Carbon Trading

Enthusiasm is spreading for cap and trade systems to regulate the amount of carbon dioxide (CO₂) emitted to Earth's atmosphere. In 1990, the U.S. Environmental Protection Agency set a limit on sulfur dioxide (SO₂) emissions from obvious point sources and allowed those who emit less than their quota to trade excess allowances. As a result, regional acid deposition was dramatically reduced. Can the world do the same for CO₂ ? Fundamental differences in the bio geochemistry of SO₂ and CO₂ suggest that establishing a comprehensive, market-based cap and trade system for CO₂ will be difficult. For SO₂, anthropocentric point sources (largely coal-fired power plants), which are relatively easy to control, dominate emissions to the atmosphere.

Natural' sources, such as volcanic emanations, are comparatively small, so reductions of the anthropocentric component can potentially have a great impact, and chemical reactions ensure a short lifetime of CO₂ in the atmosphere.CO₂ , in contrast, comes from many distributed sources, some sensitive to climate, others sensitive to human disturbance such as cutting forests. It is thus impossible to control all of the potential sources. combustion are one of the smaller components of the atmospheric flux of CO₂. which is dome• noted by exchange between forests and the oceans. During most of the past so,000 years, the uptake and loss of CO₂ from forests and the oceans must have been closely balanced, because atmospheric CO₂  showed' little variation until the start of the Industrial Revolution. CO, from coal, oil, and natural gas combustion now comics from many segments of society. including electric power generation, industry, home heating, and transportation. Unbalanced by equivalent anthropological sinks for carbon, fossil fuel emissions account for the vast majority of the rise of CO₂ in Earth's atmosphere. Caps on emissions, like those instituted for SO₂ ,will be difficult to institute if the burden of reducing CO₂  is to be borne equally by all emitters. Because land plants take up CO₂  in photo syn• thesis and store the carbon in biomass, forests and soils seem to be attractive venues to store CO₂ . Market•based schemes propose substantial payments and credits to those who achieve net carbon storage in forestry and agriculture, but these projected gains are often small and dispersed over large areas. Carbon Trading news in freshsciencenews
 We will need to net any such carbon uptake against what might have occurred without climate-policy intervention. Conversely, will Canada and Russia be billed for incremental CO₂  releases that stem from the warming of cold northern soils as a result of global warming from the use of fossil fuels worldwide? If credit is given to those who choose not to cut existing forests, the increasing total demand for forest products will shift deforestation to other areas.

Carbon Trading Over Taxes

As the United States moves inevitably toward climate legislation, discussion has shifted from the science to the policy options for slowing emissions of carbon dioxide CO₂ and other greenhouse gases. Some favor a tax on CO₂ emissions—referred to as a C tax (r). Others favor government subsidies (2). If high enough to alter consumer behavior, a carbon tax would reduce emissions by raising the effective price of carbon-intensive energy relative to carbon-free sources. Subsidies may speed development of specific, targeted low-C technologies. But a market-based system with an economy wide cap on emissions and trading of emission allowances would do the same, while having distinct advantages 0). Most important, a cap and trade system, coupled with adequate enforcement, would assure that environmental goals actually would be achieved by a certain date. Given the potential for escalating damages and the urgent need to meet specific emission targets (4), such certainty is a major advantage. A federal cap and trade system could be incorporated into existing emissions-trading frame-works and markets, such as the Kyoto Protocol's international market or sub rational ones like the Regional Greenhouse Gas Initiative. Earth's climate is agnostic about the location and type of CO₂ emissions and is sensitive only to the total burden of CO₂ It makes sense, therefore, to design a climate policy that taps all possible avenues to limit net  CO₂ emissions. Trading of emissions Science news articles across all sectors of the economy addresses this by allowing emitters to purchase carbon offsets from businesses that are able to lower their own emissions below their allocation. If trading were incorporated into an international system, U.S. firms and consumers could meet emissions targets at reduced costs by substituting less expensive cuts in, for example, developing countries, for expensive emissions cuts in the United States. Because investment would be funneled to technologies that reduce CO₂ emissions at the least ant, the overall expense of the program would be minimized. Cutting emissions of pollutants is admittedly notes  complicate crosscutting      CO₂        emissions, and transaction costs can be a factor. Nevertheless, the United States was able to reduce sulfur oxide emissions ahead of schedule and at 30% of the projected cost using a market-based cap and trade system (5). Elimination of lead from gasp. line and phaseout of ozone-depleting chemicals were also facilitated by emissions-trading programs. 

A Guide to Sequestration

Climate change concerns may soon force drastic reductions in carbon dioxide CO₂ emissions. In response to this challenge, it may prove necessary to render fossil fuels environmentally acceptable by capturing and sequestering CO₂  until other inexpensive, dean, and plentiful technologies are available. Today's fossil fuel resources exceed 5000 megatons of carbon (GT C) (I), compared with world consumption of 6 Gt C /year, assuring ample transition time. However, by 2050, the goal of stabilizing the atmospheric CO₂   con, cent ration while maintaining healthy economic growth may require "carbon-neutral" energy in excess of today's total energy consumption (2). Lowering world CO₂ emissions to 2 GT C/year 

 Estimated storage capacities and times for various sequestration methods science daily. The "fossil carbon" range includes at its upper end methane hydrates from the ocean floor. The "oxygen limit" is the amount of fossil carbon that would use up all oxygen available in air for its combustion. Carbon consumption for the zits century ranges from 600 Gt (current consumption held con-stent) to 2400 Gt. "Ocean acidic" and "ocean neutral" are the ocean's uptake capacities for carbonize acid and neutralized carbonize acid, respectively. The upper limits of capacity or lifetime for underground injection and mineral carbonates are not well constrained. 

Preparing to Capture Carbon

Carbon sequestration from large sources of fossil fuel combustion, particularly coal, is an essential component of any serious plan to avoid catastrophic impacts of human-induced climate change. Scientific and economic challenges still exist, but none are serious enough to suggest that carbon capture and storage will not work at the scale required to offset trillions of tons of carbon dioxide (COR) emissions over the next century. The challenge is whether the technology will be ready when society decides that it is time to get going. Strategies to lower CO2 emissions to mitigate climate change come in three flavors: reducing the amount of energy the world uses, either through more efficient technology or through changes in lifestyles and behaviors; expanding the use of energy sources that do not add to the atmosphere; and capturing the CO2 from places where we do use fossil fuels and then storing it in geologic repositories, a process known as carbon sequestration. A survey of energy options makes clear that none of these is a silver bullet. The world's energy system is too immense, the thirst for more and more energy around the world too deep, and our dependence on fossil fuels too strong. All three strategies are essential, but the one we are furthest from realizing is carbon sequestration. The crucial need for carbon sequestration can be explained with one word: coal. Coal produces the most CO2 per unit energy of all fossil fuels, nearly twice as much as natural gas. And unlike petroleum and natural gas, which are predicted to decline in total production well before the middle of the century, there is enough coal to last for centuries, at least at current rates of use, and that makes it cheap relative to almost every other source of energy (Table r). Today, coal and petroleum each account for roughly 40% of global CO2 emissions. But by the end of the century, coal could account for more than 80%. Even with huge improvements in efficiency and phenomenal rates of growth in nuclear, solar, wind, and biomass energy sources, the world will still rely heavily on coal, especially the five countries that hold 75% of world reserves (see (6)): the United States, Russia, China, India, and Australia (1). As a technological strategy, carbon sequestration need not apply only to coal plants; indeed, any point source of CO2 can be sequestered, including biomass combustion, which would result in negative emissions. latest tech fresh news Carbon sequestration uptake through reforestation or fertilization of marine photo plankton. But the potential to enhance bio-logical uptake of carbon pales in comparison to coal emissions, ever more so as India, China, and the United States expand their stock of coal-fired power plants. So developing and deploying the technologies to use coal without releasing CO2 to the atmosphere may well be the most critical challenge we face, at least for the next too years, until the possibility of an affordable and completely non—fossil energy system can be realized. 

