“1. Use historical climate record and credible climate change projections in planning.” (Draft Report on the Houston Region Foresight Panel on Environmental Effects – Executive Summary, p. 2)
Dear H-GAC Foresight Panel,
In most respects, the first listed strategy can be broadly applied to the investigation of effects and impacts of climate change in our region, and relied upon to add credence to proposed mitigation and adaptation strategies. In one or two absolutely critical areas, however, this approach falls flat. One such application is toward estimating sea-level rise, the other toward subsidence. I wish to challenge two false assumptions that most analysts are accepting without much critical thought.
The fourth, and latest, IPCC Assessment Report in 2007 stated only what is known with certainty about sea level rise. The dynamics of sea-level rise are driven by three factors whose relative contributions change over a period now expected to extend on the order of decades and centuries, rather than centuries and millennia. The first of these factors is the physical coefficient of expansion as water gains heat on or near earth’s surface. This is a well known phenomenon that varies directly with the amount of heat. The next factor is the addition of fresh water to the world ocean from melting mountain glaciers, and the end of many is in sight within the matter of a few decades. This is uncontroversial because the evidence of it through direct observation and gravity measurements is well along. The third factor has not yet greatly expressed itself, but because the largest amount of fresh water on earth is locked within them, the contributions of ice melt and dynamical ice flows from grounded ice caps will increasingly and perhaps rapidly override the other two components of sea level rise. This is where the ICCP could not reach worldwide agreement among a range of scientists. On one end are the defenders of traditional millennial ice change models based on the common natural past behaviors exhibited by ice covers as the primary input of heat to their melting was the tiny gradual shifts in orbital trajectories and orientations to our single central star, multiplied by positive feedbacks in the climate system. On the other extreme are those who consider the current case to be atypical of almost all natural changes recorded in the fossil record. These considered the unprecedented speed and magnitude of the rate of climate change today to be most similar to the rapid volcanic/tectonic inputs that released a similar amount of carbon to what humans are releasing in these centuries, but into an atmosphere then much less starved of greenhouse gasses 55 million years ago. In its chummy, inimitable way, the IPCC “put its foot down” and did not allow the big argument over the larger factor to muddy the clearer science of the smaller components. It made a plain statement to the world that the factor of dynamical ice flows is not yet well enough understood to hazard a best guess. I suppose the IPCC collectively expected the world to use common sense and place a large but for now uncertain placeholder into the figures for ice melt and sea level rise. How large? Let us consider the big picture. “Oceans contain 97 % of the earth's water while the remaining 3 % is classified as freshwater. Seventy-seven percent of this surface freshwater is stored as ice and 22% as groundwater and soil moisture. The remaining freshwater, making up less than 1 % of the world total, is contained in lakes, rivers and wetlands.” - Elementary Themes, Fresh Water Ecology and Pollution web site at http://www.cdli.ca/CITE/water.htm. Here is a table showing global water status:
Oceans | Ice | Groundwater | Flowing Water | |
Saltwater | 97% | |||
Freshwater | 2.31% | 0.66% | <0.03% |
Frozen water moves from a grounded state into the ocean as either solid ice or as liquid melt water. The fresh melt water is already about 2.6% greater in volume than the saltwater it would have displaced as floating ice, bumping up the ocean surface level when it enters. Calved icebergs, however, initially displace their own weight in seawater, and then grow about 2.6% in volume while melting. Calved sea ice extends the time it takes sea level to rise by providing a bump upon calving from grounded ice and then a longer pulse to reach the same 2.6 % volume increase that melt water supplies in one pulse (Noerdlinger & Brower, 2007). So the original ice volume increases in its entirety by 2.6% when that ice is melted into the ocean.
Oceans | Ice | Groundwater | Flowing Water | |
Saltwater | 97% | |||
Freshwater | 2.31% | 0.66% | <0.03% |
Ocean volume therefore increases from baseline by 2.6% x 2.31% = 6.006% at full cryosphere meltdown simply by turning all the ice into water. Beginning with a global mean depth of 3794 m, total meltdown implies about 23 meters of sea-level rise, to 3817 m. That is as much water volume as would be contributed by a 5 degree C temperature thermal expansion.
