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2013年8月9日金曜日

気になった一文集(English ver. No. 16)

Obama broke a long silence on global warming.

The power sector produces some 40% of total US emissions, and administration officials have long said that they would fill the regulatory void if Congress failed to act.

The US Environmental Protection Agency (EPA) has already proposed a regulation that would essentially ban the construction of new power plants unless they are equipped to capture and sequester carbon.

Obama’s ‘climate action plan’ contained a variety of other initiatives, including calls for a new round of appliance standards, fuel-economy regulations on heavy-duty vehicles and various efforts intended to prepare the country for a warmer climate.

Rather than focusing purely on technological upgrades such as requiring more efficient boilers, the EPA may be able to improve on broader incentives that would require deeper reductions while, for example, allowing utilities to work with customers to curb electricity demand.

Whatever form the regulations take, and however ingeniously the administration can work around political opposition, the full scale of the climate challenge is more than any president could accomplish independently of Congress. Obama urged politicians and public servants to rise above the political fray and think beyond the next election, to live up to their obligations not just as “custodians of the present, but as caretakers of the future”.

Obama is just six months into his second term, but these are the words of a president who no longer needs to worry about re-election. Obama is now thinking about his place in history. Although his broader climate agenda has been stymied in Congress, Obama has laid out a solid path forward. Now he must follow it through.

More than hot air」Nature (4 July 2013)
気候変化に対して消極的な姿勢であったオバマ大統領がついに重い腰を上げた。

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In the UK, for instance, within-country emissions decreased by 5% between 1992 and 2004, whereas consumption-based emissions increased by 12%. In the USA, within-country emissions increased by 6% between 1997 and 2004, whereas consumption-based emissions increased by 17%. In both cases, a key factor driving the growth in consumption-based emissions was the import of manufactured products from China. Taken together, these studies imply that a considerable share of the growth of emissions from non-Annex B countries was associated with international trade.
自国内で排出されるCO2だけでなく、国際貿易を介して排出されるCO2も見過ごせないということ。特に中国の近年の排出量の急増は海外輸出用の製品の生産による部分も多いという。

Emissions from LUC (Land use Change) are the second-largest anthropogenic source of CO2. Deforestation, logging and intensive cultivation of cropland soils emit CO2. These emissions are partly compensated by CO2 uptake from the regrowth of secondary vegetation and the rebuilding of soil carbon pools following afforestation, abandonment of agriculture (including the fallow phase of shifting cultivation), fire exclusion and the shift to agricultural practices that conserve soil carbon. Unlike fossil fuel emissions, which reflect instantaneous economic activity, LUC emissions are due to both current deforestation and the carry-over effects of CO2 losses from areas deforested in previous years.
土地利用の変化がもとで起きるCO2排出の複雑さ。

In the deforestation process, fire is the primary means by which forests are converted to pastures or croplands, after timber exploitation.

As a result of all CO2 sources and sinks, atmospheric CO2 growth was 3.9 ± 0.1 Pg C yr−1 in 2008, an increase of 1.8 ppm, which is 0.6 Pg C yr−1 less than the average of the previous three years despite there being an increase in CO2 emissions from fossil fuel combustion. Average atmospheric CO2 in 2008 reached a concentration of 385 ppm, which is 38% above pre-industrial levels. The lower-than-average atmospheric growth rate was probably driven by a high land CO2 uptake due to the La Niña state of ENSO, and by reduced rates of deforestation in southeast Asia and in the Amazon, as indicated by lower rates of fire and clear-cut activities measured at the deforestation frontier.
2008年の大気中CO2濃度の増加率がやや小さかったことの説明。

To fill this gap, the residual CO2 flux from the sum of all known components of the global CO2 budget needs to be reduced, from its current range of ± 2.1 Pg C yr−1, to below the uncertainty in global CO2 emissions, ± 0.9 Pg C yr−1. If this can be achieved with improvements in models and observing systems, geophysical data could provide constraints on global CO2 emissions estimates.
今後、それぞれのシンク・ソースの見積もりをより正確にする必要がある。

If the model response to recent changes in climate is correct, this would lend support to the positive feedback between climate and the carbon cycle that was predicted by many coupled climate–carbon cycle models. However, these models do not yet include many processes and reservoirs that may be important, such as peat, buried carbon in permafrost soils, wild fires, ocean eddies and the response of marine ecosystems to ocean acidification.
モデルでまだうまく取り入れられていないもの。

Trends in the sources and sinks of carbon dioxide
Le Quere et al., 2009, Nature Geoscience
大気中のCO2濃度と化石燃料・セメント生産・土地利用変化によるCO2排出量のデータから、モデルシミュレーションを通して陸と海のCO2吸収量とその近年の変化傾向について考察。

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Because natural processes cannot quickly remove some of these gases (notably carbon dioxide) from the atmosphere, our past, present, and future emissions will influence the climate system for millennia.
そうした気体(とりわけ二酸化炭素)を大気から自然のプロセスですみやかに取り除くことは不可能であり、我々の過去・現在・未来の排出は千年間にわたって気候システムに影響する。

Furthermore, surprise outcomes, such as the unexpectedly rapid loss of Arctic summer sea ice, may entail even more dramatic changes than anticipated.
予期せぬほど急速な北極海の夏の海氷の消失など、さらに驚くべき結果が予想されるものよりもさらに劇的な変化を伴う可能性もある。

The community of scientists has responsibilities to improve overall understanding of climate change and its impacts. Improvements will come from pursuing the research needed to understand climate change, working with stakeholders to identify relevant information, and conveying understanding clearly and accurately, both to decision makers and to the general public.”
科学者のコミュニティーは気候変化とその影響に関する総合的理解を改善する責任を負っている。そうした改善は気候変化を理解するために必要な研究を追い求めること、政策決定者とともに関連した情報を特定すること、その理解を政策決定者と一般の両方に明瞭に・正しく伝えることによって可能となる。


AGU "Revised Position on Climate Change" (August 2013)

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Anthropogenic climate change is now a part of our reality.
人為的な気候変化は今や我々の現実の一部だ。


Once and Future Climate Change
Science (2 August 2013) Special Issue "Natural Systems in Changing Climates"

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The problem is even more difficult because the very factors that influence temperature changes, such as ocean circulation and terrestrial ecosystem responses, will themselves be altered as the climate changes. With so many potential climate-sensitive factors to consider, scientists need ways to narrow down the range of possible environmental outcomes so that they know what specific problems to tackle.