Critical Assumptions in the stern

 In November 2006, the British government presented a comprehensive study on the economics of climate change , the Stem Review. It painted a dark picture for the globe: 'III we don't act, the overall costs and risks of climate change will be equivalent to losing at least 5% of global GDP [gross domestic product] each year, now and forever. If a wider range of risks and impacts is taken into account, the estimates of damage could rise to 20% of GDP or more." The Stem Review recommended urgent, immediate, and sharp reductions in greenhouse-gas emissions. These findings differ markedly from economic models that calculate least cost emissions paths to stabilize concentrations or paths that balance the costs and benefits of emissions reductions. Mainstream economic models definitely find it economically beneficial to take steps today to slow warming, but efficient policies generally involve modest rates of emissions reductions in the near term, followed by sharp reductions in the medium and long term (2-5). A standard way of showing the stringency of policies is to calculate the ''carbon tax," or penalty on carbon emissions. A recent study by the author estimates an optimal carbon tax for ions of about $30 per ton carbon in today's prices, rising to $85 by the mid-21st century and further increasing after that (5). A similar carbon price has been found in studies that estimate the least-cost path to stabilize carbon dioxide concentrations at two times protein dust rial levels (2). The sharply rising carbon tax reflects initially low, but rising, emissions reduction rates. We call this the climate-policy ramp, in which policies to slow global warming increasingly tighten or ramp up over time. A $30 carbon

 Comparing the optimal carbon tax under alternative discounting assumptions. Integrated model of clinical trials news. Climate and the Economy (DICE model) (5) integrates the economic cods and benefits of greenhouse gases (Gig) reductions with a simple dynamo representation of the scientific and economic links of output, emissions, concentrations, and clip' mate change. The DICE model is designed to choose levels of investment in tangible capital and in Gallic re:Inchon% that maximize economic welfare. It calculates the optimal carbon tax as the price of carbon emissions that will balance the incremental of abating carbon emissions with the incremental benefits of lower future damages from climate change. Using the DICE model to optimize climate policy leads to an optimal carbon tax in boos of around Ssh per ton carbon (shown here as 'DICE baseline). If we substitute the Stern Review-s assumptions about tune astounding and the consumption elasticity into the DICE model, the calculated optimal carbon tax is much higher and rises much more rapidly (shown as 'Stern assumption:). tat may- appear to he a modest target. but it is at least to times the current globally averaged carbon tar implicit in the Kyoto Protocol (shown as Stern assumptions). What in the logic of the ramp? In a world when- capital la productive and damages are far in the fun in (see chart affirm). the highest. return investments today are primarily in Ian. gable, nontechnical. and human capital. In the inning decade.. damages are predicted to rise relative to output. As that occurs. rt becomes efficient to shift investment toward more intensive emissions reductions and the IRK COM paying higher carbon taxes. The exact time  of emissions reductions depends on details of emit. damages, learning, and the extent In which climate change and damages are nonlinear and semitrailer. The Stern Review proposes to rime Ill to inn table for emissions reductions slur . forward. It suggests global emulsions reductions of between yo% and 70%  the neat two decades. °bin-Me consistent with a carbon tat of about  per ton today. or about to times the level mg. Rested by standard economic models. Green that the Stern Review embraces . traditional economic techniques such as those described in it-t). how does 0 get such differ.  results and strangles, Flaying analyzed the Stern Review in (6) 'which also contains a list of recent analyses). I find that the difference sterns ah nowt emirs-Is-from Its technique for cal. cabling disgusting rates and only marginally on new science or economics. The reasoning has questionable foundations in terms of its ethical assumptions and also leads to economic results that are inconsistent with market data. Some background on growth economics and discounting concepts I. necessary to under-stand the debate. monogramming alternative trajectories for emissions reductions. the key  variable is the real return on capital. which measures the net yield on investments in capital. education. and technology. In principle. this is observable in the marketplace. For rumple. the real pretax return on U.S. snipe rate capital over the last four decades has aver-aged about 0.07 per year. Estimated real returns on human capital range from 0.06 to > 0.20 per year, depending on the country and time period (7). The return on capital is the "discount rate" that enters into the determination of the efficient balance between the cost of emissions reductions today and the benefit of reduced climate damages in the future. A high return on capital tilts the kids science magazines balance toward emissions reductions in the future, whereas a low return tilts reductions toward the present. The Stern Review's economic analysis recommended immediate emissions reductions because its assumptions led to very low assumed real returns on capital. Where does the return on capital come from? The Stern Review and other analyses of climate economics base the analysis of real returns on the optimal economic growth theory (8, 9). In this framework, the real return on capital is an economic variable that is determined by two normative parameters. The first parameter is the time discount rate, denoted by p, which refers to the discount on future utility or wel-fare (not on future goods, like the return on capital). It measures the relative importance in societal decisions of the welfare of future generations relative to that of the current generation. A zero discount rate means that all generations into the indefinite future are treated the same; a positive discount rate means that the welfare of future generations is reduced or "discounted" compared with nearer generations. Analyses are sometimes divided between the ''descriptive approach," in which assumed discount rates should conform to actual political and economic decisions and prices, and the "prescriptive approach," where discount rates should conform to an ethical ideal, sometimes taken to be very low or even zero. Philosophers and economists have conducted vigorous debates about how to apply discount rates in areas as diverse as economic growth, climate change, energy, nuclear waste, major infrastructure programs, hurricane levees, and reparations for slavery. The Stern Review takes the prescriptive approach in the extreme, arguing that it is indefensible to make long-term decisions with a positive time discount rate. The actual time discount rate used in the Stern Review is 00.01 per year, which is vaguely justified by estimates of the probability of the extinction of the human race. 

Sea Level Rice

A semi-empirical relation is presented that connects global sea level rise Tc global mean surface temperature. It is proposed that, for time scales relevant to anthropocentric warming, the rate of sea level rise is roughly proportional to the magnitude of warming above the temperatures before the Industrial Age. This holds to good approximation for temperature and sea level changes during the both century, with a proportionality constant of 3.4 mm/year per °C. When applied to future warming scenarios of the Intergovernmental Panel on Climate Change (IPECAC), this relation-ship results in a projected sea level rise in 2100 of o.5 to 1.4 m above the 1990 level. Understanding global sea level changes is a difficult physical problem, because complex mechanisms with different time scales play a role Oh including thermal expansion of water due to the uptake and penetration of heat into the oceans, input of water into the ocean from glaciers and ice sheets, and changed water storage on land. Ice sheets have the largest potential effect, because their complete melting would result in a global sea level rise of about 70 m. Yet their dynamics are poorly understood, and the key processes that control the response of ice flow to a warming climate are not included in current ice sheet models [for example, melt water lubrication of the ice sheet bed (2) c increased ice-stream flow after the removal c buttressing ice shelves (3)]. Large uncertainties exist even in the projection of thermal expand Sion, and estimates of the total volume of ice it] mountain glaciers and ice caps that are remote from the continental ice sheets are uncertain by a factor of two (4). Finally, there are as yet NC published physically based projections of ice Los* from glaciers and ice caps fringing Green lark and Antarctica. For this reason, our capability for calculating future sea level changes in response to a given surface warming scenario with present physics based models is very limited, and models are not able to fully reproduce the sea level rise of recent decades.  climate of current events earth science and ice sheet models are generally lower than observed rates. Since 1990, observed sea level has followed the uppermost uncertainty limit of the IPECAC Third Assessment Report (Algal), which was constructed by assuming the highest emission scenario combined with the highest climate sensitivity and adding an ad hock amount of sea level rise for Mice sheet uncertainty" (1). While process-based physical models of sea level rise are not yet mature, semi-empirical

