Article: Global Action to Mitigate Greenhouse Gas Emissions

Many governments from developed countries have made explicit commitments to reduce greenhouse gas (GHG) emissions in the near-term, but the declared targets are not ambitious enough. The combined effect of the developed country targets to reduce emissions would lead to only about 8-14 percent reduction in their emissions by 2020 compared with 1990. This falls short of the 25 to 40 percent reduction that the Intergovernmental Panel on Climate Change (IPCC) has suggested is needed for developed countries to put emissions on a pathway that would prevent temperatures from rising by more than 2oC, a goal supported by world leaders from a number of developed and developing countries at L’Aquila.

The United Nations Framework Convention on Climate Change (UNFCCC) recognizes that along with adaptation, mitigation is one of the two central approaches in the international climate change process. Mitigation involves human interventions to reduce the emissions of greenhouse gases by sources or enhance their removal from the atmosphere by “sinks”. A “sink” refers to forests, vegetation or soils that can reabsorb carbon dioxide (CO2). CO2 is the largest contributing gas to the greenhouse effect. In the 200 years since 1800, levels have risen by over 30 percent. Since levels of greenhouse gases are currently rising even more steeply, leading to the most dramatic change in the atmosphere’s composition in at least 650,000 years, international action on mitigation is urgently required.

An important part of combating climate change is mitigating GHG emissions. Opportunities for mitigating GHG fall into three broad categories:

  • Reducing emissions;
  • Enhancing removals; and
  • Avoiding (or displacing) emissions.

The concept of “Mitigation Potential” has been developed to assess the scale of GHG reductions that could be made, relative to emission baselines, for a given level of carbon price (expressed in cost per unit of CO2 equivalent emissions avoided or reduced). Mitigation potential is further differentiated in terms of “Market Potential” and “economic potential.

Market potential is the mitigation potential based on private costs and private discount rates which might be expected to occur under forecast market conditions, including policies and measures currently in place, noting that barriers limit actual uptake.

Economic potential is the mitigation potential, which takes into account social costs and benefits and social discount rates, assuming that market efficiency is improved by policies and measures and barriers are removed.

The United States Environmental Protection Agency (EPA) published a new report in June 2015 with the title “Climate Change in the United States: Benefits of Global Action”. The report is the product of the Climate Change Impacts and Risks Analysis (CIRA) project which is a peer-reviewed study comparing impacts in a future with significant global action on climate change to a future in which current GHG emissions continue to rise.

This report illustrates that global action on climate change will significantly benefit Americans by saving lives and avoiding costly damages across the US economy. It estimates the physical and monetary benefits to the US of reducing global GHG emissions.

The report used the following scenarios for estimating and here are the characteristics of the Reference and Mitigation Scenarios in 2100:


This report describes climate change damages in the US across multiple sectors using a consistent set of scenarios and underlying assumptions. In doing so, the study estimates the physical and economic risks of unmitigated climate change and the potential benefits to the US of reducing global GHG emissions. Importantly, only a small portion of the impacts of climate change are estimated, and therefore this report captures just some of the total benefits of reducing GHGs. Looking across the large number of sectoral impacts described in this report, a number of key findings emerge:

  • Unmitigated climate change is projected to profoundly affect human health, the US economy, and the environment. The CIRA analyses demonstrate substantial and far-reaching changes over the course of the 21st century—and particularly at the end of the century—with negative consequences for a large majority of the impact sectors. In addition, the analyses suggest that climate change impacts will not be uniform across the US, with most sectors showing a complex pattern of regional-scale impacts;
  • Global action to mitigate GHG emissions is projected to reduce and avoid impacts in the US that would otherwise occur in a future with continued high growth in GHG emissions. Importantly, these benefits are projected to increase over the course of the century. The analyses indicate that risks and impacts over the long term will not be avoided unless there is near-term action to significantly reduce GHG emissions. This report presents benefits for one illustrative global GHG mitigation scenario. More stringent emissions reductions would likely increase the benefits compared to the Reference scenario, and, conversely, less stringent reductions would likely decrease the benefits;
  • Global GHG mitigation substantially reduces the risk of some extreme weather events and their subsequent impacts on human health and well-being by the end of the century;
  • Adaptation, especially in the infrastructure sector, can substantially reduce the estimated damages of climate change. For some impacts, such as those described in the Coastal Property section, well-timed adaptation can have a larger effect on reducing the risks of inaction than global GHG mitigation, particularly in the near term, highlighting the need for concurrent mitigation and adaptation actions; and
  • For some impacts, the effects of global GHG mitigation can vary across different projections of future climate. This is particularly true for those sectors sensitive to changes in precipitation. For a few of these sectors, mitigation results in either benefits or dis-benefits depending upon the simulated level of future precipitation.  By analyzing multiple types of impacts by sector, such as flooding, drought, water quality, and supply/demand in the water realm, and using a range of projections for future precipitation, a more comprehensive understanding of potential impacts and mitigation benefits is gained.