Researchers have turned to the geologic record to obtain ground truth about patterns of change for use in climate models. Information from prior epochs reveals evidence for conditions on Earth that might be analogs to a future world with more CO2. Projections based on such previous evidence are still uncertain, because there is no perfect analog to current events in previous geologic epochs; however, even the most optimistic predictions are dire.

Tackling problems of cumulative dimensions is a priority if we are to find viable solutions to the real environmental crises of the coming decades. There is a need for all scientists to rise to this challenge.


Climate Change ImpactsScience (2 August 2013) Editorial

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Our results show that if we continue on our current emissions path, by the end of the century there will be no water left in the ocean with the chemical properties that have supported coral reef growth in the past.

To save coral reefs, we need to transform our energy system into one that does not use the atmosphere and oceans as waste dumps for carbon dioxide pollution.


Major changes needed for coral reef survival

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Successful strategies for maximizing biodiversity while supporting human needs depend on understanding how species differ in their resilience and adaptability to broad environmental change.
「人々のニーズを満たしながら生物多様性を最大にする」という戦略が成功するかどうかは、様々な環境の変化に対する各生物の脆弱性・適応度の違いをどれほど理解できるかにかかっている。

Climate change may lead to completely new species assemblages, and conservation decision-makers must understand species responses so that responsible actions can be implemented.
気候変化は完全に新しい種の集団を作り出すかもしれず、保全の政策決定を行うものは責任ある行動がとれるように生物種の応答を理解しなければならない。


Pathways for ConservationScience (19 July 2013) Editorial

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Arctic permafrost degradation is a good example of the severe difficulty of climate prediction in general. It is a likely and potentially large positive feedback expected to play out over many decades, while the rate and the specific mechanisms have not been quantified or identified.

We do know that there are plausible feedbacks that could lead to catastrophic climate change, large enough to threaten the stability of our civilization. The probability is not vanishingly small.

Despite the difficulty of long-term CO2 projections, some things are clear: fossil fuel burning has driven the CO2 increases thus far, the ocean will eventually take up the largest portion of the emissions, and the enhancement of CO2 in the atmosphere and ocean will last for a very long time.

Rapid invention, technical development, and scaling up of alternatives, including efficiency and conservation, is crucial. Without them, the increasing demand for better living standards for more people will almost certainly force us into the large-scale exploitation of unconventional fossil fuel resources with little regard for the consequences of climate change, accompanied by accelerating environmental destruction, acidification of ocean waters, resource wars, and other negative impacts.


An Accounting of the Observed Increase in Oceanic and Atmospheric CO2 and an Outlook for the Future」Tans, P. (2009) Oceanography 22, 26-35

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Detailed knowledge of the geochemistry of CO2, the signature molecule of the 21st century, is a modern day requirement for almost all geochemists. Concerns over CO2 driven contemporary climate change, its relationship to past climates in Earth history, skills required for geologic CO2 sequestration, and the rapid emergence of ocean acidification as an environmental threat are all prime subject matter for the literate geoscientist today.

地中海で発見された海底下のクレーター内部に蓄積するCO2が関心を集めている。

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The loss of over 2 million km2 of arctic sea ice since the end of the last century represents a stunning loss of habitat for sea-ice algae and sub-ice phytoplankton, which together account for 57% of the total annual primary production in the Arctic Ocean.

Disruption of the seasonality of the ice algal and phytoplankton blooms by ice thinning, accelerated melt timing, and an increase in the length of the annual melt season by 20 days over the past three decades has created mismatches for the timing of zooplankton production, with consequences for higher consumers.

Hence, replacement of thick, multiyear ice by thin, first-year ice as the Arctic warms may contribute to increases in the frequency and magnitude of algae and phytoplankton blooms. However, the roles of sea-ice loss and ocean freshening in the tradeoffs between light versus nutrient limitation of arctic marine primary productivity remain poorly understood.

Sea-ice loss may also influence ecological dynamics indirectly through effects on movement, population mixing, and pathogen transmission.

Ecological Consequences of Sea-Ice Decline」Post et al. (2013) Science 341, 519-524.
北極海の海氷の後退による、生態系への影響。今回は海洋生態系に関するもののみをピックアップ。

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In the early 1960s, humans released about 2.5 billion tonnes of carbon into the air each year, and CO2 levels rose about 0.8 ppm annually; today, we spew out more than 10 billion tonnes, and CO2 is climbing at about 2 ppm per year.
1960年代初頭には、人類は年間25億トンの炭素を大気中へ放出していて、CO2濃度は年間約0.8ppmずつ上昇していた。今や、我々は年間100億トンを排出しており、CO2濃度は年間約2ppmの割合で上昇し続けている。

Our current climate has not yet had a chance to catch up with our high CO2 levels.
我々の現在の気候は高いCO2濃度にまだ追いつけていないのである。

Troubling milestone for CO2」by Nicola Jones, Nature Geoscience (Aug 2013) "in the Press"
2013年5月、ついに大気中CO2濃度が400ppmに達した。各雑誌の対応なども紹介。