2001: An Alternative Climate Scenario: Energy Choices for the 21st Century

The amount of CO₂ in the atmosphere has increased approximately 30% since pre-industrial times. It is believed that the majority of this increase is due to increased energy use, specifically the burning of fossil fuels (coal, oil and gas), which releases CO₂ to the air. It is also believed that this increase, together with the increase of other greenhouse gases, has been a prime cause of the global warming of 0.6C in the last 100 years.

After World War II global economies grew rapidly, driven by the burning of fossil fuels. Fossil fuel use has continued to grow since the 1970s, but the growth rate has declined. The growth rate of fossil fuel use was 4% per year after WW II. During the past 25 years, CO₂ emissions increased at a rate of about 1% per year both globally and in the United States.

How difficult would it be to reduce this rate of increase to 0% per year? This would imply a constant emission at today's values, with no increases from year-to-year. Pessimists assume that the growth rate of climate forcings will increase. They suggest population will explode; the developing world will burn energy as fast as we do, and they will use similar fuels.

The Intergovernmental Panel Climate Change emphasizes such a "business-as-usual" scenario in climate simulations for the period 2000-2050, which yields an increase of climate forcing of about 3 Watts. An Alternative Scenario would seek to achieve an increased forcing of only about 1 Watt (per square meter). The BAU scenario leads to climate disaster, while the climate change is more moderate in the A scenario.

There are three key elements in the A scenario:

1) the CO₂ growth rate levels out and begins to decline slightly during the 50 year period 2) the CH₄ growth rate, which has been declining in the past 20 years, declines further and becomes negative, such that CH₄ in 2050 is actually less than it is today 3) black carbon (BC) aerosols, which cause warming, will decrease, or at least their growth rate will slow down enough that the net aerosol forcing will not increase (sulfates, which cause cooling, may decrease in amount, at least in many regions).

This summer's research focuses on developing a quantitative approach to achieve the aspect of the Alternative Scenario that calls for reducing CO₂ growth rate. Your team, the A team, has been called in by the new President. He must determine an economically practical policy for the country to pursue to address an international protocol that slows climate change. The proposed protocol would require the U.S. to reduce its CO₂ emissions to a substantially lower level a decade or so in the future, while in fact emissions in recent years have been sky-rocketing.

He realizes he cannot follow a Business-as-Usual path - he must find an Alternative Scenario. But he needs reliable scientific advice - what can he do that would, from an environmental and climate perspective, address the spirit of the protocol and at the same time avoids the economic problems? So he calls for the A-team: you. Your job is to give dispassionate objective quantitatively meaningful assessments of the elements that are candidates for making up an Alternative Scenario.

In order to do this, we have to make some assumptions about expected growth rates. We will use 1.5% per year growth in energy demand. 1.015**20 in 20 years would be about a 35% growth in energy needs. This may be consistent with Vice President's Cheney's original statement that the U.S. needed 1300 new power plants in the next 20 years.

There are a number of ways we can reduce our CO₂ emissions. Using energy more efficiently in industry, businesses and homes would reduce CO₂ emissions, but an up-front investment is required to install more efficient equipment. Making automobiles more efficient in their use of gasoline would reduce emissions, but increase the price of cars. Another approach is to look for alternative sources of energy that produce little or no CO₂. How would an increase in the use of natural gas, solar energy, methanol, nuclear power, etc., reduce the CO₂ emissions if the energy use from each alternative source was increased by 25%?

Breakdown of Research Team Roles

Each team member will be responsible for developing an understanding of one energy source, as well as collecting the data and calculating the statistics for the each source.

• Leila Woolley, Hydroelectric
• Umit Kenis, Nuclear
• Jane Zeng, Energy Efficiency and Clean Coal
• Crissaris Sarnelli, Geothermal
• Tanya Martinez, Wind
• Betsy Hernandez, Solar

Guiding Science Questions

Part 1: Defining the Project

How has the use of different energy sources changed over the last 50 years in the U.S., e.g. coal, oil, gas, nuclear, hydropower, solar, wind, etc.? How much do each of these contribute to total U.S. energy consumption today? How much do each of them contribute to CO₂ emissions?

What are the specific things that could be done to improve efficiency/increase conservation, and how can these be evaluated. For example, what proportion of oil is used for transportation? If automobile mpg were increased 50%, how much would that reduce oil requirements and CO₂ emissions? If lighting efficiency were doubled, e.g., with use of fluorescent bulbs, how much would that reduce energy requirements and CO₂ emissions?

What are the candidate alternative energy sources that produce no CO₂ or less CO₂ and how can their potential for the U.S. be quantified? How much would CO₂ emissions be reduced if coal power plants were all replaced with gas? How much energy would be provided if the output of existing nuclear plants was increased 50%?

Part 2: Producing a Quantitative Assessment

Based on projected future energy use in the US, what are the best candidate alternative resources and/or energy efficiency strategies satisfy the future energy needs of the US, while reducing the CO₂ emissions over the next 20 years from 1.5% growth per year to .5% to 0% growth?

How much of assumed energy demand do you estimate could be satisfied by improved energy efficiency? What leads you to that estimate? How much would need to be taken up by a fuel source that does not produce CO₂ (such as solar power or wind power)?

• How much energy is derived from the energy source/strategy?
• What is the growth rate of the energy source/strategy?
• How many people does this energy source/strategy support?
• How much CO₂ is saved? Does this source zero-out CO₂ or reduce it (by how much)?
• How is the source producing cleaner energy? What are the environmental effects?
• Is this a cost effective energy source/strategy?
• What is the state of our technological capability to utilize this energy source/strategy?

Is it practical for the non-CO₂ sources to increase enough so that the use of those that produce CO₂ (coal plus oil plus gas) does not increase?

What is the potential from each alternative energy source? Provide a qualitative discussion of the pros and cons of the option, environmental concerns, etc., which are also elements that a decision-maker will want to consider.

What would need to be done to reduce U.S. CO₂ emissions still further, say by the amount called for in the Kyoto protocol?

Basic Science Concepts and Questions

• What is Greenhouse Gases (GG), and what do they have to do with a Greenhouse?
• What are the main Greenhouse Gases in the atmosphere?
• What is the Natural Greenhouse Effect (GE), and what GG is most important here?
• What is the Anthropogenic Greenhouse Effect, and what GGs play a role here? Which GG is most important and why?
• How do the different GG in question 4 differ in their ability to trap heat?
• Based on question 5 what would be the most efficient way of reducing the Anthropogenic GE? (Alternative Scenario?)
• Do aerosols affect the GE? Which ones and how?
• Would changes in sulfate aerosols increase or decrease the GE?
• Would changes in black soot aerosols increase or decrease the GE?