There fore a much bigger ozone hole. Also and any one can research and verify this during zonal winters in the northern hemisphere areas such as Greenland, Alaska, and other artic regions are often below normal!!! While the midlatitudes (continental US) are above normal. This november Fairbanks Alaska rercorded its 4th coldest november on record, of course this wasn't paid much attention because it doesn't help the global warming hysteria. Member Since: 9 août 2006 Posts: 217 Comments: 332

270. ZRR 01:15 GMT le 17 janvier 2007
This is a good site to get an understanding of what the polar vortex is and how it is related to all layers of the atmophere. http://www.aero.jussieu.fr/~sparc/News15/15_Salby.html Member Since: 9 août 2006 Posts: 217 Comments: 332

271. 882MB 01:19 GMT le 17 janvier 2007
Hey everybody, I was in ACCUWEATHER.COM and all they are talking about is a very STORMY AND COLD EASTCOAST for the END OF JANUARY INTO FEBRUARY with big storms coming out of the GULF OF MEXICO, take a look at what i just read:The GFS shows a storm blowing up in the Gulf of Mexico as colder air is on the way in next Wednesday, but sends the storm to the east. If the upper-level support ends up a little farther west, it could come up the East Coast. Member Since: 29 septembre 2006 Posts: 0 Comments: 334

272. flsky 01:24 GMT le 17 janvier 2007
How nice to read some interesting and informative comments tonight! Member Since: 24 octobre 2006 Posts: 0 Comments: 1276

274. ZRR 02:50 GMT le 17 janvier 2007
True statospheric temperatures have droped and leveled out since the early 90's, and ozone depletion is a valid theory, my point is the low levels noticed over the northern hemisphere recently and all interannual variation of ozone at both poles are almost directly related to atmopheric circulation and polar temperatures. And everytime the media picks up a record low level of ozone, or record ozone hole it always seems to be related to weather patterns over the poles. Member Since: 9 août 2006 Posts: 217 Comments: 332

275. bappit 03:55 GMT le 17 janvier 2007
Thanks for the link ZRR! Stupendous stuff. All I know about the stratosphere is what I read in my Golden Nature Guide book as a kid. LOL! Member Since: 18 mai 2006 Posts: 3 Comments: 4381

276. ZRR 04:20 GMT le 17 janvier 2007
Quote Dr. Masters - We need only look as far as our sister planet, Venus, to see the truth of this theory. Venus's atmosphere is 96.5% carbon dioxide, which has triggered a run-away greenhouse effect of truly hellish proportions. The average surface temperature on Venus is a very toasty 894 �F! However, Venus's upper atmosphere is a startling 4-5 times colder than Earth's upper atmosphere. The explanation of this greenhouse gas-caused surface heating and upper air cooling is not simple, I have to take issue with compairing our atmosphere with that of venuses. Venus's atmophere is about 100 times more dense than ours. If our atmosphere could contain 95% carbon dioxide it still would be a much smaller amount of carbon dioxide than on venus. The fact that venus is shrowded in dense cloud cover is probably a bigger factor in its greenhouse effect. Venus's atmosphere is a thick soup of totally different chemical composistion. As far as its upper atmophere being much colder than ours, well think of the last hurricane image you viewed in the infared satelite loop. Look at the temperature/color scale, those high convective cloud tops that punch into the upper atmophere sometimes -100F or more. Seing that venus is so cloudy I think that has something to do with it. Its crazy that all the weather problems in the solar sytem must be due soley to this single devestating molecule ( a mear trace gass on earth and will probably always be that way) we call CO2. Or thats the perception they want people to believe. Using concepts and theories we don't fully understand to build more concepts and theories just leads us further into rediculous science fiction. Venus is indeed a nasty place but the fact is we don't know, maybe there was race of humans living there long ago, raised the CO2 levels to a tipping point and the oceans boiled and .....I swear from some of the stuff I read they would have you believe that. Member Since: 9 août 2006 Posts: 217 Comments: 332

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