Scripps' climate researchers: How Global Warming May Affect U.S. Beaches, Coastline

How Global Warming May Affect U.S. Beaches, Coastline

The Louisiana coastline could feel the impacts of hurricanes, even those that don't make landfall. (Credit: Image courtesy of Global Warming Art)

ScienceDaily (Nov. 24, 2008) — In “Dover Beach,” the 19th Century poet Matthew Arnold describes waves that “begin, and cease, and then again begin…and bring
the eternal note of sadness in.”

But in the warming world of the 21st Century, waves could be riding oceans that will rise anywhere from 0.5 meters (19 inches) to 1.4 meters (55 inches), and researchers believe there’s a good chance they will stir stronger feelings than melancholia.

Several scientists from Scripps Institution of Oceanography at UC San Diego are finding that sea level rise will have different consequences in different places but that they will be profound on virtually all coastlines. Land in some areas of the Atlantic and Gulf coasts of the United States will simply be underwater.

On the West Coast, with its different topography and different climate regimes, problems will likely play out differently. The scientists’ most recent conclusions, even when conservative scenarios are involved, suggest that coastal development, popular beaches, vital estuaries, and even California’s supply of fresh water could be severely impacted by a combination of natural and human-made forces.

Scripps climate scientists often consider changes in average conditions over many years but, in this case, it’s the extremes that have them worried. A global sea level rise that makes gentle summer surf lap at a beachgoer’s knees rather than his or her ankles is one thing. But when coupled with energetic winter El Niño-fueled storms and high tides, elevated water levels would have dramatic consequences.

The result could transform the appearance of the beaches at the heart of California’s allure.

“As sea level goes up, some beaches are going to shrink,” said Scripps oceanographer Peter Bromirski. “Some will probably disappear.”

Sea level has been trending upward for millennia. For the last 6,000 years, it is estimated that global sea levels have rising an average of five centimeters (2 inches) per century. Before that, between 18,000 and 6,000 years ago, the seas rose a full 120 meters (400 feet). Step by step, they bit into rocky coastlines like California’s by smashing cliffs, creating beaches with the debris, rising a bit more, and repeating the process over and over again.

Humans are speeding up the pace of that assault. The United Nations-sponsored Intergovernmental Panel on Climate Change (IPCC) reported that sea level rose, on average, 1.7 millimeters (0.07 inches) per year over the entire 20th Century. But recent estimates from satellite observations find a marked increase, at 3.1 millimeters (0.12 inches) per year since 1993.

The oceans are rising because the warming ocean water increases in volume and because water is being added from melting glaciers and land-based ice sheets. The complex difficult-to-predict contribution of the latter is such a matter of controversy that the recent IPCC Fourth Assessment report didn’t factor glacial melt into its sea level rise estimates. Today there is quite broad-based opinion that the IPCC estimates are considerably lower than the higher range of possible sea level rise. Some individuals, pointing to the quantity of water frozen in Greenland and Antarctica and to ancient sea level evidence, have suggested that sea level rise could reach several meters by the end of the 21st Century. However, an August paper in the journal Science co-authored by former Scripps postdoctoral researcher Shad O’Neel suggests that some of the more exaggerated claims that water could rise upwards of 10 meters (33 feet) by century’s end are not in the realm of possibility. O’Neel and co-authors indicate that the realities of physics impose a cap of 2 meters (6.6 feet) for possible sea level rise by 2100.

“That’s fine,” said Scripps climate researcher Dan Cayan, who is leading an analysis of climate change scenarios for the state of California, “but two meters is still enough to do a lot of damage.”

Recent news footage of overtopped levees makes it easy to envision what two meters’ difference means to low-lying cities like New Orleans, especially when extreme events like hurricanes are factored in. Any flooding would be proportionately higher than it is now. Additionally Bromirski recently showed that sea level rise will amplify the power and frequency of hurricane-generated waves that reach shore, even if the storms themselves don’t make landfall.

In contrast to the beaches of the East Coast, many of which are covered with vast expanses of sand, California’s coastline is predominantly bedrock covered by a relatively thin veneer of sand. That sand can shift or disappear during storms. Thus, preserving the precious supply that keeps the tourists coming has for decades been a priority for state officials. Resource management, however, has required them to make trade-offs. They have constructed seawalls to protect houses built on ocean cliffs. They have dammed rivers to create supplies of water for drinking and to prevent floods and debris from damaging downstream developments.

In so doing, nature’s two primary sources of beach replenishment have been muted in a process known as passive erosion. Managers have compensated through artificial beach replenishment projects but at a costs that approach $10 per cubic yard. Since usually millions of cubic yards of sand need to be moved, there are monetary limits to what they can reasonably accomplish.

Reinhard Flick, who received his doctorate in oceanography from Scripps in 1978, needs only to look out his office window to watch the losing battle of beaches unfold. During his student days, he used to play volleyball on stretches of sand that are now underwater except during low tide. Rocks buried under several feet of sand four decades ago are now exposed for large parts of the year.

The staff oceanographer for the California Department of Boating and Waterways, Flick said that seawalls causing passive erosion will likely combine with sea level rise to doom some Southern California beaches. The change will become most apparent during El Niño events, when a pool of warm Pacific Ocean water settles off the coast for a year or two. El Niño has a dual effect on the West Coast. It not only feeds more intense storms but the warm ocean water itself causes a temporary spike in sea level that is above and beyond the rise that climate change is causing. During the 1997-98 El Niño, for instance, tide gauges off San Francisco recorded that sea level was 20 centimeters (8 inches) above normal for more than a year, including the winter storm season. That temporary rise is about equal to the rise observed for the entire 20th Century.

If sea levels rise substantially, when a large storm coincides with a high tide during an El Niño event, there could be widespread inundation along the California coast. Effects could range from a submersion of areas of San Diego’s Mission Beach to an inundation of the Sacramento-San Joaquin Delta. There, an overtopping of the delta’s levees by brackish water could paralyze the main component of the state’s water delivery system. Cayan noted that repairs to the system could take months.

