A cautionary tale--the PETM
One frequently hears comments like, "Earth has had many periods of warmth far exceeding the warmth of today's climate, so we should not be surprised if the current warming of the globe is a natural phenomena". This view is especially prevalent among geologists, who take a very long view of history and are among the most skeptical scientists regarding the reality of human-caused climate change. It is true that Earth's past has had many episodes of natural global warming that we can learn from. But the greatest natural global warming episode of the past 65 million years, the Paleocene-Eocene Thermal Maximum (PETM) event of 55 million years ago, presents us with a cautionary tale of how massive releases of greenhouse gases--similar in scale to what humans are now producing--may cause extreme warming of the climate.
Earth's orbital variations--the most common form of natural global warming
The most common cause of natural global warming over time has been changes in Earth's orbit. Three oscillations in Earth's orbit with periods of 26,000, 41,000, and 100,000 years (called Milankovitch cycles) cause ice ages to be triggered when summer sunshine at 65°N reaches a minimum. The reduced sunlight over Canada, Siberia, and Scandinavia allows winter snowfall to persist through the summer, and thus accumulate and build Northern Hemisphere ice sheets. There isn't enough land in the Southern Hemisphere to allow large, land-based ice sheets to build there, so it is the growth and decay of Northern Hemisphere ice sheets that has controlled the timing of ice ages and warm inter-glacial periods over the past three million years. Earth's orbit is currently in a phase where the amount of sunlight falling at 65°N is changing very little. Thus, the primary mechanism for past natural global warming events is not to blame for the current warming. According to the "official" word on climate, the 2007 report of the U.N.'s Intergovernmental Panel on Climate Change (IPCC), the amount of sunlight falling at 65°N is expected to change little over the next 30,000 years, and "it is very unlikely that the Earth would naturally enter into another ice age for at least 30,000 years".
Pumping huge amounts of carbon into the atmosphere coincided with extreme climate warming during the PETM
Natural global warming has also occurred in the past due to changes in solar brightness, and natural emissions of natural carbon dioxide (CO2) and methane (methane is the primary component of the natural gas we use to heat our homes, is a potent greenhouse gas 20 - 25 more effective at heating the Earth than than CO2, with a lifetime of about 9 years in the atmosphere before reacting with the OH radical to form CO2). I discussed one example of natural global warming in my previous post--volcanoes have emitted enough CO2 over time to account for a large portion of Earth's natural greenhouse effect. However, volcanoes only put about 1 - 3% as much CO2 per year into the atmosphere as human activities do. What, then, does Earth's past tell us about what might happen if we dump 100 times more carbon than volcanoes do into the atmosphere, over a period of a few centuries?
The end of Earth's Paleocene era, 55 million years ago, was a time of great warmth on planet Earth. Subtropical vegetation grew in Greenland and Patagonia, and crocodiles swam off the coast of Greenland. Sea surface temperatures at the North Pole were a toasty 64°F (18°C). Tropical palm forests in northern Wyoming played host to early primates. Despite the fact that the sun put out 0.5% less energy than today (equivalent to a global temperature that would be 0.5°C cooler), there was no polar ice cap or Greenland Ice Sheet. The higher temperatures of that era were probably due to high carbon dioxide levels of 560 - 600 ppm. This is far higher than the 280 ppm seen in the 1800s, and the 383 ppm as of 2009. The continents had a different configuration due to continental drift, and this may have kept the world warmer as well.
Figure 1. Global temperature change (right scale) as inferred from oxygen-18 isotope measurements (left scale) from fossil ocean microorganisms (Zachos et al., 2001). Oxygen-18 levels in these fossils are proportional to the temperatures of the era when the fossils were formed. The Paleocene-Eocene Thermal Maximum (labeled PETM) shows a sharp upward spike in temperatures occurred. This spike is likely to be understated by a factor of 2 - 4 due to coarse sampling and averaging in this data set. For more detail, see the Wikipedia entry for the PETM.