Prioritizing Climate Chance

Investments aimed at improving agricultural adaptation to climate change inevitably favor some crops and regions over others. An analysis of climate risks for crops in 12 food-Secure regions was conducted to identify adaptation priorities, based on statistical crop models and climate projections for 2030 from 20 general circulation models (Gyms). Results indicate South Asia and Southern Africa as two regions that, without sufficient adaptation measures, will likely suffer negative impacts on several crops that are important to large food-insecure human populations. We also find that uncertainties vary widely by crop, and therefore priorities will depend on the risk attitudes of investment institutions. Adaptation is a key factor that will shape the future severity of climate change impacts on food production (2). Although relatively inexpensive changes, such as shifting planting dates or switching to an existing crop variety, may moderate negative impacts, the biggest benefits will likely result from more costly measures, including the development of new crop varieties and expansion of irrigation (2). These adaptations will require substantial invest-mints by farmers, governments, scientists, and development organizations, all of whom face many other demands on their resources. Prioritization of investment needs, such as through the identification of "climate risk hot spots" Oh is therefore a critical issue but has received limited attention to date.components to science magazines for kids be essential to any prioritization approach: (i) selection of a time scale over which impacts are most relevant to investment decisions, (ii) a clear definition of criteria used for prioritization, and (iii) an ability to evaluate these criteria across a suite of crops and regions. Here, we focus on food security impacts by 2nd—a time period most relevant to large agricultural investments, which typically take 15 to 30 years to realize full returns (4, 5). We consider several different criteria for this time scale. First is the importance of the crop to a region's food-insecure human population [hunger importance (HI)]. Second is the median projected impact of climate change on a crop's production by 2030 (indicated by CO), assuming no adaptation. For this analysis, we generate multiple (i.e., IMO) projections of impacts based on different models of climate change and crop response; in order to capture relevant uncertainties. The projections are then ranked, and the average of the 5th and 51st values are used as the median. A third criterion is the fifth percentile of projected impacts by 2030 (where Com indicates the fifth value of the ranked projections), which we use to represent the lower tail, or "worst case," among the projections. Finally, we consider the 95th percentile of projected impacts by 2030 (where C indicates the 95th value of the ranked projections), which we use to represent the upper tail, or "best case," among the projections. We first identified 12 major food-insecure regions. each of which (i) comprise groups of countries with broadly similar diets and agricultural production systems and (ii) contain a notable share of the world's malnourished individuals as estimated by the Food and Agriculture Organization (MO) (Table r; see fig. Si online for details on regions). For each region, we computed the HI value for each crop by multiplying the number of malnourished individuals by the crop's percent contribution to average per-capital calorie consumption [see supporting online material (SOME) Text Si and table Si J. A hunger importance ranking (HIRE) was then generated by ranking the HI values for all crop-by-region combinations. Rice. maize, and wheat contribute roughly half of the coal-rise currently consumed by the world's poor and

Michael Oppenheimer

We disagree with Solomon eta . that our Policy Forum was misleading. We correctly noted that model-based numerical ranges for century sea level rise presented in the Working Group I (WIG) "Summary for Policymakers" (SPAM) (Table SPAM-3) did not account for the uncertainty resulting from potential increases in the rapid dynamic response of ice sheets. Solomon a AL. challenge this assertion by pointing instead to qualitative statements in the SPAM, implying that the latter provide a satisfactory accounting of uncertainty. But the distinction between numerical values highlighted in a prominent table and narrative qualifications of such numbers is critically important. Numbers are powerful, grabbing the readers' attention, whereas qualifications are often ignored. For example, the tabular values, indicating a maximum sea level rise of 59 cm during the 21st century, are cited frequently in the public discussion absent any qualification. We did not imply, as Solomon ET AL. argue, that the WEI SPAM omitted information from paleolithic studies in evaluating uncertainty in sea level rise beyond the 21st century. We suggested that it gave too much credence to ice sheet health articles models compared  For example, in reporting only a model-based estimate for the time scale of a long-term contribution (from Greenland), the WIG SPAM gives short shrift to the implications of observations of fast responses in the ice sheets in both Greenland and western Antarctica, narrative qualifications to the contrary notwithstanding. Such an approach understates the range of opinion in the relevant expert community on the potential magnitude and rate of the ice sheet contribution as indicated by studies reviewed during the Fourth Assessment Report (ARE) (i). Further perspective on this question is provided by the ARE Synthesis Report (2). Finally. contrary to Solomon ct Al.'s assertion, our suggestions for improving the treatment of uncertainty were made specifically with the shortcomings of ice sheet modeling in mind. It makes little sense to highlight model-based projections of sea level rise when models that are supposed to account for the ice sheet component have failed the test against reality. Other approaches provide important additional perspectives. For example, the fact that two independent semi-empirical analyses estimating uncertainties in future sea level rise have been published recently (3, 4) suggests that observation-based methods yield important insights where models are deficient. We do not propose that IPECAC conduct new research: Rather, we argue that it take full advantage of what has already been produced. IPECAC also has the flexibility to fill gaps in modeling and analysis where the completeness of assessment calls for it, and it has done so many times. In anticipation of a Fifth Assessment. and realizing that ice sheet models may not improve rapidly, IPECAC should encourage the development of more comprehensive approach to uncertainty. As it has done for other arenas, such as emissions scenarios or abrupt climate change, I P CC could spur research into empirical approaches, formalized expert elicitation, and comprehensive analysis of Paleocene extent and sea level, each carried out with a specific view toward informing quantitative judgments on the range of future sea level. Holding work-shops on this problem over the next few years would fit neatly into IPECAC tradition. Three of us are authors of ARE, well aware of the difficulty of assessment. A premise of our Policy Forum is that I P CC has done a superb job of establishing the scientific consensus. But in a high-stakes problem like global warming. governments need to calibrate policy to the full range of plausible outcomes, for sea level rise and for all other key uncertainties.

A Closer Look at the Ipcc Report

In the future, Arctic warming and the melting of polar glaciers will be considerable, but the magnitude of both is uncertain. We used a global climate model, a dynamic ice sheet model, and paleolithic data to evaluate Northern Hemisphere high-latitude warming and its impact on Arctic ice fields during the Last Inter glaciation. Our simulated climate matches paleolithic observations of past warming, and the combination of physically based climate and ice sheet modeling with ice core constraints indicate that the Greenland Ice Sheet (GUYS) and other circumstantial ice fields likely contributed 2.2 to 3.4 m of sea level rise during the Last Interrelation. 

Determining the sensitivity of the Arctic climate system to anomalous forcing and understanding how well climate models can simulate the future state of the Arctic are critical priorities. Over the past 3 years, Arctic surface temperatures have increased o.3°C per decade (0); September Arctic sea-ice extent has decreased 7.7% per decade (2); and the seasonal ablation area for Greenland has increased, on average, by 16% (3-3). The global climate models being used to estimate future scenarios of Arctic warmth give polar warming of o.7°C to 4.4°Ca large ranges well as a reduction of Arctic sea ice of up to 65% at the time of the doubling of atmospheric CO (6). The Last Inter glaciation (LUG, about 130,000 to 116,000 years ago) is the last time that the Arctic experienced summer temperatures markedly warmer than those in the 20th century and the late Holocene, and it also featured a significantly reduced GUYS. Climate models need to be able to current event science articles. reproduce this large. warm climate change in the Arctic if they are to lie trusted in their representation of Arctic processes and their prediction for the future. Prerecords indicate much warmer Arctic summers during the LUG. Storm beaches and ancient barrier islands with mollusks of LUG age indicate that the open water north of Alaska was more extensive and Listed seasonally longer (7) Arboreal forest communities expanded pollard by as much as boo to moo km in Russia (8). reaching the coast everywhere crept in Alaska (9) and central Canada. Total gas evidence from L ice in the Greenland Ice Core Proctor (GRIP) ice (Orr indicates that the Summit region remained ice centered. although possibly up to about Soto m lower than the we level at per', rm. at sonic tune m the LING (soy In contrast. basal ice at Dye-3 (southern Greenland); in the Agassi Demon. and Meighen ice caps in the Canadian Arctic; and possibly in Camp Century (northwest Greenland) suggest that these doll sites were Refine during the LING (so. 1). The increased presence of vegetation over southern Greenland is reconstructed from plant macro. fossils 07) and fern spores (0). Elsewhere. pol• lens. Insects. marine plankton. and other pros ices document the magnitude of LUG summer warmth across the Arctic (14). We conducted climate simulations for the LUG with a global coupled ocean-atmosphere-land sea ice general circulation model National Center for Atmospheric Research (N CAR) Community Climate System Model (COSMIC) Dem. We also used we sheet simulations with a three-dimensional. coupled kindhearted-flow model 06). which spans the entire western 