The threat resonates with state officials, who have tasked Scripps and other institutions with creating and updating sea level rise scenarios.

“There’s no clear path forward with sea level rise,” said Tony Brunello, deputy secretary for climate change and energy at the California Resources Agency, a key Scripps partner in developing the state’s response to manifestations of global warming. “You typically want to work with one number (but) what we want people to do is work with the whole range of estimates.”

Cayan and other Scripps researchers who are collaborating to study sea level rise emphasize that there remains a great deal of uncertainty in the creation of estimates for the coming century. The range of rise estimated by Cayan is based on scenarios of global air temperatures over the next 100 years, which range from about 2° C (3.6° F) to about 6° C (10° F). By 2100, global sea level rise reaching a half-meter seems likely, and if the higher rates of potential warming occur it could rise by more than one meter. The potential cost of any government project or policy change puts a high premium on narrowing this range. As O’Neel and his co-authors observed in their paper, the cost of raising Central Valley levees only 15 centimeters (6 inches) to prepare for higher sea levels has been estimated at more than $1 billion.

“These are very broad-brush preliminary kinds of studies right now, but you have to start somewhere,” said Scripps coastal oceanographer Bob Guza.

Flick said it will be essential for scientists to be able to study the effects of the next El Niño so they can begin to understand not just where damage will happen on the California coast but to what extent. He only had surveyor’s equipment and aerial photos available to him to measure beach changes after the 1982-83 El Niño, but Guza and his collaborators now have light detection and ranging (LIDAR) and GPS technologies to make precise surveys of beach and cliff damage. Guza and Flick hope that Scripps can not only enhance its use of such technology but to deploy it within hours of a major storm event.

“We need to be geared up to quantify what beach changes are,” said Flick. “We have to do an even better job of studying wave forces and wave climate.”

If there’s any good news for Southern California, Scripps climate scientist Nick Graham has estimated that ocean warming trends will drive storm tracks farther north, perhaps sparing the state’s lower half from the full brunt of buffeting El Niño waves the 21st Century will generate. Graham compared winds produced in three different simulations of climate change with those generated in the late 20th Century. The models showed that Southern California can expect a moderate decrease in wave size of about 0.25 meters (10 inches). But even there, Graham sees a problem.

“I’m a surfer. I think that’s horrible,” he said.

---

Adapted from materials provided by University of California, San Diego, Scripps Institution of Oceanography, via Newswise.

University of California, San Diego, Scripps Institution of Oceanography (2008, November 24). How Global Warming May Affect U.S. Beaches, Coastline. ScienceDaily. Retrieved November 27, 2008, from http://www.sciencedaily.com­ /releases/2008/11/081122083051.htm

Miami Isopycnic Coordinate Ocean Model used to show what is driving the Circumpolar Deep Water.

Environmental Research Web, November 21, 2008

Changing winds affect ice shelves

Regional wind-forcing plays a critical role in controlling delivery of ocean heat to Amundsen Sea ice shelves. So say researchers at the British Antarctic Survey (BAS) who have modelled the circulation in this region to understand what drives relatively warm Circumpolar Deep Water (CDW) onto the continental shelf. The CDW is responsible for the high melt rates observed underneath the floating tongues of the major outlet glaciers that drain into Pine Island Bay.

The new result is significant, explains team member Adrian Jenkins, because the timescales needed for atmospheric warming to penetrate key water masses are centuries or longer, which would suggest that ice sheets are relatively immune to recent climate change. However, if temperature increases in the atmosphere are accompanied by changes in atmospheric circulation, then ice sheets could be affected much sooner. The model suggests that any changes in the atmosphere, be they natural or anthropogenic, that alter regional winds will affect how ocean heat is delivered to Antarctica's ice shelves and floating glacier tongues.

The researchers used a version of the Miami Isopycnic Coordinate Ocean Model adapted for domains that include ice shelves. This was coupled to a dynamic/thermodynamic sea ice model, forced with surface pressure – from which surface winds were derived – and temperature from NCEP/NCAR reanalyses.

Jenkins stresses, however, that the results are a simply a "hindcast". "We have offered one possible explanation for glaciological changes that have been observed," he told environmentalresearchweb. "However, we have not made any predictions about the future and have stressed that our results show decadal variability rather than a long-term trend."

He adds that it is not yet possible to extract a trend from the variability or say whether it is entirely natural or related to anthropogenic forcing.

The Amundsen Sea is an important location for climate change studies. Indeed, a US cruise early next year, led by team member Stan Jacobs of the Lamont-Doherty Earth Observatory, will continue oceanographic observations on the Amundsen Sea Continental Shelf and deploy instruments for year-round ocean monitoring. The UK will participate thanks to the Natural Environment Research Council's autonomous underwater vehicle, Autosub-III, which will be used to directly measure ocean properties beneath the floating ice shelves, explains Jenkins.

"These results should provide us with more information on the variability of ocean forcing on ice shelves and the processes by which the warmth of ocean waters leads to melting," he adds. "This will help improve our model representation of the continental shelf and floating ice shelves."

The team is now running its model at higher resolution and extending the length of the integrations.

The work was reported in Geophysical Research Letters.

About the author

Belle Dumé is a contributing editor to environmentalresearchweb.

Link to article: http://environmentalresearchweb.org/cws/article/research/36623

Environmental Research Letters: Focus on connections between atmospheric chemistry and snow and ice

Environmental Research Letters, 3 (2008) o45oo4.

EDITORIAL

Ice in the environment: connections to atmospheric chemistry

V Faye McNeill et al 2008 Environ. Res. Lett. 3 045004 (1pp) doi: 10.1088/1748-9326/3/4/045004

	PDF (33 KB)

V Faye McNeill¹ and Meredith G Hastings^2
1 Columbia University, New York, NY, U.S.A.
² Brown University, Providence, RI, U.S.A.