Thermal expansion at full equilibrium with a 10 degree C average surface termperature rise, from 10 degree C to 20 degree C for the top 10% ocean layer, would compound ocean water volume by about an additional 12.56%. Beginning with a global average depth of 3817 m, thermal expansion implies a rise to 73.67 m at equilibrium, bringing global mean depth to 3864.64 m. The result is a permanent (on the scale of human endeavors) increase of 70.64 meters. Some additional mechanisms may provide additional rise not counted herein, such as temporary color changes due to blooms and extinctions of zooplankton, or constraining shape of the ocean basin and in the long run rebalancing effects as the weight of ice and water overburden redistributes, and volcanism or even tectonic changes could occur as a result.
If eighty meters (252’) of sea level rise are possible within a rapid climate change century-scale scenario, the questions remain in the timing. Examination of somewhat similar greenhouse gas-dominated climate changes reveal more immediate and longer lasting climate responses than most scientists expected only a decade ago. From an urban planning perspective, we are certainly pressed to accomplish the integrated mitigation and adaptation sequences that must be attempted with sacrificial fervor, singular focus and breathtaking scope.
Using a straightforward projection of recent trends, sea level rise as a consequence of climate change seems to be doubling about once per decade as ice cap melt begins to dominate remaining mountain glacier runoff and thermal ocean expansion components. The rate of temperature increase is established for the next forty years based on known short-term inertias in climate responses to prior and current greenhouse gas concentrations. Long term (millennial) reinforcement will only exacerbate the problems in the atmosphere. Non-linearity would tend to shorten this projection because of known positive feedback mechanisms and a lack of known negative feedbacks.
Beginning with the recent rate of 0.5 cm per decade (1.5-2 mm per year), it could be a matter of 13 decades until all ice on earth has dissolved. To expect that effective mitigation is either affordable or geo-engineer-able borders now on wishful thinking. Dynamical ice flows which the conservative 2007 IPCC 4th Assessment Report found impossible to estimate are speeding up. IPCC has for now left blank the largest driver of sea level rise in our future. The long-pull inertia of climate reactions and the amounts of heat gain already “in the pipeline” reemphasize the environmental and intergenerational justice issues. Put in development terms there may be only time enough for 26 - 5 year architectural fads, four 25-year comprehensive urban plans, and one-to-two total building lifecycles. It is questionable whether this time is sufficient to move our major coastal population centers to safety, let alone to reestablish wetland coastal buffer zones and recover enough habitats for threatened and endangered species or even arable soil for sufficient food production.
Decadal chg Decade Eustatic Sea Level
+0.5 cm 2000 120.01 m above eustatic sea-level (ESL) at Last Glacial Maximum (LGM)
+1 cm 2010 120.02 m above ESL at LGM
+2 cm 2020 120.04 m above ESL at LGM
+4 cm 2030 120.08 m above ESL at LGM
+8 cm 2040 120.16 m above ESL at LGM
+16 cm 2050 120.32 m above ESL at LGM
+32 cm 2060 120.64 m above ESL at LGM
+64 cm 2070 121.28 m above ESL at LGM
+1.28 m 2080 122.56 m above ESL at LGM
+2.56 m 2090 125.12 m above ESL at LGM
+5.12 m 2100 130.24 m above ESL at LGM
+10.24 m 2110 140.48 m above ESL at LGM
+20.48 m 2120 160.96 m above ESL at LGM
+39.04 m 2130 200 m above ESL at LGM
And such is the result of melting all the ice that exists on earth today, 80 m (252 feet) total sea-level rise. The years after 2110, when sea-level rise breaches 1 meter per year in this projection, could see a 20-year flood of biblical proportions, ending in the final years with greater than 4 m annual rise. Harris County in sum total will return to the ocean bottom. At that time, seawater will permanently (from a human point of view) cover downtown Houston up to the 15th floor level of employment center skyscrapers. Ice flowing away from grounded ice caps is the least understood phenomenon of current atmosphere-ocean coupled general circulation models used for sea level rise scenario prediction. Dr. James E. Hansen of Columbia University and NASA states with “likely” certainty “meter-scale sea level rise this century, and ice sheets in a state of disintegration that guarantees future sea level rise in the 10-meter-scale, with a continual reworking of future global coastlines” out of control of humanity. To quote his abstract to “Target Atmospheric CO2: Where Should Humanity Aim?” published recently in The Open Atmospheric Sciences Journal:
“The conclusion that humanity must aim for a CO2 amount less than the current amount is a dramatic change from most previous studies, which suggested that the dangerous level of CO2 was likely to be 450 ppm or higher. The change is caused by realization that ‘slow’ feedback processes, such as ice melt and release of greenhouse gases by the soil and ocean in a warming climate, can occur on the time scale of decades and centuries. This realization stems from both improving data on the Earth’s climate history and ongoing observations of change, especially in the polar regions.
