Climate Protection Strategies for the 21st Century: Kyoto and Beyond
Special Report by the German Advisory Council on Global Change, WBGU, Berlin, 2003, ISBN 3-936191-04-2, 77 pp., available at http://www.wbgu.de .
The world is nearing a critical climate demarcation point. As this report shows, we must reduce annual carbon emissions by 45-60% by 2050, relative to 1990. Failure implies multiple climate catastrophes. Yet emissions since 1990 have increased by over 10%. The United States increased emissions by 18% during 1990-2000 and has announced a plan that would allow emissions to continue growing at 14% per decade. The European Union (1.8% decrease during 1990-2000), and in particular Germany (19% decrease) and the United Kingdom (5% decrease), have been notable good guys.
The German Advisory Council on Global Change (WBGU) is an interdisciplinary council of experts that reviews research findings and derives policy recommendations. It currently comprises nine members, including Hartmut Grassl (chair), Director of the Max Planck Institute for Meteorology in Hamburg, and leading experts in economics, business law, applied sciences, solar energy, international development, public health, climate change research, and biogeochemistry. They have issued 15 reports on sustainable energy and other topics since 1992, available in German and English at the above web site.
This report is the first complete plan I’ve seen for getting safely and equitably through the energy transition that is essential to preventing dangerous global warming. It is well referenced, thoroughly researched, and as comprehensive and detailed as one could imagine in only 77 pages.
The introduction recognizes the Kyoto Protocol as only a first step, emphasizing that, “as there are no alternatives, calling the Kyoto Protocol into question throws global climate policy back by many years and severely hampers efforts to prevent dangerous climate impacts.”
The analysis begins by estimating the temperature threshold beyond which unacceptable damage would probably occur. WBGU estimates this to be around 2oC above the pre-industrial value, i.e. an additional 1.4oC above today’s value. Beyond this lie unacceptable risks: 20% of ecosystems would shift significantly, numerous species would be endangered, food production would be reduced in many areas by severe weather and pests, world food disparities would increase, net food production losses could set in and cause widespread famine, an additional two billion people would become at risk for water shortage, large regions would face intolerable economic burdens, most people would suffer economic losses, and hundreds of millions more would be exposed to malaria, malnutrition, diarrhea and flood-related accidents. The possibility of catastrophically large nonlinear events would pose a “devastating risk.” Although low in annual probability, “the impacts could be so abrupt and severe that damages would be very high and adaptation almost impossible.” These changes, which must be prevented, include a North Atlantic thermohaline circulation shutdown, a runaway greenhouse effect due to marine methane hydrate destabilization, transformation of the Asian monsoons, long-term disintegration of the West Antarctic ice sheet, and an irreversible melting of the Greenland ice in its entirety. WBGU warns that “even within these [2oC warming] limits, the risk of triggering irreversible large-scale events is not negligible.”
The 2oC limit implies a certain atmospheric carbon limit, which in turn depends on the “climate sensitivity,” defined as the amount of warming caused by a doubling of carbon concentrations from their pre-industrial 280 ppm. Based on computer simulations, the Intergovernmental Panel on Climate Change (IPCC) estimates climate sensitivity as 1.7-4.2oC, a range that is the most significant global warming uncertainty. Clearly, to keep warming below the 2oC limit with high probability, concentrations should remain well below 560 ppm. Research shows that it’s very costly to set a limit that turns out to be dangerously high and to then be forced to rapidly reduce this limit. So WBGU recommends a 400-450 ppm limit. Note that concentrations are already 373 ppm.
What is the best pathway to such a limit? Arguing that only an equal per-capita emission right can be considered just, WBGU recommends a “contraction and convergence” model: During the next several decades, the world should reduce (contract) emissions in such a way as to arrive, during 2050-2100, at a global concentration of 400-450 ppm, while converging on equal per-capita emission rights for all nations.