Ice in the environment, whether in the form of ice particles in clouds or sea ice and snow at the Earth's surface, has a profound influence on atmospheric composition and climate. The interaction of trace atmospheric gases with snow and sea ice surfaces largely controls atmospheric composition in polar regions. The heterogeneous chemistry of ice particles in clouds also plays critical roles in polar stratospheric ozone depletion and in tropospheric chemistry. A quantitative physical understanding of the interactions of snow and ice with trace gases is critical for predicting the effects of climate change on atmospheric composition, for the interpretation of ice core chemical records, and for modeling atmospheric chemistry.

The motivation behind this focus issue of Environmental Research Letters (ERL), and the special session at the Fall 2007 meeting of the American Geophysical Union that generated it, was to enhance communication and interactions among field and laboratory scientists and modelers working in this area. Members of these three groups are each working toward a mutual goal of understanding and quantifying the connections between the chemistry of snow and ice in the environment and atmospheric composition, and communication and collaboration across these traditional disciplinary boundaries pose a challenge for the community.

We are pleased to present new work from several current leaders in the field and laboratory communities in this focus issue. Topics include the interaction of organics and mercury with snow and ice surfaces, halogen activation from halide ice, and the emissions of reactive nitrogen oxides from snow. Novel experimental techniques are presented that make progress towards overcoming the experimental challenges of quantifying the chemistry of realistic snow samples and ice chemistry at temperatures relevant to the polar boundary layer. Several of the papers in this issue also touch on one of the significant gaps in our current understanding of the atmospheric chemistry of ice: the role of a quasi-liquid layer (QLL) or quasi-brine layer (QBL) at the ice surface.

The studies presented here advance our understanding of the complex interactions of snow and ice with important reactive components in our atmosphere. It has become clear in recent years that the polar regions do not act as an ultimate sink for many compounds—the release of halogens and reactive nitrogen oxides from ice and snow are examples of this. Two notable implications arise from these findings (i) the impact of anthropogenic pollutants in our environment may extend further than we fully appreciate with current global atmospheric chemistry models and (ii) our interpretation of chemical records in ice cores requires that we fundamentally understand and quantify air–snow and air–ice interactions. Additionally, laboratory studies are elucidating the details of heterogeneous reactions that are prevalent on ice and snow surfaces throughout the troposphere, and we are poised to make significant strides in the near future quantifying these effects on regional and global scales. We look forward to continued progress in this field in the coming years, and we will continue to work to connect those conducting modeling, field and laboratory studies.

Focus on Connections between Atmospheric Chemistry and Snow and Ice Contents

HONO emissions from snow surfaces
Harry Beine, Agustín J Colussi, Antonio Amoroso, Giulio Esposito, Mauro Montagnoli and Michael R Hoffmann

Heterogeneous ozonation kinetics of phenanthrene at the air–ice interface
T F Kahan and D J Donaldson

Release of gas-phase halogens from sodium halide substrates: heterogeneous oxidation of frozen solutions and desiccated salts by hydroxyl radicals
S J Sjostedt and J P D Abbatt

Uptake of acetone, ethanol and benzene to snow and ice: effects of surface area and temperature
J P D Abbatt, T Bartels-Rausch, M Ullerstam and T J Ye

Interaction of gaseous elemental mercury with snow surfaces: laboratory investigation
Thorsten Bartels-Rausch, Thomas Huthwelker, Martin Jöri, Heinz W Gäggeler and Markus Ammann

Major solutes, metals, and alkylated aromatic compounds in high-latitude maritime snowpacks near the trans-Alaska pipeline terminal, Valdez, Alaska
Jonathan P Bower, Eran Hood and Lisa A Hoferkamp

Link: http://www.iop.org/EJ/abstract/1748-9326/3/4/045004

Andrew Glikson: 21st Century climate tipping points

Link to this article: http://www.opednews.com/articles/1/21st-century-climate-tippi-by-Andrew-Glikson-081121-208.html

Recent climate developments in the polar cryosphere and the oceans suggest the atmosphere is tracking toward conditions similar to those of ~2.8 Ma (mid-Pliocene: +2–3 oC; sea level + 25±12 metres; permanent El-Nino) (Haywood and Williams, 2005; Dowsett et al., 2005) and a possible tipping point. The polar Sea ice and continental ice sheets, which serve as Earth’s climate thermostat, are changing at an accelerated rate. Developments to date include:

A. The rise of mean Arctic and sub-Arctic temperatures in 2005–2008 by near +4 oC relative to 1951–1980 (NASA-GISS);

B. Arctic Sea ice melt rates of ~5.4% per-decade since 1980, increasing to >10% per year during 2006–2007 (NSIDC, 2008);

C. West Antarctica sea ice melt rates >10% per decade culminating in mid-winter ice shelf breakdown (Wilkins ice shelf; June, 2008, NSIDC, 2008);

D. Advanced melt of Greenland ice;

E. Slow-down of the North Atlantic thermohaline conveyor belt and down-welling water columns (NASA, 2004; Bryden et al., 2005), with attendant danger of its cessation analogous to conditions ~8.2 kyr ago (Alley et al., 1997), considered in a Pentagon inquiry (Stipp, 2004);

F. Temperature projections for the North Atlantic Ocean (Keenlyside et al., 2008) may reflect the effect of Greenland ice melt waters;

G. Increased frequency and intensification of categories 4 and 5 hurricanes (Webster et al., 2005) and, not least, elevated methane release from Arctic Sea sediments and sub-Arctic permafrost (Walter et al., 2006; Rigby, 2008).

