IPCC AR4 Summary for Policymakers
Released on November 17, 2007, the Summary for Policymakers of the IPCC Fourth Assessment Synthesis Report represents the IPCC’s most comprehensive and definitive statement to date on climate change. The report presents the key findings of the three Working Group reports released earlier this year by the Nobel Peace Prize winning-IPCC.
The following are some of the key highlights addressed in the Synthesis Report:
- There is strong certainty that most of the observed warming of the past half-century is due to human influences, and a clear relationship between the growth in manmade greenhouse gas emissions and the observed impacts of climate change.
- The climate system is more vulnerable to abrupt or irreversible changes than previously thought.
- Avoiding the most serious impacts of climate change -- including irreversible changes – will require significant reductions in greenhouse gas emissions.
- Mitigation efforts must also be combined with adaptation measures to minimize the risks of climate change.
The Synthesis Report is the fourth and final installment of the Fourth Assessment Report. The previous three installments published earlier this year examined the physical science basis for climate change, the impacts of global climate change, and the solutions to global climate change, particularly options for reducing greenhouse gas emissions.
November 19, 2007
The latest IPCC report underscores the need for immediate and sustained action to reduce greenhouse gas emissions, both in the United States and globally. In the United States, many states are demonstrating strong leadership, and I am confident Congress is on the path to enacting a comprehensive mandatory policy in the near future.
Globally, 2008 marks a significant milestone as the Kyoto commitments take effect. But many already have their sights set on a post-Kyoto framework, and steps toward a new international agreement will be the key issue before negotiators next month in Bali.
The ideal outcome from Bali would be a clear mandate to negotiate a comprehensive post-2012 agreement establishing fair, effective, and binding commitments for all major economies. Unfortunately, despite the latest wakeup call from the IPCC, it appears that the United States and some other key governments are not yet prepared to negotiate real commitments. Even if a clear negotiating mandate isn’t possible, it is imperative that any process launched in Bali leave the door open to negotiating commitments. That way, when a new U.S. administration takes office, governments can quickly get down to the business of forging an effective and durable post-2012 framework.
What is the IPCC and why is it important?
The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide the world with a clear scientific review of the current state of knowledge on climate change.
Thousands of scientists from all over the world volunteer and are selected to review and assess the latest relevant scientific, technical and socio-economic data to understand climate change, its potential impacts, and options for adaptation and mitigation. The IPCC aims to reflect a range of views and expertise in order to publish comprehensive and objective assessments.
The IPCC does not conduct independent research, rather it convenes climate experts from around the world every five to seven years to synthesize the latest climate research findings in peer-reviewed and published scientific/technical literature. The IPCC issued comprehensive assessments in 1990, 1995, 2001, 2007 and 2014.
IPCC reports are never policy prescriptive but the conclusions are relevant to nations, states, and businesses interested in enacting policies to limit future warming and reduce the costs of climate change.
What is the Fifth Assessment report?
The Fifth Assessment Report (AR5) is the latest in a series of reports from the IPCC assessing scientific, technical, and socio-economic information regarding climate change. It was released in three installments over the course of 2013 and 2014, and an additional synthesis report was published in November 2014.
More than 830 scientists are involved in writing the reports and hundreds more will review and edit the draft reports.
AR5 is broken up into three sections, or working groups:
- Working Group I provides a comprehensive assessment of the physical science basis of climate change: Released Sept. 27, 2013.
- Working Group II assesses the scientific, technical, environmental, economic and social aspects of vulnerability to climate change as well as consequences for ecological systems, socio-economic sectors and human health: Released March 31, 2014.
- Working Group III assesses all relevant options for mitigating climate change through limiting or preventing greenhouse gas emissions and taking actions to remove them from the atmosphere: Released April 11, 2014.
The syntheses report was released Nov. 2, 2014
Each working group report has a Summary for Policymakers that distills the key points from the hundreds of pages found in the respective full report. The Summary for Policymakers tend to be of most interest to the media and non-scientists.
What are the key points in the IPCC Working Group I Summary for Policymakers?
The Summary for Policymakers includes the key conclusions from the longer report in a format suitable for a broader audience. The SPM will include observations of changes in the atmosphere, ocean, and cryosphere, including changes in sea level. It will also discuss our confidence in attributing climate change to human activities. The SPM will also include projections of global and regional climate change for the 21st century, including projected changes in the water cycle, extreme weather, sea level, sea ice, and the carbon cycle.
It answers such questions as:
- What is the state of the science in understanding and attributing climate changes?
- What are the primary drivers of climate change?
- How do recent changes compare to paleoclimatic records?
- In what ways is climate change is already occurring around the globe and how fast are these systems changing?
