Wednesday, September 12, 2007
configuration that can change over the period of hundreds of millions
of years, GHGs are still considered an primary driver of average
surface temperature. Which is why the publication by Veizer et al in
2000 (ref 4 in abstract below) of a sea surface reconstruction of
temperatures from the Palaeozoic era had led to some confusion. What
they had found was that during a period of high CO2 the sea surface
temperature had not been greatly affected. Or, there had been a
decoupling of CO2 and temperature. In today's Nature a new
reconstruction has been presented that uses a different proxy method
and finds sea surface was indeed much warmer during high CO2 periods
than during low CO2 periods. This then throws into question CO2
decoupling during the Palaeozoic era.
Nature 449, 198-201 (13 September 2007) | doi:10.1038/nature06085;
Received 15 April 2007; Accepted 3 July 2007
Coupling of surface temperatures and atmospheric CO2 concentrations
during the Palaeozoic era
Rosemarie E. Came1, John M. Eiler1, Ján Veizer2, Karem Azmy3, Uwe
Brand4 & Christopher R. Weidman5
Atmospheric carbon dioxide concentrations seem to have been several
times modern levels during much of the Palaeozoic era (543–248 million
years ago), but decreased during the Carboniferous period to
concentrations similar to that of today1, 2, 3. Given that carbon
dioxide is a greenhouse gas, it has been proposed that surface
temperatures were significantly higher during the earlier portions of
the Palaeozoic era1. A reconstruction of tropical sea surface
temperatures based on the delta18O of carbonate fossils indicates,
however, that the magnitude of temperature variability throughout this
period was small4, suggesting that global climate may be independent
of variations in atmospheric carbon dioxide concentration. Here we
present estimates of sea surface temperatures that were obtained from
fossil brachiopod and mollusc shells using the 'carbonate clumped
isotope' method5—an approach that, unlike the delta18O method, does
not require independent estimates of the isotopic composition of the
Palaeozoic ocean. Our results indicate that tropical sea surface
temperatures were significantly higher than today during the Early
Silurian period (443–423 Myr ago), when carbon dioxide concentrations
are thought to have been relatively high, and were broadly similar to
today during the Late Carboniferous period (314–300 Myr ago), when
carbon dioxide concentrations are thought to have been similar to the
present-day value. Our results are consistent with the proposal that
increased atmospheric carbon dioxide concentrations drive or amplify
increased global temperatures1, 6.
Tuesday, September 11, 2007
Other scientists have also recently come to the conclusion that northern forests, although critically important in maintaining biodiversity, might be less important in slowing climate change than tropical forests. Govindasamy Bala and Ken Caldeira found that tropical forests help cool the Earth in two ways: by storing carbon and also by reflecting the suns warming rays back to space5. "Unlike tropical forests, high latitude forests darken the Earth's surface, causing the earth to absorb more sunlight, an effect that is most pronounced in snowy regions. This darkening of the surface has a warming influence that can be stronger than the cooling influence of carbon storage in these forests," says Caldeira. This suggests that removing high-latitude forests would have a net cooling effect on the planet, whereas removal of tropical forests would result in warming.
What is interesting here is what has been happening for the past 30 to 50 years. Northern forests have been growing and tropical forests have been shrinking. Thus, according to the above, this should lead to warming. How much of this land use change impact is included in the models of climate change? Not sure.
Friday, August 10, 2007
A new model, published in Science, that includes more information about the internal variability of the Earth system (e.g. El Ninos, etc.) predicts some potential for ameliorating anthropogenic warming in the next tens years (yet about 50% of the years after 2009 are still predicted to be warmer than 1998 (the warmest so far)).
Science 10 August 2007:
Vol. 317. no. 5839, pp. 796 - 799
Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model
Doug M. Smith,* Stephen Cusack, Andrew W. Colman, Chris K. Folland, Glen R. Harris, James M. Murphy
Previous climate model projections of climate change accounted for
external forcing from natural and anthropogenic sources but did not
attempt to predict internally generated natural variability. We
present a new modeling system that predicts both internal variability
and externally forced changes and hence forecasts surface temperature
with substantially improved skill throughout a decade, both globally
and in many regions. Our system predicts that internal variability
will partially offset the anthropogenic global warming signal for the
next few years. However, climate will continue to warm, with at least
half of the years after 2009 predicted to exceed the warmest year
currently on record.
Fig. 4. Globally averaged annual mean surface temperature
anomaly (relative to 1979–2001) forecast by DePreSys starting from June
2005. The CI (red shading) is diagnosed from the standard deviation of
the DePreSys ensemble, assuming a t distribution centered on
the ensemble mean (white curve). Also shown are DePreSys and ensemble
mean NoAssim (blue curves) hindcasts starting from June 1985 and June
1995, together with observations from HadCRUT2vOA (black curve).
