The most recent assessment report from the IPCC is from 2007.

The Task Group 'RCP Concentrations Calculation and Data' harmonised and consolidated greenhouse gas concentration and emission datasets for the pre-industrial control runs, 20th century, and the Representative Concentration Pathways (RCPs). The mixing ratios for the long-lived greenhouse gases provided below are the CMIP5 recommendation for Earth System Models in preparation of the IPCC Fifth Assessment Report. On this website: we provide as well additional background data, which is NOT part of the CMIP5 recommendations. For more information, please see the and the and our documentation:

The resulting report (IPCC 2001) is about 1000 pages long and involves 14 chapters.

Given that hundreds of thousands of hectares of forest are regenerated annually in Canada, assisted migration of commercial tree species, or the human-assisted movement of plants and seeds to new and more suitable locations, could represent a relatively low-risk and potentially effective approach to introducing a degree of climate change resilience into Canadian forests in the future."

IPCC, 2001: Climate Change 2001.

The following is my interpretation of the IPCC report and other recent findings.1.

The at-risk species data from the Tree Atlas were then combined with stand inventory data to evaluate the potential for climate change-related declines within an individual stand. This is done by calculating the relative dominance of each species within a stand in terms of importance value.

IPCC Fifth Assessment Report - Wikipedia

Catholic social teaching calls for bold and generous action on behalf of the common good. "Interdependence," as Pope John Paul II has written, "must be transformed into solidarity. . . . Surmounting every type of imperialism and determination to preserve their own hegemony, the stronger and richer nations must have a sense of moral responsibility for the other nations, so that a real international system may be established which will rest on the foundation of the equality of all peoples and on the necessary respect for their legitimate differences." 11

The common good is built up or diminished by the quality of public debate. With its scientific, technological, economic, political, diplomatic, and religious dimensions, the challenge of global climate change may be a basic test of our democratic processes and political institutions. We respect the inquiry and dialogue which has been carried forward by a wide variety of scientists, diplomats, policy makers, and advocates, not only in the United States but around the world. These efforts should not be demeaned or distorted by disinformation or exaggeration. Serious dialogue should not be jeopardized by public relations tactics that fan fears or pit nations against one another. Leaders in every sector should seek to build a scientifically based consensus for the common good; avoid merely representing their own particular interests, industries, or movements; and act responsibly to protect future generations and the weak.

In the past decade, a continuing process of international diplomacy has led to agreements on principles and increasingly on procedures. In 1992, more than 160 nations, including the United States, ratified the first international treaty on global climate change at Earth Summit in Rio de Janeiro, Brazil, which was known as the United Nations Framework Convention on Climate Change (UNFCCC). In 1997, parties to the UNFCCC including the United States negotiated the Kyoto Protocol, which established mandatory emission reduction targets, market-based procedures for meeting those targets, and timetables for industrialized nations.

Without endorsing the specifics of these agreements and processes, we Catholic bishops acknowledge the development of these international negotiations and hope they and other future efforts can lead to just and effective progress. However, serious deliberations must continue to bring about prudent and effective actions to ensure equity among nations.

As an act of solidarity and in the interest of the common good, the United States should lead the developed nations in contributing to the sustainable economic development of poorer nations and to help build their capacity to ease climate change. Since our country's involvement is key to any resolution of these concerns, we call on our people and government to recognize the seriousness of the global warming threat and to develop effective policies that will diminish the possible consequences of global climate change. We encourage citizens to become informed participants in this important public debate. The measures we take today may not greatly moderate climate change in the near future, but they could make a significant difference for our descendants.

We also hope that the United States will continue to undertake reasonable and effective initiatives for energy conservation and the development of alternate renewable and clean-energy resources. New technologies and innovations can help meet this challenge. While more needs to be done to reduce air pollution, through the use of improved technologies and environmental entrepreneurship, the United States has made significant environmental gains over the last several decades. Our hope is that these technologies along with other resources can be shared with developing countries.

Within the United States, public policy should assist industrial sectors and workers especially impacted by climate change policies, and it should offer incentives to corporations to reduce greenhouse gas emissions and assistance to workers affected by these policies.

We encourage all parties to adopt an attitude of candor, conciliation, and prudence in response to serious, complex, and uncertain challenges. We hope the continuing dialogue within and among the diverse disciplines of science, economics, politics, and diplomacy will be guided by fundamental moral values: the universal common good, respect for God's creation, an option for the poor, and a sense of intergenerational obligation. Since religious values can enrich public discussion, this challenge offers opportunities for interfaith and ecumenical conversation and cooperation.

Finally, we wish to emphasize the need for personal conversion and responsibility. In our pastoral reflection Renewing the Earth, we wrote the following:

Grateful for the gift of creation . . . we invite Catholics and men and women of good will in every walk of life to consider with us the moral issues raised by the environmental crisis. . . . These are matters of powerful urgency and major consequence. They constitute an exceptional call to conversion. As individuals, as institutions, as a people, we need a change of heart to preserve and protect the planet for our children and for generations yet unborn. 12 Each of us should carefully consider our choices and lifestyles. We live in a culture that prizes the consumption of material goods. While the poor often have too little, many of us can be easily caught up in a frenzy of wanting more and more—a bigger home, a larger car, etc. Even though energy resources literally fuel our economy and provide a good quality of life, we need to ask about ways we can conserve energy, prevent pollution, and live more simply.

IPCC; Assessment reports: First (1990) 1992 sup

The Science of Global Climate Change

The photographs from the Apollo missions show earth glowing in the stillness of space like a blue-white opal on black velvet. Cool and beautiful, it hurries along in the Sun's gravitational embrace. The earth is our home, our whole wide world.