The following tables illustrate the estimated physical and monetary benefits (Avoided Impact) to the US of global GHG mitigation compared to the reference scenario in the year 2050 and 2100 for all six sectors. Although not available for all sectors, cumulative benefits for the entire 21st century would likely be much larger than the annual estimates presented in the tables. In addition, the individual monetized estimates are not aggregated, as only a subset of climate change impacts is quantified in this report, and there are differences in the types of costs being quantified across the sectors:

1. Health Sector:  Climate change is projected to harm human health in a variety of ways through increases in extreme temperature, increases in extreme weather events, decreases in air quality, and other factors. Extreme heat events can cause illnesses and death due to heat stroke, cardiovascular disease, respiratory disease, and other conditions. Increased ground-level ozone is associated with a variety of health problems, including reduced lung function, increased frequency of asthma attacks, and even premature mortality. Higher temperatures and changes in the timing, intensity, and duration of precipitation affect water quality, with impacts on the surface water we use. There are a variety of other impacts driven by climate change that are expected to pose significant health hazards, including increases in wildfire activity.


Here is the table which illustrates estimates for each section in terms of fewer deaths and corresponding values as a result of mitigations efforts:

1        HEALTH: Global GHG Mitigation is Projected to Result in…
1.1 Air Quality Estimated Fewer Deaths from Poor Air Quality:
2050 1,700 Fewer Deaths Valued at $160 Billion
2100 12,000 Fewer Deaths Valued at $200 Billion
1.2 Extreme Temperature Estimated Fewer Deaths from Extreme Heat and Cold in 49 Major Cities:
2050 1,700 Fewer Deaths Valued at 21 Billion
2100 12,000 Fewer Deaths Valued at $200 Billion.
1.3 Labour Estimated Avoided Loss:
2050 360 Million Labour Hours Valued at $18 Billion
2100 1.2 Billion Labor Hours Valued at  $110 Billion
1.4 Water Quality Estimated Avoided Damages from Poor Water Quality:
2050 $507 to $700 Million
2100 $2.6 to 3.0 Billion

Here are the Regional Highlights on each sub-sector:

  • Air Quality: In 2100, areas of the Southeast are projected to experience an annual increase in ozone (O3) and fine particulate matter (PM2.5) of 0.7 ppb and 1 μg/m-3, respectively. In the Mitigation scenario, the levels of O3 and PM2.5 are projected to decrease by 120 percent and 88 percent, respectively, compared to the Reference;
  • Extreme Temperature: Without mitigation, major cities in the Northeast from D.C. to Boston are projected to suffer a combined 2,600 extreme temperature mortalities in 2100, compared to 190 in the Mitigation scenario;
  • Labor: In 2100, the Southwest is projected to experience a 3.4 percent decrease in high-risk labor hours worked in the Reference scenario, compared to a decrease of 0.82 percent in the Mitigation scenario; and
  • Water Quality: The Southwest is projected to experience water quality damages of approximately $1.8 billion in 2100 under the Reference scenario, compared to $470 million in the Mitigation scenario.

 2.  Infrastructure Sector:  Experience over the past decade provides compelling evidence of how vulnerable infrastructure can be to climate change effects, including sea level rise, storm surge, and extreme weather events. Climate change will put added stress on the nation’s aging infrastructure to varying degrees over time. Sea level rise and storm surge, in combination with the pattern of heavy development in coastal areas, are already resulting in damage to infrastructure such as roads, buildings, ports, and energy facilities. Floods along the nation’s rivers, inside cities, and on lakes following heavy downpours, prolonged rains, and rapid melting of snowpack are damaging infrastructure in towns and cities, on farmlands, and in a variety of other places across the nation. In addition, extreme heat is damaging transportation infrastructure such as roads, rails, and airport runways.

