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1、新着論文 2、論文概説 3、コラム 4、本のレビュー 5、雑記(PC・研究関連)
6、気になった一文集(日本語English) 7、日記(日本語English

2014年10月31日金曜日

これまででもっとも細かい大気CO2濃度記録:最終退氷期(Marcott et al., 2014, Nature)

Centennial-scale changes in the global carbon cycle during the last deglaciation
Shaun A. Marcott, Thomas K. Bauska, Christo Buizert, Eric J. Steig, Julia L. Rosen, Kurt M. Cuffey, T. J. Fudge, Jeffery P. Severinghaus, Jinho Ahn, Michael L. Kalk, Joseph R. McConnell, Todd Sowers, Kendrick C. Taylor, James W. C. White & Edward J. Brook
Nature 514, 616–619 (30 October 2014)

より。
西南極氷床から得られたアイスコア(WDC)の、これまでで最も高い解像度の最終退氷期(20-10ka)における大気CO2濃度変動記録を報告。

2014年10月25日土曜日

ハマサンゴは海洋酸性化に対して強い?

成長速度が早く(年間1-2cm)、場合によっては数百年生きることから、古気候研究において広く使用されているハマサンゴ。
長寿命であることや分布範囲が広いことから、環境ストレスに強いことが想像されるが、こと海洋酸性化に対してはどうだろうか?

野外調査や飼育実験を通してこれまでに分かっている知見をまとめてみたい。おそらく下に挙げるもの以外にもあるため、実際にはもっと複雑なのかもしれない。

2014年10月23日木曜日

氷期の赤道大西洋のCO2放出は今よりも大きかった?(Foster & Sexton, 2014, Geology)

Enhanced carbon dioxide outgassing from the eastern equatorial Atlantic during the last glacial
G.L. Foster and P.F. Sexton
Geology doi: 10.1130/G35806.1 (October 7, 2014)

より。
ちなみにGeologyだけどオープンアクセス。

ホウ素同位体(δ11B)-pH-pCO2プロキシを用いた赤道大西洋の最終氷期以降の海洋表層pCO2復元に関する論文。

2014年10月15日水曜日

海底の引っ搔き傷から氷期の北米氷床から流出した氷山がどう流れるかを推定(Hill & Condron, 2014, Ngeo)

Subtropical iceberg scours and meltwater routing in the deglacial western North Atlantic
Jenna C. Hill & Alan Condron
Nature Geoscience, AOP (2014)

個人的に非常に面白く、そして大変重要だと感じた論文。

氷期や最終退氷期における北米大陸氷床からの氷山流出とその融水放出(ハインリッヒ・イベント、8.2 kaイベントなど)が大西洋子午面循環だけでなく、全球の気候に大きな影響を与えたことが世界中の様々な記録から示唆されている(中国・インドネシア・ブラジルの鍾乳石、北半球中・高緯度の堆積物コアなど)。

ただし、これまでの知見からは(そして僕の抱いていたイメージからは)、氷山流出の範囲というものは亜寒帯循環に捕われた形で終結しており、あまり南方までは運ばれることはなかったというのが通説であった。

2014年10月9日木曜日

気になった一文集(English ver. No. 24)

That goal seems far off, given the continued lure of oil and gas and the huge amount of ‘locked-in’ emissions from the army of new coal-powered plants in China and elsewhere. And the world population keeps growing: by mid-century, when global emissions will already need to have declined substantially to avoid excessive warming, billions of ‘consumers’ in Africa and Asia will remain trapped in the fossil-fuel age regardless of the low-carbon technologies that might then be available — unless they are helped out of poverty.
石油・天然ガスの誘惑と中国やその他の国の石炭火力発電所の大群のことを考えると、その目標ははるか未来のことのように思える。また世界の人口は増え続けている:極端な温暖化を避けるために今世紀半ば頃には世界のCO2排出はかなり減っていなければならないという事情にも関わらず、貧困から救済されることなしには、アフリカやアジアの数十億人の’消費者’たちはおそらく将来利用可能な低炭素技術を使用することなく化石燃料燃焼時代に捕われたままだろう。

Warming upNature 514, 5–6 (01 October 2014)

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The Canadian project is just the first of what will need to be thousands of clean coal plants by 2050 to put a significant dent in emissions. (Coal-burning alone produced 15 billion tonnes of CO2 worldwide in 2012, 43% of the world’s total). On current timetables, the world is nowhere close to achieving this: the technology is just too expensive, and so far there’s been no political will to tax fossil fuels on the basis of their emissions, which would be an incentive for clean coal.
2050年までにかなりの排出量を減らすために必要な数千ものクリーンな石炭発電所 のうち、カナダの計画は単に最初のものというだけに過ぎない。(2012年に世界で排出された150億トンのCO2のうち、石炭燃焼だけでも世界全体の排出量の43%を担っている。)現在の予定表であれば、世界はちっともこの目標に近づいていない。その理由としては、その技術があまりに高額であり、クリーンな石炭発電のインセンティブになるような化石燃料に課される排出量に応じた課税をどこの政治も行っていないことが挙げられる。