Our enfolding blanket of air, our atmosphere, is both the physical condition for human community and its most compelling symbol. We all breathe the same air. Guarding the integrity of the atmosphere—without which complex life could not have evolved on this planet—seems like common sense. Yet a broad consensus of modern science is that human activity is beginning to alter the earth's atmospheric characteristics in serious, perhaps profound ways. For the past century, researchers have been gathering and verifying data that reveal an increase in the global average temperature. Until recently, scientists could not say with great confidence whether or not this phenomenon was in any way the result of human activity or entirely the result of natural changes over time.

To deal with the difficulty of making precise measurements and arriving at definite conclusions, the World Meteorological Organization and the United Nations Environment Programme established the Intergovernmental Panel on Climate Change (IPCC) to seek a clear explanation of the causes and possible impacts of this global climate change. 14 Because of the large number of scientists involved in the IPCC and its process of consultation, its reports are considered widely as offering the most authoritative scientific perspectives on the issue. IPCC's findings have met with general—but because of remaining uncertainties, not complete—agreement within the wider scientific community.

In 1996, the IPCC issued its Second Assessment Reports, which summarized the current state of knowledge. The first of these reports concluded that " the balance of evidence suggests that there is a discernible human influence on global climate." 15 The Third Assessment Reports, approved in early 2001, found even stronger evidence and concluded, " most of the observed warming over the last 50 years is likely to have been due to the [human-induced] increase in greenhouse gas concentrations" (italics added). 16

The IPCC offers convincing evidence that there exists if not a clear and present danger then a clear and future one, and that coming changes will affect all aspects of the environment and societal well-being. Based on measurements taken over both land and sea, the global average surface-air temperature has increased by about one degree Fahrenheit since 1860, building up as the Industrial Revolution was hitting full stride. While this is hardly a frightening increase for a particular geographic location, the temperature change is global in extent, so one must read it against the background of the earth's average temperature during historic times. According to IPCC, the rate and duration of warming in the twentieth century appears to be the largest in the last one thousand years. The twentieth century also experienced precipitation increases in mid- and high-northern latitudes; drier conditions in the subtropics; decreases in snow cover, mountain glaciers, and Arctic sea ice; and a rise of four to eight inches in mean sea level. 17

The "greenhouse effect," though complex in detail, is simple enough in outline. Not considering the internal heating due to radioactive decay and volcanism, the earth draws its thermal energy from the Sun. Atmospheric gases form a protective cover that makes our planet hospitable to life, transmitting visible light, blocking out harmful high-energy radiation like ultraviolet rays, and keeping temperatures comfortable by moderating the escape of heat into space. However, the precise mix of these gases is quite delicate, and changing that mix alters the atmosphere's properties. An increase in the relative abundance of the greenhouse gases (carbon dioxide, methane, chlorofluorocarbons, tropospheric ozone, and nitrous oxide) causes the earth to trap more of the Sun's heat, resulting in what is called "global warming." Since the beginning of the industrial period, the IPCC reports, the concentration of the principal greenhouse gas, carbon dioxide, has increased by 30 percent and is now greater than at any time in the past 20 million years. 18 The presence of methane (150 percent increase) and nitrous oxide (16 percent increase) is also growing. The result is the small but alarming temperature rise science has detected. 19

What causes greenhouse gases to accumulate in the atmosphere? Emissions from cars and trucks, industry and electric plants, and businesses and homes are the largest part of the answer, although other factors such as deforestation contribute. The Industrial Revolution was built on furnaces and engines burning fossil fuels (coal, natural gas, oil, and such derived products as gasoline and heating oil). These fossil fuels now power the U.S. and global economy. Although some of the smoke particles and other pollutants (such as sulfur dioxide) now streaming from chimneys and tailpipes can actually cool the earth if they take an aerosol form, the great bulk of our emissions are contributing a warming influence. Reflecting upon studies completed since its last report in 1996, the IPCC says, "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities." 20

Whatever the extent, severity, or geographical distribution of global warming impacts, the problem is expected to disproportionately affect the poor, the vulnerable, and generations yet unborn. Projected sea level rises could impact low-lying coastal areas in densely populated nations of the developing world. Storms are most likely to strain the fragile housing infrastructure of the poorest nations. The migration of diseases could further challenge the presently inadequate health care systems of these same nations. Droughts or floods, it is feared, will afflict regions already too often hit by famine, hunger, and malnutrition. Because the number of days with high heat and humidity are likely to increase, heat stress impacts will also increase, especially among the elderly, the sick, children, and the poor. 21

The scientific reports of the IPCC portray the long-term challenge global climate change poses. Its findings, while not complete, are widely accepted in the scientific community. In June 2001, the National Academy of Sciences released a report, prepared at the request of President Bush, summarizing a prestigious panel's understanding of global climate change and an assessment of the work of the International Panel on Climate Change. The panel said that "greenhouse gases are accumulating in the Earth's atmosphere as a result of human activities. . . ." It also found that "we cannot rule out that some significant part of these changes are also a reflection of natural variability. . . . Because there is considerable uncertainty in current understanding of how the climate system varies naturally and reacts to emissions of greenhouse gases and aerosols, current estimates of the magnitude of future warming should be regarded as tentative and subject to future adjustments (either upward or downward). . . ." The report noted that while the full implications of climate change remain unknown, the panel "generally agrees with the assessment of human-caused change presented in the IPCC Working Group I scientific report." 22