Here is the table which illustrates estimates for each section in terms of vulnerability, avoided adaptation costs, avoided adaptation, and avoided damages, etc.:

2.    IFRASTRUCTURE: Global GHG Mitigation is Projected to Result in…
2.1 Bridges Estimated Fewer Bridges Made Structurally Vulnerable:
2050 160 to 960 Fewer Bridges Valued at $0.12 to $1.5 Billion
2100 720 to 2,200 Fewer Bridges Valued at $1.1 to 1.6 Billion
2.2 Roads Estimated Avoided Adaptation Costs:
2050 0.56 to $2.3 Billion
2100 $4.2 to $7.4 Billion
2.3 Urban Drainage Estimated Costs in Avoided Adaptation from the 50-year Storm & 24hrs.
2050 $56 Million to $2.9 Billion
2100 $50 Million to $6.4 Billion
2.4 Coastal Property Estimated Costs in Avoided Damages and Adaptation:
2050 $0.14 Billion from Sea Level Rise and Storm Surge
2100 $3.1 Billion from Sea Level Rise and Storm Surge

Here is an image:


Here are the Regional Highlights:

  • Bridges: In the Great Lakes region, approximately 520 bridges are projected to be vulnerable in 2100 under the Reference scenario, compared to 65 in the Mitigation scenario;
  • Roads: In 2100, the Great Plains region is projected to incur road damages of approximately $3.5 billion in the Reference scenario, compared to $1.1 billion in the Mitigation scenario;
  • Urban Drainage: In 2100, major cities analyzed in the Great Plains are estimated to incur $2.1 million per square mile in damages associated with urban drainage systems in the Reference scenario, compared to $750,000 per square mile in the Mitigation scenario; and
  • Coastal Property: In 2100, coastal property in the Tampa Bay area is projected to incur $2.8 billion in damages from sea level rise and storm surge in the Reference scenario without adaptation. When adaptation measures are implemented, total costs in 2100 fall to $500 million in the Reference scenario, compared to $450 million in the Mitigation scenario.

3. Electricity:  Climate change has implications for electricity production, distribution, and use. For example, coastal electricity infrastructure, such as power plants and substations, are vulnerable to storm surge and wind damage. Elevated temperatures diminish thermal power plant efficiency and capacity, and can reduce the capacity of transmission lines. In addition, effects on water supply alter the quantity and temperature of cooling water available for thermoelectric generation. On the demand side, warmer winters decrease the demand for heating. However, this reduction is smaller than the increase in electricity demand for cooling due to higher summer temperatures. Across the U.S., higher minimum temperatures increase the number of days in a year when air conditioning is needed, and higher maximum temperatures increase the peak electricity demand, further stressing our aging power grid.

Here is an image:


Here is the table which illustrates estimates only for 2050:

3        ELECTRICITY: Global GHG Mitigation is Projected to Result in…
3.1 Demand and Supply Estimated Reduction and Savings in Power System Costs:
2050 1.1% to 4.0% reduction in energy demand and $10 to $34 Billion in savings.
2100 Not Estimated

Here is the Regional Highlight:

  • Electricity Demand: The South Central region is projected to experience a 2.0 percent to 4.2 percent increase in electricity demand under the Reference scenario in 2050. In the Mitigation scenario, the projected change in demand ranges from -1.4 percent to 1.6 percent.

4. Water Resources:  Important regional changes may be masked when results are presented at the national level. For example, the wildfire analysis reveals that the projected changes in the Southwest and Rocky Mountain regions are the primary drivers of national trends of increasing wildfire activity over time.

