http://climateprogress.org/2008/10/26/study-water-vapor-feedback-is-strong-and-positive-so-we-face-warming-of-several-degrees-celsius/
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Study: Water-vapor feedback is “strong and positive,” so we face
“warming of several degrees Celsius”
A new study in Geophysical Research Letters (subs. req’d), “Water-vapor
climate feedback inferred from climate fluctuations, 2003–2008” analyzed
recent variations in surface temperature and “the response of
tropospheric water vapor to these variations.” They concluded that the
“water-vapor feedback implied by these observations is strongly
positive” and “similar to that simulated by climate models.” The
analysis concludes:
The existence of a strong and positive water-vapor feedback means
that projected business-as-usual greenhouse-gas emissions over the next
century are virtually guaranteed to produce warming of several degrees
Celsius. The only way that will not happen is if a strong, negative, and
currently unknown feedback is discovered somewhere in our climate system.
A “warming of several degrees Celsius” = the end of life as we know it
(see “Is 450 ppm politically possible? Part 0: The alternative is
humanity’s self-destruction“).
While some denyers/delayers/inactivists, like MIT’s Richard Lindzen,
have argued that negative feedbacks dominate the climate — all of the
evidence points to amplifying feedbacks dominating (except the one
negative feedback that the deniers fiercely fight, discussed below).
That was a key point of my post “Are Scientists Underestimating Climate
Change, Part 1“: In the real world, key climate change impacts — sea ice
loss, ice sheet melting, desertification, and sea level rise — all are
either near the top or actually in excess of their values as predicted
by the IPCC’s climate models. For a more recent detailed discussion of
accelerating climate impacts and what that portends for the future on
our current emissions path, see the new WWF report “Climate Change:
faster, stronger, sooner.”
The major climate models are missing key amplifying feedbacks, some of
which were discussed in “Are Scientists Underestimating Climate Change,
Part II.” These feedbacks include:
* The defrosting of the permafrost
* The drying of the Northern peatlands (bogs, moors, and mires).
* The destruction of the tropical wetlands
* Decelerating growth in tropical forest trees — thanks to
accelerating carbon dioxide
* Wildfires and Climate-Driven forest destruction by pests
* The desertification-global warming feedback
* The saturation of the ocean carbon sink
And this all supports the analysis that the climate is much more
sensitive to changes in greenhouse gas emissions and other “forcings”
than the IPCC models have been saying and that a doubling of atmospheric
concentrations of carbon dioxide from preindustrial levels to 550 ppm
will ultimately warm the planet far more than 3°C, as NASA’s James
Hansen argues (see ‘Long-term’ climate sensitivity of 6°C for doubled CO2).
A number of major studies looking at paleoclimate data come to the same
conclusion. Here are three:
Scientists analyzed data from a major expedition to retrieve deep
marine sediments beneath the Arctic to understand the Paleocene Eocene
thermal maximum, a brief period some 55 million years ago of
“widespread, extreme climatic warming that was associated with massive
atmospheric greenhouse gas input.” This 2006 study, published in Nature
(subs. req’d), found Artic temperatures almost beyond imagination–above
23°C (74°F)–temperatures more than 18°F warmer than current climate
models had predicted when applied to this period. The three dozen
authors conclude that existing climate models are missing crucial
feedbacks that can significantly amplify polar warming.
A second study, published in Geophysical Research Letters (subs.
req’d), looked at temperature and atmospheric changes during the Middle
Ages. This 2006 study found that the effect of amplifying feedbacks in
the climate system–where global warming boosts atmospheric CO2
levels–”will promote warming by an extra 15 percent to 78 percent on a
century-scale” compared to typical estimates by the U.N.’s
Intergovernmental Panel on Climate Change. The study notes these results
may even be “conservative” because they ignore other greenhouse gases
such as methane, whose levels will likely be boosted as temperatures warm.
The third study, published in Geophysical Research Letters (subs.
req’d), looked at temperature and atmospheric changes during the past
400,000 years. This study found evidence for significant increases in
both CO2 and methane (CH4) levels as temperatures rise. The conclusion:
If our current climate models correctly accounted for such “missing
feedbacks,” then “we would be predicting a significantly greater
increase in global warming than is currently forecast over the next
century and beyond”–as much as 1.5°C warmer this century alone.
Yes, natural negative feedbacks exist that would “eventually” absorb any
excess carbon dioxide, but as one of the authors of a 2008 Nature
Geosciences article explained, “not for hundreds of thousands of years”
(see “Humans boosting CO2 14,000 times faster than nature, overwhelming
slow negative feedbacks“).
Truly only one negative feedback in the planet’s overall carbon cycle
can act with sufficient speed and strength to avert catastrophic climate
impacts: The dominant carbon-based life form on this planet will have to
respond to the already painfully clear impacts of our carbon emissions
by slashing those emissions sharply and eventually running the planet on
carbon-negative power.
The time for this negative feedback is now.
This entry was posted on Sunday, October 26th, 2008 at 12:32 pmand is
filed under Science. You can follow any responses to this entry through
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5 Responses to “Study: Water-vapor feedback is “strong and positive,” so
we face “warming of several degrees Celsius””
1. Magnus Westerstrand Says:
October 26th, 2008 at 2:22 pm
Might want to have a look at this feedback to…
http://westerstrand.blogspot.com/ 2008/ 09/ methane-hot-topic.html
2. john Says:
October 27th, 2008 at 10:10 am
The WWF study left out one of the more serious feedbacks — the
dying of the boreal and alpine forests.
Boreal forests are the largest terrestial carbon sink, and they
are shifting form sink to source as they are assaulted by pine bark beetles.
There are other, less well known but significant feedbacks. For
example as ice shrinks populations of krill are plummeting. Aside from
being a key species in the food chain, their feeding habits also remove
substantial amounts of carbon from the atmosphere. Less Krill means more
carbon staying in the atmosphere.
The plain truth is, there are a lot of “minor” feedbacks such as
this that cumulatively explain why our models have failed to keep up
with reality.
3. paulm Says:
October 28th, 2008 at 1:30 am
This is the reality…not nice.
Australia’s Stern review warns of runaway global warming
“Carbon emissions are rising so fast that the world has no chance
of hitting climate targets, says Australian economist”
http://www.guardian.co.uk/ environment/ 2008/ oct/ 27/
climate-change-australia
The only way that we can limit the rise to 2C is if we have a deep
global depression now and throw everything in to coming out of it with
zero emission technology!
Even at 2C we might have gone past major thresholds so its still
fingers crossed.
4. paulm Says:
October 28th, 2008 at 2:12 pm
Here is more reality….were probably fried!
Looking at CO2 levels (forget temp) - Pretty much every relative
CO2 rise in history as resulted in mass extinction. See..
http://www.coasttocoastam.com/ timages/ page/ Extinction101506a.jpg
http://www.sciam.com/
article.cfm?articleID=00037A5D-A938-150E-A93883414B7F0000&pageNumber=1&catID=2
Now look at the recent levels of CO2….
http://www.estrellamountain.edu/ faculty/ farabee/ biobk/ CO2conc.gif
5. Hank Roberts Says:
October 29th, 2008 at 8:15 pm
Paulm, pointer to graphics that also state the data sources, which
may be useful in explaining this stuff:
http://www.globalwarmingart.com/ wiki/
Image:Carbon_Dioxide_400kyr_Rev_png
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