America’s Climate Choices: The U. S. National Academies Report

Summary.  The U. S. National Academies has issued a report, America’s Climate Choices, assessing climate change and strongly recommending that steps be taken to address it.  These include a) substantially reducing greenhouse gas emissions with great urgency, b) beginning societal efforts to adapt to global warming already under way, c) supporting research in climate change, d) developing new information systems useful to inform the public about this issue, and to actively involve the public in policy development, and e) coordinating our global warming initiatives with other efforts worldwide.  The report urges that iterative risk management, a repetitive cycle of policy development and implementation, be employed in these efforts.  It is urgent to begin these measures right away in order to avert even more serious consequences than have already happened.

Introduction.  The global average temperature, measured over the long term, has been increasing since the beginning of the industrial revolution.  The trend has become more pronounced in recent decades, and is forecast to continue increasing even more strongly in the future because of humanity’s increasing demand for energy and a growing global population.  This increase in temperature correlates with, and is due to, the increased burning of fossil fuels for energy by mankind.  Fossil fuels, coal, oil and natural gas, are all carbon-based and emit carbon dioxide (CO₂), a principal greenhouse gas, into the earth’s atmosphere in direct proportion to the amount of fuel that is burned.

The nations of the world have gathered, starting in the early 1990’s, to try to reach agreement on limiting emissions of greenhouse gases under the United Nations Framework Convention on Climate Change (UNFCCC).  The two most recent meetings, in Copenhagen in 2009, and Cancun in 2010, adopted the goal of limiting the atmospheric concentration of CO₂ and other greenhouse gases to the level that would constrain the overall increase in global average temperature to 2ºC (3.6ºF) above the level that prevailed prior to the start of the industrial revolution.  The nations of the world, however, have not been able to agree on adopting the requisite measures that would result in achieving this goal.  The Kyoto Protocol of 1997 committed industrialized countries to reduce annual emission to at least 5 per cent below 1990 levels in the commitment period 2008 to 2012.  Developing countries were excluded from coverage under Kyoto.  Although many signatory nations agreed to the Protocol, the U. S., by refusal in the U. S. Senate, opted not to be bound by the Protocol.

Present World Status.  The European Union (EU), which had joined the Kyoto Protocol, recently issued its report “Roadmap for moving to a competitive low carbon economy in 2050”.  The Roadmap expands on the EU’s previous goal of reducing its rate of  greenhouse gas emissions by 20% below the levels of 1990 by the year 2020.  The goal in the Roadmap is the stringent restriction of reducing the greenhouse gas emission rate by 80 to 95% from the emission rate of 1990, by 2050, as recommended by the Cancun Agreement.  The Roadmap details numerous pathways and practices to attain that goal.

The Great Britain is reported to be setting still more rigorous objectives for itself of reducing greenhouse gases emission rates to 50% of the amount emitted during 1990 by 2025.  This is a considerably deeper reduction than the EU has set, and is more stringent than that of any similar-sized country, such as Germany.

China’s 12^th Five Year Plan, covering 2011-2015, envisions overall expansion of its production of energy and consumption of fossil fuels, especially coal.  Its emphasis is on increasing the efficiency of its use of energy, resulting in lower energy intensity, i.e., the amount of energy needed for a fixed amount of its economic output.  Renewable energy other than hydroelectric generation constitutes a very small part of China’s energy economy, but under the Plan this sector is intended to expand rapidly.

Present Status in the U. S. The United States is the only major emitter of greenhouse gases without a national energy and climate change policy in place.  Ever since the Senate’s rejection of the Kyoto Protocol, numerous legislative efforts have been made to establish a policy that addresses climate change, but have failed.  In the resulting vacuum at the national level, three regional greenhouse gas agreements have recently been adopted among various American states and Canadian provinces—the Western Climate Initiative, the Midwest Greenhouse Gas Reduction Accord, and the New England and mid-Atlantic Regional Greenhouse Gas Initiative.  These programs have varying levels of coverage and differing terms duration.  Being agreements between sovereign states and provinces, actual implementation requires that each participating state or province pass its own legislation in order to put the terms of the agreement in force.  These factors obviously render compliance complicated and regionally inconsistent.  Commercial and industrial activity is impeded by not having a single national policy covering the countries in question.

U. S. National Academies Report: America’s Climate Choices.  The National Research Council, a section of the National Academies, issued its report, America’s Climate Choices, on May 12 2011 (see Note 1).  The report is summarized here, and further details are presented below under the heading Details.

The Earth is warming, and will continue to do so.  The report summarizes known climate science and develops forecasts of future trends using three emissions “scenarios”.  Since the industrial revolution, the time trends of a) mankind’s burning of fossil fuels, b) increasing atmospheric concentrations of the greenhouse gas CO₂, and c) increasing average global temperatures all follow similar, linked paths.  For these and other reasons global warming is understood to be due to the man-made emissions of greenhouse gases.  Using computation-based climate models and three scenarios of further emissions of greenhouse gases, the report predicts worsening trends of scenario-dependent increased global warming in the future, and its consequences for the earth and for us, its inhabitants.

