Whatever your political leaning, there's now little doubt about the scientific community's consensus that global climate is warming and that human behavior is likely responsible. As this consensus has solidified, government and business leaders in the US and around the world are acting to mitigate the potential risks.
History of Consensus in the Scientific Community
The Intergovernmental Panel on Climate Change (IPCC), established in 1998 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP), to evaluate the risk of climate change brought on by humans, issues its Fourth Assessment report, which further strengthens the consensus and need for action on the part of the international community. "Highlights" include:
- Warming of the climate system is unequivocal.
- The majority of the observed increase in globally averaged temperatures since the mid-20th century is very likely (confidence level >90%) due to the observed increase in anthropogenic (human) greenhouse gas concentrations.
- Hotter temperatures and rises in sea level "would continue for centuries" even if greenhouse gas levels are stabilized, although the likely amount of temperature and sea level rise varies greatly depending on the fossil intensity of human activity during the next century.
- The probability that this is caused by natural climatic processes alone is less than 5%.
- World temperatures could rise by between 2.0 and 11.5 °F during the 21st century (table 3) and that:
- Sea levels will probably rise by 7.08 to 23.22 in
- There is a confidence level >90% that there will be more frequent warm spells, heat waves and heavy rainfall.
- There is a confidence level >66% that there will be an increase in droughts, tropical cyclones and extreme high tides.
- Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium.
- Global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values over the past 650,000 years
In June of 2005, the U.S. National Academy of Sciences joined the national science academies of China, France, Germany, India, Russia, and the United Kingdom in making a strong statement on climate change entitled "Global Response to Climate Change." The Academies called on world leaders "to acknowledge that the threat of climate change is clear and increasing, to address its causes, and to prepare for its consequences." The statement noted, "the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action." The Academies urged nations to "identify cost-effective steps that can be taken now to contribute to substantial and long-term reductions in net global greenhouse gas emissions that cause global warming."
The United Nations' Intergovernmental Panel on Climate Change issued it's Third Assessment Report, strengthening its conclusions about climate change and human behavior, saying, "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities". The IPCC's report noted risks of unchecked global warming including damage to ocean ecosystems and land habitat changes for wild and domesticated animals, weather-related destruction, rising sea levels putting coastal residents worldwide at risk, and threats to human health through expansion of range of tropical disease, flooding, and drought.
The Second IPCC Assessment is issues and notes, 1) greenhouse gas concentrations have continued to increase, 2) the balance of evidence suggests a discernible human influence on global climate (considerable progress since the 1990 report in distinguishing between natural and anthropogenic influences on climate), and 3) climate is expected to continue to change in the future (increasing realism of simulations increases confidence; important uncertainties remain but are taken into account in the range of model projections).
In November 1992, the Union of Concerned Scientists issued the World Scientists' Warning to Humanity, signed by nearly 1,700 of the world's leading scientists from 63 countries, including 110 Nobel laureates and 60 US National Medal of Science winners, including the majority of Nobel laureates in the sciences. The appeal included the directive "We must, for example, move away from fossil fuels to more benign, inexhaustible energy sources to cut greenhouse gas emissions and the pollution of our air and water."
The IPCC first assessment report was issued and served as the basis of the United Nations Framework Convention on Climate Change (UNFCCC). The executive summary notes: 1) global mean surface air temperature increased by 0.3 to 0.6 °C over the last 100 years, 2) emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases and these increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth's surface, and 3) based on current models, we predict: an increase of global mean temperature during the 21st century of about 0.3 °C per decade, greater than that seen over the past 10,000 years.
The Intergovernmental Panel on Climate Change (IPCC) is established by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP), to evaluate the risk of climate change brought on by humans. The IPCC does not carry out research, nor does it monitor climate or related phenomena. One of the main activities of the IPCC is to publish special reports on topics relevant to the implementation of the UN Framework Convention on Climate Change (UNFCCC). (The UNFCCC is an international treaty that acknowledges the possibility of harmful climate change; implementation of the UNFCCC led eventually to the Kyoto Protocol.) The IPCC bases its assessment mainly on peer reviewed and published scientific literature and all IPCC technical reports face extensive scientific review. (Source: Wikipedia)