Hoffert: Low-Carbon Sustainable Energy

The following was sent by contributor Martin Hoffert of New York University, who has recently written extensively on energy technology requirements for stabilizing the climate. The most dramatic image here is the chart of US government funding priorities for the past 5 decades:

showing an absolute abdication of responsibility by the US since 1980 in funding relevant energy research.

Low-Carbon Sustainable Energy in the Greenhouse Century?

presented at "Whole Earth Systems: Science, Technology and Policy. A Festschrift for Steve Schneider"
Stanford University, Feb. 10-12, 2005
Marty Hoffert, Physics Department
New York University, New York, NY

Limiting atmospheric carbon dioxide emissions to minimize "dangerous anthropogenic interference" with climate as the human economy continues its historical growth will require a revolutionary change of the world energy system. For example, holding global warming below "only" 2 degrees Celsius -- an amount which could itself create serious adverse impacts -- implies adding the equivalent of one large power plant per day emitting no CO2; or comparable reductions in demand in the sense of Lovins' "negawatts " by improvements in energy efficiency and/or energy-conserving behavior. Massive emission cuts increasing with time relative to those that would be produced if carbon intensity (C/E) remained constant will be needed, with emissions declining to near zero by the century's end.

Civilization today is energized overwhelmingly by fossil fuels, increasingly we predict by high-carbon-emitting coal, as oil and gas production will likely peak in coming decades, and energy demand continues to rise. Beyond the screen of obfuscation and denial of global warming by "skeptics" and special interests are emerging policy questions: Can "existing" energy technology simultaneously run the world economy and stabilize the fossil fuel greenhouse? Or, as I will argue, is an aggressive R & D effort led by the US urgently needed to develop new high-technology energy sources in parallel with implementation of existing emission-limiting measures? Holding that "technology exists" is the IPCC Third Assessment Report mitigation working group who in their Summary for Policymakers said "known technological options could achieve a broad range of atmospheric CO2 stabilization levels, such as 550 ppm, 450 ppm, or below over the next 100 years," defining "known technological options" as already existing in operation or in pilot plants. This definition excludes carbon capture and sequestration (CCS) plants -- perhaps the most "market ready" technology -- because first pilot plant won't exist until 2010 at best. Likewise, Pacala and Socolow claim that "Humanity already possesses the fundamental scientific, technical, and industrial know-how to solve the climate problem for the next half century." This might be the case in the sense that humanity had the know-how to build nuclear weapons in the late 30s or go to the Moon in the 50s. But it took the Manhattan and Apollo programs to make it so.

Stabilizing climate change is a hard problem. I will argue that although technologies capable of slowing global warming cost and otherwise effectively over the next fifty years don't exist in an operational sense, they can be developed, and deployed in time to matter, if broad-spectrum research, development and demonstration were initiated now, preferably with the urgency of World War II mobilization. This is justified by the threat of global warming, but is no excuse for not deploying emission-limiting measures that can be implemented today.

An assessment is presented of fossil fuel (with CCS), nuclear and renewable energy technologies options, and of enabling transmission and storage technologies, to supply the required amounts of emission-free power at the required times. In light of the 10-100 year time scale -- roughly 60 years separate the Wright brothers from Neil Armstrong's walk on Moon -- emphasis is placed on innovative opportunities from recent discoveries in material science (high-temperature superconductivity, carbon nanotubes); the geophysics of available energy fluxes in space (solar power satellites, lunar power systems), at Earth's surface (Massive offshore wind farms, PV panels in the US southwest and the Sahara), tropospheric jet streams (tethered high-altitude autogyros) and in ocean boundary currents (seawater uranium harvesting) and geothermal heat flows (hot rock drilling & mining for heat); and electric grid and storage systems supportive of renewable energy (direct current, superconducting and smart grids, distributed generation, hydro, flywheel and inductive electrical storage); and approaches to replacing liquid hydrocarbons derived from fossil fuels (hydrogen, CO2 removal from the atmosphere, biofuels, microwave beaming to cars and aircraft).

As with biological evolution, technology evolution requires mutations. Most mutations are unsuccessful. But without them evolution stops. Some who characterize advanced energy technologies to reduce carbon emissions as "blue sky" might have said the same of flying machines and radio a hundred years ago, when innovations like computers and nuclear reactors would have been to most pundits unimaginable. History suggests we avoid such dismissals. Particularly telling is the recent 911 Commission finding that the greatest failure by intelligence organizations in anticipating fundamental challenges to our civilization like 911 was "failure of imagination."

[Editors's note: the remainder of this article derives from Hoffert's actual presentation, so images outweigh the text.]

Global warming in the last millenium
Very rapidly we've entered uncharted climatic territory - the anthropocene. Over the 20th century, human population quadrupled and energy consumption increased sixteenfold. Near the end of the last century, a critical threshold was crossed, and warming from the fossil fuel greenhouse became a dominant factor in climate change. Hemispheric mean surface temperature is higher today than at any time in the last millennium -- the so-called Mann et al. "hockey stick." Temperatures are likely to go "off the scale" in the 21st century.

Ken Caldeira, Atul Jain, and Martin Hoffert published on "Climate Sensitivity Uncertainty and the Need for Energy Without CO2 Emission", in the March 28, 2003 issue of science:

The UN Framework Convention on Climate Change calls for "stabilization of greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system." Even if we could determine a "safe" level of interference in the climate system, the sensitivity of global mean temperature to increasing CO2 is known perhaps only to a factor of three or less. Here we show how a factor of three uncertainty in climate sensitivity introduces even greater uncertainty in allowable increases in atmospheric CO2 concentration and allowable CO2 emissions. Nevertheless, unless climate sensitivity is low and acceptable amounts of climate change are high, climate stabilization will require a massive transition to CO2 emission-free energy technologies.

Figure 3: Mean rate of increase in installed capacity in carbon-emission-free primary power required over the period from year 2000 to year 2050 to stabilize climate, shown as a function of climate sensitivity to a carbon dioxide doubling and equilibrium global warming for the GDP and energy demand growth assumptions of the IPCC IS92a scenario. To hold global warming below 2oC with a climate sensitivity of 2.5 degrees C/CO2 doubling requires adding the equivalent of one 1000 MW (thermal) emission-free power plant every day for the next 50 years.

Figure 5: Per Capita Carbon Emissions Versus Per Capita GDP of 100 Nations
Note that carbon intensity is defined as the ratio of carbon emissions to GDP (gross domestic product). It can be broken down as the product of energy intensity E/GDP and the carbon emission factor, C/E

What does the SRES emission uncertainty range mean?

(Editor's note: SRES = IPCC Special Report on Emissions Scenarios)

Figure 6: Global carbon dioxide emssions related to energy and industry from 1900 to 1990 and for 40 SRES scenarios from 1990 to 2100, shown as an index (1900 = 1). Colored lines are individual SRES scenarios. The area shaded in blue is the range of scenarios in the literature documented in the SRES database.

Fossil Fuel Emissions and Stabilization Triangles

ExxonMobil Energy Projections

Milestones in predicting the probable evolution of societies

Created: 2005-02-02 05:05:54 by Arthur Smith
Modified: 2005-02-02 05:32:02 by Arthur Smith