IPCC
Main article: Intergovernmental Panel on Climate Change
The IPCC (created in 1988 by the World Meteorological Organization and the UN’s Environmental Programme) said in its Second Assessment Report (SAR) in 1995, "the balance of evidence suggests that there is a discernible human influence on global climate." Note that "balance of evidence" is not intended to suggest unambiguous proof; it is a reference to the standards of proof required in English civil law (balance of evidence) as opposed to criminal law (beyond reasonable doubt). This statement was strengthened in the
Third Assessment Report (TAR) in 2001, in which the IPCC said:
- "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities."
- "In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations [1]."
[edit] Joint science academies’ statement
In 2005 the national science academies of the
G8 nations, plus
Brazil,
China and
India, three of the largest emitters of greenhouse gases in the developing world, signed a statement on the global response to climate change. The statement stresses that the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action
[2], and explicitly endorsed the IPCC consensus.
[edit] US National Research Council, 2001
In 2001 the Committee on the Science of Climate Change of the
National Research Council published
Climate Change Science: An Analysis of Some Key Questions [3]. This report explicitly endorses the IPCC view of attribution of recent climate change as representing the view of the science community:
The IPCC's conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue.
[4] The summary begins with:
Greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise. Temperatures are, in fact, rising. The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability. Human-induced warming and associated sea level rises are expected to continue through the 21st century. (ibid.)
[edit] American Meteorological Society
The
American Meteorological Society (AMS) statement adopted by their council in 2003 said:
There is now clear evidence that the mean annual temperature at the Earth's surface, averaged over the entire globe, has been increasing in the past 200 years. There is also clear evidence that the abundance of greenhouse gases in the atmosphere has increased over the same period. In the past decade, significant progress has been made toward a better understanding of the climate system and toward improved projections of long-term climate change... The report by the IPCC stated that the global mean temperature is projected to increase by 1.4 °C–5.8 °C in the next 100 years... Human activities have become a major source of environmental change. Of great urgency are the climate consequences of the increasing atmospheric abundance of greenhouse gases... Because greenhouse gases continue to increase, we are, in effect, conducting a global climate experiment, neither planned nor controlled, the results of which may present unprecedented challenges to our wisdom and foresight as well as have significant impacts on our natural and societal systems. It is a long-term problem that requires a long-term perspective. Important decisions confront current and future national and world leaders.
[5]
[edit] Federal Climate Change Science Program, 2006
On May 2, 2006, the Federal Climate Change Science Program commissioned by the Bush administration in 2002 released the first of 21 assessments that concluded that there is
clear evidence of human influences on the climate system (due to changes in greenhouse gases, aerosols, and stratospheric ozone) [6]. The study said that
observed patterns of change over the past 50 years cannot be explained by natural processes alone, though it did not state what percentage of climate change might be anthropogenic in nature.