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An overview from the Royal Society and the US National Academy of Sciences Climate Change Evidence & Causes
2 Clim ate Cha nge n summ ary CLIMATE CHANGE IS ONE OF THE DEFINING ISSUES OF OUR TIME. It is now more certain than ever, based on many lines of evidence, that humans are changing Earthâs climate. The atmosphere and oceans have warmed, accompanied by sea-level rise, a strong decline in Arctic sea ice, and other climate-related changes. The evidence is clear. However, due to the nature of science, not every single detail is ever totally settled or completely certain. Nor has every pertinent question yet been answered. Scientific evidence continues to be gathered around the world, and assumptions and findings about climate change are continually analysed and tested. Some areas of active debate and ongoing research include the link between ocean heat content and the rate of warming, estimates of how much warming to expect in the future, and the connections between climate change and extreme weather events. The Royal Society and the US National Academy of Sciences, with their similar missions to promote the use of science to benefit society and to inform critical policy debates, offer this new publication as a key reference document for decision makers, policy makers, educators, and other individuals seeking authoritative answers about the current state of climate-change science. The publication makes clear what is well established, where consensus is growing, and where there is still uncertainty. It is written and reviewed by a UK-US team of leading climate scientists. It echoes and builds upon the long history of climate-related work from both national science academies, as well as the newest climate- change assessment from the United Nationsâ Intergovernmental Panel on Climate Change. Scientific information is a vital component of the evidence required for societies to make sensible policy decisions. Climate-change science will continue to help society make informed decisions about how to reduce the magnitude of climate change and to adapt to its impacts. The Royal Society and the US National Academy of Sciences will continue to support the use of robust science toward these critical goals. In 2008 Raymond and Beverly Sackler established the USA-UK Scientific Forum to help the scientists of the United Kingdom and the United States forge an enduring partnership on topics of worldwide scientific concern. As Presidents of the Royal Society and National Academy of Sciences, we are pleased to introduce the latest piece of work supported by the Sacklersâ inspired generosity. Dr. Ralph J. Cicerone President, National Academy of Sciences Sir Paul Nurse President, Royal Society Foreword