- What are models projecting for the 21st century climate and how accurate are they?
- Which types of climate changes might be irreversible?
What are the key points in the IPCC Working Group II Summary for Policymakers?
The Summary for Policymakers includes important statements and conclusions from the WGII report and is aimed at a broader audience. The WGII SPM is divided into three sections: 1. Observed Impacts, Vulnerability, and Adaptation in a Complex and Changing World; 2. Future Risks and Opportunities for Adaptation; and 3. Managing Future Risks and Building Resilience.
The WGII SPM answers such questions as:
- What climate-related impacts are already being observed today?
- What are the key future risks in areas such as water resources, coastal and marine systems, food security, human health, security, and economic growth?
- Which groups of people are the most vulnerable?
- What kind of adaptation actions have already been undertaken and which actions could be taken to reduce these future risks?
- How can adaptation decisions be made when the future is uncertain?
- What constitutes effective adaptation action and climate-resilient development?
What are the key points in the IPCC Working Group III Summary for Policymakers?
The Summary for Policymakers includes key statements and conclusions from the WGIII report and is aimed at a broader audience. It assesses all relevant options for mitigating climate change through limiting or preventing greenhouse gas emissions, as well as activities that remove them from the atmosphere. It lays out a number of baseline scenarios that, without mitigation efforts, would lead to substantial warming by the end of the 21st century.
It also describes a number of potential mitigation scenarios:
- To avoid 2 degrees C (3.6 degrees F) of warming relative to pre-industrial time, the report indicates that atmospheric concentrations of greenhouse gases need to be stabilized around 450 ppm CO2-eq or lower. Given that we are currently around 430 CO2-eq, this is a tall order, requiring large-scale changes in energy systems and land use. For example, achieving this level of stabilization will require more rapid improvements in energy efficiency and a tripling to nearly a quadrupling of the share of zero- and low-carbon energy supply from renewables, nuclear energy, and fossil energy with carbon capture and storage, or bioenergy with carbon capture and storage, by the year 2050.
- The aggregate economic cost of mitigation varies widely, but generally increases based on the stringency of the level of mitigation. In general, the costs of mitigation only offset a relatively small fraction of global projected economic growth for the 21st century.
- The 2020 individual country-pledged goals (under the Cancún Agreements) are unlikely to put us on a path to avoid 2 degrees C (3.6 degrees F) of warming; further substantial reductions beyond 2020 would need to be made. Continuing on the pathways consistent with the Cancún pledges is more consistent with scenarios likely to keep temperature change below 3 degrees C relative to pre-industrial levels.
- If we do not strengthen mitigation efforts between now and 2030, it will be more difficult and more expensive to achieve warming targets, such as avoiding 2 degrees of warming relative to pre-industrial levels.
IPCC AR4 WGII: "Impacts, Adaptation & Vulnerability"
The second installment to the IPCC Fourth Assessment Report was released April 6, 2007. The Working Group II installment to the report addresses "Impacts, Adaptation and Vulnerability". The WGII report provides a detailed analysis of observed changes in natural and human systems and the relationship between those observed changes and climate change, as well as a detailed assessment of projected future vulnerability, impacts, and response measures to adapt to climatic changes for main sectors and regions.
According to the IPCC, the report from Working Group II on the impacts of climate change answers the following questions:
- What is the current state of knowledge on impacts of climate change?
- What is the state of knowledge on impacts under different levels of adaptation?
- What are the impacts under different levels of mitigation?
- What is the state of knowledge concerning observed effects?
IPCC AR4 WGI: "The Physical Science of Climate Change"
The first installment to the IPCC Fourth Assessment Report was released February 2, 2007. According to the IPCC, the Working Group I Report, "The Physical Science Basis", assesses the current state of knowledge about the natural and human drivers of climate change, reflecting the progress of the climate change science in the observation of the atmosphere, the Earth's surface and oceans. It provides a paleoclimatic perspective and evaluates the Earth's surface and oceans. Main topics include changes in atmospheric composition, observation of various climate parameters, coupling between changes in climate and biogeochemistry, evaluation of models and attribution of climate change.
Working Group I Report, "The physical science basis", assesses the current state of knowledge about the natural and human drivers of climate change, reflecting the progress of the climate change science in the observation of the atmosphere, the Earth's surface and oceans. It provides a paleoclimatic perspective and evaluates future projections of climate change. Main topics include changes in atmospheric composition, observation of various climate parameters, coupling between changes in climate and biogeochemistry, evaluation of models and attribution of climate change..
According to the IPCC, the report from Working Group I on the science of climate change answers the following questions:
- What progress has been made in understanding and attributing climate change?