To study detailed pathways to this goal, the report begins from three IPCC emission scenarios. For example, the most optimistic IPCC scenario assumes rapid economic growth, dynamic technology development, globalization, strong emphasis on sustainability, a less materialistic lifestyle, low population growth (9 billion in 2050, 7 billion in 2100), and a 2%/year reduction of energy intensity. To this scenario, WBGU adds its own requirements: The development of sustainable energy systems, and contraction and convergence to 400 ppm by 2050-2100. From WBGU’s previous studies, “sustainable energy systems” means biomass ≤ 100 EJ/y (1 exajoule = 1018 J), wind ≤ 140 EJ/y, hydro ≤ 15 EJ/y, fission is phased out (Germany is phasing out nuclear power), fusion = 0, while solar electricity (photovoltaics and solar thermal for electricity and for making hydrogen) and solar heat are essentially unlimited. CO2 storage is permitted temporarily, to be phased out by 2100.
It then becomes an exercise to work out the implications of this scenario. Some of the results (presented as detailed graphs): World energy production increases from its present 400 EJ/y to 900 EJ/y in 2060 then down to 700 EJ/y in 2100, coal zeroes out by 2060, oil and natural gas increase slightly until 2060 and then decline to100 EJ/y by 2100, solar electricity and solar hydrogen increase to 200 EJ/y by 2040 and level off at 400 EJ/y by 2080, other renewables including wind and solar heat increase and level off at 150 EJ/y by 2040.
Carbon emissions rise from their present 6.5 Gt/y (giga-tonnes per year) to nearly 8 Gt/y in 2020, then drop to 5.5 Gt/y in 2040, 3 Gt/y in 2060, and 1.5 Gt/y in 2100. Carbon reductions are caused in roughly equal parts by price-driven demand reductions, structural changes due to resource shifting, and carbon storage. Carbon storage begins in 2020, reaches a maximum of 4 Gt/y in 2060, and declines to zero by 2100.
Warming increases from its present 0.6oC to 1.1oC in 2020, 1.7oC in 2040, and levels off at 1.9oC by 2080. But the uncertainty in this final value ranges over 1.1-2.9oC, so even if this optimistic scenario is followed there is still considerable chance of exceeding the 2oC “safety zone.” Sea-level, relative to 2000 levels, rises roughly linearly by 35 cm by 2100, showing little sign of slowing at that time.
Per-capita emissions (enforced by issuing emissions rights under international agreement) for North America drop by a factor of 6 from their present 5.8 t/y to their “convergence” value of 0.9 t/y in 2050. Western European per-capita emissions drop from 2.5 t/y to 0.9 t/y, China rises from 0.6 to 0.9 t/y, Africa rises from 0.2 to 0.9 t/y. The world as a whole drops from 1.2 today to 0.9 t/y in 2050. All nations then drop from 0.9 in 2050 to 0.3 t/y by 2100.
Emissions trading is essential. A “cap and trade” system in assigned emission rights will encourage underdeveloped regions to expand renewable energy sources, leaving them with excess emissions certificates that can then be sold to developed regions that remain temporarily trapped in fossil-fuel economies. The price of carbon certificates is expected to reach $250 (expressed in year 2000 dollars) per ton of carbon (or 75¢ per gallon of gasoline) in 2020, and peak at $750 per ton in 2050. Annual worldwide economic costs of the transition are expected to peak at 1.5% of world GDP in 2050—far smaller than the costs of waiting until too late to act against global warming.
Land-use changes, which contribute 10-30% to global emissions, are treated in detail in a separate chapter. In order to avoid complicating international negotiations, WBGU recommends covering these in a separate agreement with its own trading scheme.
WBGU anticipates that essentially all nations, including the USA but excepting a few very poor nations, will join the emissions control regime by 2012. But it “is aware that individual states could entirely refuse to adopt emission limits.” The report recommends that the cooperating nations agree in advance to impose political and economic sanctions against such “free rider” nations.
The conclusion stresses that “without a fundamentally new orientation of energy systems towards sustainability, it will not be possible to protect the world’s climate.” And finally: “With every further delay of consistent climate protection policy, the scope for action narrows.”
Art Hobson
Physics, University of Arkansas