“It is becoming increasingly clear that we are responsible for warming of the Earth primarily due to the burning of fossil fuels. Predicting the implications of this or how the picture will change in the future are big challenges for scientists and today’s report by the IPCC, whilst recognising uncertainties, gives us the best possible insight into what may lay ahead. Those who predict imminent disaster are probably overstating the case, but equally those who claim that we can carry on regardless are likely to be burying their heads in the sand.
“Predicting what will happen to climate is very complicated and there is still a lot that we do not know, but we cannot afford to wait until we can predict the future with absolute certainty before addressing the risks. We invest substantially, both as a country and individually, to insure ourselves against a wide range of risks that are less likely than climate change.
“The IPCC report provides a sound evidence base on which policy makers can make their decisions on appropriate action. Ignoring the problem is simply not sensible and most governments, businesses and individuals recognise that. The more convincing the evidence becomes, the more confident I am that rationality and science will win out and we will grasp the opportunities that decarbonising our economy offers.”
Additional comments from Fellows of the Royal Society who are climate scientists:
Professor Eric Wolff FRS, Royal Society Research Professor, Department of Earth Sciences, University of Cambridge:
"The new report confirms how unprecedented the kick that we are giving the climate system is: concentrations of greenhouse gases are probably higher, and rising faster, than at any time in the last 800,000 years."
Professor Tim Palmer FRS,Royal Society Research Professor in Climate Physics, University of Oxford
“This new IPCC assessment report provides a snapshot of the evolving state of climate science. Above all, it confirms that the threat of dangerous man-made changes to global climate is quite unequivocal. It follows that if we want to reduce this threat, we must cut our emissions of greenhouse gases. Additionally, and for the first time, the report discusses attempts to predict our changing climate over the next few decades. This is becoming an increasingly important area of research as we start to ask how society can adapt to future climate change.
“Climate models encode the equations which describe the laws of physics as they apply to Earth's climate. These models therefore provide the best tools that science can provide to estimate future climate change. One way of testing the reliability of these models is to assess the extent to which they can simulate today's climate, and forecast weather and predictable short-term climate fluctuations e.g. associated with El Nino. Overall these models do a remarkably good job at describing what is an exceptionally complex self-interacting system. There are shortcomings in current generation climate models and these will be alleviated in future years as supercomputer systems become yet more powerful, allowing a reduction of uncertainty about future climate. Overall, climate scientists are confident in the reliability of contemporary climate models to make the type of probabilistic projections of climate as presented in the 5th Assessment Report.”
Professor John Shepherd FRS, Ocean & Earth Science, University of Southampton:
“As expected, the main message is still the same: the evidence is very clear that the world is warming, and that human activities are the main cause. Natural changes and fluctuations do occur but they are relatively small. There are still uncertainties but the signal is clear enough to justify action: in fact we need less talk and more action. Uncertainty is a reason to be cautious, but not a reason to do nothing. On the contrary, uncertainty is a reason for taking action to avoid possible serious risks.
“The recent slow-down in warming is interesting, but it may still be just a wiggle, maybe caused by a natural cycle in the ocean. If so we should expect more rapid warming in a few years time. There is no reason whatever to suppose that the slow-down is permanent: these things have happened before (e.g. 1950 to 1970), and no-one ever claimed that climate models could predict all these decadal wiggles.”
Professor Joanna Haigh CBE FRS, Professor of Atmospheric Physics, Imperial College London
“The new IPCC report confirms, with even greater confidence than in previous reports, that global warming continues and that this is largely a result of greenhouse gases produced by human activity. The concentration of carbon dioxide in the Earth’s atmosphere now exceeds anything it has experienced in the past 3 million years and its continuing upward trend is almost certain to result in further global warming. Changes in solar activity alone cannot explain the global surface temperature variations of the past 150 years and, even if the Sun were to enter a new ‘grand minimum’ state within the next century, would be very unlikely to provide more than a small, temporary, partial compensation for likely anthropogenic warming.”
Professor Sir Brian Hoskins FRS, Director of the Grantham Institute for Climate Change at Imperial College London:
“This Summary for Policy Makers provides further strong confirmation that human activity is having a significant and growing impact on the climate.
“It is based on a comprehensive review and rigorous assessment of the state of climate science by some 850 scientists, who reviewed over 9000- scientific articles, and includes voices from all sides of the issue. This report significantly strengthens the consistent message from the four previous assessment reports; we are conducting a dangerous experiment with our planet.
“The evidence of changes in many different aspects of the climate system, from the ice sheets to the deep ocean, shows that climate change is happening. To reduce the serious risks posed by increasing changes in the climate, we need to redouble our efforts globally to limit carbon dioxide and other greenhouse gas emissions.”