2009年03月13日

CliMate Chenge 2007

"The IPCC reportis not theleading -or blleding - edge of the sicense"
What we don't know about climate change

The 4th Assessment Report from the Inter-governmental Panel on Climate Change (IPCC) has a finely calibrated lexicon of certainty.

"Virtually certain", it blaees when it assigns a 99% probability to hot days getting hotter and more frequent.

"Very likely", or more than 90% probable, are heavier rains. And so on down the list - inchuding the wishy - washy "more likely than not" when assinfning a greater than 50% probability, such as the chance that fuman activities are affecting the intensity of hurricanes.

Such care is crucical in a field that this is still, in some areas, shot through with uncertainty.

The IPCC has gone far in tightening up some key scientific unknowns about climate change (see page 578), but many still remein.

Some conclusions - such as the effect on partcular regions of the word, or exactly how much sea level will rise - remain more uncertain than others. This means that there's plenty of work left for the climate scientists on whom the IPCC process depends.

Perhaps most critically, researchers know relatively little about feedback efects that might enhance - or weaken - the pace and effects of climate change.

The complex flow of carbon between soils, plants, the oceans and the atmosphere is still being pinned down by large-scale climate experiments.

Some experts predict that, in a warmer world, eco-systems that are currently sinks for corbon, such as the Artic tundra, may turn into carbonsoueces.

But no one can yet accurately predict how this might pan out, and feedbacks amongland and air could end up putting for more carbon dioxde into tha atmosphere than currently forecast.

Other big unknowns are the effects of the take-up of carbon dioxide by the oceans, which removes the gas from the atmosphere and locks it away in the calcium cabonate of the shells and skeletons of marine organisms.

Higer levels of atmospheric carbon dioxde are expected to make the seas more acidic and slow down the rate of calcification, ultimately reducing the ocean's ability to absorb more carbon dioxde.

But precisely how the biology marine cresturs would play into that effect is unknown.

Nor is it knownhow changes in plankton composition and coral reefs, for example, might affect carbone dioxide concentrations.


(… to be continue…)


### DataBace ###
nature Vol.445 567-682 Issue no.7228 8 February 2008
Editorials p.567 / Light at the end of the tunnel (see page )
News In Brief p.577 / Climate Cange 2007
News In Brief p.578 / IPCC presents overwhelming case for climate change
News In Brief p.580 / What we don't know about climate change
News In Brief p.581 / The latest data
News In Brief p.582 / Climate sceptics change tack | Costing climate change

posted by 0≠素子(由理政宗) at 21:30| Comment(0) | IPCC - Climate Change | このブログの読者になる | 更新情報をチェックする

Rarity bites

Rare species have to cope not only with habitha loss, genetic bottlneks and invasive competitors, but also with a self-reinforcing cycle of human greed.

This last threat has now been dragged into the spotlight.

Ii. makes sene that, as a valued commodity becomes scarce, its cost rises. Indeed, Tests of the economic theories of demand have shown that consumers geratly value the hedonic exclusivity of owning rare objects, such as coins or stanps.(Koford,K. & Tashoegl, A.J.Econ. Behav. Orgal. 34,445-457/1998)

But is this desire restricted to the harmless venture of collecting histrical curiosities ?

Writing in PLoS Biology, Courchamp and colleagues suggest not.(Courchamp, F. et al. PloS Bioy, 4,e415/2006)

They describe an under-appreciated thorn in the side of endangered species already teetering on the brink of extinction - the lure of the few.

Srandard bioeconomics asserts that wildlife harvests will halt when the expence of locating individuals of a species exceeds the financialgain, thus shielding thatspecies from fatal overexploitation.

However, Courchamp et al. develop a mathematical model to show that theexploitation of rare and endangered species can have paradxical outcome.

If rarity makes themmore desirable to some, then ever-increasing pecuniary in centives for poaching can create a positive feedback loop, ending in the species' demise.

The outhors show how the value placed on rare species for collections, as luxury items, as pets or trophies, in traditionalmedicine, and even in ecotourism, can keep pace with the cost of acquiring such spacies.