- What do observations of the atmosphere, oceans, sea level, snow and ice tell us?
- How has climate been behaving in the last hundreds of thousands of years?
- Which are the projections of future changes?
Intergovernmental Panel on Climate Change (IPCC) Releases New Assessment Report on the Impacts of Climate Change
Statement by the Pew Center on Global Climate Change
April 6, 2007
The IPCC Fourth Assessment “Summary for Policymakers” Working Group II report represents the IPCC’s strongest statement to date on the impacts of global climate change. Because of a dramatic increase in the number and quality of observations, this report concludes that, “it is likely [better than 2:1 odds] that anthropogenic warming has had a discernible influence on many physical and biological systems.” The report also projects with greater confidence than in the past that many regions, including North America, will experience severe impacts in the future, even for moderate warming scenarios. Particularly vulnerable are low-lying coastal regions worldwide. Many poor countries at low latitudes are also particularly vulnerable because of a combination of strong climate impacts, low capacity for adaptation, and heavy reliance on climate-impacted resources, such as local food and water supplies.
The assessment is based on extensive published, peer-reviewed scientific literature. Today’s report is the second of three major studies that comprise the Fourth Assessment with input from more than 1,200 authors and 2,500 scientific expert reviewers from more than 130 countries. The first report, released in February 2007, examined the physical science basis for climate change. The third report, to be released in May 2007, will explore the solutions to global climate change, particularly options for reducing greenhouse gas emissions.
Statement by Eileen Claussen, President Pew Center on Global Climate Change
April 6, 2007
This week began with a landmark decision by the US Supreme Court and ended with the release of the IPCC's 4th Assessment on climate change impacts. Following the Supreme Court's decision, it's clear that EPA has the authority – and should -- regulate CO2, and the IPCC report delivered the strongest statement to date on the consequences of climate change. Taken together with increasing calls from CEOs, states, and the public, the message is loud and clear: Read our lips - We need mandatory climate policy in the United States.
This figure shows emissions of carbon dioxide (CO2) by fuel source across all sectors of the economy. The fuels shown are coal, natural gas, petroleum, as well as the total emissions.
Overall, coal and petroleum consumption are down since 2007, while natural gas use has increased. In the electric power and indutrial sectors, natural gas, which emits about half the amount of CO2 as coal, is being used more extensively due to its lower price. In the transportation sector, petroleum consumption is down due to an increase in car and light truck fuel economy (for a similar number of vehicle miles traveled, year-on-year). Correspondingly, total emissions have generally declined since 2007.
Source: EIA (2014)
This figure shows the emissions of carbon dioxide (CO2) from the burning of fossil fuels for electric power generation. The electricity-generating fuels shown here are coal, natural gas, petroleum and non-biomass waste. Natural gas, which emits about half the amount of CO2 as coal, is being used more extensively due to its lower price and displacing coal-fired generation, while petroleum-fired electricity generation continues to be retired.
Source: EIA (2015)
This figure shows the trend in U.S. greenhouse gas emissions between 1990 and 2014. Emissions increased by 7.7 percent between 1990 and 2014.
Greenhouse gas emissions have been declining since 2007 for a few reasons:
- A greater share of electricity is being generated with natural gas and renewable energy. This has offset coal-fired electricity generation, which emits about two times the amount of carbon dioxide (a greenhouse gas) as natural gas-fired electricity generation per unit of electric energy. Energy efficiency has also contributed by keeping electricity demand growth very low.
- Economic activity decreased during the Great Recession, which ran from December 2007 until June 2009. Additionally, the structure of the U.S. economy continues its long-term shift from a manufacturing-based to a service-based economy, which is less energy-intensive.
- Consumption of fossil fuels in the transportation sector has decreased due to lower economic activity, more fuel-efficient vehicles on the road, greater use of biofuels and other social shifts that reduce total vehicle miles traveled, including an aging population, technology (telework), growing cities and greater use of public transportation.
Emissions have decreased 8 percent from 2005 to 2014.
In 2014, the United States emitted 6.9 billion metric tons of greenhouse gases (CO2e). Greenhouse gases are emitted by all sectors of the economy, including electric power (30% of total), transportation (27%), industry (20%), residential & commercial (13%), and agriculture (10%).
In 2014, the United States emitted 6.9 billion metric tons of greenhouse gases (CO2e). Carbon dioxide accounted for the largest percentage of greenhouse gases (81%), followed by methane (10%), nitrous oxide (6%), and other greenhouse gases (3%). Total U.S. emissions for 2014 totaled 6,873 million metric tons of CO2e and net emissions, taking sinks into account, totaled 6,187 tons CO2e.
Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2014 (EPA 2016)