Increasingly an analogy emerges between these developments and aspects of abrupt climate changes associated with the last glacial termination. As stated by Alley et al. (2003) “Large, abrupt, and widespread climate changes with major impacts have occurred repeatedly in the past, when the Earth system was forced across thresholds.” Ice core and sedimentary evidence for the Pleistocene (1.8 Ma – 10,000 years ago) demonstrate abrupt glacial terminations, intra-glacial global warming events (Dansgaard–Oeschger cycles; Broecker, 2000; Ganopolski & Rahmstorf, 2002; Braun et al., 2005) as well as sharp to protracted cooling periods. The latest glacial termination includes a number of tipping points which involve sharp rise and fall of temperatures by several degrees C over time scales of centuries, decades, or even a few years (Clark et al., 2003; Kobashi et al., 2008; Steffensen et al., 2008), affecting both high latitudes and tropical zones (Hughen et al., 1996).

Comparisons between CO2, CH4, temperature and sea level changes during glacial terminations, post-1850 and 20th–21st century climate change rates (Table 1; Glikson, 2008) suggest:

1. CO2 rise rates: Late 20th century and early 21st century rates averaging 1.45 ppm/yr and rising to 1.8 ppm/yr in 2006 and 2.2 ppm/yr in 2007, exceed 1850–1970 rates by factors of ~4–5 and are two orders of magnitude higher than mean CO2 rise rates of the last glacial termination (~0.014 ppm/yr) (Rahmstorf et al., 2006; Global Carbon Project, 2008).

2. CH4 rise rates: A 10 ppb/yr rise in methane during 2007 (http://web.mit.edu/newsoffice /2008/techtalk53-7.pdf), exceeding the 1850–1970 rise (~5.4 ppb/yr), is orders of magnitude higher than during the last glacial termination. Methane deposits potentially vulnerable to climate change reside in permafrost (~900 GtC), high latitude peat lands (~400 GtC), tropical peat lands (~100 GtC), vulnerable vegetation (~650 GtC) and methane hydrates and clathrates in the ocean and ocean floor sediments (>16,000 GtC). The total exceeds the atmospheric level of carbon (~750 GtC), carbon emissions to date (~305 GtC) and known economic carbon reserves (>>4000 GtC).

3. Temperature rise rates: Mean temperature rise rates of 0.016 oC during 1970–2007 were about an order of magnitude higher than during 1850–1970 (0.0017 oC) and the last glacial termination. As indicated by deuterium studies of Greenland ice cores, abrupt tipping points during the last termination (14.7–11.7 kyr) resulted in extreme temperature changes on the scale of several degrees C in a few years (Steffensen et al., 2008).

4. Sea level rise rates: Mean sea level rise rate of ~0.32 cm/yr during 1988–2007 more than doubled relative to the mean ~0.14 cm/yr rate of 1973–1988 and three times those of 1850–1970. In so far as doubling of sea level rise rates continues at this rate through the 21st century, they may approach rates similar to those of the last glacial termination (1.3–1.6 cm/yr) before mid-century, with sea level rise by several metres toward the end of the century as estimated by Hansen et al. (2007).

Whereas larger ice sheets existed on Earth at the outset of the last glacial termination, when the large Laurentian and Fennoscandian ice sheets began to melt, than during the Holocene, comparisons between climate forcings during the glacial termination and those operating since about 1750 may be instructive:

1. The last glacial termination, triggered by insolation peaks, involved total radiative forcing rise of about 6.5 Watt/m2, including ~3.0±0.5 Watt/m2 induced by rising greenhouse gases (GHG: CO2, CH4, NxO) and 3.5±1.0 Watt/m2 induced by lowered albedo associated with melting of ice sheets and spread of vegetation. Both factors, including their feedback effects, result in mean global temperature rise of ~5.0±1.0 oC (Hansen et al., 2008).

2. Since about 1750 global warming is driven by radiative GHG forcing of near + 3.0 Watt/m2 consequent on rise of GHG (CO2, CH4, NxO, ozone, halocarbons), compensated in part by albedo increase due to land clearing (–0.2 Watt/m2), aerosols (–0.5 Watt/m2) and clouds (–0.7 Watt/m2). When the albedo loss due to melting of the Arctic and Antarctic sea ice, the margins of Greenland and Antarctic ice sheets and mountain glaciers, is accounted for, the total forcing would be tracking toward values about half those of the last glacial termination of 6.5±1.5 Watt/m2.

Detailed deuterium proxy-based paleo-temperature studies of Greenland ice cores GISP-2 indicate that, far from smooth, the transitions associated with the glacial terminations involved abrupt tipping points where temperatures rose or fell sharply by several degrees C over time scales as short as a few decades or even a few years (Kobashi et al., 2008; Steffensen et al., 2008). A potential onset of such tipping points in the context of 21st century climate change is consistent with observations pertaining to the last glacial termination, current methane release from sediments off-shore Siberia and from permafrost, Arctic Sea ice melt, Antarctic sea ice and ice shelf melt and intensifying Atlantic hurricanes.

A marked climate tipping point is defined about 1975–76, with abrupt rise of temperature and temperature rise rates. 1975–2008 climate change developments incurred CO2 rise by 55 ppm (332–387 ppm) and mean temperature rise of ~0.9 oC for the Northern Hemisphere (mean CO2 rise ~1.7 ppm/yr; temperature rise 0.027 oC/yr; 0.016 oC per 1 ppm CO2). In so far as the relations between CO2 and temperature during 1975–2008 can be used as a baseline, a rise of CO2 levels to 450 ppm by 2050 would result in minimum additional temperature rise by approximately 1.0 oC relative to 2008.

Conservative estimate of the "climate sensitivity," estimated at 3 degrees rise per doubling of CO2 for fast climate feedback processes (water vapor, clouds, aerosols, sea ice), implies a rise of CO2 by 100 ppm (from 450 to 550 ppm CO2) will elevate global temperatures by about 1.0±0.5 oC, where a trajectory toward 550 ppm threatens to raise temperatures to about 2.6 oC later in the 21st century. However, slow climate change feedbacks (reduced continental ice sheets, increased vegetation cover in permafrost-melt areas) ensue in climate sensitivity of ~6 oC per doubling of CO2 – consistent with the last glacial termination (Hansen et al., 2008).