In 2009, the IEA published a road map calling for 100 large CCS projects by 2020, but in July 2013, with projects failing to materialize, it downgraded that to just 30. And even that is ambitious.
2009年に国際エネルギー機関(IEA)は2020年までに必要な100カ所の巨大炭素捕獲貯留(CCS)計画のロードマップを公表したが、そうした計画が実現しなかったために、2013年7月にはその数をたった30に減らすに至った。しかもそれだけでも十分野心的な目標値となっている。

World’s first ‘clean coal’ commercial power plant opens in Canada
Richard Van Noorden, Nature NEWS BLOG (02 Oct 2014)

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Values may vary according to, for example, age, wealth, education, sex, culture and religion. One group of people might see adopting nuclear power as a practical way to avoid greenhouse-gas emissions; another would find it unpalatable.

More surveys and longitudinal studies are needed to find out what sorts of risks individuals say they will react to most strongly, and how they actually respond. For example, a study of migration intentions in rural Pakistan from 1991 to 2012 showed that extreme heat influenced people’s choices but flooding did not. The main reason was that heat waves do not attract as much financial compensation as flood relief. 

Model human adaptation to climate changeNature 512, 365–366 (28 August 2014)

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Today, the rate of extinction of species is estimated to be 100 to 1,000 times more than what could be considered natural. 

loss of biodiversity can increase the vulnerability of terrestrial and aquatic ecosystems to changes in climate and ocean acidity, thus reducing the safe boundary levels of these processes. There is growing understanding of the importance of functional biodiversity in preventing ecosystems from tipping into undesired states when they are disturbed. This means that apparent redundancy is required to maintain an ecosystem’s resilience. Ecosystems that depend on a few or single species for critical functions are vulnerable to disturbances, such as disease, and at a greater risk of tipping into undesired states.

(…) because many of the boundaries are linked, exceeding one will have implications for others in ways that we do not as yet completely understand. There is also significant uncertainty over how long it takes to cause dangerous environmental change or to trigger other feedbacks that drastically reduce the ability of the Earth system, or important subsystems, to return to safe levels.

A safe operating space for humanityNature 461, 472-475 (24 September 2009)

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The 2 °C limit has been widely considered a prime example of science-based policymaking, but it is currently under scrutiny as the conditions to meet the target continue to deteriorate. What once seemed a non-negotiable planetary threshold might need to be renegotiated soon.

A number of experts had already criticized the 2 °C target before its adoption by the UNFCCC, arguing that a single metric cannot represent the threshold to ‘dangerous’ climate change and that abstract long-term targets usually don’t catalyse tangible short-term action.

there is no doubt that the global emissions trajectory, which is still rising, is unlikely to be reversed in just a few years. 

Empirical findings indicate, however, that political effectiveness and public trust cannot be reduced to a function of the breadth and depth of scientific consensus. While the IPCC has been able to provide a common knowledge base for international climate policy, the uptake of its findings and the credibility of the institution itself in the eyes of citizens and policymakers worldwide still vary significantly.

Scientific or expert judgements can only inform, not replace, public debate on the moral, social, political, ethical and economic ramifications of the different possible responses to climate change.

If climate change is one of the main challenges of the future, then climate policy should not be derived from ‘planetary boundaries’ exclusively determined by science.

Renegotiating the global  climate stabilization targetNature Climate Change 4, 747–748 (2014)

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The amount of change that would typ­i­cally occur in about 10 mil­lion years is being con­densed into a 300-​​year period.

A slightly more acidic ocean may help coral speciesnews@Northeastern (5 November 2014)

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Politically, it has allowed some governments to pretend that they are taking serious action to mitigate global warming, when in reality they have achieved almost nothing.

Pretending that they are chasing this unattainable goal has also allowed governments to ignore the need for massive adaptation to climate change.

The answer almost certainly lies in the oceans. The oceans are taking up 93% of the extra energy being added to the climate system, which is stoking sea-level rise and other climate impacts.

Instead, a set of indicators is needed to gauge the varied stresses that humans are placing on the climate system and their possible impacts. Doctors call their basket of health indices vital signs. The same approach is needed for the climate.

Sucking up all that greenhouse gas actually helps offset global warming, but the ocean pays a price.

SCU project looks at how fast climate change killing reefsNorthern Star News (7 Nov 2014)

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In the year or so before Copenhagen there were, like today, many bold pronouncements but few specifics. Massive disagreements over who would pay the cost of controlling emissions and adapting to climate change loomed large with no serious solutions in sight.

What really matters now are answers to questions about human behaviour, including political action — the realm of social sciences and the humanities that the IPCC and governments have been most uncomfortable letting into the room.