The temporal scale of climate change impact is also important. While some impacts are likely to occur gradually over time, others may exhibit threshold (tipping point) responses to climate change, as large changes manifest over a short period of time. For example, high-temperature bleaching events projected to occur by 2025 are estimated to severely affect coral reefs in the Caribbean. Therefore, simply analyzing an impact in one time period (e.g., 2100) may mask important temporal dynamics that are relevant to decision-makers.

water resources

The following table illustrates estimates for each section in terms of flooding damages, fewer sever/extreme droughts with avoided damages, and avoided damages due to water shortage:

4        WATER RESOURCES: Global GHG Mitigation is Projected to Result in…
4.1 Inland Flooding Estimated Change in Flooding Damages Ranging:
2050 From $260 Million to $230 Million in Avoided Damages
2100 From $32 Million to $2.5 Billion in Avoided Damages
4.2 Drought Estimated Fewer Severe/Extreme Droughts with Avoided Damages:
2050 29% to 45% reduction and App. $1.2 to $1.4 Billion Avoided  Damages
2100 40% to 59% reduction and $2.6 to $3.1 Billion Avoided Damages.
4.3 Water Supply & Demand Estimated in Avoided Damages due to Water Shortages:
2050 $3.9 to $54 Billion
2100 $11 to $180 Billion

Here are the Regional Highlights:

  • Inland Flooding: In Texas, projected damages associated with the 100-year flood event are $3.6 billion in 2100 under the Reference scenario, compared to $2.6 billion in the Mitigation scenario;
  • Drought: In the Southwest, the number of severe and extreme droughts is projected to nearly quadruple by the end of the century in the Reference scenario compared to today. In the Mitigation scenario, the incidence of drought is not projected to change substantially from present day; and
  • Water Supply and Demand: California is projected to incur $4.5 billion in damages in 2100 due to changes in water supply and demand in the Reference scenario. However, climate change under the Mitigation scenario is projected to result in an increase in welfare of $40 million.

5. Agriculture and Forestry:  US agricultural and forest production are sensitive to changes in climate, including changes in temperature and precipitation, more frequent and severe extreme weather events, and increased stress from pests and diseases. At the same time, climate change poses an added risk to many forests due to ecosystem disturbance and tree mortality through wildfire, insect infestations, drought, and disease outbreaks. Climate change has the potential to both positively and negatively affect the location, timing, and productivity of agricultural and forest systems, with economic consequences for and effects on food security and timber production both in the US and globally. Adaptation measures, such as changes in crop selection, field and forest management operations, and use of technological innovations, have the potential to delay and reduce some of the negative impacts of climate change, and could create new opportunities that benefit the sector.

agriculture and forestry

Here is the table which illustrates estimates in terms of avoided damages for agriculture as well as forestry:

5        AGRICULTURE & FORESTRY: Global GHG Mitigation is Projected to Result in…
5.1 Agriculture Estimated in Avoided Damages:
2050 $1.5 to $3.8 Billion
2100 $6.6 to 11.0 Billion
5.2 Forestry Estimated Avoided Damages:
2050 $9.5 to $9.6 Billion
2100 $520 Million to $1.5 Billion

Here are the Regional Highlights:

  • Agriculture: In the Southeast, yields of irrigated soybeans are projected to decrease 23 percent in 2100 under the Reference scenario. Under the Mitigation scenario, yields are projected to increase 4.7 percent; and
  • The forestry analysis was conducted using a national market model, and as such, the results did not lend themselves to a regional highlight for this sector.

6. Ecosystems:  Ecosystems are held together by the interactions and connections among their components. Climate is a central connection in all ecosystems. Consequently, changes in climate will have far-reaching effects throughout Earth’s ecosystems. Climate change can affect ecosystems and species in a variety of ways; for example, it can lead to changes in the timing of seasonal life-cycle events, such as migrations; habitat shifts; food chain disruptions; increases in pathogens, parasites, and diseases; and elevated risk of extinction for many species.2 Climate change directly affects ecosystems and species, but it also interacts with other human stressors on the environment. Although some stressors cause only modest impacts by themselves, the cumulative impact of climate and other changes can lead to dramatic ecological impacts. For example, coastal wetlands already in decline due to increasing development will face increased pressure from rising sea levels.