Predicting Fate Of Glaciers Proves Slippery Task

Earlier this month, the Intergovernmental Panel on Climate Change (IPECAC) declined to extrapolate the recent accelerated loss of glacial ice far into the future. Too poorly understood, the IPECAC authors said. Overly cautious, some scientists responded in very public complaints. The accelerated ice loss apparently driven by global warming--could raise sea level much faster than the IPECAC was predicting, they said. Yet almost immediately, new findings have emerged to support the Ipecac's conservative stance. In a surprise development, sociologists reported online last week in Science that two major outlet glaciers draining the Greenland Ice Sheet---Scandalmonger and Heidelberg a lively two-step in the first part of the decade. By gauging the elevation and flow speed of the glaciers using satellite data, Ian Howard of the University of Washington's Applied Physics Laboratory in Seattle and his colleagues found that Dangerous sped up abruptly in 2005, no doubt accelerating sea level rise just a bit. But then it fell back to near its earlier flow speed by the next year. .Heimlich gradually accelerated over several years, also sped up sharply in zoos, and then slowed abruptly to its original flow speed. Apparently, these glaciers were temporarily responding to the loss of some restraining ice at their lower ends, much as a river's flow would temporarily increase with the lowering of a darn. Helen Frolicker of Scrips Institution of Oceanography in San Diego. California, and her col-leagues report another sociological surprise in a paper published online today in Science. Flicker also presented the study this morning at the annual meeting of the American Association for the Advancement of Science (which publishes Science Now) in San Francisco, California. Using a new satellite-based laser technique, the team discovered an unexpectedly active network of linked lakes beneath two ice millstreams and Mercer- draining the West Antarctic Ice Sheet. Researchers knew of pools of melt water at the base of Antarctic ice, but Frolicker and her colleagues recorded the rising and falling of the surface by up to 9 m over )4 patches of ice, the largest three spanning to to 500 km. Water that could lubricate the base of the ice and perhaps accelerate its flow was seeping from one sub glacial lake to another in a matter of months, and in one case escaping to the sea. "We didn't know as much about the Antarctic Ice Sheet as we thought we did," says Frolicker. Sociologist Richard Alley of Pennsylvania State University in State College agrees. "Lots of people were saying we FCC authors] should extrapolate into the future," he says, but "we dug our heels in at the IPECAC and said we don't know enough to give an answer." Researchers will have to understand how and why glacier speeds can vary so much, he adds, before they can trust their models to forecast the fate of the ice sheets, much less sea level. 

Recent Sea Level

A her a century of polar exploration, the past decade of satellite measurements has painted an altogether new picture of how Earth's ice sheets are changing. As global temperatures have risen, so have rates of snowfall, ice melting. and glacier flow. Although the balance between these opposing processes has varied considerably on a regional scale, data show that Antarctica and Greenland are each losing mass overall. Our best estimate of their combined imbalance is about ray megatons (Ct) of ice per year. enough to raise sea level by 0.35 mm per year. lids is only a modest contribution to the present rate of sea level rise of 3.0 mm per year. However, much of the loss from Antarctica and Greenland is the result of the flow of ice to the ocean from ice streams and glaciers. which has accelerated over the past decade. In both continents, there are suspected triggers for the accelerated ice discharge surface and ocean warming, respective, over the course of the amt century, these processes could rapidly counteract the snowfall gains predicted by present coupled climate models. Antarctica and Greenland hold enough ice to raise global sea levels by some 70 m (2), and, according to the geological record (2), collapses of Earth's former ice sheets have caused in-creases of up to so m in less than 500 years. Such a rise, were it to occur today, would have tremendous societal implications (3). Even a much more gradual rise would have great impact. Accordingly, one goal of sociological survey (e.g., (4.511 is to determine the contemporary sea level contribution due to Antarctica and Greenland. For much of the moth century, however, the size of these ice sheets hindered at-tempts to constrain their mass trends, because estimating whole ice sheet mass change could be done only by combining sparse local sue. keys. with consequent uncertainty. For example. a 1992 review (6) concluded that the available sociological measurements allowed Antarctica to be anything from a Goo Ct/year sink to a Sui Gt/year source of ocean mass Boo Ct of ice equals 1.4 mm equivalent sea level (ESL)). accounting for nearly all of the both•century sea level trend of r.8 mm/year (s) or, in the other direction, leaving a mass shortfall of some moo Gather. Even the ZOOS Intergovernmental Panel on Climate Change (IPECAC) report (s) preferred models to observations in estimating Antarctic and Greenland sea level contributions. However, in the past decade, our knowledge of the contemporary mass imbalances of Antarctica and Greenland has been trans-formed by the launch of a series of satellite. based sensors. Since 1998, there have been at least 54 satellite-based estimates (7-20) of the mass imbalance of Earth's ice sheets (Table 1). At face value. their range of some -366 to 53 Gt/year, or 1.0 to -0.15 mm/year sea level rise equivalent, explains much of the ecstatic component of century sea level rise (x.5 mm/year in (as)), but we argue that the contribution is smaller and the problem of closing the century sea level budget remains. Equally, the new observations provide a picture of considerable regional variability and, in particular, the long•predicted OAT snowfall-driven growth [e.g., (so, 2.2)] is being offset by large mass losses from particular ice-stream and glacier flows (e.g.,  23)1. There is, more-over, evidence in Greenland and Antarctica of recent accelerations in these flows (12, 24, as). It is apparent that the late both and early ant-century ice sheets at least are dominated by regional behaviors that are not captured in the models on which the Intergovernmental Panel on Climate Change (IPECAC) predictions have depended, and there is renewed speculation (26, ) or accelerated scan level rise from the ice sheets under a constant rate of climate • warming. Methods and Their Sensitivity to Accumulation Rate The Massachusetts method [e.g., (9, 12)compares the mass gain due to snowfall with mass losses due to sublimation, melt water runoff, and ice that flows into the ocean. It has been given new impetus by the capability of inter thermometric synthetic aperture radar (In STAR) to determine ice surface velocity. This has improved earlier estimates of the ice flux to the ocean (5) and pm. vised a capability to identify accelerations of ice flow. The method is hampered by a lack of accuse-rate accumulation and ice thickness data. For Antarctica, where surface melting is negligible, accumulation may be determined by spatially averaging the history of accumulation recorded in ice cores, or from meteorological forecast models. Estimates of the temporally averaged accumulation or 'mean" accumulation range. respectively, from 1752 to 1924 Gt/year (t) and from 1475 to 2331 Gt/year (28). The meteorological data are acknowledged to be of inferior 

Dwindling Days For Article

If computer models are correct, by 7050, Arctic sea ice will shrink during late summer by more than twice as much as it does now. The results of a new study by researchers at the National Oceanic and Atmospheric Administration (NOAH) add weight to speculation that a northern.sea route will open up from Europe to Asia for the first time in recorded history. The Arctic ice cap remains one of the most variable features of our planet. For many millennial, the frozen areas of the Northern Hemisphere have advanced and retreated, while a similar but smaller variation occurs on a sea: tonal basis. Now. between ice ages and in the midst of an upward trend in aver. age temperatures, the Arctic Ocean's ice is showing signs of unprecedented summer shrinkage. that development could be a boon to international ship commerce but a potentially serious threat to the ecosystems that have emerged within polar environments. Furthermore, the transformation of the reflective white ice into absorbing seawater could further accelerate the warming of the planet. To carry out their study, oceanographer tames Overland of Nona's Pacific Marine Environmental Laboratory and meteorologist Mu yin Wang of the agent• cay's Joint Institute for the Study of the Atmosphere and Ocean at the University of Washington, both in Seattle, selected is climate models that closely per. dieted actual amounts of Arctic ice area (1.0,7,1979 to 1999. used they directed the computer programs to look ahead to 2050. The result, the team reports in the 8 September 7007 issue of Geophysical Research Letters, is that summer Arctic sea•ice area could shrink by more than 40% and could open waters off Alaska, Canada, and Russia that historically have remained icebound. That compares with about 18% summer shrinkage, on average, from 1979 10 1999. The models also project less ice formation during the winter in the Bering and Barents Seas and in the Sea of Okhotsk, although not in Canada's Baffin Bay. The 40% figure could be conservative, says ice scientist Walled Ablative of NASA's Goddard Space Flight Center in Greenbelt, Maryland, 'as even the best models have historically underestimated the current rate of ice decline." But one thing is clear, he says: "The dramatic losses we are seeing in Arctic ice cover are not expected to slow down." Research scientist Hamlin Chen of the University of Texas. Austin, thinks that the planet will experience a "snowball effect." Shrinking sea ice will increase the ocean's heat absorption, he says, which will in turn `further increase the melting of sea ice and contribute to global warming.". 