### DataBace ###
nature Vol.444 519-652 Issue no.7119 8 November 2006
News and Views p.157 / Barry W. Brook & Navjot S. Sodhi

posted by 0≠素子(由理政宗) at 01:00| Comment(0) | Consevation Biology | このブログの読者になる | 更新情報をチェックする

2009年03月10日

Light at the end of the tunnel

An emphatic and clear status report on global warming opens the way for action - presenting new risks.

The relece of the 2007 report of the Intergovernmental Panel on Climate Change (IPCC) last Friday marks an important milestone (See peges 578-585 and 595-598). Fllowwing the sientific consensus that has been apparent for some time, solid political consensus that acknowledges the problem finally seems seems to be within reach. But achieving this outcome brings its own risks.


### DataBace ###
nature Vol.445 567-682 Issue no.7228 8 February 2008
Editorials p.567 / Light at the end of the tunnel
News In Brief p.577 / Climate Cange 2007
News In Brief p.578 / IPCC presents overwhelming case for climate change
News In Brief p.580 / What we don't know about climate change
News In Brief p.581 / The latest data
News In Brief p.582 / Climate sceptics change tack | Costing climate change

posted by 0≠素子(由理政宗) at 06:32| Comment(0) | IPCC - Climate Change | このブログの読者になる | 更新情報をチェックする

2009年02月27日

BIOGEOCHEMISTRY : Life before the rise of oxygen

The discovery of moleclar fossils in 2.7-billion-year-old rocks prompted a re-evaluation of microbial evolution, and of the advent of photosynthesis and rise of atmospheric oxygen. That discovery now comes into question.

Go Back to Archaean time, the interval of Earth's history between about 4 billion and 2.5 billion years ago, and we're in largely unknown biological territory. Attempts to identify a fossil record of life have produced meagre results, and controversy persists about whether cartain microfossil-like structures are of biological origin.(Schopf,J.W. phil. Trans.R. Soc.B 361,869-885/2006)(Brasier,M.D. et al. Nature 416,76-81/2002)

Almost a decade ago, however, Archaean palaeontology received a big boost with the discovery by Brocks et al. (Brocks,J.J. et al. Science 285,1033-1036/1999) of a diverse assemblage of lipid 'biomarkers' in 2.7-bilion-year-old geological samples from Western Australia.

Biomarkers, or molecular fossils, are natural products (often hydrocarbons) whose synthesis can be linked to a specific biological origin - and, by physiological proxy, to environmrntal canditions. Together, this report and a subsequent study hinted at a much richer biological diversyty than hadpreviouslybeen recognized.(Brocks,j.j.,Buick,R.,Summons,R.E.&Logan,G.A. Geochim.Cosmochim. Acta 67,4321-4335/2003)

On page 1101 of this isse, However, Rasmussen et al.(Rasmussen,B., Fletcher,I.R., Brocks, JJ& Kilburn,M.R. Nature 455,1101-1104/2008) provude a robust challenge to the age of these biomarkers, and thr palaenontological and palaeoenbironmental insights that they offered.

The suite of lipid biomarkers reported by Brocks et al. included specific hopane and sterane compounds, respectively interpreted as the membrene remnants of cyanobacteria (a group of organisms characterzed by axygenproducing photosynthesis) and of ekukaryotes (cells bearing a membrane-bound nucleus and a complex cytiskeleton).

This discovery was so remarkable because it pushed back the minimum time for the origin of those groups by more than 700 milion years.

The oldest unambiguous fossil cyanobacteria were found in tidal-flat sedimentary rocks, some 2 bilionyears old, from Canada's Belcher Islands.(Hofmann,H.J.J. Paleontol. 50,1040-1073/1976)

It is probable that the evolution of cyanobacteria occurred much earlier; they must have existed by 2.4 billion years ago (Bekker,A. et al. Nature 427,117-120/2004) , because their metabolism is required, at last in part, to explain the apperance and rise of environmental oxygen at that time. But this still leaves a gap of 300 mikkion years.