Given the onset of the Antarctic ice sheet at or below 500 ppm CO2 at ~34 Ma (late Eocene), and of the Arctic Sea ice below 400 ppm at 2.8 Ma (mid-Pliocene) (Haywood & Williams, 2005), the projected consequences of CO2 trajectories toward 550 ppm are likely involve catastrophic climate tipping points.

The IPCC 2007 and Garnaut Review 2008 climate change projections

The termination of glacial periods through insolation maxima associated with Milankovic eccentricity, obliquity and precession cycles, effecting 40–60 Watt/m2 spikes at latitude 65N (Roe, 2005), trigger forcing of ~6–7 Watt/m2 and associated carbon cycle and ice melt/water feedback effects (Hansen et al., 2006, 2007, 2008). However, feedback effects are neglected in the IPCC-2007 report, which states: “The emission reductions to meet a particular stabilization level reported in the mitigation studies assessed here might be underestimated due to missing carbon cycle feed-backs (see also Topic 2.3) AR4 caption to Table 5.1”.

Wigley (1993, 2006) and Wigley et al. (2007) modeled CO2 trajectories, accounting for carbon feedbacks, reversal of atmospheric CO2 overshoots and stabilization, stating: “Stabilization of the climate system requires stabilization of greenhouse-gas concentrations. Most work to date has considered only stabilization of CO2, where there are choices regarding both the concentration stabilization target and the pathway towards that target. Here we consider the effects of accounting for non-CO2 gases (CH4 and N2O), for different CO2 targets and different pathways. As primary cases for CO2 we use the standard “WRE” pathways to stabilization at 450 ppm or 550 ppm. We also consider a new “overshoot” concentration profile for CO2 in which concentrations initially exceed and then decline towards a final stabilization level of 450 ppm, as might occur if an initial target choice were later found to be too high.”

However, the recent history of the atmosphere betrays little evidence for stabilization scenarios. By contrast, glacial-interglacial cycles culminate with runaway warming and tipping points preceding sharp or gradual temperature declines (Broecker, 2000; Alley et al., 1997, 2003; Braun et al., 2005; Roe, 2006; Hansen et al., 2006, 2007, 2008; Steffensen et al., 2008; Kobashi et al., 2008)

Principal alternatives considered in the Garnaut (2008) Climate Change Review include (p. 277):

1. “Australia’s full part for 2020 in a 450 scenario would be a reduction of 25% in emissions entitlements from 2000 levels, or one-third from Kyoto compliance levels over 2008–2012, or 40% per capita from 2000 levels. For 2050, reductions would be 90% from 2000 levels (95% per capita)”.

2. “Australia’s full part for 2020 in a 550 scenario would be a reduction in entitlements of 10% from 2000 levels, or 17% from Kyoto compliance levels over 2008–2012, or 30% per capita from 2000. For 2050, reductions would be 80% from 2000 levels or 90% per capita.”

3. “If there is no comprehensive global agreement at Copenhagen in 2009, Australia, in the context of an agreement among developed countries only, should commit to reduce its emissions by 5% (25% per capita) from 2000 levels by 2020, or 13% from the Kyoto compliance 2008–2012 period.”

The differences between the 550 ppm and 450 ppm scenarios are as follows (p.86):

No-mitigation case. A global emissions case in which there is no action to mitigate climate change—the Garnaut–Treasury reference case—was developed as part of the Review. This emissions case recognizes recent high trends in the emissions of carbon dioxide and other greenhouse gases. Emissions continue to increase throughout the 21st century, leading to an accelerating rate of increase in atmospheric concentrations. By the end of the century, the concentration of long-lived greenhouse gases is 1565 ppm CO2-e, and carbon dioxide concentrations are over 1000 ppm—more than 3.5 times higher than pre-industrial concentrations.

550 mitigation case. Emissions peak and decline steadily, so that atmospheric concentrations stop rising in 2060 and stabilize at around 550 ppm CO2-e—one-third of the level reached under the no-mitigation case.

450 mitigation case. Emissions are reduced immediately and decline more sharply than in the 550 case. Atmospheric concentrations overshoot to 530 ppm CO2-e in mid-century and decline towards stabilization at 450 ppm CO2-e early in the 22nd century.”

The Review (p. 95) acknowledges: “The small change in global average temperature between the 550 and 450 mitigation pathways could have a relatively large impact on sea-ice extent.” Yet Table 11.1 and Figure 44 of Garnaut-2008 Review, suggest the difference by 2050 is no more than 0.1 oC:

1. A CO2-e rise of 450 ppm by 2050 would raise temperature by +1.6 oC relative to 1990

2. A CO2-e rise of 550 ppm by 2050 would raise temperature by +1.7 oC relative to 1990.

As indicated above, these estimates are near one order of magnitude low as compared to projections based on climate sensitivity, estimated at 3±1.5 oC per doubling of CO2 concentration (Charney, 1979).

To summarize:

1. IPCC-2007 and Garnaut-2008 CO2 stabilization scenarios, derived from modeled equilibrium states (Wigley, 1993, 2006; Wigley et al., 2007; Archer, 2005; Bender et al., 2005; Lenton and Britton, 2006) appear to take little account of methane release, the effects of ice sheet melt and potential tipping points.

2. Garnaut-2008’s choice between a 450 ppm and 550 ppm trajectory for 2050, projected difference of 0.1 oC per 100 ppm CO2-e rise for these trajectories, and the assumption of CO2 ‘stabilization,’ are difficult to reconcile with extensions of the 1975–2008 CO2 trend. These projections take little account of the consequences of non-linear climate feedback processes due to methane release from sediments and permafrost, ice sheet breakup, infrared absorption by exposed sea water, and consequent climate tipping points.