Perspectives on the Arctic's

Linear trends in arctic sea-ice extent over the period 1979 to 2006 are negative in every month. This ice loss is best viewed as a combination of strong natural variability in the coupled ice-ocean-atmosphere system and a growing radioactive forcing associated with rising concentrations of atmospheric greenhouse gases, the latter supported by evidence of qualitative consistency between observed trends and those simulated by climate models over the same period. Although the large scatter between individual model simulations leads to much uncertainty as to when a seasonally ice-free Arctic Ocean might be realized, this transition to a new Arctic state may be rapid once the ice thins to a more vulnerable state. Loss of the ice cover is expected to affect the Arctic's freshwater system and surface energy budget and could be manifested in middle latitudes as altered patterns of atmospheric circulation and precipitation. The most defining feature of the Arctic Ocean is its floating sea-ice cover, which has traditionally ranged from a maximum extent of about 16 x rob km in March to a mini-mum extent of 7 x 106 km 2 at the end of the summer melt season in September (Fig. r). Consistent satellite-derived monthly time series of sea-ice extent are provided by the Nimbus-7 Scanning  Multiplicand  Microwave Radiometer 

(October 1978 to August 1987) and the Defense Meteorological Satellite Program Special Sensor Microwave Image (1987 to present). Based on regression analysis of the combined record over the period 1979 to 2006, ice extent has declined for every month (Fig. 2), most rapidly for September. for which the trend is –8.6 2.9% per decade or about loo,000 km per year. Ice extent is defined as the area of the ocean with a fractional ice cover (i.e., an ice concentration) of at least 15% ft –3). Every year since atom has yielded pronounced September minims, the most extreme of which was in 2005 (5.56 X 10 G km). When compared with the mean ice extent over the period 5979 to zoo*, this represents a spatial reduction of 25% (1.6 x to km 2), an area roughly the size of Alaska (Fig. Comparisons with earlier records, which combine visible•band satellite imagery and aircraft and ship reports, suggest that the September zoos ice extent was the low-est in at least the past 50 years. Data for the past few years suggest an accelerating decline in winter sea-ice extent (4). Evidence for accompanying reductions in ice thickness (5) is inconclusive. Upward-looking sonar aboard submarines provides informs. tron on ice draft—the component of the total thickness (about 90%) that projects below the water surface. Comparisons between early Mar records (5958 to 1976) and those for 1993 to 1997 indicate reductions of I.) m in mean late summer ice draft over much of the central Arctic Ocean (6). but sparse sampling complicates interpretation. Further analysis of the 

Bright Nights Dim Survival Chances

WASHINGTON, D.C.At a conference here yesterday, researchers reported That even low levels of light from incandescent, fluorescent, or motherland• made sources can befuddle creatures that require a period of nighttime darkness. The findings add to the evidence that artificial lighting is interfering with the development, reproduction, and survival of species across the taxonomic 
All animals from one-celled critters to humans produce melanin,  a hormone that regulates cell metabolism-, protects against the formation of cancerous tumors in larger animals, and allows-many mammals and humans to enjoy restful sleep. But the hormone accumulates most efficiently in-recur-ring or total darkness. such as in regular nightclothes. When those cycles are disrupted, so is melanin production. On the behavioral side, even seeing artificial illumination such as streetlights or indoor lamps shining through windows- at night can throw off foraging and migration in many species. To find out how brighter nights are altering metabolism and reproduction, herpetologist Bryant Buchanan of Nautical College in New York and colleagues ' exposed snails and larval frogs to different levels of artificial light over periods lasting up to two months. With even the slightest amount of artificial light, the Percentage of frogs developing normally dropped as low as 10%, compared with about 40% under more natural lighting conditions. The snail experiments produced similar results. Artificial illumination appears to produce "a dose response, not an on-off switch." Buchanan says. Constant lighting at night also suppressed the frogs' normal calling behavior and kept the snails hiding under leaf litter instead of searching for food. Buchanan's findings are consistent with results for other species, says ecologist Travis Long core of The Urban Wild lands Group in Los Angeles, California. The introduction of light even light that we would consider dim will disrupt the natural cycles of animals, including humans," he says. An overlooked problem, he adds, is that outdoor lighting can hamper attempts to protect endangered wildlife living in or near urban areas. Long core says he knows of one species of snake that disappeared from an urban habitat specifically set aside for it after steady levels of artificial light apparently disrupted its depredation patterns, by exposing it either to its prey or to its own predators. "If we don't take [lighting effects) into account." he says. our best-laid conservation plans will not succeed." 

Rapaid Advance Of Spring Arrival Dates in Long

Several bird species have advanced the timing of their spring migration in response to recent climate change. European short-distance migrants, wintering in temperate areas, have been assumed to be more affected by change in the European decimate than long-distance mi-grants wintering in the tropics. However, we show that long-distance migrants have advanced their spring arrival in Scandinavia more than short-distance migrants. By analyzing a long-term data set from southern Italy, we show that long distance migrants also pass through the Mediterranean region earlier. We argue that this may reflect a discriminate evolutionary change in the timing of spring migration. Many biological processes are affected by climate, and in temperate areas, the increasing spring temperature over the past so to 30 years has caused an advancement of phonological events in plants and invertebrates (1, 2). The earlier onset of spring has consequences for the timing of breeding in birds, which has evolved to match peak food availability (3, 4). We may therefore expect the timing of breeding to track any temporal shift in food availability caused by a trend in spring temperature (5). Most pas serine birds (which constitute more than half of all 

bird species) breeding in temperate areas of the Northern Hemisphere are seasonal migrants, and the timing of migration ultimately con-strains when breeding can start (6, 7). Short-distance migrants, spending the winter dose to the breeding grounds, may be able to adjust the timing of migration in response to local climate change, which will be correlated to the conditions on the breeding grounds. In tropical-wintering long-distance migrants, the timing of migration is under endogenous control (8, 9), and the cues needed to trigger the onset of migration are unlikely to be linked to the climate on their breeding grounds. Therefore, it has been assumed that short-distance migrants are more likely than long-distance migrants to vary migration timing in response to climate change (10). Here we show that such an assumption is not empirically justified. We estimated trends in arrival time for the early, middle, and late phases of migration (that is, the species- and site-specific loath, loath, and Both percentiles of the spring arrival distribution) in short- and long-distance pas serine migrants, based on long-term banding and observational data (from 1980 to 2004) from four bird observatories in Scandinavia and a site in southern Italy (RR). We also investigated whether year-to-year variation in arrival time can be explained by short-term climate variability as measured by the North Atlantic Oscillation (NANO) (re). As explanatory variables, we used the calendar year (TIME) and the deviations from linear regression of the winter NANO index on year (MAO) [the trend in NANO was weakly negative over this time period (n)]. Spring migration might advance for two distinct reasons. First, there can be a micro evolutionary (genetic) response to the selection pressures for earlier breeding. Second, the migrants can show a photogenically plastic response to trends in weather or climatic patterns on the wintering ground and/or along the migration route, whereby if spring arrives early on the wintering grounds, spring migration will also start early. Thus, a response to TIME may reflect either micro evolutionary change or phenotype plasticity, whereas a response to DNA indicates exclusively phenotype plasticity in the migratory behavior. Long-distance migrants have advanced their arrival in northern Europe in all phases of migration (see tables Si to Se online and Fig. a). The advancement in long-distance migrants is strongest in the early phase of migration, and there is limited variation between species. Furthermore, the analysis of the data set from Italy (from the island of Capri) showed that long-distance migrants wintering south of the Sahara are actually arriving in southern Europe progressively earlier. In fact, all of the nine species analyzed show a trend for earlier spring arrival at Capri in most phases of migration (see table 4 online and Fig. a). The long term trend on Capri is at least as strong as that observed in Scandinavia. In short-distance migrants, 