Then, 55 million years ago, the fossil record shows that an extraordinary drop in the ratio of carbon-13 to carbon-12 occurred, indicating that a massive amount of "light" carbon with low levels of the carbon-13 isotope was emitted into the atmosphere in a very short amount of time--just 500 - 20,000 years. The most likely source of carbon-13 depleted carbon would have been methane from ocean sediments or land vegetation. If it was methane, about 1,000 - 2,000 gigatons of carbon would have had to be injected into the atmosphere, in order to account for the observed fossil deposits. For comparison, the total amount of carbon in today's atmosphere, primarily as CO2, is a factor of two or three less--about 810 gigatons. The fossil record shows that extreme climatic warming occurred nearly simultaneously with this massive release of carbon into the atmosphere. Global average temperatures rose 9°F (5°C) in a geological instant--1,000 - 10,000 years (Sluijs et al., 2007). Average sea surface temperatures at the North Pole reached 74°F (23°C). The warmth lasted 120,000 - 220,000 years before weathering of silicate rocks was able to remove the CO2 from the atmosphere and return the climate to its former state. This was the largest global warming event since the time of the dinosaurs, 65 million year ago (Moran et al., 2006). The resulting impact on Earth's climate was so severe that a new geological era was born--the Eocene. The warming event has been dubbed the Paleocene-Eocene Thermal Maximum (PETM), since it occurred at the boundary of these two eras. Ocean circulation patterns changed radically during the first 5,000 years of the PETM (Nunes and Norris, 2006), and the deep oceans became 11°F (6°C) warmer, severely depleted in oxygen, and more acidic. A mass extinction of deep ocean microorganisms resulted, though the exact reasons remain unclear. The PETM did not cause mass extinctions on land of plants and animals, but a major turnover in mammalian life occurred at that time. Many of today's major mammalian orders emerged in the wake of the PETM. The new geological era it ushered in, the Eocene, is named for the Greek goddess of the dawn (Eos), since this was the dawn of the era of large mammals.
It is extremely difficult to explain the warmth of the PETM without assuming that the huge amount of "light" carbon pumped into the atmosphere created intense warming due to the greenhouse effect. The controversial question is, how did this carbon get into the atmosphere? Did PETM happen because of the greenhouse effect from all the carbon added to the atmosphere, or did the carbon get released into the atmosphere in response to climatic warming from another cause (and boosting the warming that was already occurring?) The mystery is a difficult one to unravel, since our vision of what happened so long ago is very fuzzy. A recent high-resolution study of ocean sediments laid down in New Jersey during the PETM (Sluijs et al., 2007) argued that about half of the PETM warming occurred 1,000 - 1,500 years before the 1,000 - 2,000 gigatons of "light" carbon got injected into the atmosphere. The authors theorize that global warming due to some other cause heated up the deep oceans enough to release methane stored in the form of methane hydrate, a form of methane 'ice' that forms in cold bottom water under great pressures and is widely distributed and plentiful in sediments on the outer edges of continental margins. The methane released was the huge pulse of "light" carbon seen in the fossil record, and this methane warmed the planet even further via the greenhouse effect. The authors argued that the warming that triggered the PETM could have been due to a variation in Earth's orbit, or due to a pulse of greenhouse gases that didn't happen to be enriched in light carbon. A wide variety of other theories abound. Dickens (2004) theorizes that a volcano in the North Atlantic erupted through a huge fossil fuel deposit in overlying ocean sediments, releasing massive amounts of the stored carbon into the atmosphere. Pancost et al. 2006 found evidence that the warming of the PETM significantly increased as carbon stored on land in wetlands was released in the form of methane. Huber (2008) argued that temperatures got so hot during the PETM that a huge die-off of tropical vegetation resulted, creating vast deserts and putting thousands of gigatons of carbon dioxide into the atmosphere, further increasing temperatures.
Figure 2. Photographs of methane hydrate as nodules, veins, and laminae in sediment. Intense warming of the deep oceans during the PETM may have released huge quantities of methane gas from ocean sediments with methane hydrates in them. Image credit: United States Geological Survey.
