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What are, in fact, the grounds for concern about global warming? Javier January 30, 2018 This is an answer to the Geological Society of London position statement on “Climate Change: evidence from the geological record,” published in November 2010, and the addendum published in December 2013. They can be found at: https://www.geolsoc.org.uk/climaterecord This article was first written as a long comment contributing to a discussion over the Geological Society statement at the energy and climate blog Energy matters. Scientists of the Geological Society that authored the statements participated in the discussion to defend their views. Climate change is a reality attested by past records. Concerns about preparing and adapting for climate change are real. However, the idea that we can prevent climate change from happening is dangerous and might be anti-adaptive. Certain energy policies that might have no effect on climate change could make us less able to adapt. Physics shows that adding carbon dioxide leads to warming under laboratory conditions. It is generally assumed that a doubling of CO2 should produce a direct forcing of 3.7 W/m2 [1], that translates to a warming of 1°C (by differentiating the Stefan-Boltzmann equation) to 1.2°C (by models taking into account latitude and season). But that is a maximum value valid only if total energy outflow is the same as radiative outflow. As there is also conduction, convection, and evaporation, the final warming without feedbacks is probably less. Then we have the problem of feedbacks that we don’t know and cannot properly measure. For some of the feedbacks, like cloud cover we don’t even know the sign of their contribution. And they are huge, a 1% change in albedo has a radiative effect of 3.4 W/m2 [2], almost equivalent to a full doubling of CO2. So, in essence we don’t know how much the Earth has warmed in response to the increase in CO2 for the past 67 years, and how much for other causes. That is the reason why, after expending billions on the question of climate sensitivity to CO2, we have not been able to reduce the range of possible values, 1.5°C to 4.5° C[3], a factor of 3, in the 1