Rolling annual mean values are plotted seasonally from March, June,
September, and December. The mean bias as a function of lead time was
computed from those DePreSys hindcasts that were unaffected by Mount
Pinatubo (SOM text) and removed from the DePreSys forecast (but not the
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Friday, July 27, 2007
Science Magazine's Donald Kennedy published an editorial today declaring the public debate over anthropogenic climate change as being over (the scientific debate has been (mostly) done for some time). Why you might ask? Well here are his words:
With respect to climate change, we have abruptly passed the tipping point in what until recently has been a tense political controversy. Why? Industry leaders, nongovernmental organizations, Al Gore, and public attention have all played a role. At the core, however, it's about the relentless progress of science. As data accumulate, denialists retreat to the safety of the Wall Street Journal op-ed page or seek social relaxation with old pals from the tobacco lobby from whom they first learned to "teach the controversy." Meanwhile, political judgments are in, and the game is over. Indeed, on this page last week, a member of Parliament described how the European Union and his British colleagues are moving toward setting hard targets for greenhouse gas reductions.
Donald Kennedy Editorial Climate: Game Over, Science 27 July 2007: Vol. 317. no. 5837, p. 425
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Wednesday, July 25, 2007
Here are some interesting tidbits:
Working for long periods in theThat is a funny line really. Who are these scientists. The line "scientists said" is almost a journalistic cliche.
harsh and unforgiving conditions near the North and South Poles
often causes people to suffer a stew of psychological symptoms
dubbed "polar madness," scientists said on Wednesday.
While some people on polar expeditions savor a gratifyingSounds like any office in town.
sense of achievement, the researchers said, 40 to 60 percent of
them may suffer negative effects like depression, sleep
disruption, anger, irritability and conflict with co-workers.
"Some people may have difficulty adjusting to the
light-dark cycles, and so they can never get a decent night
sleep and experience a sleep disorder," he said. "Some people
can get clinically depressed. Some people just can't handle the
confinement, with seeing the same people day in and day out for
extended periods of time."
Palinkas cited more recent examples of "polar madness" atHumor is a cure all.
research stations, including one staffer clubbing another with
a claw hammer and another beating a co-worker with a pipe.
"There was a saying at the station for the remainder of the
winter that 'If you've got a gripe, use a pipe,"' he said.
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The editorial seems fair in its treatment of both sides. One of the interesting points it made is the importance of public relations in establishing its scientific credentials with the general public. This is a point that many in the realm of science and in the realm of policy do not understand. The extreme value there is to be placed on, what I shall call advertising, the important role that government agencies play in our national lives. It has seemed to me that one of the key failings of government has been its public relations inaction in the face of the negative sentiment of the past twenty years. For us scientists all one has to do is look at NASA to understand the importance of public relations. Sure, they have a very exciting product (many of the other branches of government do too) but only a portion of the money spent goes to that product.
Towards this NOAA administration has been passing decrees (which, though politically insensitive, is fitting with its traditional military command structure) which has been unpopular with workers within NOAA. As Nature says:
NOAA scientists have also been unhappy in recent months aboutBut here I disagree with Nature. It makes absolute sense that NOAA would want its name associated with its two most highly regarded products. But I also understand the importance of keeping these organization's identities. This seems like the perfect situation for compromise. The two organizations should add NOAA to their names such as "NOAA National Weather Service" or "National Hurricane Center NOAA" thus keeping the history and associated quality while melding that scientific quality with NOAA in the public mind.
management decrees suggesting, for example, that they improve the
agency's branding by substituting 'NOAA' for 'National' in the names of
centres such as the National Weather Service and the National Hurricane
Center. Both of these outfits have distinguished histories and
identities of their own, and NOAA needs to find ways of asserting
itself and its mission in the public eye without diminishing them.
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Friday, March 2, 2007
New studies show that aerosol particles have a far greater impact on global climate than was originally believed. This is due to how aerosols change the pattern of heating and cooling regionally.
Aerosols impact on surface heating depends largely on the type of aerosol. Some are very effective reflectors leading to localized cooling. These type of aerosols were the more widely known and studied until recently. The most common reflective aerosol is derived from sulfur emissions from power plants which were greatly reduced by the late 1990s by sulfur reduction regulations.
The other type of aerosol absorbs heat and can lead to warming over a region. These types, called black carbon, are more typical of fossil fuel (and other fire) emissions. A lot less is know about the hows and wheres of this aerosol with respect to localized warming.
What the latest round of studies show is that these aerosols, by altering the regional pattern of heating and cooling, have a larger (zonal and global) impact by altering the patterns of winds and ocean circulation.
What does this mean for anthropogenic climate change?
Well it potentially complicates attribution to the source of climate change in that more seems to be attributable to changes in circulation stemming from these aerosols but not necessarily. But this complication does not necessarily reduce the impact on climate of greenhouse gases, only complicates the picture. That said these studies only add fuel to the fire since humans are likely overwhelmingly responsible for the increase in aerosol load due to fossil fuel and other burning.