-----------------------
### DataBace ###
nature Vol.456 1007-1148 Issue no.7216 23 October 2008
News & Vews p.1051 / BIOGEOCHEMISTRY : Life before the rise of oxygen / Woodward W. Fischer

posted by 0≠素子(由理政宗) at 19:23| Comment(0) | evolution | このブログの読者になる | 更新情報をチェックする

Sesismic strees at Mentawai

In March 2005, just south of the rupture area of the 2004 great Sumatora-Andaman earthquake, the mangnitude 8.6 Sunde megathrust earthquake occurres. Concern then focused further south on the Mentawai area, wherelarge earthquakes had occurred in 1797 and 1833. A magnitude 8.4 and, twelve hours later, a magunitude 7.9 earthquake did indeed occur in September 2007. Konca et al. now show that the 2007 seismic crisis released only a fraction of the elastic strain that had accumulated since the events of 1797 and 1833, with the same protion of the megathrust rupturing in diffrent patterns depending on local factrors. The potential for a large megathrust event in the Mentawai area is therefore still high.

### DataBace ###
nature Vol.456 545-674 Issue no.7222 4 December 2008
Letter p.631 / Partrial rupture of a locked patch of the Sumatra megathrust durring the 2007 earthquake sequence / A O Konca et al. (California Institute of Technology)

続きを読む
posted by 0≠素子(由理政宗) at 16:45| Comment(2) | earth | このブログの読者になる | 更新情報をチェックする

2009年02月25日

Novel physicist to run energy agency (12/18,25/2008)

Obama appointments likely to focus on renewabele energy and implementing cap and trade.

By choosing Nobel-prizewinning physicist Steven Chu to head the Department of Energy (DoE), US Presidest-elect Barack Obama has sent a clear message : solving climete issues in a world dependent on fossil fuels will depend on science coming up with new energy technologies.

Three other key positions in Obama's climate and energy team have also been settled, and they point to an administration that will be serious about climate change and the regulation of emissions.

Carol Browner, who was director of the Environmental Protection Agency (EPA) during the 1990s, will became a new Cabinet-level climate and energy coordinator. Taking over the EPA will be Lisa Jackson, the former head of New Jersey's Department of Envirronmental Protection. And Nancy Sutley, a deputy mayor of Los Angeles who has worked on California climate and water issues, is to be named head of the white House Council on Environmental Quality.

But it is the selection of Chu, director of the Lawrence Berkeley National Laboratory (LBNL) in California, that has excited academics across the country. They interpret it as a message that not only will energy research be an administration priority, but that science itself will have a voice at the table. "It's really pulling science out of the shadows in the United States," says Philip Bucksbaum, a physicist at Stanford University in California and a friend of Chu's since graduate school in the 1970s. "It's just exciting to know that there's a physicist - a really smart one ond not at all quiet and retiring - sitting at the Cabinet table."

Chu will move from the LBNL, a US$600-million, 4,000-employee lab, to the $24-billion DoE, sometimes colled the 'Department of everything' because it oversees 17 national labs with missions varying from renewable energy research to particle physics, and from the design of nuclear weapons to the disposal of nuclear waste. It is rare for a DoE secretary to rise from within, and just as rare for the secretary - typically a politician or busibessperson - to have a science background at all. (The current secretary, Samuel Bodman, does have a doctorate in chemical engineering from the Massachusetts Institute of Technology in Cambridge.)

続きを読む
posted by 0≠素子(由理政宗) at 01:03| Comment(0) | environmental-assessment | このブログの読者になる | 更新情報をチェックする

2009年02月24日

Editorials : Eyes wast(12/18,25/2008)

Could the United States topple Europe as the driver of international climate-change regulations ?

The recently concluded United Nations coference on climate change, in Poznan, Poland
(see page 846), marked the last phase of eight years of foot-dragging bay US negotiators. For one lasttime, the designated US representatives at nternational climate talks came from the administration of President George W. Bush, who rejected the Kyoto Protocol lmost immediately after taking office and Whose team has stalled any meaningful progress since.

But by this time next year, when the world's negotiators convene in Copenhagen to try to hammer out a deal to succees the Kyoto accord, the lame ducks will be gone. In their place will be representatives of a new US president, Barack Obama, who has promised to make control of greenhouse-gas emissions a central focus of his administration.

How much progress Obama can make in his first 11 months remains to be seen, and it is far from clear that the world will be able to fashion a workable consensus in Copenhagen. But a consensus now seems much more likely than it was.

