Limiting the Magnitude of Future Climate Change (2010) / Chapter Skim
Currently Skimming:
2 Goals for Limiting Future Climate Change
2 Goals for Limiting Future Climate Change
Pages 21-50
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 21... ...
We first assess future domestic and global "reference" GHG emission scenarios, that is, scenarios that would result without new policies to limit future emissions. We then outline the key steps involved in formulating goals for policies that limit climate change and recommend that goals be framed in terms of limits on cumulative domestic GHG emissions over a specified time period.
|
From page 22... ...
. The main drivers of GHG emissions include population growth and economic activity, coupled with the intensity of energy use per capita and per unit of economic output.
|
From page 23... ...
as well as increasing energy efficiency per unit of economic output. Trends in GHG emissions are closely associated with energy consumption.
|
From page 24... ...
GHG emissions (including CO2, CH4, N2O, HFCs, PFCs, and SF6, but excluding net land-use emissions) and indices of key emission drivers: population, primary energy use, and economic growth (gross domestic product [GDP]
|
From page 25... ...
The combined assumptions of lower economic growth and less carbon-intensive energy use produce lower GHG emissions in the MERGE reference projection. Recognizing the inherent uncertainty associated with making long-term projections, two key insights emerge from the reference projections: • In the absence of emission mitigation policies, annual U.S.
|
From page 26... ...
The mean of the global population estimates for 2010 is about 7 billion people. Global population projections for 2050 have a mean of about 9 billion people.
|
From page 27... ...
By the end of the century, global energy production is projected to be between 2.5 and 3.5 times greater than today's levels. The key reasons for differences in total primary energy projections include assumptions about population and economic growth; improvement in energy intensity, that is, the relationship between energy consumption and economic output over time; the abundance of different fuels and their relative prices; and the availability and deployment of energy technologies.
|
From page 28... ...
are projected to grow more quickly than those of high-income countries. Figure 2.8 shows historical and projected contributions to global emissions out to 2100 from several sources.
|
From page 29... ...
in the absence of efforts to address climate change, from the EMF22 study. The left panel shows global (fossil and industrial)
|
From page 30... ...
See Chapter 7 for a fuller discussion of these issues. SETTING CLIMATE CHANGE LIMITING GOALS International policy goals for limiting climate change were established in 1992 under the UNFCCC, in which the United States and more than 190 other nations set the goal of "stabilization of GHG concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system." Subsequent scientific research has sought to better understand and quantify the links among GHG emissions, atmospheric GHG concentrations, changes in global climate, and the impacts of those changes on human and environmental systems.
|
From page 31... ...
To systematically derive an emissions budget from global temperature and FIGURE 2-8 editable concentration goals requires establishing three crucial links: 1. a target global atmospheric GHG concentration that is consistent with an ac ceptable global mean temperature change, 2.
|
From page 32... ...
Nonetheless, for the purposes of this report, we use these two concentrations (450 and 550 CO2-eq) as guideposts for considering global emissions budgets and U.S.
|
From page 33... ...
In addition, the models assume transparent markets, no transaction costs, and perfect implementation of emissions-reduction measures throughout the 21st century. At the same time, the delayed participation scenarios assume a highly inefficient architecture in which many of the low- and middle-income countries undertake no emissions reductions before 2030 or even 2050.
|
From page 34... ...
The quantitative relationship between long-term temperature changes and atmospheric GHG concentrations is very difficult to specify, due primarily to the large uncertainty of climate sensitivity. Climate sensitivity is typically defined as the global mean equilibrium temperature response to a doubling of CO2 concentrations.
|
From page 35... ...
delays in global participation, no models could produce the scenario that met 450 ppm CO2-eq by 2100. The EMF22 results indicate that atmospheric GHG concentrations can be kept below 450 ppm CO2-eq only if the United States and other high-income countries, along with China, India, and many other low- and middle-income countries around the world,, many take aggressive actions to reduce emissions starting within the next few years.
|
From page 36... ...
EMISSION TARGETS U.S. GHG emissions reductions will not by themselves have a decisive impact on global atmospheric GHG concentrations, but actions that the United States might take over the coming decades to reduce domestic emissions do need to be considered within the context of the ultimate goal of stabilizing global climate.
|
From page 37... ...
. • Many of the EMF22 models allow the examination of technology deployment requirements for meeting domestic emissions budgets.
|
From page 38... ...
. The level of international action is either "Full," meaning all countries undertake emissions mitigation starting in 2012, or "Delay," meaning low- and middle-income countries do not begin climate mitigation until 2030 or beyond.
|
From page 39... ...
emissions reductions. This budget range also relates usefully to the EMF22 international scenarios, where modeling results for global emissions reduction were disaggregated (using the global least-cost criteria described earlier)
|
From page 40... ...
developed a global emissions budget and applied the criterion of equal per capita emissions among all 0
|
From page 41... ...
If the United States elected to make additional commitments beyond the least-cost allocated domestic budget mentioned above, it would be reasonable to achieve these additional commitments through a mechanism for investing in emissions reductions elsewhere in a way that does not increase the total cost of meeting the global emissions budget. The purchase of international offsets or participation in a global carbon pricing system would in principle provide such a mechanism.
|
From page 42... ...
Hence, for practical purposes, aggregate economic metrics are often used to represent the change in well-being that is brought on by emissions reductions. Typical metrics include CO2 prices (which, while not a direct measure of cost, can be used to determine effects on basic energy goods such as gasoline or natural gas for home heating and cooking)
|
From page 43... ...
FIGURE 2.11 EMF22 electricity and transportation CO2 emissions and reduction for 167 and 203 Gt CO2-eq goals. Note that the electricity sector generates greater emissions reductions than the transportation sector in all scenarios.
|
From page 44... ...
(See Chapter 5 for more discussion about technological innovation as a key factor for modulating GHG emission-control costs.) Aggregate economic indicators such as GDP or consumption losses are another common way to represent the costs of GHG emissions reduction.
|
From page 45... ...
emissions budget. SOURCE: Fawcett et al.
|
From page 46... ...
Economic losses increase over time, so the expectation is that they will be larger through and beyond 2050 than they are through 2030. It is important to note that none of these GDP impacts include estimates of the welfare benefits that would be associated with reducing GHG emissions.
|
From page 47... ...
noted above, none of these GDP impacts includes estimates of the benefits that would be associated with reducing GHG emissions. A Congressional Budget Office report on the economic effects of GHG limiting policies (CBO, 2009)
|
From page 48... ...
Recent integrated assessment modeling studies indicate that limiting the increase in global atmospheric GHG concentrations to 450 ppm CO2-eq this century (which can be related, in probabilistic terms, to the goal of limiting global mean temperature rise to 2ºC above preindustrial levels) would require aggressive emissions-reduction efforts by all major GHG-emitting nations, starting within the next few years.
|
From page 49... ...
emissions by 80 and 50 percent, respectively, by 2050 -- targets that have been used in many recent policy proposals -- and because studies indicate that they are roughly consistent with the goals of limiting global GHG concentrations to 450 and 550 ppm, respectively (using global least-cost criteria for allocating a global emissions budget)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.