Recommendations. The report makes several recommendations.  It emphasizes that, in view of the long time period involved in combating global warming, repetitive cycles of identifying problems, developing goals, creating policies and practices to achieve the goals, and assessing attainment of the goals, will necessarily be involved.  The report calls this process iterative risk management.  It is highly recommended by the report because many aspects of climate change, the models used for predicting future trends, and the models used to predict effects of policies and practices, are complex and imperfect, and are likely to improve with time.

First, the report recommends substantially reducing greenhouse gas emissions.  This is considered a matter of great urgency, to be begun without delay.

Second, the U. S. government in conjunction with other levels of government and members of the private realm should begin efforts for adapting to the effects of global warming now.  Its effects are already being felt.  Society should begin practices and development of infrastructure to deal with these and further adverse effects of warming, those that we already know about and those that remain to be identified.

Third, the U. S. government should invest in the science of climate change.   Research into understanding climate change and predicting its effects are needed to limit its progress and to adapt to its effects.

Fourth, the U. S. government should sponsor development of new information systems that promote informing the public as to the choices confronting us concerning measures and policies addressing climate change.

Fifth, in the U. S. the response mechanism should include widespread deliberations among the public in order to develop and implement public policies, and review them regularly.

Sixth, the report recognizes that the U. S. is not alone in dealing with global warming, but that it is in fact a planet-wide challenge requiring coordinated efforts around the world.  Therefore the U. S. should actively participate in world-wide responses to climate change.  These must address reducing greenhouse gas emissions, improving adaptation policies, and developing effective reporting modalities.

Seventh, it should be the role of the U. S. government to coordinate the development and implementation of America’s varied responses to global warming.  Presently several response mechanisms are being created at the municipal, state and regional levels.  These risk lacking cohesion and creating mixed, if not conflicting, response mechanisms.  The federal government has a leading role to play in this endeavor.

Conclusions.  America’s Climate Choices affirms the broad acceptance in the scientific community that global warming is due to atmospheric emissions of man-made greenhouse gases, predicts that warming and its effects will worsen in the future without action, and outlines broad policy recommendations to address this issue.  As noted by both supporters and opponents, the report does not make specific recommendations concerning the nature of policies to put in place and actions to take (see comment in the New York Times).  This cannot be considered a critical failing.  The report rather urges us to action, leaving the details of what actions to take up to us, the public and our elected representatives, and to America’s corporate citizens.

The report stresses the necessity to address global warming using the tools of risk assessment, since the computational climate models are probabilistic in nature, and other factors, including the nature of human and economic behavior, are poorly modeled in these terms.  The report points out that in our ordinary lives, we buy insurance (at some economic costs) to protect against a perceived risk that has a relatively low probability of coming to pass (providing some economic benefit). 

A pertinent example that comes to mind, at the time of this writing, is the flooding along the Mississippi river now happening.  This nation has invested major financial resources to “buy flood insurance” in the form of erecting the vast levee system along the river.  The levees are our insurance policy, countering the risk of major economic and societal disruptions from flooding were they not in place.

Finally, the report stresses the necessity of early and meaningful action.  Delay only makes the problems facing humanity in confronting global warming more critical on the short term, leading perhaps to greater expenditures and a greater possibility of being too late to avert major consequences.

Details.

Historical Climate and Energy Patterns are Closely Correlated.

The annual average values of global temperature have been increasing since the beginning of the industrial revolution, when humanity began burning fossil fuels in earnest to supply its energy.  This is seen in the following graphic which shows

Copyright © National Academy of Sciences; reproduced with permission.

year-by-year global average temperatures from 1880 to 2010 (black squares and lines), and smoothing obtained by averaging each year over a window of five years (red curve).  It is seen that global temperatures have increased about 0.8ºC (1.4ºF) over the 130 years shown and are increasing more rapidly as the curve approaches the present.  Most of this change, about  0.6ºC (1.0ºF), has occurred in the last 30 years.

The shape and duration of the temperature dependence on time mirror closely both the accumulated total of CO₂ released by burning fossil fuels over this time period (navy blue curve and amounts on the right axis), as well as the measured increase in concentration of CO₂ in the atmosphere (magenta curve and amounts on the left axis), seen in the following graphic. (Note that the curves are compressed toward the right, compared to FIGURE 2.1 because the time axis here extends from 1800 to 2010.)

Copyright © National Academy of Sciences; reproduced with permission.

The preponderance of the scientific evidence supports that the temperature increase is man-made, due largely to the use of fossil fuels.  According to the report, the atmospheric concentration of CO₂ is now higher than at any time in at least the last 800,000 years (citing D. Lüthi, and coworkers, Nature 453:379-382, 2008).

In the U. S., the adverse effects of the warming already experienced have led to increased temperatures, increased overall precipitation by about 5%, rising sea levels that erode shorelines and damage wetlands, thawing of Alaskan permafrost, reductions in mountain snowpacks that affect water flow in rivers, altered precipitation patterns including increased intensity coupled elsewhere with increased aridity, and substantial increase in number and seasonal length of wildfires.