3. The assumption that CO2 levels can be reversed from 550 ppm, once reached, to 450 ppm over acceptable time scales, finds little support in the centuries-scale atmospheric residence time of CO2 and in past atmospheric records.

Climate models, effective in modeling 20th and early 21st century climate change, tend to underestimate the magnitude and pace of global warming (Rahmstorf et al., 2007). According to Hansen et al. (2008) “Climate models alone may be unable to define climate sensitivity more precisely, because it is difficult to prove that models realistically incorporate all feedback processes. The Earth’s history, however, allows empirical inferences of both fast feedback climate sensitivity and long term sensitivity to specified greenhouse gas change including the slow ice sheet feedback.”

The Earth atmosphere is already tracking toward conditions increasingly similar to the mid-Pliocene ~3.0 Ma, with temperatures higher than mean Holocene temperatures by +2–3 oC, ice-free Arctic Sea, tens of metres sea level rise and a permanent El-Nino (Dowsett et al., 2005; Haywood & Williams, 2005; Gingerich, 2006). Additional anthropogenic GHG forcing and methane emission threaten conditions approaching those of the Paleocene-Eocene Thermal Maximum (PETM) 56 Ma, when the eruption of some 1500 GtC (Sluijis et al., 2007), inferred from low δ13C values (–2 to 3‰ 13C), resulted in global warming of ~6 oC, development of subtropical conditions in the Arctic circle (sea temperatures 18–23 oC (Sluijis et al., 2007), ocean acidification and mass extinction of 3035% of benthic plankton (Panchuk et al., 2008). The recent history of the atmosphere, and the presence of thousands of GtC in metastable methane hydrates, clathrates and permafrost, suggests a CO2 trajectory toward 550 ppm may lead toward conditions similar to the PETM.

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Movements in glacial lakes have an effect on acceleration of Antarctic glaciers

Floods Beneath Antarctica’s Ice Sheet Create a Glacial Slip-and-Slide

Deep beneath the Antarctic ice sheet, floods of water from buried lakes can hurry glaciers along on their slow slide towards the sea, according to a new study that tracked recent floods beneath the Byrd Glacier. “It’s like putting in a squirt of oil,” says Andy Smith of the British Antarctic Survey, who was not involved in this latest study. “The water lubricates the base of the glacier” [New Scientist]. The findings will help researchers understand the movement of glaciers around the world, a matter of great interest to climate scientists who are investigating how rapidly ice sheets may melt into the ocean due to global warming.

Researchers discovered only recently that inaccessible subglacial lakes in Antarctica periodically shed huge quantities of water. Data collected by a satellite launched in 2003 … revealed a complex network of subglacial plumbing in which water periodically cascades from one hidden reservoir to another [AFP]. The water in the lakes remains liquid, despite being buried beneath a mile of ice in some places, due to warmth from the underlying rock. Now, researchers have shown that these hidden floods affect the thick mountains of ice above.

As reported in Nature Geoscience [subscription required], researchers measured the elevation of the ice in the Byrd Glacier by satellite. When the subglacial lakes fill up, they raise the elevation of the ice above them, and when the water spills over in a flood, the elevation sinks again, allowing researchers to track the water. Between December 2005 and February 2007 researchers saw rapid changes in the ice elevation that coincided with a marked increase in the speed of the ice flow. Conversely, the movement of the glacier slowed when the flood ceased and the lakes began to refill [New Scientist].

Researchers stressed that the floods beneath the Byrd Glacier were not caused by global warming: The lakes probably flood and drain on a regular basis that has nothing to do with atmospheric or ocean warming. However, the scientists say the mechanisms involved need to be understood so the knowledge can be applied to those ice masses which are being exposed to warmer temperatures, such as in Greenland [BBC News]. The International Panel on Climate Change (IPCC) has said that one of the great unknowns regarding climate change is what proporition of the world’s ice sheets will melt into the ocean, and how much that will raise sea levels.

Link to article:

http://blogs.discovermagazine.com/80beats/2008/11/17/floods-beneath-antarcticas-ice-sheet-create-a-glacial-slip-and-slide/

BAM, a ceramic alloy of boron, aluminum, magnesium, and titanium boride slippier than Teflon can same millions in energy costs

Material slicker than Teflon discovered by accident

by Kurt Kleiner, New Scientist, November 21, 2008

A superhard substance that is more slippery than Teflon could protect mechanical parts from wear and tear, and boost energy efficiency by reducing friction.

The "ceramic alloy" is created by combining a metal alloy of boron, aluminium and magnesium (AlMgB14) with titanium boride (TiB2). It is the hardest material after diamond and cubic boron nitride.

BAM, as the material is called, was discovered at the US Department of Energy Ames Laboratory in Iowa in 199, during attempts to develop a substance to generate electricity when heated.

Eternal lubricant

BAM didn't do that, but was found to have other desirable characteristics. "Its hardness was discovered by accident. We had a terrible time cutting it, grinding it, or polishing it," says Alan Russell, a materials scientist at Iowa State University in Ames.

Those chance findings have now developed into a $3-million programme at the Ames Lab to develop the BAM into a kind of eternal lubricant, a coating for moving parts to boost energy efficiency and longevity by reducing friction.

BAM is much slipperier than Teflon, with a coefficient of friction of .02 compared to .05. Lubricated steel has a friction coefficient of 0.16.

One way to exploit this slipperiness is to coat the rotor blades in everyday pumps used in everything from heating systems to aircraft, says Russel. A slick BAM coating of just 2 microns (see image, top right) could reduce friction between the blades and their housing, meaning less power is needed to produce the same pumping power.

Mystery material

Bruce Cook, lead investigator on the Ames Lab project, estimates that merely coating rotors with the material could save US industry alone 330 trillion kilojoules (9 billion kilowatt hours) every year by 2030 - about $179 million a year.

