The scientific community has reached a strong consensus that global temperatures are rising rapidly as a direct result of billions of tons of carbon dioxide and other greenhouse gas emissions from human-made sources.

The world’s leading scientific body focused on climate change is the Intergovernmental Panel on Climate Change   (IPCC https://www.ipcc.ch/), formed in 1988 by the World Meteorological Organization and the United Nations Environment Programme. The IPCC, made up of hundreds of scientists with relevant expertise from throughout the world, evaluates the state of peer-reviewed[1] and published climate research every few years. The IPCC first expressed the scientific consensus that climate change is real and caused by humans in 2001. The group of international experts came to the same conclusion in the 2007 IPCC Fourth Assessment Report, stating that all available evidence pointed to a more than 90% probability that human activities are warming the planet.[2]

The Intergovernmental Panel on Climate Change (IPCC) released the Summary for Policymakers  (https://www.ipcc.ch/report/ar5/wg1/)  for the Fifth Assessment in September 2013. This report finds that evidence of warming is “unequivocal” and that it is “extremely likely” that human influence has been the dominant cause of that warming. The latest observations illustrate the changes that are already underway. The observations show: increasing atmospheric carbon dioxide concentrations, rising air and ocean water temperatures, declines in the extent of arctic ice, and declining pH in ocean waters.[3]

To view more information about how climate change has changed over time, and to “plot” your own times series graph using data from 1895 through 2012, please visit the NOAA Plot Time Series Website   maintained by the National Climatic Data Center’s Climate Services and Monitoring Division.

Every major scientific organization in the United States with relevant expertise has confirmed the IPCC’s conclusion, including the National Academy of Sciences,[2] the American Meteorological Society,[5] the American Geophysical Union,[6] and the American Association for the Advancement of Science.[7] The list of international scientific organizations affirming the worldwide consensus on climate change is even longer (see List of Organizations http://www.opr.ca.gov/facts/list-of-scientific-organizations.html). Several studies have shown that about 97% of climate scientists actively doing research agree that climate change is happening and is human-caused.[8],[9] A study published in May, 2013 examined 11,944 climate abstracts from 1991–2011 in peer-reviewed scientific literature and affirmed that 97.1% of these scientists endorsed the consensus position that humans are causing global warming.[10]

Does this mean that no scientific questions remain about climate change? Of course not. Scientists continue their efforts to better understand the many complex issues associated with climate change, including the rate of warming in the future, the specific climate impacts local areas will face, and the future rate of ice melt and sea level rise. The basic, fundamental facts that climate change is occurring and its central cause is human-made emissions are no longer subject to meaningful scientific debate: climate change is real, it’s caused by human activities, we are already seeing the effects, and our current path has put us on course for dire results in the not-too-distant future.

The US National Academy of Sciences and The Royal Society cordially invite you to join us for the release of “Climate Change: Evidence & Causes,”  (http://nas-sites.org/americasclimatechoices/events/a-discussion-on-climate-change-evidence-and-causes/) a new publication produced jointly by the two institutions. Written by a UK-US team of leading climate scientists and reviewed by climate scientists and others, the publication is intended as a brief, readable reference document for decision makers, policy makers, educators, and other individuals seeking authoritative information on the some of the questions that continue to be asked.

Several studies have shown that about 97% of climate scientists actively doing research agree that climate change is happening and is human-caused.8,9 A study published in May, 2013 examined 11,944 climate abstracts from 1991–2011 in peer-reviewed scientific literature and affirmed that 97.1% of these scientists endorsed the consensus position that humans are causing global warming.10 For more information about scientific consensus around climate change, please visit the American Association for the Advancement of Science “What We Know”   website.

http://www.opr.ca.gov/facts/scientific-consensus.html