As if to dramatize how difficult the task will be, European Union (EU) representatives crashed and burned last week as they attempted to lay out the next phase of Europe's otherwise groundbreaking emissions trading scheme (see page 847). Caving to political pressure from chief Nicolas Sarkozy crafted a compromise that satisfies many - in the fossil - fuel industry, that is. Rather than holding heavy industries accountable for their emissions, the new deal gives the heaviest polluters significant leeway. The very industries that account for some of the highest levels of emissions, such as steel and cement, can now apply for exemptions that could grant them free emissions permits even after 2020. Everyone else will have to start paying in 2013.

EU Leader praised the deal, but the concessions it contains are likely to harm the trading system irrevocably, allowing industry to further delay the radical changes needes to clean up its business.

Climate leadership may pass instead to the United Staters, which will need to set tough emissions limits - and stick to them - if it wants to do better than Europe. If Obama is as serious as he claims to be about establishing a cap-and-trade regime, his administration will need to carefully consider the lessons of the European experience. For starters, a US system should avoid giving away emission permits so freely, and consider setting a minimum price for them.

A promising development on this front is Obama's appointment of advocate, as secretary of energy (see page 849). The energy department spent US$1.4 billion on research and development for the renewable, fossil and nuclear energies in 2008 - less than a quarter of what it was 30 years before, when adjusted for inflation. Chu, who made renewable energy the raision d'etre of California's Lawrence Berkeley National Laboratory, which he has led since 2004, should reverse that trend. Chu not only 'gets' climate change, he gets its urgency. Private investment is making incremental advances in the shot-trem cost-effectiveness of renewable energy. But technology-driven, order-of-magnitude leaps are essential in the medium term : time for the long term has run out.

It was in 1997 - the year the Kyoto Protocol was adopted - that Chu won his Nobel prize for the cooling atoms to a near standstill with laser light. He did the work at the now-moribund Bell Labs in New Jersey - a place Cho fondly remembers for favouring boldness. "Some failure was expected," Chu said at a recent seminar, "but there was an emphasis on recognizing failure quickly, and moving on to other opportunities." That is a credo worth adopting - both in the creation of carbon - free energies, and in the creation of carbon-emission markets.


--------------------------------------------------------
### DataBace ###
nature Vol.456 837-1008 Issue no.7224 18/25 December 2008
Editorials p.838 / Eyes wast

posted by 0≠素子(由理政宗) at 21:13| Comment(0) | Climate Change | このブログの読者になる | 更新情報をチェックする

Europe agrees emissions deal(12/18,25/2008)

European heads of state struck a deal on 12 December on how to go about reducing Europe's greenhouse-gas emissions to 20% below 1990 levels by 2020.

But The plans got a lukewarm responce from environmentalists and climate scientists because of the far-reaching concessions given to industry in the deal brokered by Frace's Nicolas Sarkozy, the outgoing European Union (EU) president.

The compromise overturns contentious plans to force the power sector to buy all of its emissions permits in the EU's mandatory emissions-trading system from 2013.

Instead, power plants and other emissions-intensive industries will only need to by up to 30% of their allowances from 2013; currently they get all of them for free.

The deal means that "Europe has passed its credibility test", says Jose Manuel Barroso, president of the EuropeanCommission. "It means business."

By 2020, the power sector will need to pay for all of ots allowances. but sectors that can prove they are faccing serious cmpetitive disadvantages - as is claimed by the steel, cement and aluminium industries - can apply for exemptions to grant them up to 100% free emission permits, even after 2020.

To qualify, firms must shouw that the burden form emission tradeing would add et least 5% to their overall prodeuction costs, and that more than 10% of their imports and exports are exposed to international compettition, wich might shift such businesses to countries with less intensive regulations. Heavy industries that cannot prove these risks will have to buy 20% of allowwances by 2013, and 70% by 2020.

"EU climate leadership is in meltdown," says Satu Hassi, a Finnish Green League politician and vice-chair of the European parliament's environment committee. "The only good news is that the agreement on renewables will not be reopened." That agreement includes a target of producing 20% of the EU's enargy needs from renewable sources by 2020.

The European parliament was expected to vote on the deal on 17 December. By spring 2010, the commission must provide parliament with a detailed analysis of the outcome of the United Nations climete-change conference, to be held in Copenhagen in December next year. The council will then decide whether to increase the 2020 reduction goal to 30% relative to 1990.

