“As two of the world’s leading scientific bodies, we feel a responsibility to evaluate and explain what is known about climate change, at least the physical side of it, to concerned citizens, educators, decision makers and leaders, and to advance public dialogue about how to respond to the threats of climate change,” said NAS President Ralph J. Cicerone.
“Our aim with this new resource is to provide people with easy access to the latest scientific evidence on climate change, including where scientists agree and where uncertainty still remains,” added Sir Paul Nurse, President of the Royal Society. "We have enough evidence to warrant action being taken on climate change; it is now time for the public debate to move forward to discuss what we can do to limit the impact on our lives and those of future generations."
Climate Change: Evidence and Causes, written and reviewed by leading experts in both countries, lays out which aspects of climate change are well-understood, and where there is still uncertainty and a need for more research.
Carbon dioxide (CO2) has risen to levels not seen for at least 800,000 years, and observational records dating back to the mid-19th century show a clear, long-term warming trend. The publication explains that measurements that distinguish between the different forms of carbon in the atmosphere provide clear evidence that the increased amount of CO2 comes primarily from the combustion of fossil fuels, and discusses why the warming that has occurred along with the increase in CO2 cannot be explained by natural causes such as variations in the Sun’s output.
The publication delves into other commonly asked questions about climate change, for example, what the slower rate of warming since the very warm year in 1998 means, and whether and how climate change affects the strength and frequency of extreme weather events.
Many effects of climate change have already become apparent in the observational record, but the possible extent of future impacts needs to be better understood. For example, while average global sea levels have risen about 8 inches (20 cm) since 1901, and are expected to continue to rise, more research is needed to more accurately predict the size of future sea-level rise. In addition, the chemical balance of the oceans has shifted toward a more acidic state, which makes it difficult for organisms such as corals and shellfish to form and maintain their shells. As the oceans continue to absorb CO2, their acidity will continue to increase over the next century, along with as yet undetermined impacts on marine ecosystems and the food web.
Even if greenhouse gas emissions were to suddenly stop, it would take thousands of years for atmospheric CO2 to return to its levels before the industrial era. If emissions continue unabated, future climate changes will substantially exceed those that have occurred so far, the publication says.
The authoring committee offers this brief explanation of the science of climate change to help inform policy debates about the choices available to nations and the global community for reducing the magnitude of climate change and adapting to its impacts.
Would you like to ask a scientist a question about climate science? Click here to submit your questions to a scientist to answer. The forum will be open from 27 February 2014 until 5pm on 5 March 2014. Answers will be posted during the following week.
An event was held to launch the publication in at the National Academy of Sciences in Washington on Thursday 27 February. Dr. Ralph J. Cicerone, President of the National Academy of Sciences and Sir Paul Nurse, President of the Royal Society gave brief introductions. Host Miles O’Brien from the PBS Newshour guided the discussion with lead authors Professor Eric Wolff FRS of the University of Cambridge, and Professor Inez Fung of the University of California, Berkeley. Video of the event will be available on our website week commencing Monday 3 March 2014.