Computer climate models fail to reproduce the PETM
A big concern about the climate models that we are using to forecast climate for the coming century is that they do a poor job of reproducing the climate of the Eocene, and, in particular, the PETM. These models fail to reproduce the high temperatures observed in the polar regions relative to the tropics during the PETM. However, in the words of climate scientists Daniel Schrag and Richard Alley in a 2004 article in Nature, "It would be a grave mistake to take these lessons from ancient climates as a reason to disregard the projections from climate models." If the observations of the climate in this far-ago era are correct, the reason that the climate models fail to correctly simulate this past climate is because the climate is more sensitive to CO2 than believed. There is a missing "feedback" causing increased warming near the pole that the models are missing. Sluijs et al. (2006) theorize that the models may be missing how hurricanes transport heat to the poles, or how polar stratospheric clouds may act to trap heat over the poles. In short, the failure of the models to correctly simulate the PETM may mean that our current estimates of the amount of global warming likely over the coming century (1.1°C - 6.4°C) are far too low. The other possibility, mentioned by Huber (2008) is that the models are correct, but the temperatures inferred for the tropics from the fossil record are in error. This wouldn't be the first time that measurements were found to be in error and the models vindicated.
Comparison with today
Since the beginning of the Industrial Revolution, humans have pumped about 500 gigatons of carbon into the atmosphere. There are about 5,000 gigatons in the planet's coal reserves, while oil and traditional natural gas deposits are hundreds of gigatons each (Rogner, 1997). Given that humans are now adding about 10 gigatons of carbon to the atmosphere each year (Global Carbon Project, 2007), we will surpass the 1,000 gigaton mark 50 years from now at current emission rates. This is at the lower end of the 1,000 - 2,000 gigatons of carbon that are estimated to have been added to the atmosphere during the PETM--the most extreme natural global warming event of the past 65 million years. Though our view of events so long ago is very fuzzy, the PETM should serve as a cautionary tale. We cannot rule out the possibility that continuation of our current rates of fossil fuel burning will lead to an extreme climatic warming event like the PETM. In particular, we need to keep a careful eye on the huge reservoirs of methane hydrate stored in marine sediments (500 - 10,000 gigatons of carbon) and stored in permafrost (7.5 - 400 gigatons). Continued warming of the planet could trigger substantial releases of these massive reservoirs of greenhouse gases, leading to a repeat of the PETM event. However, a 2008 study by the U.S. Climate Change Science Program (CCSP, 2008) concludes that there is currently no evidence that a sudden catastrophic release of methane stored in ocean sediments or in permafrost will happen over the next century. It should take at least a century for global warming to penetrate the deep oceans and permafrost regions containing these significant reservoirs of methane hydrates. The study concludes, "Catastrophic release of methane to the atmosphere appears very unlikely in the near term (e.g., this century)...Although the prospect of a catastrophic release of methane to the atmosphere as a result of anthropogenic climate change over the next century appears very unlikely based on current knowledge, many of the processes involved are still poorly understood, and developing a better predictive capability requires further work. On a longer time scale, methane release from hydrate reservoir is likely to be a major influence in global warming over the next 1,000 to 100,000 years". So, the bottom line is: don't expect global warming to be able to cause huge releases of methane hydrates in the coming century, such as may have occurred during PETM. But it is wise to ponder that a release of greenhouse gases similar in magnitude to what we are doing now coincided with the most extreme global warming event of the last 65 million years. We should not be surprised if our human greenhouse gas emissions cause a similar massive climate perturbation over the next 1,000 years, leading the dawn of a new geological era--the Anthropocene.
For more information
The best resource I found while researching this was a December 2008 report from the U.S. Climate Change Science Program (CCSP), titled, Abrupt Climate Change. Chapter 5, "Potential for Abrupt Changes in Atmospheric Methane" [1.3 Mb] was the relevant chapter.
References
Archer, D., 2007, "Methane hydrate stability and anthropogenic climate change", Biogeosciences, 4, 521544,.