The Feedback Effect

In "Penputires on the .trues Sharkskin Sat-Ice Cone," Mark Sneeze. Mink, InJuhenn. CometImes the Untrenory of (nloradn and the National Center Am Atinmplices Rowellboth in Boulderhate mammal the trends to Anew senke num since tn. Windt of this work has teen bawd on satellite mugn and deemed nurowan data The data showMet anew kc Cutts is any prep mouth hat elochned m the Toned t929ownwpb the decrease egret rally model (is, September. the month in winds (he ice cover h types ally minimal. For that o ash. the act Ion betoken men and 0th amounted to an area the ore of A Mankind the 2005 Se men feat the Invent is so nun, according to ukase DNA and a sine circumflex rep mu lee lam II row only affected Inc Meal innate warming it is also influenced by ocean ...cm. an mean•atmospherics coupling the may miry from year to year. i >ewe< these Moon. the articulation of enthrallment gum plan a wry or it is mint role. and the model. used In the !ICC did seasonably well at die obey( the changes this had occurred during the townee penal What doer this tell us about dissemble futures? An especially important skeet tithe low Cd Arctic ice a who n called the see -stem feedback cycle An re outface reflects a IMO all Impinging airman. whereof the dark rulers« Me +en the ice melts alienation light. Including the longwerelength iodation char warms the mime Lyre "I Me wall. in nun. delay further ire formation n closet approache and will smack to thinnerirc  in the follovring wank Thin the diem of global winning at high Latitude, exert. an additional inflames on the divine lulante Interest in high - Inuude to Is 904 fellrlf led to what kens en the sea surface. Antarctica and (Cantina are covered wick inamive cc l.20. YAM I) haft amused attrition because cri them potential truculence on global WON Levitt which would me 11 about 70 ti 11 111 their ice were to met The tram of a Lake Oat Kr TV delineated by the amount of mow added by superstate. Iamb may be expected to rue at gleul warming takes place 11.is input ef new ice if balanced by low through mauves. which will alsoilOat•SC 10 rate at the teannuute a infututei It chew two are in oquilibnem. the ice cap or glacier is and to be in nuts balance klenutentents tithe Chetah/0 Ice Cap tend to thou a low but pm atiallifl foe Antarctica have rem different *amen to the question of whether that Ile cap if lining to gaining nun_ Andrew Shepherd and 'human Wingham. espeets Mon two Centre. for Polk Obke anion and Modelling, repot( what has mote km-tidy been learned from satellite-based measurement, of tlw mass imbalance in Antarctica and the Gtemland he Cop Some of thew are coon ;on tithe granuttinal 'Mattoon of the ke rheas. other, Me altimeter cc inectlemenetry mean renentt that can be used to tokabte man The methods do on abort. ..gee fey The aulhon ate ate autlxlen able to reach tonic fOnek072112 tic (001ribLe101% of Laws to mop balance to global wa Iffel rur lbw WTI CPU7 to be rather mutt nrcounring Ss cede • little more Men nat-senth of de observed annual sea loci gam of to min per year lhat it a very una II coate-wenn compared with neumus cermet

Impacts on Living Things

Among the biological consequences of global warming that might be expected are those that depend on climate cues that a variety of organisms take from annual temperature cycles. The flowering times of plants, the arrival times of migrating birds, and collateral events are collectively called phenomenological effects. In zoos, Jon zen ET at —an international group led from Sweden but including representation from Italy and other Scandinavian countries—published a Science Report examining what has happened to the arrival times in Europe of birds char migrate over various distances. Making use of sites in Scandinavia and one located in southern Italy, the authors compared arrival times of short-distance migrants (those whose migrations begin from points close to the breeding grounds) with those of long-distance migrants whose trips begin in Southern Africa. One theory predicted that short-distance migrants would be most affected by global warming; the rationale is that because the climate signals where they begin their migration closely resemble those on the breeding grounds, birds might advance their departure on that basis. But the data showed that long-distance migrants advanced their arrival times more—especially in the early phases of the migration. Different hypotheses might explain the effect: either these migrants accelerated their speed during the northward trip, or they left earlier. or both. The evidence suggested that the effects are not due to changes in forage availability on the wintering grounds, which might have triggered an earlier departure. Instead, it seems more probable that rapid evolutionary change, brought about during the period in which global warming was changing the signal, was responsible. Many animals exhibit strong temperature optima and exhibit preferences dependent on them. For stationary species, global warming would be expected to initiate policewoman or up-slope changes in distribution. For migrants, the situation is more complex. Changes in the distribution of prey species or food plants could take place both on the wintering ground and in the breeding locale. Either could result in evolutionary changes in behavior that would be reflected in altered migratory patterns. Perhaps the most dramatic indicators of the influence of global climate change on animal species are the sad pictures of polar bean, apparently trapped on ice floes floating in the Arctic Ocean. Climate models have consistency shown that the effects of rising average global temperatures will be more severe at high latitudes, and popular recent accounts have suggested that the "Northwest Passage," once a fiction, may become open to shipping

Fire, Drought, and Flood

This last connection is explored in the next Ste ti OD, in which a group investigation-ton associated with the Scrips Institution of Oceanography, the Laboratory of Tree :Ring Research at the University of Arizona. the University of California, and the U.S. Geological Survey have sought to analyze the history of wildfires in the western United States. In an analysis of fire history, their Research Article published in &tut in 2°06 shows an abrupt (fourfold) increase in wildfire frequency during the outpost. Associated with glossolalia warming, higher springtime temperatures in the Rocky Mountains begin earlier than (omit*, and of cone snowmen is accelerated. The result is drier forests and a fire season that begins much earlier and lasts longer. The increase in early snowmen has been associated not only with an increased fire frequency, but also with increases in the area burned. The focus on snow and snowmen naturally calls to mind the question of how much effect global warming may have on the amount of precipitation and on its timing--and the importance of these changes for human residents. Higher average temperatures not only influence the melting times of mountain snowfall. They also strongly influence the water content of the snow pack that accumulates during the winter. This is a critically important issue, since melting snow packs supply water for irrigation, industrial use, and human consumption on dependent flat lands. Thus, for example, residents of causal California and the Central Valley can anxious glances toward die High Sierra hoping for a good snow pack and listen eagerly to the regular forecasts of its water content. Of course, precipitation is not all in the form of snow. Rainfall and its distribution is critical to human life: an excess produces floods and landslides, whereas an insufficiency may result in droughts. Went, Tricia dully, Hill burn, and Mars analyzed the question "How Much More Rain Will Global Warming Bring?" in a Zukor Selma Report. It is known that evaporation of water from the ocean surface increases as the avenge temperature increases, which in turn should make precipitation events more frequent and severe, at lean in certain regions. But various models predict that rainfall would increase far more slowly than the data on evaporation rates would suggest. So Went Te at compared results from different models and looked at historical data on the increase in global rainfall to sec whether the models used to "Lind cast" the observed changes in precipitation did so accurately. The empirical observations actually showed that the increase in rainfall—over a time period that included two Fl Inflow events—matched the increase in evaporation much more closely than the models had predicted. The result clearly suggests that as global warming continues, we can expect the kinds of rainfall events that have already been experienced as hazardous landslides and local flooding in some pans of the world—and droughts in other places.