Climate Predictions for the U. S.  The report predicts future climate trends to 2100 using a variety of computational global climate models particularized to the U. S., and three greenhouse gas emission “scenarios” drawn from the U. N. Intergovernmental Panel on Climate Change.  Results are shown in the following graphic, for, bottom to top, the case of continuing emissions along a trajectory from the 20^th century (green line); “lower emissions” (blue line); “higher emissions” (orange line); and “even higher emissions” (pink line).

Copyright © National Academy of Sciences; reproduced with permission.

The solid heavy black lines at the left are the actual historical data up to about 2008.

These images represent annual rates of adding CO₂ from burning fossil fuels to the atmosphere (left panel), where for each year the height of a curve represents how much is added during that year only, and the cumulative amount of CO₂ present in the atmosphere (right panel), where each year’s value on a curve represents the total amount added from the beginning of the model up to the year in question, added to the base level of CO₂ at the beginning of the industrial revolution.

To help understand the left and right panels above, let’s imagine a bathtub filling with atmospheric CO_2.  The left panel above can be considered the faucet, adding CO₂ to the tub.  The right panel can be considered the bathtub, filling higher and higher with more and more CO₂ with each year.  This is because the drain is mostly closed so that most of the CO₂ is retained in the tub.

The effects of the predicted atmospheric CO₂ concentrations (right panel) on predicted global temperature deviations from an average baseline over 1950-1970 is shown in the following graphic for, bottom to top, the “lower emissions scenario”, the “higher emissions scenario” and the “even higher emissions scenario”.

Copyright © National Academy of Sciences; reproduced with permission.

In the graphic above, the jagged black line from 1900 to 2010 shows the actual temperature deviation.  The green line shows a model simulation for the same time period, indicating that the model reproduces observed temperatures well.  This gives confidence in the use of the model.  The colored lines from 2010 to 2100 are the same scenarios as in FIGURE 2.3.  They show the results of modeled temperature increases for each case.  In none of the scenarios does the temperature stop increasing.  Additionally, no significant differences between the scenarios become apparent until about 20 years from now.  I.e., we in the U. S. will not be able to know until then whether adopting one or another of the scenarios will have serious consequences.  The report points out that this is a serious risk of continuing on a “business as usual” emissions trajectory.

The report also  points out that these various trajectories carry with them numerous known and unknown climatic risks due their impacts on life and the physical world.  A few examples of predicted changes include worse heat waves; global sea level rise; bleaching and loss of coral reefs; greater aridity in the Southwest; effects on agriculture due to higher photosynthetic activity, temperature, precipitation, and insect infestations; changes in forest species prevalence; and public health and economic risks including dangers from extreme weather events.

Managing Environmental Risk.  In addition to the above predictions, which can be modeled reasonably well, the report points out that many of the effects of global warming are less capable of being modeled or estimated.  As a result they need to be analyzed by methods of risk assessment, which ultimately needs to be done on a societal level, involving serious consideration in the scientific, political and public realms.  Costs and benefits of actions cannot easily be evaluated.  If we choose to implement certain actions to counter global warming, their costs are felt right away, but the intended benefit may not become evident for many years, and both aspects may affect future generations of people. 

Iterative Risk Management Approach.  For these and other reasons the report recommends following a cycle of trying particular measures, assessing whether and how effectively they work, and changing or reinforcing the measures depending on the outcome.  This is termed iterative risk management, and is illustrated using the following graphic.

Copyright © National Academy of Sciences; reproduced with permission.

We Need to Begin Acting Now. As shown in the report, climate change due to man-made emissions of greenhouse gases is already occurring.  Delaying efforts to reduce emissions means later measures would have to be more dramatic, immediate, and expensive.  Delay also increases the risk of being left with adverse effects that can’t be reversed.  Immediate action is necessary because the main greenhouse gas, CO₂, persists in the atmosphere for centuries or longer so that its effects on global warming will persist.  The U. S. and the rest of the world are currently installing new energy facilities, many of which will continue to emit greenhouse gases, which risks making global warming worse.  All these considerations point to the need to begin reducing greenhouse gas emissions right away.

Note 1. The report is the result of a legal mandate enacted by Congress in 2008 and is to be delivered to it for its consideration.  Congress directed the National Academy of Sciences to “investigate and study the serious and sweeping issues relating to global climate change and make recommendations regarding what steps must be taken and what strategies must be adopted in response to global climate change”.  America’s Climate Choices summarizes and develops recommendations based on four preceding reports issued under this mandate that present aspects of this topic in greater detail.  These are:

Advancing the Science of Climate Change;

Limiting the Magnitude of Future Climate Change;

Adapting to the Impacts of Climate Change; and

Informing an Effective Response to Climate Change.

The reports were prepared by a large panel of experts drawn from the academic realm, nongovernmental organizations, governmental agencies, and the commercial world.  Each report, including America’s Climate Choices, was reviewed by several outside experts likewise drawn from these three areas of society, and finally approved by the National Research Council.

© 2011 Henry Auer