Dickens, G.R., 2004, "Hydrocarbon-driven warming", Nature 42, 429, pp513-515, 3 June 2004.
Huber, M., 2008, "A Hotter Greenhouse?", Science 321, no. 5887, pp. 353-354, DOI: 10.1126/science.1161170
Moran, et al., 2006, "The Cenozoic palaeoenvironment of the Arctic Ocean", Nature 441, 601-605 (1 June 2006) | doi:10.1038/nature04800.
Nunes, F. and R.D. Norris, 2006, "Abrupt reversal in ocean overturning during the Paleocene/Eocene warm period", Nature 439 (7072): 603. doi:10.1038/nature04386
Pancost, R.D., et al., 2006, "Increased terrestrial methane cycling at the Palaeocene-Eocene thermal maximum", Nature 449, 332-335 (20 September 2007) | doi:10.1038/nature06012
Rogner, H.-H, 1997, "An assessment of world hydrocarbon resources", Annu. Rev. Energy Environ., 22, 217-262.
Sluijs, A., et al., 2006, "Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum", Nature 441, 610-613 (1 June 2006) | doi:10.1038/nature04668
U.S. Climate Change Science Program (CCSP), 2008: Abrupt Climate Change. A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research [Clark, P.U., A.J. Weaver (coordinating lead authors), E. Brook, E.R. Cook, T.L. Delworth, and K. Steffen (chapter lead authors)]. U.S. Geological Survey, Reston, VA, 459 pp.
Zachos, J. C., U. Rohl, S.A. Schellenberg, A. Sluijs, D.A. Hodell, D.C. Kelly, E. Thomas, M. Nicolo, I. Raffi, L.J. Lourens, H. McCarren, and D. Kroon, 2005, "Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum", Science, 308, 1611-1615
Portlight.org relief walk in Destin, FL a big success
Over the weekend, the portlight.org disaster relief charity ran a highly successful relief walk in Destin, FL, to raise money for the disaster relief. The theme of this walk was to raise relief money not only for people, but for pets as well, with 25% of the money raised intended for taking care of pets injured or abandoned during disasters. As detailed in the portlight.org blog, the pet theme was a great way to raise money, and about $5000 was raised. The other relief walks this year raised $1500 in New Orleans and $542 in Kissimmee. Many more walks are planned this year, with the next one being this weekend (May 2) in Summerville, SC. Portlight also helped out with disaster relief operations for the South Carolina fires yesterday.
Jeff Masters
Reader Comments
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Yes,here is the image.
Link
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Hi pottery is your calabash tree droping leaves already?
By the way do you live in a 'bushy' area?
Send it now! the sky is getting dark right now, to my west is the first thunderstorm cloud i've seen and heard in months.LOL
A regional earthquake located 630 mi SW of Anchorage occurred at 6:19 pm, preliminary magnitude of 5.6.
Ok, I looked.. I give up..whats a moab?
Really nice clear picture today :)
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By the small sample generated, it's not suppressing warming. The time without the contrails produced warmer days and even cooler nights. ie The contrails are better at reflecting the ground's heat (infrared) back down to the ground during the night than at reflecting the Sun's light back out into space during the day.
So the effect appears to be that contrails increase the daily temperature average when nighttime and daytime temperatures are combined.
But as has been pointed out by the study's author and repeated by antiAnthopogenicGlobalWarming sceptics, the numbers of days sampled are too few and over such a limited part of the year that it cannot be ruled out that the apparent effect is just a part of normal daily variations.
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you can down lode fire foxs 3.0.10
2008 may 1
2009 may 1
Tropical Cyclone Bulletin #6
===========================
Tropical Depression "DANTE" has remained quasi-stationary.
At 11:00 PM PhST, Tropical Depression Dante located at 13.7ºN 124.4ºE or in the vicinity of Catanduanes has 10 minute sustained winds of 30 knots. The depression is reported as almost stationary
Signal Warnings Number One (30-60 kph winds)
Luzon Region
-------------
1.Camarines Norte
2.Camarines Sur
3.Albay
4.Sorsogon
5.Catanduanes
6.Masbate
7.Burias Island
8.Southern Quezon
Visayas Region
------------
1.Northern Samar
Residents living in low lying and mountainous areas under signal # 1 are alerted against flashfloods and landslides.