“The authors conclude that “humanity today, collectively, must face the uncomfortable fact that industrial civilization itself has become the principal driver of global climate.” Specifically, they say that humanity “must begin now to move toward the era beyond fossil fuels”, and “the most difficult task, phase-out over the next 20-25 years of coal use that does not capture CO2, is
Herculean, yet feasible when compared with the efforts that went into World War II. The stakes, for all life on the planet, surpass those of any previous crisis. The greatest danger is continued ignorance and denial, which could make tragic consequences unavoidable.”
James Hansen,1,2, Makiko Sato1,2, Pushker Kharecha1,2, David Beerling3, Robert Berner4, Valerie Masson-Delmotte5, Mark Pagani4, Maureen Raymo6, Dana L. Royer7 and James C. Zachos8
1NASA/Goddard Institute for Space Studies, New York, NY 10025, USA
2Columbia University Earth Institute, New York, NY 10027, USA
3Dept. Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
4Dept. Geology and Geophysics, Yale University, New Haven, CT 06520-8109, USA
5Lab. Des Sciences du Climat et l’Environnement/Institut Pierre Simon Laplace, CEA-CNRS-Universite de
Versailles Saint-Quentin en Yvelines, CE Saclay, 91191, Gif-sur-Yvette, France
6Dept. Earth Sciences, Boston University, Boston, MA 02215, USA
7Dept. Earth and Environmental Sciences, Wesleyan University, Middletown, CT 06459-0139, USA
8Earth & Planetary Sciences Dept., University of California, Santa Cruz, Santa Cruz, CA 95064, USA
The realization that phenomena formerly considered millennially slow, like sea level rise, can happen in decades and centuries, is jarring indeed. Much of the information leading to complacency is simply not up to date with recent findings. Consider our conditions: an increase to at least nine billion human population, the global hope for freedom to attain an energy-intensive lifestyle, the forty-year periods required for adopting widespread use of different technologies under capitalist market cost-plus-profit recovery times, and the “least common denominator” effects of federal policy or international treaty making. In the real world it is highly unlikely that humanity will be able to reverse the increase of carbon in the atmosphere back down to more of a 1960s level by 2070. Yet considering inertial climate forces that is the amount and timeframe required to gain a twenty-year margin of safety at the very end of the cryospheric meltdown process. Twenty years is precious little time to adjust efforts if they prove either insufficient (draconian or totalitarian intervention can then assumed to be initiated) or excessive (allowing some relaxation of precautionary mitigation measures). And really, what difference to our coastal civilization will be 20 meters total esl rise, perhaps the best outcome we may now expect, versus worst case 80 meters esl rise?
The second assumption concerns our programmatic ability to halt land and groundwater subsidence, which are exacerbating the problems of climate-driven sea-level rise. This is of particular concern in many deltaic settlements that have grown at the mouths of rivers where they enter the ocean. Subsidence has been occurring with urban growth because of a number of factors, but principally due to groundwater mining. In the oil-rich coastal prairie, where salt domes rose with their captive deposits of petroleum, mining those resources has also removed buoyant supports for the land. Using the historical record in O’Neil and VanSiclen’s 1984 “Gulf Coast Faults” article in the Bulletin of the Association of Engineering Geologists, p. 73-87, the rate of subsidence may be conservatively estimated to drop both land and water table at more than 6” per 7 years recently. In our region much of the soil exhibits low permeability that creates a constant and considerable suction, ensuring that groundwater movements along a declining water table will continue for many years. In a changing climate, higher runoff rates and lower rates of groundwater recharge combine with persistent drought and both soil and surface water evaporative losses to increase downward pressure on urbanized land.