Introductiom

The Bio fuels Conundrum debates about climate change have centered on a significant dimension: the steady increase, notably over the past too years, in the average temperature of the globe. Global warming has thus come to dominate the policy discussions that now surround the relationship between climate and energy. This issue has both a future and a past. The planet is already warmer on average by about 0.7°C. But much of the debate about future climate policy focuses on the challenge of predicting what will happen in the next Zs, so, or too years. That will be the subject of the next section of this book, but it is important to note here that much of the discussion about whether "global warming is real" concerns scientific disagreements about the general circulation models (Gums) that are used in making predictions and their capacity for producing accurate forecasts. The authors of this book believe that the weight of the evidence favors the conclusions summarized in the most recent reports of the Intergovernmental Panel on Climate Change (IPECAC). These project, first of all, that by mid-century, average global temperatures will have increased by between 2.5°C and 7.0°C, and sea level will have risen between about 20 and 70 cm. A combination of model prediction and the continuation of human activity in releasing carbon dioxide into the atmospherethrough the combustion of fossil fuels or the burning of forests—leads to those conclusions. There is some scientific disagreement here. It is believed by many scientists that the IPECAC consensus underestimates the extent of sea level rise. An important issue here is whether the warming of Earth's climate will continue in a steady, ramp-like increase in average temperature, or whether the temperature change might pass the threshold of a dynamic, nonlinear process that could alter the climate dramatically. Were the major ice sheets in the Antarctic and Greenland to experience sudden increases in the rate of melting, that could lead to much larger increases in sea level, which could change the dynamics of ocean circulation especially in the North Atlantic and produce much colder temperatures in Europe. The changes we have already observed, however, provide fewer sources for argument. Current models support that global warming will result in an increase of extreme weather events.

Science in the News

On paper, making bio fuels from switch grass and other perennials that need not be replanted seems like a brainpower. Use the Sun's energy to grow the crop, and then convert it to liquid fuels to power our cars without the need for gasoline. But so far, experiments with these "cellulose" crop-based fuels have only been conducted on small scales, leaving open the question of how lea sable the strategy is. Now, the first large-scale study shows that switch grass yields more than five times the energy needed to grow, harvest, and transport the grass and convert it to ethanol. The results could propel efforts to sow millions of hectares of marginal farmland with bio fuel crops. Previous studies on switch grass plots suggested that ethanol made from the plant would yield anywhere from 343% to 700% of the energy put into growing the crop and processing it into bio fuel. But these studies were based on lab-scale plots of about 5 square meters. So 6 years ago, Kenneth Vowel, a geneticist with the U.S. Department of Agriculture in Lincoln, Nebraska, and colleagues set out to enlist farmers for a much larger evaluation. Farmers planted switch grass on Io farms, each of which was between 3 and 9 ha. They then tracked the inputs they used diesel for farm equipment and transporting the harvested grasses. for examples well as the amount of grass they raised over a 5-year period. After crunching the numbers, Vowel and his colleagues found that ethanol produced from switch grass yields 540% of the energy used to grow, harvest, and process it into ethanol. Equally important, the researchers found that the switch grass is carbon-neutral, as it absorbs essentially the same amount of greenhouse gases while it's growing as it emits when burned as fuel. A final significant finding. Vowel says, is that yields on farms using fertilizer and other inputs, such as herbicides and diesel fuel for farm machinery, were as much as six times higher than yields on farms that used little or no fertilizer, herbicides, or other inputs to grow a mixture of native prairie grasses. That result contrasts sharply with a controversial study published just over a year ago in Science that suggested that a mixture of prairie grasses farmed with little fertilizer or other inputs would produce a higher net energy yield than ethanol produced from corn (Science, 8 December zoom, p. 1598). Instead, the current study published online in Proceedings of the Notional Academy of Sciences shows that switch grass farmed using conventional agricultural practices on less-than-prime cropland yields only slightly less ethanol per hectare on overage that corn. "The bottom line is that low-input systems are not economically viable;' Vowel says. "This is a really important paper," says Christopher Servile. who directs the Energy Bio sciences Institute at the University of California, Berkeley The impressive  science news articles from this week.  yield numbers, he adds, will likely serve as a baseline for future studies, because agricultural scientists are making rapid strides at creating new, higher-yielding switch grass strains.

Carbon-Negative Biofuels from Low-Input High-Diversity Grassland Biomass

B fuels derived from low-input high-diversity (LIND) mixtures of native grassland perennials can provide more usable energy, greater greenhouse gas reductions, and less hemispherical pollution per hectare than can corn grain ethanol or soy-bean bio diesel. High-diversity grasslands had increasingly higher bio energy yields that were 238% greater than mono culture yields after a decade. 1.I H D bio fuels are carbon-negative because net ecosystem carbon dioxide (CO) sequestration (44 mega-gram (Mg) per hectare (ha) per year of CO 2 in soil and roots) exceeds fossil CO 2 release during bio fuel production (0.32 Mg/ha per year). Moreover, LIND bio fuels can be produced on agriculturally degraded lands and thus need to neither displace food production nor cause loss of biodiversity via habitat destruction. Globally escalating demands for both food (I) and energy (a) have raised concerns about the potential for food-based bio fuels to be sustain-able, abundant, and environmentally beneficial energy sources. Current bio fuel production competes for fertile land with food production, increases pollution from fertilizers and piste ides and threatens biodiversity when natural lands are converted to bio fuel production. The two major classes of biomass for bio fuel production recognized to date are mono culture crops grown on fertile soils (such as corn, soybeans, oil seed rape, switch grass, sugarcane, willow, and hybrid poplar) (3-6) and waste biomass (such as straw, corn stove, and waste wood) (7-9). Here, we show the potential for a third major source of bio fuel biomass: high-diversity mixtures of plants grown with low inputs on agriculturally degraded land, to address such concerns.

The Biofuels Conundrum

This story begins with good news, followed by a problem. Many governments around the world, and even some states within the United States, are finding ways to reduce greenhouse gas emissions. A major step is the almost completed buyout of the giant Texas electric utility nu by an improbable concatenation of big investors, environmental organizations, and bankers. This promising deal would kill 8 of it projected coal-fired power plants and require the others to meet environmental performance standards. That's like a 5th seed making the Final Four or Waterford winning the FA Cup. Meanwhile, there is hopeful talk in Silicon Valley about "dean tech," and "mobilizes" is the new entrepreneurial mantra there. But the problem is that limiting
carbon emissions with bio fuels like ethanol is complex terrain, and most proposals turn out to carry external costs. Let's start with the explosive growth of a corn ethanol industry in the tall grass prairies of America's West. This boon for those rural economies succeeds a long history of dual-purpose farm legislation, in which production objectives are mixed with rural welfare goals. Refineries now number well over zoo, with more being added rapidly, as farmers expand cultivation into lands formerly set aside for conservation and drop soybeans to make room for corn. Even if corn could yield 3o% of the equivalent energy of gasoline (the goal set by the Secretary of Energy), that would create a whole array of collateral distortions.

 Another would be distortion of the price structure of an important grain commodity that is traded in world markets and used in livestock production. Will that make maize or meat more affordable to poor countries that must import it, or to the poor people who need to buy it? Not likely. Ethanol derived from sugarcane is better: Growing the plant is energetically less costly. and extraction and fermentation are more eff• sent.That's what must have interested President Bush during his "Chavez shadow tour• of South America in March. Of course, U.S. companies would love to import this valuable product. which now accounts for a quarter of the ground transportation fuel in Brazil. Despite such hopes, some senators supporting alcohol-from. corn have helped lay a heavy U.S. protective tariff on Brazilian alcohol derived from sugar. If we got rid of that, it would reduce total carbon emissions, though only if Brazil could expand its production substantially. Is there some deal in progress? Alas, nothing's up. Sugar alcohol is better than corn alcohol, but palm oil is even better in your tank (though not in your martini). Its relatively high energy efficiency per unit volume makes it a good No-diesel fuel. Trucks can run entirely on palm oil, although it is usually mixed with conventional fossil fuels. A large-scale effort is under way to convert lands in Indonesia to palm oil plantation agriculture, with plans to double current production in a few years. But again, the effort has a downside. Not only will the needed rain-forest destruction (by burning) partly cancel any energy advantage supplied by the palm oil. but the conversion will also threaten orangutans and other endangered species. The best course is to abandon this cluttered arena and invest seriously in a direct approach. As Chris Servile pointed out in this space (r), the conversion of cellulose biomass (corn stove, wood chips) has a far higher potential for fuel production than any of the above bio fuels. The challenge is biochemical: plant lining occlude the cellulose cell walls, so they must be removed, and then the entomology of cellulose conversion needs to be worked nut. The technology is complex (2). No commercial reactor has yet been built, though six are funded. Some hope has been raised by new commitments, like the $500 million joint project between British Petroleum and the Universities of California and Illinois. Nevertheless, as Servile notes, the sobering reality is that what the U.S. government spends on all of plant physiology is only on•hundredth of the research budget of the National Institutes of Health. That's far too little for a venture this important.