The public and the disaster coordinating councils concerned are advised to take appropriate actions and watch for the next bulletin to be issued at 5 A.M. tomorrow.
.
Good comment for GFS! ;D
Anyway, that area seems to be the best for tropical development in the next days. Enough far away of the Subtropical Jet.
2009 SSTs may surpass 2008's
Earlier this year, the SSTs were much below 2008's average
Certainly the Bay of Campeche is warmer this year.
Mirror Site
Daily Area of Interest
Click to enlarge
RTLSNK is still getting his name shown way to often in the DAI
Tropical Cyclone Advisory #1
TROPICAL DEPRESSION
3:00 AM JST May 3 2009
================================
At 18:00 PM UTC, Tropical Depression (1004 hPa) located at 13.6N 124.2E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as almost stationary.
Dvorak Intensity: T2.0
Forecast and Intensity
=======================
24 HRS: 14.0N 126.0E (CAT 1/Tropical Storm)
Its different! I have a feeling that this will be a Gulf Season, Tropical Storms forming early on their and Hurricanes late on...
New forecast based on what I'm seeing:
12-15 Tropical DepressionS
8-12 Tropical Storms
7 - 9 Hurricanes
1 Major Hurricane
0 Cape Verde Cyclones
Taz.. I've tested numerous browsers lately and it seems that Firefox 3.5 Beta 4 works best for Wunderground.... however I personally use Google Chrome.
Yeah, 2007 easily surpasses both at this stage.
http://www.aoml.noaa.gov/phod/dataphod1/work/HHP/NEW/2007122atsst.png
2008:
2009:
Though it is still early, if the TCHP doesn't pick up, particularly in the Caribbean, we may be looking at far less potential for rapidly intensifying hurricanes, unlike last year with Gustav, and unlike 2007 with Dean and Felix.
Also, 2009's Caribbean SSTs are the coolest observed this time of year since 2000.
Tropical Cyclone Bulletin #7
===========================
"DANTE" has intensified into a storm
At 5:00 AM PhST, Tropical Storm Dante located at 14.3ºN 124.3ºE or off the northern coast of Catanduanes has 10 minute sustained winds of 35 knots with gusts of 45 knots. The storm is reported as moving north northeast slowly
Signal Warnings Number Two (60-100 kph winds)
Luzon Region
-------------
1.Catanduanes
Signal Warnings Number One (30-60 kph winds)
Luzon Region
-------------
1.Camarines Norte
2.Camarines Sur
3.Albay
4.Sorsogon
5.Masbate
6.Burias Island
7.Southern Quezon
8.Polillo Island
Visayas Region
------------
1.Northern Samar
Residents living in low lying and mountainous areas under signal #2 and 1 are alerted against flashfloods and landslides.
The public and the disaster coordinating councils concerned are advised to take appropriate actions and watch for the next bulletin to be issued at 11 A.M. today.
MSLP was also above normal for the entire tropical Atlantic, during April.
It should be noted that it's not the entire Atlantic saw cooling. There were mesoscale variations (eddies, islands, currents) that caused some areas within the MDR to have above normal SSTs.
And one final note, the ocean is very dynamic and the best example would be the winter of 2007-2008 when we had a positive NAO that caused trades to run 5-10 m/s above normal. This caused SSTs to cool considerable across the Atlantic but warmed along the African coast. Despite this, by the summer of 2008, SSTs were high enough to support a major hurricane in every month between July and November, something not seen this decade, not even in 2005. In addition, Bertha became a major hurricane north of 20N in early July. So just as fast as they cool, just as fast they can warm.
The interesting thing for me from both maps is the warm patch of water between Cuba, Hispaniola and Jamaica that was obvious in the 2008 version. That area seemed to attract storms later that season.