A program to protect freshwater supplies in underground aquifers is attempting to more fully exploit surface water resources. Yet the growth pressures on the Houston metropolitan community are such that it is hard to imagine both surface and deep water resources will not be called upon to satisfy future demand. Unless we stop withdrawing from the dwindling aquifers, no amount of surface water utilization will halt continuing ground subsidence. One look at the abundance of wetland resources recorded in maps of the Houston area around 1983 readily shows that the water table has sunk along with the land. In environmental reviews of federally funded projects we find areas that would have been covered by wetland marshes a generation ago, but now are dry down to depths of six to ten feet. Manicured storm water retention ponds in such areas, often lined with clay bottoms, are the only visible reminder that a water table does exist below the surface. Storm water is treated more as an unwanted alien ready for deportation rather than as a helpful recharger welcomed with respect and care to replenish our thirsty aquifers. Subdivisions continue to be platted and constructed without regard for the natural lines of ridges and flow. Our sense of safety seems enhanced by the receipt of a LMAR that extends congratulations for filling in a part of the floodplain. Moving the waters more swiftly and in greater concentration by artificial barriers and hard channels should ring a warning bell in us when soils are dryer than ever before. Homeowners desperately spray potable water across their plantings and into the gutter in the name of greening the neighborhood, though far off icecaps prepare to slide catastrophically into the sea. Unless we have measurable data that confirms that freshwater withdrawal is lessening, we should not assume that our surface water transportation initiatives have halted subsidence. Our flood control measures should consider the health of aquifers in a freshwater-constrained world.
One final point. In “How we grow” beginning on page 7, the combined threat of hurricane storm surge and sea level rise may already be sufficient to consider all building in elevations below 30 feet during the current development cycle to be temporary in nature. Even as New Orleans, Kemah and Galveston proceed to rebuild, we should know enough at this point to avoid risking hazard insurance on buildings in high risk areas, or at least to require rebuilding to occur on strategically safer and higher ground in other parts of the greater community. A lower limit elevation benchmark for permanent structures should move higher with the passing years to proactively prepare for the possibility of catastrophic ice sheet failure and eventually a general cryospherical collapse. Heavy investment in new hurricane-resistant buildings should consider the need for permanent resilience against rising sea levels. In many cases, the impossibility to secure essential horizontal infrastructure may preclude otherwise well hardened facilities. Historical sites such as JSC in harm’s way are especially troubling.
One resolution to the dilemma between spending good capital to meet green building standards, hardening against hazards and treating all development as temporary in nature is to begin to design all development for eventual disassembly, transport, upcycling and reuse. McDonough and Braungart in Cradle to Cradle (2002) particularly inspire living within the laws of nature.
Postscript:
Thanks for letting me submit these unsolicited comments about the draft. I was excited to see that this project was so well developed, and that Alan Clark was taking a lead planning role. I particularly appreciated the bottom of page 9, items 24 and 25, about providing counties ordinance authority over development in high hazard areas, and partnering to assist climate change planning and adaptation. If the academic participants on the Foresight Panel would care to criticize my own work toward adaptation planning in the Urban Planning-Environmental Policy PhD program at TSU, I truly welcome the opportunity. I am intensely interested in the climate inertias in oceans and icecaps, and whether we can expect them to survive societal inertia.
Sincerely yours,
Paul M. Suckow
Senior Planner
Harris County
Community Services Department
Office of Housing and Community Development
Planning & Development Section
8410 Lantern Point
Houston, TX 77054
713-578-2018
Appendix:
Due to the high specific heat and low conductivity of water, only the uppermost 10% of the oceans is able to undergo any significant temperature change.
The natural variation in ocean levels is about 10 cm from September to March. By how much does the mean temperature of the upper ocean change during this time?
About 4.5 m per degree C, so 1/45 of a degree, or 0.022 degrees C? wow.
Global warming is likely to cause a rise in sea level for a number of reasons, one of which is the thermal expansion of water. Determine the rise in sea level for every 1.0 C° temperature increase in the upper ocean.