BAM is also potentially attractive as a hard coating for drill bits and other cutting tools. Diamond is commonly used for this, and is harder, but it reacts chemically with steel and so degrades relatively quickly when used to cut the metal.

By contrast, BAM is cheaper and does not degrade when used with steel.

The exact reason for the new material's characteristics is still unclear, Russell told New Scientist. Most superhard materials, such as diamond, have a simple, regular and symmetrical crystalline structure. But BAM is complex, unsymmetrical, and its lattice contains gaps, none of which would be expected in a hard material.

Its slipperiness is also not entirely understood. Although Russell says the best theory is that the boron interacts with oxygen to make tiny amounts of boron oxide on its surface. They would attract water molecules from the air, to make a slippery coating.

"It's almost as if it's a self-lubricating surface. You don't need to add oil or other lubricants. It's inherently slippery," he says.

Link to article: http://www.newscientist.com/article/dn16102-material-slicker-than-teflon-discovered-by-accident.html

1st anniversary of "Climate Change -- The Next Generation" blog by Tenney Naumer

Yesterday, November 20, 2008, marked the first anniversary of this blog.

I hope that you, the readers, have benefitted from the 463 articles posted here for your erudition.

I will try to continue the blog for one more year, if necessary, in order that the truth be heard.

Best regards to all my readers,

Tenney

Andrew Dessler et al.: Water Vapor Confirmed As Major Player In Climate Change Using Data from AIRS on NASA's Aqua Satellite

Water Vapor Confirmed As Major Player In Climate Change

ScienceDaily, Nov. 18, 2008 — Water vapor is known to be Earth's most abundant greenhouse gas, but the extent of its contribution to global warming has been debated. Using recent NASA satellite data, researchers have estimated more precisely than ever the heat-trapping effect of water in the air, validating the role of the gas as a critical component of climate change.

Andrew Dessler and colleagues from Texas A&M University in College Station confirmed that the heat-amplifying effect of water vapor is potent enough to double the climate warming caused by increased levels of carbon dioxide in the atmosphere.

With new observations, the scientists confirmed experimentally what existing climate models had anticipated theoretically. The research team used novel data from the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite to measure precisely the humidity throughout the lowest 10 miles of the atmosphere. That information was combined with global observations of shifts in temperature, allowing researchers to build a comprehensive picture of the interplay between water vapor, carbon dioxide, and other atmosphere-warming gases. The NASA-funded research was published recently in the American Geophysical Union's Geophysical Research Letters.

"Everyone agrees that if you add carbon dioxide to the atmosphere, then warming will result," Dessler said. "So the real question is, how much warming?"

The answer can be found by estimating the magnitude of water vapor feedback. Increasing water vapor leads to warmer temperatures, which causes more water vapor to be absorbed into the air. Warming and water absorption increase in a spiraling cycle.

Water vapor feedback can also amplify the warming effect of other greenhouse gases, such that the warming brought about by increased carbon dioxide allows more water vapor to enter the atmosphere.

"The difference in an atmosphere with a strong water vapor feedback and one with a weak feedback is enormous," Dessler said.

Climate models have estimated the strength of water vapor feedback, but until now the record of water vapor data was not sophisticated enough to provide a comprehensive view of at how water vapor responds to changes in Earth's surface temperature. That's because instruments on the ground and previous space-based could not measure water vapor at all altitudes in Earth's troposphere -- the layer of the atmosphere that extends from Earth's surface to about 10 miles in altitude.

AIRS is the first instrument to distinguish differences in the amount of water vapor at all altitudes within the troposphere. Using data from AIRS, the team observed how atmospheric water vapor reacted to shifts in surface temperatures between 2003 and 2008. By determining how humidity changed with surface temperature, the team could compute the average global strength of the water vapor feedback.

"This new data set shows that as surface temperature increases, so does atmospheric humidity," Dessler said. "Dumping greenhouse gases into the atmosphere makes the atmosphere more humid. And since water vapor is itself a greenhouse gas, the increase in humidity amplifies the warming from carbon dioxide."

Specifically, the team found that if Earth warms 1.8 degrees Fahrenheit, the associated increase in water vapor will trap an extra 2 Watts of energy per square meter (about 11 sq. ft.).

"That number may not sound like much, but add up all of that energy over the entire Earth surface and you find that water vapor is trapping a lot of energy," Dessler said. "We now think the water vapor feedback is extraordinarily strong, capable of doubling the warming due to carbon dioxide alone."

Because the new precise observations agree with existing assessments of water vapor's impact, researchers are more confident than ever in model predictions that Earth's leading greenhouse gas will contribute to a temperature rise of a few degrees by the end of the century.

"This study confirms that what was predicted by the models is really happening in the atmosphere," said Eric Fetzer, an atmospheric scientist who works with AIRS data at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Water vapor is the big player in the atmosphere as far as climate is concerned."

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Adapted from materials provided by NASA/Goddard Space Flight Center.

NASA/Goddard Space Flight Center (2008, November 18). Water Vapor Confirmed As Major Player In Climate Change. ScienceDaily. Retrieved November 18, 2008, from http://www.sciencedaily.com­ /releases/2008/11/081117193013.htm

Link to article and animated graphs of water vapor around the planet:
http://www.nasa.gov/topics/earth/features/vapor_warming.html

Highly recommended further reading:
http://earthobservatory.nasa.gov/Features/WaterVapor/water_vapor.php

E. Rignot et al.: Mass balance of the Greenland ice sheet from 1958 to 2007

Geophysical Research Letters, Vol. 35, L20502, doi:10.1029/2008GL035417, 2008

Mass balance of the Greenland ice sheet from 1958 to 2007

E. Rignot (Department of Earth System Science, University of California, Irvine, California, USA; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), J. E. Box (Byrd Polar Research Center, Ohio State University, Columbus, Ohio, USA), E. Burgess (Department of Geography, University of Utah, Salt Lake City, Utah, USA), and E. Hanna (Department of Geography, University of Sheffield, Sheffield, UK)