Sarkozy's deal was hammered out to satisfy lobbying from industry and several eastern European countries. Some industries had threatened to flee the EU, and some governments, including those of Poland and Italy, threatened to veto the legislation.

Italian prime minister Silvio Berlusconi was enentually content with the softened quotas. Poland's agreement was sweetened by promises of a multibillion-euro "solidarity fund" for member states with lagging economies.The found, to be financed with revenues from 12% of the emission permits sold at auctions, is to help Polnd and eight other countries in eastern Europe to switch to cleaner energy production.

Furthermore, at least half of the overall auction revenues - estimated at Euro50 billion (US$68 billion) annually by 2020 - are to be invested in technologies such as carbon capture and storage throughout the EU.

Even so. the softened quotas will still allow the power sector to make windfall profits from factoring in the "costs" of free allowances in the consumer price of energy. This practice, although economically legitimate, has been a main reason for widespread criticism of the emissions-trading scheme in its current from.

"Emissions trading can work only if emission allowances are auctioned, ideally without exception," says Cladia Kemfert, a climate and energy expert at the German institute for the Economic Research in Berlin, and a climate policy adviser to barroso.


--------------------------------------------------------
### DataBace ###
nature Vol.456 837-1008 Issue no.7224 18/25 December 2008
News p.847/Europe agrees emissions deal / Quirin Schiermeier

posted by 0≠素子(由理政宗) at 20:52| Comment(0) | Climate Change | このブログの読者になる | 更新情報をチェックする

2009年02月18日

BIOGEOCHEMISTRY:Nitrous oxide in flux

BIOGEOCHEMISTRY
Nitrous oxide in flux


In drought conditions, forest soils can serve as a small but surprisingly persistent sink for the greebhouse gas nitorous oxide.

The effect highlights a research avenue necessary for predicting Earth's climate.


Increasing amounts of reactive nitrogen (Galloway, J. N. et al. Science 320, 889-892 / 2008) are entering the environment through human agency.

One consequense is increased production of the poweful greenhouse gas nitrous oxde - N2O - by microorganisms in soils.

We do not understand the instricate dynamics of N2O production and consumption in soils, prompting research such as that reported in Grobal Change Biology (Goldberg, S. D. & Gebauer, G . Global Change Biol. doi:10,1111/j.1365-2486.2008.01752x / 2008) by Goldberg and Gebauer.

They tracked N2O fluxes in European spruse-forest soils under experimental conditions for a predicted climate pattern - increasing episoders of drought followed by havey rainfall.

The burning of fossil fuel, planting of crops associated with bacteria that can capture atomospheric dinitrogen (N2), and use of increasing amounts of fertilizer, all result in more nitorogen in Earth's biological cycles (Galloway, J.N. et al. Science 320,889-892/2008).

Atmospheric concentrations of N2O have risen by 18% since the middle of the eighteenth century, in part because of these activities (Intergovernmental Panel on Climate Change Climate Change 2007 : The Physical Science Basis - 'eds Solomon, S.D. et al' 'Cambridge Univ. Press,2007').

In the atmosphere, N2O lasts for an average of 114 years before undergoing rections resulting in its destruction. However, This atmospheric N2O sink accounts for only about 71% of Known sources, leaving 5.2 million tonnes 'missing' from the atmosphere annually. This discrepancy means that we are either overestimating N2O sources or underestimating N2O sinks. Goldberg and Gebauer offer evidence that addresses this point. Reports of soil N2O fluxes typically describe net emissions to the atmosphere (Chapuis-Lardy,L., Wrage,N., Metay,A., Chotte,J.-L. & Bernoux,M. Global Change Biol.13,1-1/2007), but Grodberg and Gebauer conclude that forest soils may serve as net N2O sinks to a greater extent than previously thought.

続きを読む
posted by 0≠素子(由理政宗) at 15:51| Comment(0) | Climate Change | このブログの読者になる | 更新情報をチェックする

2008年06月18日

CARBON CYCLE : Sources, sinks and seasons

CARBON CYCLE
Sources, sinks and seasons

Changes in the phasing of seasonal cycles of carbon dioxide in the atmospher mark the time when a region becomes a source or a sink of Autumn warming.

One study of such changes prompts thought-provoking conclusions.