Data for the Oceans
surface area
3.61 × 1014 m2
mean depth
3794 m
mean temperature, overall
3.5 °C
mean temperature, top 10%
10 °C
10% of 3.61x10^14 sq m x 3794 m = 1369.634 x 10^14 cu m subject to expansion, average temperature 10 degrees C; 12,326.706x10^14 in deep ocean not subject to expansion at 3.15 degrees C; total 13696.34x10^14 cu m at average temperature 3.5 degrees C.
top 10% of ocean | reference sea level (m) |
water, solid ice (0 °C) | 17.50 |
water, liquid (1 °C) | (49.47) |
water, liquid (2 °C) | (49.47) |
water, liquid (3 °C) | (41.01) |
water, liquid (3.5 °C) | (36.73) |
water, liquid (4 °C) | (32.39) |
water, liquid (5 °C) | (31.37) |
water, liquid (6 °C) | (29.38) |
water, liquid (7 °C) | (26.48) |
water, liquid (8 °C) | (21.02) |
water, liquid (9 °C) | (4.49) |
water, liquid (10 °C) | - |
water, liquid (11 °C) | 4.51 |
water, liquid (12 °C) | 9.08 |
water, liquid (13 °C) | 13.71 |
water, liquid (14 °C) | 18.38 |
water, liquid (15°C) | 23.12 |
water, liquid (16 °C) | 27.91 |
water, liquid (17 °C) | 32.75 |
water, liquid (18 °C) | 37.66 |
water, liquid (19 °C) | 42.62 |
water, liquid (20 °C) | 47.64 |
water, liquid (21 °C) | 51.74 |
water, liquid (22 °C) | 55.88 |
water, liquid (23 °C) | 60.06 |
water, liquid (24 °C) | 64.28 |
water, liquid (25 °C) | 68.54 |
water, liquid (26 °C) | 72.84 |
water, liquid (27 °C) | 77.18 |
water, liquid (28 °C) | 81.57 |
water, liquid (29 °C) | 85.99 |
water, liquid (30 °C) | 90.46 |
Coefficients of Thermal Expansion for Selected Materials | ||||
material | linear |
| Material | volume |
aluminium | 23.1 |
| alcohol, ethyl | 1120 |
barium ferrite | 10 |
| Gasoline | 950 |
brass | 20.3 |
| jet fuel, kerosene | 990 |
carbon, diamond | 1.18 |
| Mercury | 181 |
carbon, graphite ∥ | 6.5 |
| water, liquid (1 °C) | −50 |
carbon, graphite ⊥ | 0.5 |
| water, liquid (4 °C) | 0 |
chromium | 4.9 |
| water, liquid (10 °C) | 88 |
concrete | 8 ~ 12 |
| water, liquid (20 °C) | 207 |
copper | 16.5 |
| water, liquid (30 °C) | 303 |
germanium | 6.1 |
| water, liquid (40 °C) | 385 |
glass | 8.5 |
| water, liquid (50 °C) | 457 |
gold | 14.2 |
| water, liquid (60 °C) | 522 |
iron | 11.8 |
| water, liquid (70 °C) | 582 |
lead | 28.9 |
| water, liquid (80 °C) | 640 |
nickel | 13.3 |
| water, liquid (90 °C) | 695 |
platinum | 8.8 |
|
|
|
plutonium | 54 |
|
|
|
silicon | 4.68 |
|
|
|
silver | 18.9 |
|
|
|
solder, lead-tin | 25 |
|
|
|
steel, stainless | 17.3 |
|
|
|
steel, structural | 12 |
|
|
|
tin | 22 |
|
|
|
titanium | 8.5 |
|
|
|
tungsten | 4.5 |
|
|
|
uranium | 13.9 |
|
|
|
water, ice (0 °C) | 51 |
|
|
|
zinc | 30.2 |
|
|
|
Solids
ΔL | = | L0 | α | ΔT |
| linear |
ΔA | = | A0 | 2α | ΔT |
| superficial (areal) |
ΔL | = | L0 | 3α | ΔT |
| volumetric |
Liquids
ΔV = V0βΔT
Liquids have higher expansivities than solids
β ≈ 10−3/K, 3α ≈ 10−5/K
0 comments:
Post a Comment