Copenhagen II or something newNature Climate Change 4, 853–855 (2014)

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(…) calcification must exceed bioerosion in order for reefs to grow and persist in the euphotic zone. Ocean acidification will drive a decrease in rates of calcification by corals and coralline algae, and ocean warming will exacerbate these impacts by inducing coral bleaching and mortality.
珊瑚礁が真光層において成長・存続し続けるためにも、石灰化は生物侵食を上回らなければならない。海洋酸性化はサンゴと石灰藻の石灰化速度を低下させるように働き、海の温暖化はサンゴの白化や致死の誘因となることでそれらの影響をさらに悪化させるだろう。

Curtailing global CO2 emissions, the primary driver of ocean acidification, cannot be tackled at a local level.
海洋酸性化の主要因である「全球のCO2排出」を減らすことはローカルなレベルでは太刀打ちできない。

Coral macrobioerosion is accelerated by ocean acidification and nutrients」DeCarlo et al., in press, Geology

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Of particular interest is how changes in the lateral supply of carbon from land will alter the sink–source balance of coastal systems, and how other perturbations, such as ocean acidification, deoxygenation and increasing nutrient load, will manifest themselves in the coastal carbon cycle and ultimately alter the coastal ocean’s ability to take up atmospheric CO2.
特に興味があるのは、陸からの炭素供給が沿岸システムの炭素の吸収-放出のバランスをどのように変化させ、そして海洋酸性化・海洋貧酸素化・栄養塩の過剰供給などの他の擾乱が沿岸の炭素循環の中でどう現れ、最終的に沿岸域が大気のCO2を吸収する能力をどのように変えるかということである。

Carbon at the coastal interface」N. Gruber, Nature 517, 148–149 (08 January 2015).

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Our results suggest that, globally, a third of oil reserves, half of gas reserves and over 80 per cent of current coal reserves should remain unused from 2010 to 2050 in order to meet the target of 2 °C. We show that development of resources in the Arctic and any increase in unconventional oil production are incommensurate with efforts to limit average global warming to 2 °C. Our results show that policy makers’ instincts to exploit rapidly and completely their territorial fossil fuels are, in aggregate, inconsistent with their commitments to this temperature limit. Implementation of this policy commitment would also render unnecessary continued substantial expenditure on fossil fuel exploration, because any new discoveries could not lead to increased aggregate production.
2 °Cという温暖化目標を実現するためには、世界的に残存する化石燃料のうち、2010年から2050年にかけて、「3分の1の石油、半分の天然ガス、80%の石炭」は手つかずのまま残しておくべきであることを、我々の結果は示唆している。北極圏の資源開発やその他の非在来型の石油生産は全球の平均的な温暖化を2 °Cに抑制する努力とは相容れないことを示す。政策決定者が陸域の化石燃料資源を早く・余すところなく開発したいという思いと、この温暖化制限の約束(政策決定者の責任)とは、全体として、辻褄が合っていないことを我々の結果は示している。いかなる新発見も総生産の増加につながらないため、こうした政策方針の実行は、化石燃料開発にかかる多額の出費を不必要に継続させることになると思われる。

The geographical distribution of fossil fuels unused when limiting global warming to 2 °C」Christophe McGlade & Paul Ekins, Nature 517, 187–190 (08 January 2015)

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For example, the Middle East, which holds the bulk of conventional oil reserves, would need to leave about 40% of those reserves underground. This corresponds to about 8 years of global production at current levels (87 million barrels per day). Similarly, countries with large coal endowments would face great challenges. China and India would have to discard 66% of their reserves, whereas Africa would have to leave 85% of them. In addition, the United States, Australia and countries of the former Soviet Union would need to leave more than 90% of their coal reserves underground, in stark contrast to the renaissance of coal use currently under way in many places.

Encouraged by the recent shale-gas production boom in the United States, several world regions, including China, India, Africa and the Middle East, are seeking to unlock their large endowments or increase existing production. However, McGlade and Ekins’ analysis shows that Africa and the Middle East would have to leave their entire unconventional gas resources underground, and that about 10% of the combined endowment of China and India (which includes substantial amounts of coal-bed methane) could be produced.

Unburnable fossil-fuel reserves」Michael Jakob & Jérôme Hilaire, Nature 517, 150–152 (08 January 2015).

2014年10月8日水曜日

Intcal13の前バージョンからの変更点

考古学・古気候学・古海洋学・炭素循環研究などで大変重要な放射性炭素年代測定。

放射性炭素年代を暦年代に較正する必要性については前回の記事「Intcalのお話」で述べました。

今回は最近公表された(といっても去年だけど)、Intcal13較正曲線の前バージョンからのアップデートについてまとめておきます。

参考にしているのは以下の論文
IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0–50,000 Years cal BP
Paula J Reimer
Radiocarbon 55, 1869-1887 (2013).