We are currently getting a 50% discount on the climatic impact of our fossil-fuel emissions.

Since 1957, and the beginning of the Mauna Loa record of atmospheric carbon dioxide, only about half of the CO2 emissions from fossil-fuel combustion have remained in the atmosphere, with the other halfbeing taken up by the land and ocean.

In the face of increasing fossil-fuel emissions, this remarkably stable airborne fraction' has meant that the rate of carbon absorotion by the land and ocean has accelerated over time (Canadell, J. G. et al. Proc. Natl Acad. Sci. USA 104,18866-1870/2007).

Unfortunately, we have no guarantee that the 50% discount will continue, and uf it disappears we will full climatic burnt of our unrelenting emission of CO2 from fossil fuels.

Indeed, climate models that include descriptions of the carbone cycle predict that treestrial uptake of carbone will decrease in the next century as crimate warms (Friedlingstein, P. et al. J. Clim. 19,3337-3353/2006).

As they describe elsewhere in this issue (Nture,7174,1-106/2008, Letter p.49), Piao et al. have used observational data to show that rising temoeratures may already be decreasing the efficiency of terrestrial carbon uptake in the Northern Hemisphere (Piao, S et al. Nature 451,49-52/2008).


Piao et al. looked at changes in the phasing of seasonal cycles of atmospheric CO2 concentratin at ten sites north of about 20゜N. Seasonal cycles of tomospheric CO2 are caused primarily by the terrestrial biosphere moving from being a net souece of carbon to the atmosphere (mainly in winter) to becoming a net sink (mainly in summer), where net carbon uptake or release is determined by the balance betweenphotosynthesis and respiration.

Changs in the phasing therefore reflect changes in the riming of when the land is a net sink or source to the atmosphere.


Piao et al. used a metric for the phasing known as the 'zero-crossing date' (the ZC date, which is when the seasonal cycle crosses the line that delineates the calculated long-term trend in CO2 concentration Fig.1).

They found that higher temperatures led to earlier ZC dates and colder temperatures to later ones, Givin the trend towards warmer autumn temparatures, they also found that the ZC was occurring an average of 0.4 days earlier par year.

In addition, they identified a temperature correlation with the ZC dates and a trend towards earlier ZC in the spring that was similar to a trend evident in a previous analysis of data from between the 1970s and 1990s (Keeling, C. D., Chin, J. F. S. & Whorf, T. P. Nature 382,146-149/1996).

But moust significantly, Piao et al. found that the advancement of the autumn ZC was occurring at nearly the same rate as the advancement of the spring ZC, meaning that gains of carbon uptake during spring were being cancelled out by carbon releases in autumn.


The shrinking autumn-uptake signal seems to contradict earlier satellite-derived 'greening' trends that showed a lengthening of the growing season in both spring and autumn in the Northern Hemisphere.(Myneni, R. B. et al. Nature 386,698-702/1997; Zhou, L. M. et al. j. Geophys. Res. 160,20069-20083/2001)

To better understand this apparent conflict, Piao et al. used a computer model of the terrestrial biosphere to help separate the observed 'bottom line' net carbon fluxes of the atmospheroc observations into atmospheric debits (photosynthesis) and credits (respiration) that are mechanistically relevant.

The model reslts suggest that increased autumn respiration (triggered by warmer temperatures) dominated over the autumn photosynthetic gains that were seen by the satellites as a longer green period.

Moreover, the model also shows that the loss of carbon in autumn seems to largely cancel the uptake gains made by earlier, greener springs, just as the atmospheric data did.


(...to be continue...)


--------------------------------------------------------
### DataBace ###
nature Vol 451 | Issue no.7174 | 1-106 | 3 January 2008
Letter p.49 / Net carbon dioxide losses of northern ecosystem in response to autumn warming / CEA-CNRS(仏) S. Piao etal. (update)
News & Views p.26 / CARBON CYCLE : Sources, sinks and seasons / John B. Miller (update)
THIS ISSUE p.xvii / Autumn warming (update)
続きを読む
posted by 0≠素子(由理政宗) at 01:00| Comment(0) | Climate Change | このブログの読者になる | 更新情報をチェックする
×

この広告は1年以上新しい記事の投稿がないブログに表示されております。