Abstract

We combine estimates of the surface mass balance, SMB, of the Greenland ice sheet for years 1958 to 2007 with measurements of the temporal variability in ice discharge, D, to deduce the total ice sheet mass balance. During that time period, we find a robust correlation (R² = 0.83) between anomalies in SMB and in D, which we use to reconstruct a continuous series of total ice sheet mass balance. We find that the ice sheet was losing 110 ± 70 Gt/yr in the 1960s, 30 ± 50 Gt/yr or near balance in the 1970s–1980s, and 97 ± 47 Gt/yr in 1996 increasing rapidly to 267 ± 38 Gt/yr in 2007. Multi-year variations in ice discharge, themselves related to variations in SMB, cause 60 ± 20% more variation in total mass balance than SMB, and therefore dominate the ice sheet mass budget.

Received 21 July 2008; accepted 22 September 2008; published 22 October 2008.

Key words: glaciology, mass balance, sea level

Index Terms: 0720 Cryosphere: Glaciers; 0726 Cryosphere: Ice sheets; 0762 Cryosphere: Mass balance (1218, 1223); 1621 Global Change: Cryospheric change (0776); 1620 Global Change: Climate dynamics (0429, 3309).

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Citation: Rignot, E., J. E. Box, E. Burgess, and E. Hanna (2008), Mass balance of the Greenland ice sheet from 1958 to 2007, Geophys. Res. Lett., 35, L20502, doi:10.1029/2008GL035417.

Copyright 2008 by the American Geophysical Union.

J. Lean & D. Rind: Climate response to solar forcing estimated at only 10% of surface warming over last 100 years, not 65%

Environmental Research Web, November 7, 2008

Climate response to solar forcing less than reported

While recent studies have found that changes in the amount of sunlight reaching Earth have caused 65% of surface warming over the last 100 years, a new study puts that figure at just 10%. The researchers found that, if anything, in the past 25 years solar forcing has caused a very slight overall cooling, not 20–30% of the warming.

Compared are geographical response patterns, each normalized to a 0.1 K global temperature change, due to ENSO, volcanic, solar and anthropogenic influences, derived from the monthly historical surface temperature records (1889–2006). Image credit: Lean and Rind.

"The influence of the Sun, in particular, versus anthropogenic influences on global change is extremely controversial and these recent articles have provoked this controversy further, evoking major consternation and confusion amongst scientist and the policy-making community," Judith Lean of the Naval Research Laboratory, US, told environmentalresearchweb. "Our own recent work analyzes the entire historical surface temperature record, using the IPCC anthropogenic and solar forcings simultaneously with ENSO [El Niño-Southern Oscillation] and volcanic influences. In this way we attempted to account simultaneously for the major forcings known to impact climate, whereas the prior studies that concluded a dominant role for solar variability neglected one or more of the other known influences."

Regional response

Lean, who worked with David Rind of NASA, reckons their results clearly show that natural changes cannot account for the significant long-term warming in the historical global surface temperature anomalies, and further strengthen the likelihood that the recent warming is anthropogenic in origin.

The pair says their findings suggest deficiencies in general circulation models used to simulate and forecast climate change. "We showed that climate appears to respond to solar variability more rapidly – within months versus years – and with larger amplitude, by a factor of four or five, than the models simulate," explained Lean. "Contrary to model-based expectations, the 11-year solar cycle is reliably detected in the historical surface temperature record. Surface temperature responds rather rapidly, in phase with and lagging only by a month or so, the solar irradiance changes."

The researchers believe that dynamical processes are involved rather than, or as well as, thermodynamic processes. "Existing circulation patterns – Hadley, Ferrel, and Walker cells – are likely engaged, along with atmosphere – ocean interactions (ENSO)," said Lean. "Furthermore, there are likely both direct (surface heating) and indirect (stratospheric influence) components. Current models are not able to represent these processes very well; many lack, for example, adequate stratospheres and ENSO representations." Lean hopes that future validation of models with the pair’s empirical results may lead to improvements, which would then enable better estimates of responses to greenhouse gases.

Lean and Rind also carried out the first comparison from observations of the geographical distributions of responses to the individual forcings. This produced the first estimate of the geographical pattern of ENSO and volcanic aerosols over the entire globe. "IPCC [2007] did not report geographical patterns of climate responses to individual natural and anthropogenic influences because of model uncertainties at smaller than continental scales and over timescales less than 50 years," said Lean. "Our derived regional response patterns presage the next IPCC (AR5), which plans to focus more on regional responses compared with the 2007 focus on global attribution."

The researchers found that anthropogenic warming appears to have a much smaller signal at northern high latitudes than the IPCC reports, and than general circulation models simulate, at least in the annual averages. "However, our analysis is confined to latitudes less than about 65°N, where more reliable surface temperature observations exist, and captures only that variability at high latitudes which linearly tracks the four forcings (at appropriate lags)," said Lean.

Next Lean and Rind plan to determine the seasonal variation in regional responses to different climate influences; to extend the analysis to the atmosphere above the surface rather than just looking at surface temperatures; to compare empirical and modeled regional response patterns in detail; and to work on forecasting surface temperatures in the next decade by looking at the response to solar and greenhouse gas changes in the context of plausible scenarios for ENSO and volcanic activity, which are difficult to forecast.

"We have completed a large suite of model simulations using the GISS Middle Atmosphere GCM of climate range in the last 50 years (see Rind et al., JGR, in press)," said Lean. "Preliminary analyses indicate significant differences between the modeled and observed temperature responses to both solar and anthropogenic forcings, which we plan to elucidate and quantify, annually and seasonally, at the surface and in the atmosphere."

The researchers reported their work in Geophysical Research Letters.

Link: http://environmentalresearchweb.org/cws/article/research/36581