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Man-Made Climate Change – Is it Trumped Up?
Estimated reading time: 5 minutes
Lecture date: Sun, 20th Nov, 2016
On Sunday 20 November I debated with Piers Corbyn on his proposal “Man-made limate change: is it all trumped up?” He proposed the motion and I opposed it. The debate itself was an interesting experience. It was quite confrontational and Piers mixed politics with science arguments to attempt to persuade us to join his “Great campaign to End the Man-Made CO2 Climate-Change fraud”. I found that Piers Corbyn made unsubstantiated statements of “fact” with little supporting science analysis or reference to scientific literature to justify his statements. In my talk I tried to challenge this unscientific approach. Science requires statements to be supported by evidence in the form of observations, theory and/or calculations. These then need to be tested and reproduced by other scientists to either falsify, confirm or refine understanding, building up knowledge over time. This progress is achieved by peer review publication and it is noticeable that Piers Corbyn has never published in such literature.
- Firstly, Piers Corbyn disputes that carbondioxide (CO2) has any warming effect at all.And even if it did, he attests that any effects ofhuman emissions would be inconsequential.Piers is correct that CO2 is a small fraction ofatmospheric mass. He is also correct that thefluxes from the natural carbon cycle are largerthan the fluxes from human activity. However,he is completely incorrect to conclude from these facts that the effects of human emissions of CO2 are inconsequential. The natural cyclemaintains CO2 levels in the atmosphere ataround 278 parts per million but since the industrial revolution human emissions haveincreased CO2 levels to over 400 parts permillion. This provides significant warming tothe Earth – enhancing the Earth’s greenhouse effect by over 1.5 watts per square metre of the Earth’s surface. This greenhouse effecthas been directly measured – see Forster et al.,2007 (https://goo.gl/xGY3OU) or New Scientist(https://goo.gl/xcR4VJ).
- Piers Corbyn states that ocean temperaturescontrol the amount of CO2 in the air, citingHenry’s Law to “prove” that increased CO2 in the air comes from the ocean. Henry’slaw is a real law which does indeed tell you that if you heat water containing CO2 it willincrease CO2 in the air whilst decreasing it inthe ocean. However, observations tell us that CO2 is rising both in the atmosphere and in the ocean, leading to ocean acidification and death of corals. These observations mean thatthe atmospheric increase can’t come from theocean as Piers Corbyn states. There is much other evidence to show all the increase in CO2 is a result of human emissions. The carbon14 isotopic record in the atmosphere shows a signature of fossil fuel burning. There is slightly elevated CO2 in the Northern hemisphere,compared to the Southern, indicating the CO2 is emitted more in the Northern Hemisphere where most fossil fuel burning occurs. If the ocean was emitting CO2, as Piers Corbyn suggests, the gradient would be reversed. There is also a record of declining oxygen which matches the burning of fossil fuels – see Forster et al., 2007 for further details.
- Piers Corbyn says that the lagged response of CO2 to warming during the ice-age is evidence of this “control”. It is true that after the ice ages CO2 increases lagged temperatures by 700 years or so and this increase in CO2 probably was released by the deep ocean. However, this ice-age effect is unrelated to the cause of CO2 rise today as it has not had time to occur. See New Scientist (https://goo.gl/A8nSJj).
- Piers Corbyn also states that the world is cooling (not warming as observations show) and that the East Anglia dataset of global temperature change is fraudulent. However, there are three other datasets, one of which –Berkeley Earth, was produced by sceptical scientists to test the veracity of the East Anglia data. The four independent datasets are in close agreement on their assessment of long-term temperature trends. All show that 2016 will be the hottest year on record, around 1.2C above its 1880 value.
- Lastly, Piers Corbyn states that the Sun drives extremes by controlling the jet stream. Over the UK and parts of North America changes in the Sun can be influential. However, the Sun has 11 and 22 year cycles of change but is very stable on the long-term, so over the last 150 years there has been little long-term effect of solar changes on climate. Many other factors such as ocean temperatures also affect the jet stream. CO2 and solar effects are included together in modern climate simulations. We do not ignore the Sun in our assessment of climate change but rather include it to aid predictive skill. – see Forster et al., 2007 or New Scientist (https://goo.gl/NiytAO).
In summary, man-made climate change is clear. Science is sure that increasing CO2 has warmed the climate and that the increased levels of atmospheric CO2 are caused almost entirely by humans. Uncertainty and/or confusion about the science should not be used to argue for a particular policy decision. We already have enough certainty to make effective decisions about most adaptation and mitigation choices. All Piers Corbyn’s statements of “fact” are either wrong or irrelevant, most are common climate “myths”.
Lastly, to make a better world for our children, we need a constructive dialogue that considers different views on climate change and works towards common solutions. I hope that different sides in the debate listen and learn from each other. Although I disagree strongly with Piers Corbyn on all his science points, I hope I listened and think I understand his underlying political reasons, and those of Donald Trump: to try and protect coal mining communities as coal use declines. To help such communities we need to listen to their concerns and think much harder about how we can make effective climate policy benefit everyone. For example, coal power with carbon capture could be part of an effective solution. I am an optimist and think climate change is solvable – so let’s solve it together. Our children will thank us if we do.
Friday, 10th Feb, 2017
Contemporary Ethical Issues