The Billion-Ton Biofuels Vision

Earth receives approximately 4000 times more energy from the Sun each year than humans are projected to use in 2nd. Some of that energy can be captured through a variety of "renewable" sources, but the only form of solar energy harvesting that can contribute substantially to transportation fuel needs at costs competitive with fossil fuel is that captured by photosynthesis and stored in bio-mass. Brazil now obtains a quarter of its ground transportation fuel from ethanol produced by the fermentation of sugarcane sugar, and in the United States, approximately 90 corn grain-to-ethanol refineries produce about 4.5 billion gal of ethanol annually. The U.S. Energy Policy Act of 2005 would increase that production to 7.5 billion gal by 2012, but the United States
currently uses about hp billion gal of  transportation fuel per year. To replace 30% that amount with ethanol of equivalent °nose content, as proposed recently by the Secretory of Energy, will require about 60 billion gal < ethanol. A recent analysis 110 concluded that the United States could produce about LI billion Dr tons of biomass each year in addition to presets agricultural and forestry• production. Because i is theoretically possible to obtain about too gal o ethanol from a ton of cellulose biomass (such a. corn strove, the stalks remaining after corn ha: been harvested), the United States could sustain ably produce about t 30 billion gal of fuel ethanol from biomass. In addition to a positive effect on the release of greenhouse gases, a biofeedback program on this scale would have substantial economic and strategic advantages. The creation of a new industry 5th grade science on that scale will require much basic and applied work on methods for converting plant nitrocellulose Tc fuels. because several significant problems must become to make the process ready for large. scale use. For example, cellulose is a recalcitrant substrate for bio conversion, and unacceptably large amounts of enzymes are required to produce sugar. Lining occludes Saccharomyces and inhibits enzymatic hydrolysis of these car. carbohydrates: energetically expensive and corrosive chemical presentments axed required for its removal. The yeast currently used in large•scale ethanol production cannot efficiently ferment sugars other than glucose. And relatively low concentrations of ethanol kill microorganisms. requiring an expensive separation of the product from large volumes of yeast growth medium. These and other technical issues associated with this emerging industry have potential soul•trons, and many incremental advances can be envisioned. However, substantial public and private investment will be needed to meet the nation's goals. For instance. competitive funding for basic research in plant biology by all federal agencies totals only about r% of the National

Ethanol for a Sustainable Energy Future

Renewable energy is one of the most efficient ways to achieve sustainable development. Increasing its share in the world matrix will help prolong the existence of fossil fuel reserves, address the threats posed by climate change, and enable better security of the energy supply on a global scale. Most of the "new renewable energy sources" are still under-going large-scale commercial development, but some technologies are already well established. These include Brazilian sugarcane ethanol, which, after 3o years of production, is a global energy commodity that is fully competitive with motor gasoline and appropriate for replication in many countries.
A sustainable energy future depends on an increased share of renewable energy, especially in developing countries. One of the best ways to achieve such a goal is by replicating the large Brazilian program of sugarcane ethanol, started in the 19705. The World Commission on Environment and Development in 1987 defined "sustainable development" as development that '`meets the needs of the present without compromising the ability of future generations to meet their own needs" (1). The elusiveness of such a definition has led to unending discussions among social scientists regarding the meaning of "future generations." However, in the case of energy, exhaustible fossil fuels represent about 8o% of the total world energy supply. At constant production and consumption, the presently known reserves of oil will last about 4x years, natural gas 64 years, and coal 155 years (2). Although very simplified, such an analysis illustrates why fossil fuels can-not be considered as the world's main source of energy for more than one or two generations.
Besides the issue of depletion, use of fossil fuels presents serious environmental problems, particularly global warming. Also, their production costs will increase as reserves approach exhaustion and as more expensive technologies are used to explore and extract less attractive resources. Finally, there are increasing concerns for the security of the oil supply, originating mainly from politically unstable regions of the world. Except for nuclear energy, the most likely alternatives to fossil fuels are renewable sources such as hydroelectric, biomass, wind, solar, geothermal, and marine tidal energy. Figure shows the present world energy use.

KEY TERM

Achieving its stated objective of being a refer-ence point for future EU activities in this area. Since my appointment as European Science and Research Commissioner in November 2004, I have insisted on the importance of sci-ence and research as the key to solving many of the challenges that we face. I can think of no bet-ter illustration of this approach than the issue of energy. Here, we have various requirements in front of us: finding secure and sustainable sources of energy that support our economic growth and competitiveness without damag-ing our environment. The answer to reconcil-ing these requirements lies in knowing more and being better. We have a chance to work together to develop solutions to the problems of climate change and energy supply that not only ensure our future economic development, but give European scientists and companies the opportunity to be (or remain) at the cutting edge of technological development. It is crucially important that we take this opportunity and make it work.Fusion energy is generated by nuclear fusion reactions, in which two light atomic nuclei (isotopes of hydrogen) fuse together to form a heavier nucleus (helium) and, in doing so, release large amounts of energy. Fusion is the fundamental energy source of the universe and is the process that powers the Sun and the stars.
Smart grids and smart energy networks are electrical transmission networks that use advanced sensing, communication, and control technologies to distribute electricity more efficiently and economically than traditional electrical grids.

Science in the News

Koonin says he spent his first year and a half in the job learning about energy, a process that changed his views. "I was more skeptical about climate change a few years ago. Now I've come round more toward the IPCC view." (The Intergovernmental Panel on Climate Change has concluded that temperatures are rising in part as a result of human activity.) Like most energy pundits, he sees no silver bullet that will save the planet from climate change, but some ammo has a bigger caliber than others." He advocates large-scale efforts in carbon sequestration at fossil fuel -burning plants, as well as a new generation of nuclear power stations. And he says it would be "irresponsible" not to investigate other ways to deal with global warming, such as geoengineering. increasing Earth's reflectivity by pumping material into the upper atmosphere. One area claiming much of his attention is biofuels. Current biofuel efforts, he argues, are strapped onto agricultural food production and are "not optimal." Koonin wants to galvanize geneticists, biotechnologsts, agricultural scientists, engineers, and others to "do biofuels right." BP has put up  million over to years to create an Energy Biosciences Institute (EBI). This initiative has won plaudits. "Koni thought hard about how to structure the EBI, and it will have a lot of impact;' says carbon sequestration expert Robert Soclw of Princeton University. "BP has made a commitment to go big in energy bio sciences. I doubt this would have happened without Steve "Koonin" says Ernest Moniz Professor of Physics at MIT. Koonin is pleased with the buzz the Ebi has caused. "Plant geneticists are talking to chemists and engineers.... Researchers are coming alive to the challenge.

European level through the creation of European technology platforms (8). Several exist in the energy field, including for hydrogen and fuel cells. photvoltaic, zero-emission fossil fuel power plants, and smart grids. Nonetheless, we have seen investment in energy research being reduced in national budgets over the past  years or so. And the research that is carried out is more often than not done in a fragmented, uncoordinated way, leading to duplication in some areas and to other important aspects being underfunded or ignored. This is the risan of the Strategic Energy Technology Plan, which will, once agreed on, provide a basis for all energy technology efforts in Europe, over-coming the lack of coherence that has unfortunately been present to a greater or lesser extent in the research programs at the national and European levels up to now. During the first half of zoo7, the European Commission will consult intensively with all those who have a role to play in such a strategic plan. On the basis of these consultations, a text will be drawn up toward the middle of the year, upon

Renewable Engery sources and the Realities of setting an energy Agenda

• Energy is undoubtedly moving up the political agenda as an issue that needs to be addressed urgently. If last year's threats to European gas supplies during the dis-pute between Russia and Ukraine did not show the immediacy of the challenges such as energy supply, then the report toward the end of last year by Sir Nicholas Stern (i) on the econom-ics of climate change must surely have rung a warning bell. The European Commission has been devot-ing considerable attention to energy issues for some time now. We were leaders in the process that brought about the Kyoto Protocol and have developed the first large-scale emissions trad-ing scheme in the world.