Perhaps the BoC theory may have some validity.
I'm also curious as to what might be causing the seas around the eastern CAR to be slightly warmer than last year. . . .
The islands may have buffered the area from strong trades that cause evaporational cooling. These are some of the mesocale effects that cause variations within the overal mean.
Tropical Cyclone Formation Alert (2200z 02MAY)
===========================================
An area of convection (97W) located at 9.6N 110.4E or 165 NM east of Nha Trang, Vietnam. Animated enhanced infrared imagery depicts a well defined low level circulation center that has tracked under an area of deep convection, which is continuing to grow larger and more organized. A 1343z ASCAT pass indicates that the low level circulation center has winds of 15-20 knots near the center with an area of 20-25 knot winds along the western periphery between the low level circulation center and coastal Vietnam. Upper level analysis indicates the low level circulation center is in an area of upper level divergence with low vertical wind shear. Sea surface temperatures are very favorable with the South China Sea providing ample development potential.
Maximum sustained winds near the center is 17-22 knots with a minimum sea level pressure of 1005 MB. The potential for this disturbance to form into a significant tropical cyclone within the next 24 hours is UPGRADED TO GOOD.
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another tropical depression..
I have two questions.
Any forecast about the NAO going negative in the comming months?
Why the Eastern Atlantic is cooler than in past years?
Tropical Cyclone Advisory #2
TROPICAL DEPRESSION
6:00 AM JST May 3 2009
================================
At 21:00 PM UTC, Tropical Depression (1002 hPa) located at 13.6N 124.5E has 10 minute sustained winds of 30 knots with gusts of 45 knots. The depression is reported as almost stationary.
Dvorak Intensity: T2.0
Forecast and Intensity
=======================
24 HRS: 14.1N 126.2E - 40 knots (CAT 1/Tropical Storm)
TC ADVISORY
DTG: 20090502/1800Z
TCAC: TOKYO
TC: NIL
NR: 1
PSN: N1335 E12410
MOV: SLW
C: 1004HPA
MAX WIND: 30KT
FCST PSN +6HR: 03/0000Z N1355 E12420
FCST MAX WIND +6HR: 35KT
FCST PSN +12HR: 03/0600Z N1400 E12440
FCST MAX WIND +12HR: 35KT
FCST PSN +18HR: 03/1200Z N1400 E12520
FCST MAX WIND +18HR: 35KT
FCST PSN +24HR: 03/1800Z N1400 E12600
FCST MAX WIND +24HR: 35KT
Firstly, the NAO is seasonal. The phase in Spring, normally continues through Summer. This was true for most year but not all. Another measure that backs this is that most models show above normal pressures in the MDR, a characteristics of a positive NAO. Which is sort of bad because the pattern being display now is similiar to 2004. In addition, though the NAO is expected to be positive it will trend negative for some periods especially during September due to intraseasonal variations. This variation was seen in every hurricane season since 1995 and suggests there is a larger scale mechanism affecting the oscillation.
Your second question is tied to the NAO. Stronger northeast trades cause two things:
1. It streghtens the Canary current which is a cold current that brings cold waters to the West Coast of Africa before turning west and out to sea. This is one of the reasons why the EATL is climatologically stable. The others being subsidence within the Azores high and SAL dust. Just after the positive NAO in the winter of 2007-2008, the high shifted west causing the current to slacken and warm waters to build along the coast.
2. Stronger northeast trades also suppresses the warm southerly flow of the SE Trades and monsoon southwesterlies south of the ITCZ and monsoon trough, respectively.
Understanding the Atlantic Hurricane Season: The SST Factor
Absolutely STUNNING sailing today - gorgeous weather, perfect wind - can't beat it. As much as I'm not fond of hurricane season, I do LOVE this perfect weather...
TCNA21 RJTD 030000
CCAA 03000 47644 NAMELESS 01139 11244 14144 225// 90303=
00:00 AM UTC May 3
NAMELESS
13.9N 124.4E
Dvorak Intensity T2.5
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well the JMA considers it a tropical storm now..
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