Here is the table which illustrates estimates in terms of avoided loss, corresponding consumer benefits, etc.:

6   ECOSYSTEMS: Global GHG Mitigation is Projected to Result in…
6.1 Coral Reefs Estimated Avoided Loss of Coral:
2050 53% in Hawaii, 3.7% in Florida, 2.8% in Puerto Rico – Valued $1.4 Billion
2100 35% Hawaii, 1.2% in Florida, and 1.7% in Puerto Rico – Valued $1.2 Billion
6.2 Shellfish Estimated Avoided Loss of with Corresponding Consumer Benefits:
2050 11% of Oyster Supply, 12% of Scallop Supply, 4.6% of Clam Supply – $85 Million
2100 34% of Oyster Supply, 37% of Scallop Supply, 29% of Clam Supply – $380 Million
6.3 Freshwater Fish Estimated change in Recreational Fishing Ranging from:
2050 $13 million in Avoided Damages to $3.8 million in Damages
2100 $95 million in Avoided Damages to $280 million in Damages
6.4 Wildfire Estimated Fewer Acres Burned and Corresponding Avoided Wildfire:
2050 2.1 to 2.2 million  – Response Cost of $160 to $390 Million
2100 6.0 to 7.9 Million – Response Cost of $940 Million to $1.4 Billion
6.5 Carbon Storage Estimated Fewer Storage of Carbon Stored, and Corresponding Costs:
2050 26 to 78 Metric Tons Storage and Corresponding Costs of $7.5 to $23 Billion
2100 1 to 26 Million Metric Tons Storage and Corresponding Costs of $880 Million to $12 Billion

Here are the Regional Highlights:

  • Coral Reefs: By the end of the century, Hawaii is projected to lose 98 percent of its current shallow-water coral in the Reference scenario, compared to 64 percent in the Mitigation scenario;
  • Shellfish:  Acidification in the Pacific Northwest is already affecting U.S. shellfish harvests. The U.S. supplies of oysters, clams, and scallops are projected to decline 45 percent, 32 percent, and 48 percent, respectively, in the Reference scenario in 2100, compared to 11 percent, 3 percent, and 11 percent, respectively, in the Mitigation scenario;
  • Freshwater Fish: Throughout the Appalachians, global GHG mitigation is projected to preserve approximately 70 percent of habitat for coldwater fish species (e.g., trout) that would otherwise be lost by the end of the century to rising temperatures from unmitigated climate change;
  • Wildfire: In the Rocky Mountains, an estimated 1.9 million more acres are projected to burn in 2100 under the Reference scenario compared to today. In the Mitigation scenario, an estimated 1.5 million fewer acres are projected to burn compared to today; and
  • Carbon Storage: The Northwest is projected to experience a 6.1 percent decrease in terrestrial carbon storage in 2100 under the Reference scenario, compared to a 2.4 percent decrease in the Mitigation scenario.

The bottomline is that this report represents a significant and important contribution to estimating the multi-sectoral benefits to the US of global GHG mitigation. Although the results presented in this report do not provide comprehensive coverage of all potential impacts, the breadth and depth of the analyses will expand in future work within the CIRA project. Comprehensive and quantitative estimates of climate change impacts are not only needed to evaluate the benefits of GHG mitigation, but also to evaluate the cost-effectiveness of adaptation responses, and to support the improvement of other economic tools used to analyze climate and energy policies. 

Although CIRA only begins to capture many of the dynamics and uncertainties involved in impact analysis (e.g., interactions among sectoral models), this report provides timely and quantitative estimates as the science continues to advance in this field. Future work to refine projections of how GHG emissions affect the climate, and how these changes affect society and the environment, will improve the understanding and confidence in the estimates presented in this report.


  1. OECD – For a stronger, Cleaner, Fairer world economy;
  2. UNFCCC – Fact Sheet: The need for mitigation;
  3. Green Facts – Climate Change Update;
  4. EPA – Climate Change in the United States – Benefits of Global Action;
  5. EPA – Climate Action Benefits;
  6. EPA – Climate Action Benefits – Health;
  7. EPA – Climate Action Benefits – Infrastructure;
  8. EPA – Climate Action Benefits – Electricity;
  9. EPA – Climate Action Benefits – Water Resources;
  10. EPA – Climate Action Benefits – Agriculture and Forestry;
  11. EPA – Climate Action Benefits – Ecosystems; and
  12. EPA – Text Version of Climate Action Benefits – Regional Highlight Map.