What does this mean for alternative fuels?
Another complication since alternative fuels are no less likely to produce the aerosols when burned than are fossil fuels. This speaks to increasing solar and wind power and centralizing burning fuel use so as to reduce emissions of particulates.Excepts from : http://www.sciencemag.org/cgi/content/full/315/5816/1217
New studies show aerosols from burning fuels altering everything from rainfall to great ocean currents, with effects that can girdle the globe
The microscopic aerosol particle has long been recognized as a mighty agent of climate change. At a micrometer or less in size, this bit of combustion crud from power plant, tailpipe, or farmer's fire can reflect sunlight back to space and cool the polluted eastern United States. Or it could suppress rainfall over smoggy Houston, Texas. But for years, atmospheric scientists generally assumed that pollutant aerosols worked locally or regionally. Most dramatically, the brown haze over Asia weakens both the Indian and Asian monsoons that bring essential rains to the continent.
So far, the expanding reach of aerosols is being documented primarily in global climate models, with tantalizing parallels with what's been happening in the real world in recent decades. In the case of Australia, Rotstayn and colleagues ran a global climate model to simulate the changing climate of the 20th century. In the past decade or two, production of aerosols over Asia has soared as developing economies cranked up, especially those of India and China. When Rotstayn and colleagues plugged increasing Asian aerosols into their model along with increasing greenhouse gases, rainfall and cloud cover increased over Australia, especially in the northwest. Yet when they omitted the distant aerosols, rainfall and cloudiness decreased, contrary to observations.
North American aerosols seem to hold sway over a far more massive moisture flow: the great "conveyor belt" of currents that carries heat from the Southern Hemisphere into the far North Atlantic, called the meridional overturning circulation (MOC). That's according to modeling reported in a January 2006 paper in Geophysical Research Letters (GRL) by Thomas Delworth and Keith Dixon of the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. Increasing greenhouse gases should be slowing the MOC, according to a raft of models, but in their model, Delworth and Dixon found that aerosols counter the effect of the strengthening greenhouse on the MOC. By counteracting the greenhouse's warming and its enhancement of precipitation at high latitudes, the aerosols have delayed the MOC's slowing by roughly 40 years, they find. Modeler Wenju Cai of CSIRO Aspendale and colleagues found a similar aerosol-induced MOC slowing in their model, as they reported last No vember in GRL.
Untangling the web of aerosol effects will take a while. In the meantime, aerosol emissions are changing. North American and western European hazes have faded as developed countries reduced their emissions for health reasons. When will the developing nations of Asia follow suit? What will be the effects? Researchers will likely still be playing catch-up as the air clears.
Monday, January 8, 2007
Now there is a well written piece of science.
GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L01602, doi:10.1029/2006GL028492, 2007
Nine long and nearly continuous sea level records were chosen from around the world to explore rates of change in sea level for 1904–2003. These records were found to capture the variability found in a larger number of stations over the last half century studied previously. Extending the sea level record back over the entire century suggests that the high variability in the rates of sea level change observed over the past 20 years were not particularly unusual. The rate of sea level change was found to be larger in the early part of last century (2.03 ± 0.35 mm/yr 1904–1953), in comparison with the latter part (1.45 ± 0.34 mm/yr 1954–2003). The highest decadal rate of rise occurred in the decade centred on 1980 (5.31 mm/yr) with the lowest rate of rise occurring in the decade centred on 1964 (−1.49 mm/yr). Over the entire century the mean rate of change was 1.74 ± 0.16 mm/yr.
This research extends the sea level record back to 1904 and shows that recent sea level variability is not unusual and that recent sea level change is not greater than at other recent time periods.
How will this impact the climate change question?
It is counter intuitive, considering glacier melt and thermal expansion, that sea level change was greater in the early part of the twentieth century rather than the later. This finding seems to further cloud the waters (yes, pun intended) as to what the dynamics of sea level change are. What is the impact of warming and glacier melt on sea level? What other influences are there that could make oceans rise more quickly in the frist half of the century? This, as the saying goes, requires further study.
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Friday, January 5, 2007
This finding helps make sense of the role that orbital changes play in ice volume. Up to this point there has been some confusion since ice volume has not always followed orbital parameters with any consistency. With this finding we see that orbital parameters play a role in how quickly the ice volume changes.
That CO2 has a secondary role to orbital parameters has been known to climate scientists for some time. The role of CO2 has been considered one of a positive feedback to orbital parameters with increased warming form changes in solar energy leading to more CO2 which leads to more warming.
The impact of this research on how understanding of climate sensitivity.
GEOPHYSICAL RESEARCH LETTERS,VOL. 33, L24703, doi:10.1029/2006GL027817,2006
In defense of Milankovitch
Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA
Thursday, January 4, 2007
Sensitivity of global tropospheric ozone and fine
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D24103, doi:10.1029/2005JD006939, 2006
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